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Thread: F54 and P90

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    Registered User Kimi's Avatar
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    Default F54 and P90

    I begin with saying that I'm sorry that I make a question that has been several times asked before. Been reading the topics, but still felt that I wanted to ask you guys for help with my engineproject.
    I bought a L28ET (F54 block and a P90 head) for my 240Z. The block has new rings and bearings, stock turbo pistons. The head has been shaved .074", with the proper single cam tower shim, multi angle valve job, intake runners ported and polished, slight deburring of combustion chambers, exhaust side just had behind the valve seat cleaned.
    So this should be a nice turbo-engine, and when I bought the engine I thought that I would use it as it is+EFI, but lately I've been playing with the idea of making it a NA with the flat-top pistons.
    In that case I probably would go with:
    - F54 block + stock F54 flat-top pistons
    - the shaved P90 head
    - MSA header + 2,5" exhaust
    - early SU carbs
    - aluminium flywheel
    But now to the question, would the stock flat-top pistons clear the shaved head and what kind of compression am I looking at. Would it be near 9.5:1?
    Don't know how well the P90 cam would perform either.
    I don't know if it would be worth the effort to change the pistons and go NA, but the sound of a nice NA L6 is so...
    Last edited by Kimi; 10-13-2012 at 03:59 PM.

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    Supporting Member Diseazd's Avatar
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    The F54 block with P79 flat top pistons and .080 shaved head would give you approximately 10 to 1 compression ratio. The pistons will clear the head. What cam do you plan to run? I run stage III Isky cams in all 3 of my L28's with the above mentioned combinations. You will enjoy that combo if you decide to go that route.......it's a great engine combo.
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    Registered User Kimi's Avatar
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    Thanks Diseazd
    Ok, sounds good. The compression should be pretty ok with this head then I know that the engine won't have the same hp as with the turbo setup, but it should be enough for me and my series 1 240Z
    Haven't thought about the cam yet, just been thinking about the pistons. Probably going to change the pistons first and try to find all the parts I need, and then choose a cam.
    Thanks for the tip too, I have to look at the Isky stage III specs. I think I will find Crane cams locally, but I have to check that too.

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    As Diseazd say, pistons would be ok.
    The combustion chamber looks like a bean, there's a flat area that would end up in front of the piston anyhow. This zone will allow the engine to have a quench effect at TDC improving air/fuel mix (= efficiency + ping resistance).

    To make sure, you'll be ok, you will have to measure some parameters: piston top vs. deck for each pistons, head gasket thickness compressed.
    head gasket thickness is usually given by manufacturer. if nothing is written, don't trust Internet value. Felpro gasket for instance are given sometimes for 1.2mm or 1.0mm, I measured it at 1.0mm but Ishibo gasket (the stock unit) is given by internet users for 1.25mm, I measured it at 1.0mm also.

    The gap at TDC for each pistons should be min at 0.023" (0.6mm) & max at 0.032" (0.8mm). If you're too short, pistons will hit the head, if you're above max, you will lower quench effect. For your info, I was conservative with my build, I shoot for 0.8mm nominal; I'd rather loose some hp than an engine.

    In stock form, if nothing has been machined on your engine block, you should be right on.
    My block has been surfaced before rebuild, I had the milled the pistons by 0.3mm with Felpro gasket.
    Without measuring gasket thickness, I would have ended up using Ishibo gasket, I would have over-estimated quench gap that could have led to engine destruction...
    Last edited by Lazeum; 10-14-2012 at 11:09 AM.
    Matt - 72' 240z

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    Quote Originally Posted by Kimi View Post
    Thanks Diseazd I think I will find Crane cams locally, but I have to check that too.
    I thought Crane stopped making cams in 2005 and sold their inventory to S&S cycle in Wisconsin. I remember reading it somewhere...
    Dont go cheap on the cam. The extra money for a post treated cam (Nitride treatment) is well worth it in durability of the cam lobes. A lot of regrinds dont have it.

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    Supporting Member Diseazd's Avatar
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    The metal to metal compatibility of the Datsun cams was excellent. The Z Doctor in Roanoke, Virginia is an expert on Z engines and firmly believes you should regrind your stock cam to maintain that durable relationship. He recommends Isky. I've used them on all 5 of my motor builds. They all perform perfectly. With a new cam, you'll want to install new or remanufactured rockers and new Isky valve springs with a lift over .460 inches. The cam is what makes the combo you refer to work so well.....go with Stage III IMO.
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    Supporting Member Diseazd's Avatar
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    Quote Originally Posted by Lazeum View Post
    As Diseazd say, pistons would be ok.
    The combustion chamber looks like a bean, there's a flat area that would end up in front of the piston anyhow. This zone will allow the engine to have a quench effect at TDC improving air/fuel mix (= efficiency + ping resistance).

    To make sure, you'll be ok, you will have to measure some parameters: piston top vs. deck for each pistons, head gasket thickness compressed.
    head gasket thickness is usually given by manufacturer. if nothing is written, don't trust Internet value. Felpro gasket for instance are given sometimes for 1.2mm or 1.0mm, I measured it at 1.0mm but Ishibo gasket (the stock unit) is given by internet users for 1.25mm, I measured it at 1.0mm also.

    The gap at TDC for each pistons should be min at 0.023" (0.6mm) & max at 0.032" (0.8mm). If you're too short, pistons will hit the head, if you're above max, you will lower quench effect. For your info, I was conservative with my build, I shoot for 0.8mm nominal; I'd rather loose some hp than an engine.

    In stock form, if nothing has been machined on your engine block, you should be right on.
    My block has been surfaced before rebuild, I had the milled the pistons by 0.3mm with Felpro gasket.
    Without measuring gasket thickness, I would have ended up using Ishibo gasket, I would have over-estimated quench gap that could have led to engine destruction...
    Good advice Lazeum.......if the engine block is decked, the pistons will come out of the cylinders. The way I've heard it, you need .040 inches ( 1 mm ) clearance. Does anyone know the compressed height of the stock Nissan gasket. Also, how much is a safe shave for a stock P79 piston ( you could shave the top of the piston versus a thicker head gasket ). If there is no decking, you have no problem.
    Last edited by Diseazd; 10-14-2012 at 05:37 PM.
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    As Diseazd said, you should regrind your stock nissan cam. The durability of the oem nissan cam is much better than the new billet cams. I myself sent my cam to a company called Web Cams and had them regrind my stock cam. You have to be careful with the base circle of the cam after the regrind, some regrind's are able to maintain the stock base circle measurement, in my case the base circle ended up being smaller so I had to compensate with thicker lash pads in order to get the correct "wipe pattern" on the rocker arms.

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    Supporting Member Diseazd's Avatar
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    Thanks Alex.....I forgot to mention that you'll need thicker lash pads......failure to geometry the rockers (center the wipe pattern) will destroy your cam and valve train.
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    Quote Originally Posted by EuroDat View Post
    A lot of regrinds dont have it.
    Just to clear up what I meant by regrind. There are a lot of aftermarket billets that shops will grind to your specs. The quality of these billets is sometime questionable. Nissan billets are very good and can be identified by "japan" stamped on the end. I reground mine and had no problems with the geometry, but my profile was mild. Hi lift would probably change that.

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    A lot of good information here, thanks
    Ok, I got to check the mentioned things and then choose the headgasket after that. As far as I know the block should be stock, but that will be seen when the pistons are installed.

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    "As far as you know" is already not a good sign better be safe than sorry, get some measurements done

    the clearance between pistons & head is a topic discussed on hybridZ with many different versions. I went with 0.8mm (0.032") and so far, so good. It was a direction given by Brian Blake (a.k.a "1 Tuff Z" who did the L28 DOHC DETT)
    Top rpm so far has been 5500rpm until I'd got bigger chokes or better: bigger carbs.

    Regarding head shaving, it is hard to tell. Some say 0.040" is good but I have less on my build and I'm above 200wph. Head builder (Braap on hbz) did not push comp ratio. There's little gain to get vs. ping safe conditions.
    I think you should focus on cam grind vs. comp ratio => meaning, talk to cam builder for proper setup - it should be a match.

    Surface treatment done on cam lobes are usually very thin (0.5mm deep - 0.020") so if you perform a regrind, a new hard layer made with some treatment is mandatory.
    Last edited by Lazeum; 10-15-2012 at 11:17 AM.
    Matt - 72' 240z

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    Quote Originally Posted by Lazeum View Post
    "As far as you know" is already not a good sign better be safe than sorry, get some measurements done

    the clearance between pistons & head is a topic discussed on hybridZ with many different versions. I went with 0.8mm (0.032") and so far, so good. It was a direction given by Brian Blake (a.k.a "1 Tuff Z" who did the L28 DOHC DETT)
    Top rpm so far has been 5500rpm until I'd got bigger chokes or better: bigger carbs.

    Regarding head shaving, it is hard to tell. Some say 0.040" is good but I have less on my build and I'm above 200wph. Head builder (Braap on hbz) did not push comp ratio. There's little gain to get vs. ping safe conditions.
    I think you should focus on cam grind vs. comp ratio => meaning, talk to cam builder for proper setup - it should be a match.

    Surface treatment done on cam lobes are usually very thin (0.5mm deep - 0.020") so if you perform a regrind, a new hard layer made with some treatment is mandatory.
    FWIW, Bryan Blake goes by "1 fast Z" on hybridz.
    2/74 260Z

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    Quote Originally Posted by Kimi View Post
    L28ET (F54 block and a P90 head) ....The block has new rings and bearings, stock turbo pistons. The head has been shaved .074", with the proper single cam tower shim, multi angle valve job, intake runners ported and polished, slight deburring of combustion chambers, exhaust side just had behind the valve seat cleaned.

    Don't know how well the P90 cam would perform either.

    I don't know if it would be worth the effort to change the pistons and go NA, but the sound of a nice NA L6 is so...
    Seems like there's been some effort put in to building a nice turbo long-block. You could probably sell it for good money and pick up a complete NA F54/P79 engine, refresh it and come out money ahead. The NA engine will already have the flat-top pistons and the correct cam for NA.

    Or you could swap the head for an N42 or N47, keep the pistons and new rings, get the CR you want with the smaller N42/N47 combustion chamber, probably along with the right cam, and sell the rebuilt turbo head or keep it as an option for later use.

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    Quote Originally Posted by LeonV View Post
    FWIW, Bryan Blake goes by "1 fast Z" on hybridz.
    You're right! I should have doublechecked
    Matt - 72' 240z

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    A lot of numbers being thrown around here. As far as 1fastz , he actually says optimum clearance of piston head is more like .021-.025. This requires shaving the block and or mating the right HG size. 1fastz doesn't put all of his info because he's afraid of steering someone into precision they can't pull off.
    I'm running around .025-.027
    I would just order a Nismo gasket and know what your getting- pricey-yes!
    I believe .040 is too much for an NA engine.
    Sounds like a good engine combo- good luck
    Steve
    71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
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    A lot of numbers being thrown around here. As far as 1fastz , he actually says optimum clearance of piston head is more like .021-.025. This requires shaving the block and or mating the right HG size. 1fastz doesn't put all of his info because he's afraid of steering someone into precision they can't pull off.
    I'm running around .025-.027
    I would just order a Nismo gasket and know what your getting- pricey-yes!
    I believe .040 is too much for an NA engine.
    Sounds like a good engine combo- good luck
    Steve
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    Dave Rebello is the one that threw out the .040 inch number......seems like a lot to me too, but I really can't argue too much with him. I think a down shift at high rpm could stretch the rods somewhat......no idea how much. Maybe John Coffey could clarify or give his clearance preferences. Does anyone know what the stock gasket compressed thickness is?
    Last edited by Diseazd; 10-15-2012 at 03:46 PM.
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    I've measured mine - a new ishino gasket - at exactly 1.00mm compressed (while others said over the web it should be 1.25mm).
    link: http://www.amazon.com/gp/product/B00...ls_o00_s00_i00
    Matt - 72' 240z

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    I thought stock compressed is .047, which is 125mm I believe. As far as an Ishino gasket, I'm not sure.
    When i removed my old HG, which I can't be certain, but I think it came from an old MSA kit, it measured right at
    .047 compressed.

    I wouldn't want to argue with Rebello either-I'm just a hack mechanic:0
    I have searched the Hybridz pages for hours, especially on the squish issue. The numbers that I quoted came from a post deep inside a thread that 1fastz commented on about squish. HE acted asif he had devulged his best secret about these motors!
    But then you get into the argument about what standard deck height is on the flat-tops, and then numbers start flying around again. Braap chimed in saying that he measured countless blocks and the flat-tops averaged .019 above deck-so is this true? I guess every engine needs to be checked by someone with some good skills and mics.
    Steve
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    this is what I've measured. For my rebuild, I bought 4 different gaskets before giving up. I then torn down the bottom end again and milled pistons to match Felpro gasket.
    Compressed thickness on headgasket needs to be measured if we want to be 100% confident. I've done it with calibrated gauges so I know how reliable my measurement were (minus my skills).

    I advice everyone to build an engine to check those dimensions, it is not hard to do but some tools & time are required.
    Matt - 72' 240z

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    I just googled stock gasket thickness for Datsun L series. The answer given was they come in two sizes.....1.5 mm ( .060 inches )and 1.25 mm ( .050 inches ), so you should be able to deck the block .010 to .020 inches and still get a cheap gasket.
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    Quote Originally Posted by madkaw View Post
    I thought stock compressed is .047, which is 125mm I believe. As far as an Ishino gasket, I'm not sure.
    When i removed my old HG, which I can't be certain, but I think it came from an old MSA kit, it measured right at
    .047 compressed.
    I measured the compressed fire ring of the HG I removed from what looked like a never disturbed, original (numbers matching), engine in my 1976. I got 1.25 mm also.

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    Quote Originally Posted by Lazeum View Post
    better be safe than sorry, get some measurements done
    Yes, I will check it if I decide to change the pistons.

    Now when I have more information I've started to to think that maybe I just should keep this L28 as a turboengine, becouse it should be a nice setup as it is. As Zed Head wrote I could sell it and buy a stock NA L28 and build it instead.
    I got to make a decision. I'll let you know if I start to work on this engine

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    Quote Originally Posted by Kimi View Post
    Yes, I will check it if I decide to change the pistons.

    Now when I have more information I've started to to think that maybe I just should keep this L28 as a turboengine, becouse it should be a nice setup as it is. As Zed Head wrote I could sell it and buy a stock NA L28 and build it instead.
    I got to make a decision. I'll let you know if I start to work on this engine
    Not sure you want to go ahead with a turbo with this set-up. You started down the path of a NA set-up with your head and now your compression ratio will be high for a turbo engine. Shaving 74 thous. off the head and now turbocharging might not be a good idea. Not sure what octane of fuel you have over there which will have some bearing on this issue. A higher compression turbo build would be great, but it would be tricky to tune and get right without blowing up!!You would need to run a better ECU than stock.
    We all made comments regarding NA motors, but not turbocharging, so you might need to think again.
    Last edited by madkaw; 10-16-2012 at 05:00 AM.
    Steve
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    Quote Originally Posted by madkaw View Post
    Not sure you want to go ahead with a turbo with this set-up. You started down the path of a NA set-up with your head and now your compression ratio will be high for a turbo engine. Shaving 74 thous. off the head and now turbocharging might not be a good idea. Not sure what octane of fuel you have over there which will have some bearing on this issue. A higher compression turbo build would be great, but it would be tricky to tune and get right without blowing up!!You would need to run a better ECU than stock.
    We all made comments regarding NA motors, but not turbocharging, so you might need to think again.
    I ment with my previous post that maybe I should let the L28ET be as it is with the turbo pistons, and get a stock NA L28 instead for the project.
    The P90 was already shaved when I bought the engine, and has been used with the F54 block, turbo pistons and a turbo before I bought it. It has not been used with a stock L28ET ECU.

    Don't get me wrong, I really appreciate all the help I get here
    Now I just need to decide what to do with the engine.

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    Maybe John Coffey could clarify or give his clearance preferences. Does anyone know what the stock gasket compressed thickness is?
    I defer to what Dave Rebello and other professional engine builders recommend.

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    Quote Originally Posted by madkaw View Post
    You started down the path of a NA set-up with your head and now your compression ratio will be high for a turbo engine. Shaving 74 thous. off the head and now turbocharging might not be a good idea.
    madkaw makes a good point. Actually, it's not clear what the intent is of the work done. I used one of the calculators and get 8.5 CR for the saved head, versus 7.3 for the stock setup. So now it's actually similar to an N42/N42 setup in CR, and with dished pistons. Plus, the calculator says that the pistons will hit the head. So you might need a thicker head gasket to get back to usable.

    Flat tops come out at 10.1 CR, but pistons still hitting the head. Looks like a 2.0 mm HG might get you back to 8.4 CR with flat tops, 7.3 with dished pistons.

    Here's the calculator if you want to explore options - http://www.ozdat.com/ozdatonline/enginedesign/ You can put a negative number in the HG thickness box to simulate the shaved head. Subtract the shave from the HG thickness.

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    Zed Head.....Am I missing something? Shaving the head doesn't put the pistons any closer to the head.....you're still .040 inches away (stock head gasket thickness). Decking the block puts your pistons closer to the head (by the amount the piston comes above the deck).
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    No, I got my thinking screwed up using the engine calculator and putting negative numbers in the head gasket box to simulate the head shave (the calculator reports piston head contact, probably because the equations used are adding the HG thickness to the deck height). You are right, shaving the head should not cause piston-head contact.

    Sorry for that, I didn't think it through before I posted.

    I think that numbers reported by the calculator are pretty close though. Of course, a .074" (1.9 mm) HG would get his head back to where it started.

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    I'm sorry that I haven't been clear enough with my question. I should have written more about the engine in my first post, my bad
    So the P90 on the F54 had already been shaved .074" when I bought the engine. I was going to install the engine as it is, with the turbo and everything. This setup has been used before I bought it so it should work.
    Then I started to look at NA setups and thought that maybe this engine could be nice as a NA too.
    Now after the help and advice here I think that maybe the best solution for me is to keep this engine a turbo.
    Thanks for the link Been playing with the calculator, looks like the CR should be a somewhere near 8 with this setup (if it has a stock HG).
    I'll probably sell this L28ET and buy a L28 NA and start to work on it, if I don't decide to use this turboengine.

  32. #32
    Supporting Member Diseazd's Avatar
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    http://www.classiczcars.com/forums/thread34448.html
    Kimi.....This thread may help.....I used the P79, which is the same as the P90 with liners. Sounds to me like what you're thinking about building. Believe me......it's an awesome combination. Good Luck......Guy
    Last edited by Diseazd; 10-17-2012 at 04:40 AM.
    http://www.flickr.com/photos/1404980...7600346077563/
    ______________________________________________
    http://www.flickr.com/photos/1404980...7603350695459/

    70, 71, 2 72's, and a 73 240z....
    90 300zx and a 1996 Acura NSX.....but who's counting?

  33. #33
    Registered User Lazeum's Avatar
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    CZCC-15411
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    I'm running as well F54/P79 with head shaved only by 0.020", Rebello cam, 3x 40DCOE, Unilite dizzy.
    I'm very happy with the build so far. Engine/car is very nice to drive.
    Matt - 72' 240z

  34. #34
    Registered User
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    Apr 2013
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    Quote Originally Posted by Diseazd View Post
    http://www.classiczcars.com/forums/thread34448.html
    Kimi.....This thread may help.....I used the P79, which is the same as the P90 with liners. Sounds to me like what you're thinking about building. Believe me......it's an awesome combination. Good Luck......Guy
    I know this thread is six months old, but I'm interested in Diseazd's build and this link only takes me to the forum homepage.

    Diseazd, does the thread still exist?
    Brian
    73 240Z HLS30-151534

  35. #35
    Supporting Member Diseazd's Avatar
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    http://www.classiczcars.com/forums/e...8-my-72-a.html

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

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



    Hope these help......I used shaved and shimmed P79 heads in all 3 builds, also used Isky Stage III cams in each........Guy
    Last edited by Diseazd; 04-16-2013 at 12:22 PM.
    http://www.flickr.com/photos/1404980...7600346077563/
    ______________________________________________
    http://www.flickr.com/photos/1404980...7603350695459/

    70, 71, 2 72's, and a 73 240z....
    90 300zx and a 1996 Acura NSX.....but who's counting?

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