Building a L28 (NA)

[TheCrazySwede]

Dear Forums,

I've been a long time lurker of these forums and of the community, but just recently, I've decided it was time I popped my Z cherry and got involved. I own a '77 280z (Motor has EFI; Transmission has 4 Gears)

I'm currently working on another L28 that I picked up (Carbed, N42 Head)) along with a 5-Speed, but due to my lack of knowledge regarding these motors (We are a family of Ford Mustang owners) I seek your help in order to make sure this build isn't a total disaster.

To start off, hello; My name is Mike
I am 20 years old and I'm a computer tech. This is my first engine rebuild, so experience is not really something I have in my corner. Luckily, my brother and my dad are both mechanics, but they decided to pretty much leave me to learn how to swim in the ocean with this build.

My goals for this motor are pretty simple and straight forward, but I would still love to get some help from some of you more knowledgeable L-Series petrol heads.
Let me start by saying that I am not power hungry. We have the pony cars for that. What I want is a responsive motor, not a powerful one.

Engine Goals (Might get redefined as I learn more about these L-series motors)

1. I would like to hit 200HP at the crank (Although not necessary)
2. I want the motor to be naturally aspirated.
3. I love the look and sound of triple Weber carbs.
4. I don't think I need a stroker motor to produce a descent amount of power, so unless it's necessary, I'd rather not go there.

Things that I am considering (Please correct me if I'm wrong!)

1. Balancing the Crank (within 0.25g)
2. Lighter, flat-top pistons (I would like to keep the stock 86mm size)
3. Stock valves look good enough! Probably just stay with those.
4. I've read a few posts where people mentioned using L24 rods. Why is that? Weight?
5. A Mild performance Cam (Schneider 270-80F), with upgraded springs. (Also getting new rocker arms, retainers and .160" lash pads)

As I mentioned above, I'm just learning about these motors, so your help is very much appreciated. I wouldn't know what to do without you guys. Also, I'm gonna post this thread over at HybridZ and see what those guys think. I'm gonna need all the knowledge I can get.

This is the motor:

So it started with this






Time to clean!







So that's pretty much it so far. Cheers guys, and thanks a lot for the help!
Not that it matters much, but here is the car: (It is currently undergoing bumper surgery!)

[siteunseen]

I held the flashlight for my Dad and fetched tools throughout my childhood. That was my mechanical education. I bought this book, How to Rebuild Your Nissan/Datsun OHC Engine: Covers L-Series Engines 4-Cylinder 1968-1978, 6-Cylinder 1970-1984: Tom Monroe: 9781931128032: Amazon.com: Books, and with the help of the good folks on this forum rebuilt a '77 motor, alone. Buy that book and don't worry about the crank, it's balanced already.

Great looking car too!

[HaZmatt]

Just out of curiosity, why dont you do a stroker?

[Diseazd]

http://www.classiczcars.com/forums/e...es-1970-a.html

[Diseazd]

http://www.classiczcars.com/forums/e...ew-engine.html

[Diseazd]

http://www.classiczcars.com/forums/e...8-my-72-a.html

These should answer most of your questions.....N42 head doesn't need the head work that the P79/p90 heads need. I've had 0 problems with Isky cam/ spring combo. I've never done an N42/n47 head, so consult someone else for help there. Remember.....when putting performance higher lift cams.....1) use new rockers 2) use correct lash pads to center wipe pattern 3) use shorter valve seals if interference from retainer and valve seal is a problem. Have an expert check valve spring retainer to valve seal clearance.

[madkaw]

You might think about flat top pistons instead of the dished. Triple carbs or modified SU's will help reach your HP goal. There's no reason why you can't get 200 at the crank with modest upgrades. I think I have about 200 at the crank and it's fun.
Don't forget about gearing and trans to add to the fun

[TheCrazySwede]

You might think about flat top pistons instead of the dished. Triple carbs or modified SU's will help reach your HP goal. There's no reason why you can't get 200 at the crank with modest upgrades. I think I have about 200 at the crank and it's fun.
Don't forget about gearing and trans to add to the fun

Yup, flat tops and triple weber carbs are on my wish-list!
I've seen a few builds with L24 crank and rods, with flat tops from the L28ET. What's the reason for the L24 crank and rods? Is it the stroke ratio? I don't know what differences the ratio will give. If want a rev happy and responsive motor, would I benefit from the L24 crank and rod? Or should I be fine with my L28 equipment and just get the flat tops?

[Diseazd]

Your first motor.....go with what you've got....L28 crank and rods. Keep it simple and cheaper. Get someone who knows what he's doing (good machine shop or local Z nut) to put together bottom end and head. Assembly's not too hard after that if you read the FSM and follow tothe letter. SU's are much simpler than trips.....you can always add triples later. IMHO

[TheCrazySwede]

Thanks for the replies everyone.

I should note that I am in no rush with this motor, so I can take my sweet time learning everything I need to know before purchasing and swapping parts. That's why I wanted to consult you guys, first.

Your first motor.....go with what you've got....L28 crank and rods. Keep it simple and cheaper. Get someone who knows what he's doing (good machine shop or local Z nut) to put together bottom end and head. Assembly's not too hard after that if you read the FSM and follow tothe letter. SU's are much simpler than trips.....you can always add triples later. IMHO

Price for me isn't too big a factor. Money = Time. The more money I spend, the slower the build, haha.
A part of me doesn't necessarily want the simplicity. I already have an L28 in my 280z that pushes enough power (completely stock) to satisfy my needs. Want I want is a build that is different, behaves and acts different, from my original 280. That's why the idea of the L24 crank sounded intriguing. Wouldn't a setup like that alter the compression ratio dramatically? I may very well do what you suggested (Stay with the L28 parts) and move onward, but I don't want to brush off other build ideas only because this way was "easier." I want the build to be something I want, rather than something I had to go with, if that makes sense. I remember boring my 289 in one of our Mustangs and going with bigger pistons. I didn't really notice much of a difference, honestly. At least, not for how much money it required. I guess I wouldn't have much of a choice if I wanted the higher compression from the flat-top pistons.

[TheCrazySwede]

Again, thanks a lot, gentlemen, for your inputs and suggestions! It really means a lot. I'm glad there's such an awesome community available out there that allows us new-comers to pick up and learn the ropes.

Thanks guys!

[madkaw]

Keep what you got and get a lighter flywheel for quicker response . Add that to triples and lower gears=fun!
Seriously - most folks wouldn't be able to discern the difference in these engines(rod/stroke ratio), but a lightened flywheel would be more evident.
Go over to Hybridz and look for at thread 200rwhp and street able

[TheCrazySwede]

Keep what you got and get a lighter flywheel for quicker response . Add that to triples and lower gears=fun!
Seriously - most folks wouldn't be able to discern the difference in these engines(rod/stroke ratio), but a lightened flywheel would be more evident.
Go over to Hybridz and look for at thread 200rwhp and street able

I'll probably end up going that route. The only other thing I wanted to change were the pistons. Are there any flat-top 86mm pistons I could use with the L28 rods?

[madkaw]

81-83 ZX flat tops

[TheCrazySwede]

The only flat tops I found were 86.1mm (ITM Brand)

Also, I won't have any problem with clearance switching to flat tops, right? Just want to take precautions...wouldn't want to hit the valves or anything.

[madkaw]

fun reading!


L6 heads; pics and descriptions - L-Series - HybridZ

L series dimensions - Stroke, Bore, Chamber cc's, etc - L-Series - HybridZ

Custom Cylinder head building.. Whatâ??s involvedâ?¦ - L-Series - HybridZ

[Jeff G 78]

200 crank HP isn't terribly hard to get with minimal cost. I built my race motor for about $1500 and it makes great power. I started with a F54/P79, but it would be about as easy to start with a N42/N42. Triple carbs are nice, but they are not needed to produce your power goals. 9.8:1 CR, a mild cam, and a good set of SU carbs will be all you need. I had my stock flywheel lightened. Make sure you replace your front pulley/harmonic balancer. Check with Dale Manufacturing to have them rebuild yours. I've seen many engines destroyed from failed dampers and a rebuilt one is not expensive.

[TheCrazySwede]

Thanks a lot for the links, madkaw!

200 crank HP isn't terribly hard to get with minimal cost. I built my race motor for about $1500 and it makes great power. I started with a F54/P79, but it would be about as easy to start with a N42/N42. Triple carbs are nice, but they are not needed to produce your power goals. 9.8:1 CR, a mild cam, and a good set of SU carbs will be all you need. I had my stock flywheel lightened. Make sure you replace your front pulley/harmonic balancer. Check with Dale Manufacturing to have them rebuild yours. I've seen many engines destroyed from failed dampers and a rebuilt one is not expensive.

Thanks for the input, Jeff!
Triple Carbs is something I want, rather than something I need. I already have a pair of SU carbs rebuilt by Rebello (Sold along with the motor when I bought it) so I'm already set in that area. TW's is something I'm going to get more down the line.
Thanks for the tip regarding the harmonic balancer! These are things I would like to know regarding the build...things that have been learned through experience. I appreciate you sharing your knowledge! I'll definitely keep that in mind, now.

I messaged someone from HybridZ who is very knowledgeable about L28's and their different builds, and he advised against getting flat-top pistons in an N42 head, and instead, told me to keep the dished ones. He told me that time and time again, he's seen the flat-top swaps done and have seen the effects of detonation in the head. The power gained from the extra compression is therefore lost due to the need to retard the timing. Since I'm keeping the stock valves and aren't planning on boring anything, I think I should heed his advise and keep the dished ones. As I mentioned, power isn't too much of a motivator. Reliability and responsiveness is what I want. A lighter flywheel is up there on the list!

Thanks a lot, again, for all of your help guys! It means a bunch.

[Jeff G 78]

Where do you live? The western part of the US doesn't have above 91 octane which limits your compression ratio. My street Z has 9.83:1 CR via flat top pistons and an N47 head and it runs great on 93 octane with no detonation. For my race motor, I went with the P79 head that is better to resist detonation just to be safe during long races as well as unknown gas near various race tracks. I shaved it to get to about 9.3:1 CR. I did not shim the towers and use longer valves, but rather just shaved and modified my chain guides and cam gear to get my chain slack and timing spot on.

[TheCrazySwede]

Where do you live? The western part of the US doesn't have above 91 octane which limits your compression ratio. My street Z has 9.83:1 CR via flat top pistons and an N47 head and it runs great on 93 octane with no detonation. For my race motor, I went with the P79 head that is better to resist detonation just to be safe during long races as well as unknown gas near various race tracks. I shaved it to get to about 9.3:1 CR. I did not shim the towers and use longer valves, but rather just shaved and modified my chain guides and cam gear to get my chain slack and timing spot on.

Hmm, that is a head scratcher. Given that this is my first build, perhaps it's better for me to be better safe than sorry, I suppose. Yeah, we only get 91 octane here in California (aka Commiefornia)...I've never used those octane boosters, so I don't even know if those things actually do anything. Back home (I'm from Sweden, in case that wasn't obvious, haha) we had up to 98 Octane at almost every gas station. That sure would be helpful over here!

What do you guys think? Is it worth it to go with the flat-tops? I was gonna call Dave Rebello and ask him what type of pistons they have (I know they have dished ones for N42 heads.) I was going to order my valvetrain upgrades from him anyway.

[TheCrazySwede]

So, I gave Rebello a call (Turns out they are about an 1 hour away from where I live!)

I asked him what type of pistons he recommends. He said he hasn't faced many issues with the flat-tops in the N42 head, but if a higher compression isn't needed, he would recommend the dished ones. I also asked him about valvetrain improvements, and he recommended a mild cam with a rather low lift (about .448) but he said that the Cam produces great torque and works great for street use. He said that Z Car Garage (Another highly rated Z specialty team) prefers that Cam Kit over most, mainly due to its power delivery.

I'm going to go over to Rebello (bring my head!) later this week, probably on Thursday, and see what can be done. They use ITM Pistons, by the way.

[Jeff G 78]

In Sweden you likely had 98 RON which is the same as our 93. In the US, we use the (RON + MON) / 2 method of calculating octane while Europe just uses RON. I have no idea why the methods are different, but the octane rating is actually about the same here and there.

I run a Web Racing #91 cam and I really like it. The engine pulls strong to 7,000 RPM. My cam is .450 lift and 280° duration. It was a new billet so I can run OE lash pads. I bought new rockers and lash pads, but I believe people have had good luck reconditioning the rockers at a much lower cost. I paid about $12 each for my rockers 20 years ago.

You can't go wrong with Rebello, but remember that speed costs money.

[TheCrazySwede]

I think you're right about the octane ratings.

Their Cam kit is around $290-300, which isn't bad.
I figure I'll go up there later this week and see what I'm in for. Ask any questions I might have an take it from there.
I'll let you know how it goes!

Cheers!

[TheCrazySwede]

Ok, so a quick update.

I dropped off my crank (w/ rods and pistons) and my block at a machine shop.
Crank just needs a polish, but the block needs to be bored.

So currently, I'm getting the block bored (0.020) and getting flat-top pistons to match. I figured I'd get the bottom end stable and ready before working on the head. Got new crank bearings, as well.

[grannyknot]

Thanks a lot for the links, madkaw!



Thanks for the input, Jeff!
Triple Carbs is something I want, rather than something I need. I already have a pair of SU carbs rebuilt by Rebello (Sold along with the motor when I bought it) so I'm already set in that area. TW's is something I'm going to get more down the line.
Thanks for the tip regarding the harmonic balancer! These are things I would like to know regarding the build...things that have been learned through experience. I appreciate you sharing your knowledge! I'll definitely keep that in mind, now.

I messaged someone from HybridZ who is very knowledgeable about L28's and their different builds, and he advised against getting flat-top pistons in an N42 head, and instead, told me to keep the dished ones. He told me that time and time again, he's seen the flat-top swaps done and have seen the effects of detonation in the head. The power gained from the extra compression is therefore lost due to the need to retard the timing. Since I'm keeping the stock valves and aren't planning on boring anything, I think I should heed his advise and keep the dished ones. As I mentioned, power isn't too much of a motivator. Reliability and responsiveness is what I want. A lighter flywheel is up there on the list!

Thanks a lot, again, for all of your help guys! It means a bunch.

I have a F54 block, N42 head that has been heavily worked with flat top pistons.
Compression was 10:1 and I was chasing ping. Tried cooler plugs, higher octane, richer settings, none of it helped. Bought a 1.5mm steel head gasket and the ping is gone and now I can finally use full advance. A longer duration cam will also fix the problem if you do end up with ping.
I'm looking forward to this build.
Chris

[TheCrazySwede]

I have a F54 block, N42 head that has been heavily worked with flat top pistons.
Compression was 10:1 and I was chasing ping. Tried cooler plugs, higher octane, richer settings, none of it helped. Bought a 1.5mm steel head gasket and the ping is gone and now I can finally use full advance. A longer duration cam will also fix the problem if you do end up with ping.
I'm looking forward to this build.
Chris

Thanks for the input, Chris!
I looked into the compression changes due to gasket sizes, too. I wanted to higher the compression with the flat-tops, and then get a slightly thicker gasket, like you, to compensate. I'm in Cali, so I gotta make due with what I've got.

Block still getting bored!

[rbates]

grannyknot - I'm assuming the higher octane (octane boost ?) allowed you to advance your timing ? I'm in a similar place to you, but still debating in my mind the thicker head gasket solution. For me I'm not sure there will be a net Power gain (what you gain in advance you lose in CR). Guess only a Dyno will be able to confirm one way or another.

[grannyknot]

In my case I had a powerful engine that could not use more than 27* advance no matter what I tried, we have 94 octane available here and I was adding booster to it.
I'm very happy with now.

grannyknot - I'm assuming the higher octane (octane boost ?) allowed you to advance your timing ? I'm in a similar place to you, but still debating in my mind the thicker head gasket solution. For me I'm not sure there will be a net Power gain (what you gain in advance you lose in CR). Guess only a Dyno will be able to confirm one way or another.

[LeonV]

grannyknot - I'm assuming the higher octane (octane boost ?) allowed you to advance your timing ? I'm in a similar place to you, but still debating in my mind the thicker head gasket solution. For me I'm not sure there will be a net Power gain (what you gain in advance you lose in CR). Guess only a Dyno will be able to confirm one way or another.

Compression ratio by itself doesn't boost power all that much. Proper spark timing is much more important.

[madkaw]

Combustion chamber design! The N42 head is an open chamber head with no quench pad thus not a great match for flat tops. Pretty sure Nissan knew that so they matched it with dished pistons. If you really study some of the "pundants" of the L engine over at hybridz they sneak out some tid bits of Lagata power formulas. 'Squish'( piston to head clearance/distance) is essential for fighting detonation and there are zones to avoid.
The 42 can be made better with some welding and reworking, but there are better alternatives like the p-79, p90 early Z heads like E31 or early E88.
Then there's timing curves as Leon mentioned. It's all in the details.

I would consider a different head, especially if the one you have needs rebuilt. Spend some money on a different core and rebuild it. Then you can use a stock Nissan sized gasket and not worry so much about pinging.

The CR numbers don't matter much if you can't run aggressive timing.

[grannyknot]

^ "The CR numbers don't matter much if you can't run aggressive timing"
I can't tell you how long it has taken me to learn that lesson.
The right cam (for what you want from the engine), proper valve adjustment,
proper timing. Get those 3 right and your halfway there.

[CG240Z]

My setup is somewhat a mixture of everything. Using a block from a '79, N47 head, flat top pistons, and stage 1 cam. Also it's fuel injected and I can only get 91 octane. Have about 400 miles on it right now. So far so good, engine is smooth and it has an awesome idle with the cam and header. Still tweaking the fuel mixture.

[TheCrazySwede]

Combustion chamber design! The N42 head is an open chamber head with no quench pad thus not a great match for flat tops. Pretty sure Nissan knew that so they matched it with dished pistons. If you really study some of the "pundants" of the L engine over at hybridz they sneak out some tid bits of Lagata power formulas. 'Squish'( piston to head clearance/distance) is essential for fighting detonation and there are zones to avoid.
The 42 can be made better with some welding and reworking, but there are better alternatives like the p-79, p90 early Z heads like E31 or early E88.
Then there's timing curves as Leon mentioned. It's all in the details.

I would consider a different head, especially if the one you have needs rebuilt. Spend some money on a different core and rebuild it. Then you can use a stock Nissan sized gasket and not worry so much about pinging.

The CR numbers don't matter much if you can't run aggressive timing.

So, I haven't started on the head, yet, although I have stripped it apart. So far, just done work on the block. Should I buy another head? I hear a lot of people going with P90 heads. Which one seems to have the best design?

[madkaw]

I don't know if there's a best or just one that might be better. Chamber design got better with the later heads as in the P-79 or P90. It's all in details though. You really need to study some threads over at Hybridz in the FAQ section under drivetrain or engines. Several good threads concerning the different year heads and how to modify them. Look over there and your line of questions will get more specific with more understanding.

[Nite_Grind]

Keep up the good work. I'm doing a oem rebuild/refresh to a l26. My first full engine build ever.

[TheCrazySwede]

So I visited the lads over at Rebello, and they advised against going for the P90, for a couple of reasons.

To start off, he mentioned how the quench pads in the P90 wouldn't leave much piston clearance if I went to flat-tops, and Dave had no idea how these motors made it out the factory.
He also mentioned how building a P90 head is not cost efficient at all, because you end up doing more work for not so much more performance.

What I was recommended was to stick with my N42, use flat-tops, and just compensate with a thicker gasket. I know there are some 2mm gaskets out there, but I can't seem to find one...according to OZDAT, it will give me a compression of 9.1:1.

I'm still debating if that's cutting it too close, running on Cali's pump gas. Would I have to run octane boosters? Do those things even work? Also, if anyone knows where I can find a good 2mm head gasket (getting the block bored .20 over, so I don't know if these things have to be retro-fitted after wards) I'd really appreciate it.

[TheCrazySwede]

Keep up the good work. I'm doing a oem rebuild/refresh to a l26. My first full engine build ever.

Glad to hear! We're on the same boat on this one, haha.

[siteunseen]

So I visited the lads over at Rebello, and they advised against going for the P90, for a couple of reasons.

To start off, he mentioned how the quench pads in the P90 wouldn't leave much piston clearance if I went to flat-tops, and Dave had no idea how these motors made it out the factory.
He also mentioned how building a P90 head is not cost efficient at all, because you end up doing more work for not so much more performance.

What I was recommended was to stick with my N42, use flat-tops, and just compensate with a thicker gasket. I know there are some 2mm gaskets out there, but I can't seem to find one...according to OZDAT, it will give me a compression of 9.1:1.

I'm still debating if that's cutting it too close, running on Cali's pump gas. Would I have to run octane boosters? Do those things even work? Also, if anyone knows where I can find a good 2mm head gasket (getting the block bored .20 over, so I don't know if these things have to be retro-fitted after wards) I'd really appreciate it.

You've saved me a lot of reading/time/money! I'm keeping the one and only N42 head that I have.

[madkaw]

Wow- Rebello can't believe these engines made it out of the factory with the close piston/head clearance . Just having a hard time believing this.
I guess the extra clearance would be the safe route.
And I am not questioning Rebello s engine building capability, but to prefer an open chambered design head for piston clearance doesn't quite make sense.

[mdec]

"I'm still debating if that's cutting it too close, running on Cali's pump gas. Would I have to run octane boosters? Do those things even work? ..."

From my experience w/o question Octane Boosters do work if your select the correct brand. I have good luck with both NOS & AMSOIL.

I was interesting to hear what dave said about going with the N42 head & a thicker gasket. Is there some calculation/model around that can calculate how gasket thk varies the CR ?

[Diseazd]

Ditto that Steve! Are you sure you heard Dave right? Just by the fact that the head is shaved, assures you that you've got head gasket clearance at the least. My guess is he'd rather not go to the trouble to measure, shave .080 inches, then shim the springs and towers if he could avoid it by using the N42 head. Many, many people are using the stock and shaved P90 and P79 heads. I'm running four right now......absolutely love the combo.....no ping at any RPM either.

[TheCrazySwede]

Ditto that Steve! Are you sure you heard Dave right? Just by the fact that the head is shaved, assures you that you've got head gasket clearance at the least. My guess is he'd rather not go to the trouble to measure, shave .080 inches, then shim the springs and towers if he could avoid it by using the N42 head. Many, many people are using the stock and shaved P90 and P79 heads. I'm running four right now......absolutely love the combo.....no ping at any RPM either.

From what I understand, that's I was told. As many of you know, and I've addressed this in my post, I'm not very experienced in these matters, so whatever advice I get from people who know what they are doing, I tend to blindly accept it.
Maybe he told me about these things because he figured I wouldn't know too much about these things in order to work out a good combo, and he figured he'd save me a lot of trouble (and money) going with my own head, which I appreciate.
He did, in fact, address his concern about clearance level. There might have been a few details here and there that I didn't understand (too many numbers for me to follow!) so I might not be telling you guys all of what he said, only what I remember.

[TheCrazySwede]

"I'm still debating if that's cutting it too close, running on Cali's pump gas. Would I have to run octane boosters? Do those things even work? ..."

From my experience w/o question Octane Boosters do work if your select the correct brand. I have good luck with both NOS & AMSOIL.

I was interesting to hear what dave said about going with the N42 head & a thicker gasket. Is there some calculation/model around that can calculate how gasket thk varies the CR ?

Cool, glad to hear! I'll be sure to check those out.

The site I used for my compression calculations is this: OZDAT.com Engine Design Utility

Play around with the gasket height on that one.

[Blue]

Wow- Rebello can't believe these engines made it out of the factory with the close piston/head clearance . Just having a hard time believing this.
I guess the extra clearance would be the safe route.
And I am not questioning Rebello s engine building capability, but to prefer an open chambered design head for piston clearance doesn't quite make sense.

Ditto for me. All of the E31 performance heads were welded and shaped like peanuts. (Have a look at Frank Honsowetz's Book). It was an evolved shape that was apparently adapted by the 280ZX P79 & P90 (and other Nissan products I assume) as well as on the Maxima N47 heads.

[TheCrazySwede]

So according to my calculations @ OZDAT,

If I grab my N42, have it bored .20", install flat-tops and a high lift cam and use a 2mm head gasket, I'll end up with 9.1 compression. (A 1.5mm gasket gets me 9.6 compression)

Now, a P90 head with the same layout (except with a 1mm gasket) gets me 8.7 compression. Without flat-tops, I get 7.5

That being said, on paper at least, doesn't the N42 head sound like a solid build? Many of you here have a lot of experience with these builds, so I'd really like to know what you guys think. Rebello suggested the N42 route, but I want you guy's opinions on the matter.

Again, I really appreciate all the help. As I've mentioned before, this is my first motor and my first "hands-on" experience with these things, so all of your help means a lot.

Thank you.

[Jeff G 78]

I have two flat top L28 engines. One has an N47 with 9.83:1 and the second is a P79 with 9.3:1. When I built the second engine, I skipped the N42/N47 heads I have and bought a P79. I think it's a better head that handles high compression better. Either head will work fine, but I chose the safe route and went with the more robust chamber design for my race engine.

[Diseazd]

I agree with Jeff.....Many have ping problems with the N42/N47....."0" problems with the modern chambered P79/P90 head.....even when running as high as 10:1 CR......but, it does cost more to mod up the P79/P90.

[TheCrazySwede]

Thanks for the input, guys.
Yeah, pinging is something I'd rather avoid. I'm just curious, but how are you guys getting such high static compression ratios with your P90/P79 heads? Would it require major work to get those numbers? I'm just using calculation tools, so they might not be 100% accurate, but I'm not getting past 8.8:1 with either one of those heads.

Would you guys mind sharing your secrets? I've looked around threads (and other forums) for builds with those, but every single one of them involves the builder knowing what he's doing, so they aren't asking the questions that I would be asking. Does anyone know a good build that wouldn't be too difficulty (although I am up for a challenge if needed) for a newbie to follow?

[Jeff G 78]

I still owe the forum a write-up on my engine, but the short story is that I got there by shaving the P79 and modifying the cam gear and chain guides to get the timing and chain tension right. I make roughly 200 crank hp and my build was done for a very small budget.

[Diseazd]

http://www.classiczcars.com/forums/e...8-my-72-a.html
Can't get any more specific than this.....plan on spending $4,500.00..

[TheCrazySwede]

I still owe the forum a write-up on my engine, but the short story is that I got there by shaving the P79 and modifying the cam gear and chain guides to get the timing and chain tension right. I make roughly 200 crank hp and my build was done for a very small budget.

Ah, so you guys shave the head? That ups the compression, right?
What else would have to be changed if you shave the head? Would I have to adapt everything to fit the new sized head?

200 to the crank is perfect. I'm not looking for some crazy numbers here. I'm going for the Lotus moto of getting more out of less.

Ok, since I'd rather have the better head rather than the head that is known as the "not better" head in terms of operation, are there any reasons why I would want a P90 over a P79 or vice versa? Seems like most people run P79's due to availability. Either one is better than the N42, I assume.

[Nite_Grind]

I've read so much, some times material get's scrambled together. What I do know, and have concluded is, if you already have it, keep it and build what you got! The gains are negligible, the differences minute, depending on application. The money saved can go to other aspects of the build to improve the engine. Madkaw was on the right track with his suggestions. Definitely let this motor be your crash course, experience your efforts first. When you get bored of it's "power," You'll already possess the knowledge to go bigger and better.

[madkaw]

Datsun P79 cylinder head mods

[TheCrazySwede]

Datsun P79 cylinder head mods

Thanks madkaw! That's just what I needed!

[madkaw]

Google is your friend!

[TheCrazySwede]

I got my car on the dyno with its stock L28 inside to see how it performed. I was pretty surprised!

[Jeff G 78]

That's stock? It seems really strong for a stock L28.

[TheCrazySwede]

That's stock? It seems really strong for a stock L28.

It's all stock. I got the car from the original owner. I haven't replaced anything in the car, except for the exhaust. (I replaced the California one with a Federal exhaust. I use the Cali one for smog purposes )

I try to keep the engine as healthy as possible. I do plugs, dizzy cap, oil changes and a few other tune-up items every 3-6 months.
It's my daily driver, so everything gets kept well lubricated and operational. I was hoping for at least 120rwhp, so I was really pleased!

[madkaw]

I can't make out the graph and blow it up to see-argh

[TheCrazySwede]

I can't make out the graph and blow it up to see-argh

Here ya go! Dyno Sheet

[Jeff G 78]

That's close to 170hp at the crank which is about 20hp over SAE Net when the engine was new.

[TheCrazySwede]

That's close to 170hp at the crank which is about 20hp over SAE Net when the engine was new.

No clue, but I know nothing has been changed that would allow 20 more horse. It runs on good oil, spark plugs and has a re-manufactured AFM (The first one crapped out) I know it's running a bit rich at the moment, but other than that, everything inside is stock. Stock cam, pistons, valves, etc. If I'm producing 20 more horse than stock, you have me curious! I honestly have no clue.

Is it possible that the reading was wrong? I sure hope not. That would kill a bit of my enjoyment of the situation, haha. Are there any dyno sheets of other stock L28's on here? I wondering if their power curves are different than mine.

[madkaw]

Yep, that's a healthy engine. Maybe just leave it alone-ha!
I guess there is always the arguement that one dyno reads higher then another. I wish more guys would dyno there engines so they have a number for reference anyway. So now for future projects if you use the same dyno you can see (real) improvements.
Now take it to your local dragstrip and see if can get 15's

[TheCrazySwede]

Yep, that's a healthy engine. Maybe just leave it alone-ha!
I guess there is always the arguement that one dyno reads higher then another. I wish more guys would dyno there engines so they have a number for reference anyway. So now for future projects if you use the same dyno you can see (real) improvements.
Now take it to your local dragstrip and see if can get 15's

Yeah, I saw a post on that one Datsun Engine Mods website, and the guy has a stock L28 with SU Carbs and he got 145rwhp @ 5,200RPM. That's just like mine, only mine has EFI, which helps a bit. After a few mods, he pushed a lot more, of course, but got some nice numbers running stock.

I'm not too concerned about power, but I sure am proud of these motors for still holding strong after all these years. I'll use the same dyno for the new engine, so I can see the power changes in effect.

[madkaw]

My L24 ran 155 with SU's, but a lot of mods. Didn't have the torque of the L28 , but close. I've driven a stock well maintained L28(77) and I was impressed

[TheCrazySwede]

My L24 ran 155 with SU's, but a lot of mods. Didn't have the torque of the L28 , but close. I've driven a stock well maintained L28(77) and I was impressed

That's awesome! Well, glad to hear that my current motor is still going strong! As I mentioned, I try to keep it well maintained as possible, so I run through the usual tune-up list every 3-6 months, depending on when I get around to it. Seeing how this motor is doing after it's been running for almost 40 years, I'm even more excited now to see how the new build will do.

To be honest, I have never revved past 4,500RPM in my Z, and yet that's where the engine actually runs the strongest, haha.
Can't wait to see how the new setup will do!

Thanks a lot everyone for helping me with this build and following up with ideas. Really keeps my spirit going knowing I'm not alone in this, haha.

Cheers!

[Zedyone_kenobi]

As far as an N42 head with flat tops, my engine came home with 10.6:1 compression with N42 and flat tops, and I can tell you the most timing I can run is 30 degrees at max advance without fuel additives. (NOS brand is a viable option BTW). I would like to dial in more advance, but I start to get pinging in 3rd and 4th if I load the engine up at low rpm. My problem is very narrow and usually I do not notice it. But one day I will probably pull the head off and get some work done to it, while I do that I will probably put on a 1.5mm head gasket and drop the compression to 10:1 and be happy with it.

[TheCrazySwede]

As far as an N42 head with flat tops, my engine came home with 10.6:1 compression with N42 and flat tops, and I can tell you the most timing I can run is 30 degrees at max advance without fuel additives. (NOS brand is a viable option BTW). I would like to dial in more advance, but I start to get pinging in 3rd and 4th if I load the engine up at low rpm. My problem is very narrow and usually I do not notice it. But one day I will probably pull the head off and get some work done to it, while I do that I will probably put on a 1.5mm head gasket and drop the compression to 10:1 and be happy with it.

I've heard some people running N42's with flat-tops and pushing close to similar compression ratios, with no issues, while others have some serious pinging. If you're able to run on that setup with an N42, I think I'll be safe with the turbo head setup.

Thanks for the input!

[TheCrazySwede]

So, I had another Juan-on-Juan with Dave, and (again) didn't recommend flat-tops with the P90 head, due to due deck height issues.

Mr. Rebello is either an L-Series wizard or extremely well at selling a product, because I am (at this point) on the edge of getting my motor built by his shop. I always thought his builds run close to the $10k mark, but he wrote me up an estimate for around $5k.

At this point, I'm still doing my research. I'm not really in a hurry, so I'll take my time with it all.

[TheCrazySwede]

Ok, so my build has taken a rather different turn.

I've gotten to the point in my research where I have learned all the things I wanted to know in order to start off a build.
I have spoken a lot with Dave Rebello and I have come to the decision that I did not want to take my motor down that route. This is not because of Dave's lack of professionalism or talent, but more in terms of needs. The different motor builds, the more I looked into them, all sounded nice, but none of them really fit what I wanted. The power figures were all nice, of course, but I decided that I didn't want an all out powerhouse of an engine....instead, I wanted a responsive one.

After talking to a few people who have worked with him before, I have decided to go with Eiji at DSI. This guy is just great. I've never encountered customer service and eye for detail on his level before. After many, many lengthy emails and phone conversations, we finally have a build down that I am completely satisfied with....well, my wallet isn't, but that's a different story!

I'll update this thread with the build details as they happen, but in short, the engine will be:

- L28 Crank
- N42/N42
- Block bored (89mm)
- DSI Pistons and Rods (I believe they are 29mm Kameari Pistons (280g!!) with custom 139.5mm rods.)
- *Cam is under consideration
- Triple 45 DCOE Webers
- Compression Approx. 10.5 - 11.0
- Power Approx. 260/250

I'll update this thread with any updates!

[Torby]

This sounds like a great project! Looking forward to updates on this!

I went the Rebello route myself, but bought all the parts and built it myself. But my goals are similar to yours, ~200 hp and a responsive engine. Good luck!

[TheCrazySwede]

Glad to hear that you're happy with your motor, Torby!
I am a bit curious, though. You went with Rebello, but you built the engine yourself?
Maybe I'm reading it wrong, haha.

[TheCrazySwede]

Got the motor ready to ship!

[TheCrazySwede]

So the motor was sent out the other day and is on its way to Eiji. As thus, the waiting begins!

[Zedyone_kenobi]

I know you will keep me in the loop, I look forward to your engine pics as soon as they start trickling in! Eiji will steer you right. The man may work at a modest pace, but his engines are art.

[TheCrazySwede]

I know you will keep me in the loop, I look forward to your engine pics as soon as they start trickling in! Eiji will steer you right. The man may work at a modest pace, but his engines are art.

I'll be hogging the refresh button on my email in the next couple of weeks, hoping to see an email from Eiji!
Thanks a lot for your help, Zedy! You're not in the clear yet, though. I'll be sure to bother you when I get the motor back!

[Zedyone_kenobi]

I will be very happy to help out however I can bud.

Good luck!

[Travel'n Man]

If you are wanting 200+ HP - you need to change crank and stroke it. My cay dyno's close to 200 but with a N42/42 combo - I don't believe you will hit your HP goals above without changing the crank.
Don't get me wrong - my horsepower is plenty of fun for me and keeps me out of trouble - but - if I had it to do again I would put a little more $ into it and get 3.0 or 3.1 out of it and change the crank.
Keep us posted with your updates

[madkaw]

I don't know Mitchell. I don't think you can make a blanket statement like that. I have read about too many strokers that have fell on there face. If the complete package is right, and the tune is done right, he should see 200HP.
I'm not sure the components the Swede is using will be the right combo. I haven't read any hp numbers from any Eiji engines---confirmed by dyno. Still waiting on "kenobi' dyno run
If you read the archives at hybridz, the N42 was not a good choice for hi-performance street, but better all out racer head.
I'm also curious what head work is proposed by Eiji. Not looking for any secrets, but how big is the cam? The head work is everything on these motors.
Just my opinions here from what I have read over the years.

[TheCrazySwede]

If you are wanting 200+ HP - you need to change crank and stroke it. My cay dyno's close to 200 but with a N42/42 combo - I don't believe you will hit your HP goals above without changing the crank.
Don't get me wrong - my horsepower is plenty of fun for me and keeps me out of trouble - but - if I had it to do again I would put a little more $ into it and get 3.0 or 3.1 out of it and change the crank.
Keep us posted with your updates

I spoke to Eiji about the crank options, and he mentioned the benefits of each (L28 vs. L28D)
I told him I wanted a fast revving L28, at the expense of power if necessary. He told me the different rod/stroke ratios, and quite frankly, the diesel crank didn't really do much for me. One of his shop cars runs on a very similar setup as my motor, and he's pushing over 200 at the wheels, with a stock crank. I read up on a lot of Eiji's work (granted, it was very hard to find) but he really knows what he's doing. He's actually very well known in the JDM tuner's community and I can't argue with all of the happy customers I've talked to.
I'm going with a stock crank, along with Kameari pistons and rods. The head work is still under discussion.

[TheCrazySwede]

@madkaw

The cam options is still under discussion. Eiji has a bunch of custom grinds, and I nibbled at the thought of a couple, but I haven't given the green flag to a single one, yet. Still talking to Eiji about it.

[jonathanrussell]

Unless I have missed it in this thread, I have not read whether you are having Eiji do any chamber and port work on the N42. Any chamber reshaping, etc?

I met with Eiji about a year or so ago. He is a very interesting guy. My recollection of my conversations with Eiji is that he really likes the N42 head especially as a platform for chamber reshaping. If I ever have someone build an engine for me he would probably be at the top of my list. I look forward to reading your story as it all comes together.

[TheCrazySwede]

Unless I have missed it in this thread, I have not read whether you are having Eiji do any chamber and port work on the N42. Any chamber reshaping, etc?

I met with Eiji about a year or so ago. He is a very interesting guy. My recollection of my conversations with Eiji is that he really likes the N42 head especially as a platform for chamber reshaping. If I ever have someone build an engine for me he would probably be at the top of my list. I look forward to reading your story as it all comes together.

I spoke to him about his plans for the head very briefly. I can't remember the details, to be honest, but it's something we would discuss more once he receives the motor so that he could inspect my head first.

[TheCrazySwede]

Eiji received the motor in yesterday, safe and sound. Excited to see the build in motion!

[Zedyone_kenobi]

You got me man. I have been swamped with roadster work lately. My Z gets driven often and enjoyed as the Roaster is getting new carbies.

I will get that done. Just need to find time to have a dyno day. My one year old has been monopolizing my time lately

[TheCrazySwede]

Did you manage to get the Z out of the batcave or is it still boxed in? :P
I need to hear your Z roar more often! It sounds as beautiful as it looks...and it looks amazing.

[Zedyone_kenobi]

Nope in my infinite wisdom I pulled the carbs on the roadster with the Z blocked in. Not my best shining moment of brilliance.

[Blue]

no carbs...no problem...you can drive in electric car mode... just use the starter with it in gear to propel yourself.... not like an ion drive but just as much fun....and slow.

[Zedyone_kenobi]

blue your avatar is freaking me out a little

[Travel'n Man]

I spoke to Eiji about the crank options, and he mentioned the benefits of each (L28 vs. L28D)
I told him I wanted a fast revving L28, at the expense of power if necessary. He told me the different rod/stroke ratios, and quite frankly, the diesel crank didn't really do much for me. One of his shop cars runs on a very similar setup as my motor, and he's pushing over 200 at the wheels, with a stock crank. I read up on a lot of Eiji's work (granted, it was very hard to find) but he really knows what he's doing. He's actually very well known in the JDM tuner's community and I can't argue with all of the happy customers I've talked to.
I'm going with a stock crank, along with Kameari pistons and rods. The head work is still under discussion.

Porting and polishing will help - it adds time to the build to get everything ground down but I'm sure that will help achieve your goals too.

[TheCrazySwede]

Aye, that's what I'm hoping. Haven't gotten into the details yet, as far as head work goes. I wanted to wait for the inspection results first to see if my head was any good. Eiji isn't one to fixate on HP numbers, and quite frankly, neither am I. I would like to hit 200+, which Eiji is confident the build will hit. Fast cars are fun, but fast engines are unique and special to me.

[Travel'n Man]

He may need your header (if you are going to use one) to get that exhaust ported and polished.
Are you going to go with a lightened flywheel and a larger exhaust - what kind of carb system?
If I had it to "do over" I would step up to a stage 3 and would have stroked it.

It's kinda like building a house - once you have spent the time to design it - blueprint it - build a replica 3d model and get it erected - then you find the obvious things that you would "do over" again.

[TheCrazySwede]

He may need your header (if you are going to use one) to get that exhaust ported and polished.
Are you going to go with a lightened flywheel and a larger exhaust - what kind of carb system?
If I had it to "do over" I would step up to a stage 3 and would have stroked it.

It's kinda like building a house - once you have spent the time to design it - blueprint it - build a replica 3d model and get it erected - then you find the obvious things that you would "do over" again.

Yes, I'm going with a 9lbs Flywheel. As far as carburetion goes, I'm upgrading to a triple Weber system. Bought a book last week about all the ins and outs of weber carbs, so I get my research done before I get my hands on them.

[Zedyone_kenobi]

no shortage of good weber help on this forum. But the book will explain how it works. Once you get that, you will not be so intimidated by tuning.

Also, a wide band O2 will do wonders for your sanity while tuning.

[TheCrazySwede]

no shortage of good weber help on this forum. But the book will explain how it works. Once you get that, you will not be so intimidated by tuning.

Also, a wide band O2 will do wonders for your sanity while tuning.

Thanks Zedy. I'll be sure to knock on your garage when I'm lost! Really looking forward to learning how to tune those beauties!

[rbates]

goal is ~ 200hp at the flywheel - what's that ~ 185 at the wheels ? what are you doing about the rest of the drivetrain ? the 280zx close ratio 5-spd & the R200 3.9 rear diff really wakes up these cars. If your CR is > 10:1 i would watch out for ping.

[TheCrazySwede]

goal is ~ 200hp at the flywheel - what's that ~ 185 at the wheels ? what are you doing about the rest of the drivetrain ? the 280zx close ratio 5-spd & the R200 3.9 rear diff really wakes up these cars. If your CR is > 10:1 i would watch out for ping.

Yup, that's my goal. According to Eiji, I'll be going past that goal in wheel horsepower, so I'm not complaining!

[Travel'n Man]

Naturally once you get that O2 sensor and gauge you will want to know where your oil temp is too.............does it ever end?!?

[TheCrazySwede]

Naturally once you get that O2 sensor and gauge you will want to know where your oil temp is too.............does it ever end?!?

[John Coffey]

208 hp at the crank is attainable with a stock internals L24, 9.5 to 1 CR, running SU carbs. 200hp with Weber 45s and a good cam on a N42/N42 combo is easy. My BSP N42/N42 L28 build made 181 hp at the wheels with SUs and a stock cam. You can even keep the dished pistons.

This formula has been discussed for 15 years over on Hybridz. Its nothing new or nothing special.