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Thread: I want to build a NA motor for my 73 240z...

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    Default I want to build a NA motor for my 73 240z...

    I want to build a NA motor for my 73 240z. Of course I am on a budget and not only that, I came from the Honda community with 13 years of building NA motor knowledge and experience. So I'm accustomed to fast natural aspirated Honda's. But old skool Datsun's is entirely new to me. I am seeking for suggestions on the best NA motor to build. Reading some stuff about the L28 blocks, sticking with the same Head and I don't know what else. Pros, please enlighten me and give me pro advice...thanks a million!!!

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    Crumudgeon
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    Lots of info on HybridZ.org regarding NA engine builds. Typically if you're starting from scratch:

    F54 or N42 block
    P90 or N42 head
    Flat top pistons

    Spend the money on the head. With a P90 you'll need to shave it .080 and shim the cam towers. You can go to 10 to 1 CR on 91 octane with a modified P90. With the N42 you're limited to about 9.5 to 1 CR on 91 octane unleaded unless you weld up part of the combustion chamber. Both heads need work on the exhaust port side, not work really needed on the intake.

    BTW... if you're looking for starting cores, I've got a 1975 N42 long block for sale for $250.

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    MP4/5Brules! YawnTee's Avatar
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    WELCOME to the S30 family. I'm new too after being a 510 guy (and still am) for 13 years.
    First off, "...best NA motor to build." and "...on a budget..." are two terms that are not best friends ha. With a B18 or a K20 etc etc you may have more aftermarket options which means competitive prices and two less cylinders to buy parts for!

    My budget build was an L28 also. I found a very low mileage freshly rebuilt N42 short block that was being cast aside because the new Z owner wanted to drop in an LS1 or something along those lines. Anyhoo, I paid $150 and was on my way. I used my buddies N42 head with a quick rebuild. Cam is a mystery haha but from the idle I suspect it's got a little more overlap then stock.

    Used a beat up 6 into 1 header and spent several hours on my garage floor with a flat file carefully going over the flange mating surface. Used a factory Nissan gasket with a TINY bead or red Permatex. And new studs for intake and exhaust. The exhaust flange was slightly different height then the intake so I cut flat washers in half and glued them to the tops of the big Nissan washers (yokes?) where the studs sandwich the two so the nuts torqued the yokes evenly and square against both. You'll see.

    Intake is three 44PHH Mikunis's, a TWM mainifold with the linkage with rose joints (pillow ball) instead of plastic cups and balls. Good place to spend money here. Sure a rebuilt set of SU's would be rad too though.

    Comp oil pump, and Nissan Head gasket.

    Ignition is a junkyard Nissan black box distributor (no points) and an MSD 6AL. NGK's opened up to @ .050".

    That's it. Start up gave me chills. How can I build another four cylinder?! I go to Monterey Historics every year but this wail is up there with CSL's and the RSK's and the GTO's for me, seriously. All my neighbors came out of the wood work and the exhaust was hooked up! Single straight through Magna Flow under the floor exiting in front of the rear wheel.
    18mpg here I come.
    '72 HLS30-cage, 2.8L, 44mm trips, 4:11LSD
    '71 PL510-cage, 2.0L, 45mm ITB's, 13x7-5 Wats
    '03 Z33 Track, stock, ie., daily driver status!

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    Quote Originally Posted by John Coffey View Post
    Lots of info on HybridZ.org regarding NA engine builds. Typically if you're starting from scratch:

    F54 or N42 block
    P90 or N42 head
    Flat top pistons

    Spend the money on the head. With a P90 you'll need to shave it .080 and shim the cam towers. You can go to 10 to 1 CR on 91 octane with a modified P90. With the N42 you're limited to about 9.5 to 1 CR on 91 octane unleaded unless you weld up part of the combustion chamber. Both heads need work on the exhaust port side, not work really needed on the intake.

    BTW... if you're looking for starting cores, I've got a 1975 N42 long block for sale for $250.
    Thanks for the info man! I appreciate it. So do guys mess with 11.1:1 CR or is like 10 the highest for NA builds? Just very curious. Plus we got that $hitty 91 gas here in LA, so can't mess with too high. What are the usual or average HP/TQ figures for NA builds?

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    Quote Originally Posted by YawnTee View Post
    WELCOME to the S30 family. I'm new too after being a 510 guy (and still am) for 13 years.
    First off, "...best NA motor to build." and "...on a budget..." are two terms that are not best friends ha. With a B18 or a K20 etc etc you may have more aftermarket options which means competitive prices and two less cylinders to buy parts for!

    My budget build was an L28 also. I found a very low mileage freshly rebuilt N42 short block that was being cast aside because the new Z owner wanted to drop in an LS1 or something along those lines. Anyhoo, I paid $150 and was on my way. I used my buddies N42 head with a quick rebuild. Cam is a mystery haha but from the idle I suspect it's got a little more overlap then stock.

    Used a beat up 6 into 1 header and spent several hours on my garage floor with a flat file carefully going over the flange mating surface. Used a factory Nissan gasket with a TINY bead or red Permatex. And new studs for intake and exhaust. The exhaust flange was slightly different height then the intake so I cut flat washers in half and glued them to the tops of the big Nissan washers (yokes?) where the studs sandwich the two so the nuts torqued the yokes evenly and square against both. You'll see.

    Intake is three 44PHH Mikunis's, a TWM mainifold with the linkage with rose joints (pillow ball) instead of plastic cups and balls. Good place to spend money here. Sure a rebuilt set of SU's would be rad too though.

    Comp oil pump, and Nissan Head gasket.

    Ignition is a junkyard Nissan black box distributor (no points) and an MSD 6AL. NGK's opened up to @ .050".

    That's it. Start up gave me chills. How can I build another four cylinder?! I go to Monterey Historics every year but this wail is up there with CSL's and the RSK's and the GTO's for me, seriously. All my neighbors came out of the wood work and the exhaust was hooked up! Single straight through Magna Flow under the floor exiting in front of the rear wheel.
    18mpg here I come.
    Would you suggest to just buy used carbs? I was just looking at the Triple Weber 45 mm's from MSA's website and it goes for like $1600. is this even something to consider or am I waaaay out of my mind? I need more info!

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    Quote Originally Posted by OneSimpleZ View Post
    Would you suggest to just buy used carbs? I was just looking at the Triple Weber 45 mm's from MSA's website and it goes for like $1600. is this even something to consider or am I waaaay out of my mind? I need more info!
    The L-series motor runs great with SU's. Get a set from ZTherapy for $700 or so, tune em once, and enjoy. With the right cam/exhaust/head work, SU's are plenty of carb for street power. Triples are sweet, but big loot.

    Just my 2....
    Paul Martin
    1973 240Z HLS30-127623 (10/72)
    4.11 R-180, 79 ZX 5-speed, ZX Distributor, ZTherapy SU's

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    Quote Originally Posted by OneSimpleZ View Post
    So do guys mess with 11.1:1 CR or is like 10 the highest for NA builds? Just very curious. Plus we got that $hitty 91 gas here in LA, so can't mess with too high.
    For today's street gas, 10.0:1 is about as far as you can safely go. The chamber shape isn't as advanced as newer engines.

    Unless you build a custom ignition with knock sensors. But that's not very budget friendly.

    Quote Originally Posted by OneSimpleZ View Post
    Would you suggest to just buy used carbs? I was just looking at the Triple Weber 45 mm's from MSA's website and it goes for like $1600. is this even something to consider or am I waaaay out of my mind? I need more info!
    Triples (Weber, Mikuni, Dellortos, or OER) are definitely the way to go for max performance, but they aren't cheap. Used sets often go for $800 or more, and may need to be rebuilt. You might consider sticking with a pair of stock SUs to begin, and move to triples later.
    Arne - Former owner, HLS30-37705, 7/71, 905 Red
    Car blogs - 240Z - Porsche 911

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    What are the usual or average HP/TQ figures for NA builds?
    There are not "usuals" or "averages." The quality of the engine and the power it makes has everything to do with the skill and labor put into the build.

    A top level build to SCCA ITS specs (2.4L, stock internals, stock head, stock block, "stock" cam, SU carbs, headers) has hit 208 hp on a certified engine dyno. Most of the effort on that engine was labor, little money was spent on parts - figure $7,500 to duplicate.

    My old racing 3L racing engine made 325 hp, 275 ft. lbs. on 14 to 1 CR, lots and lots of head and crank work, custom cam, Motec, etc. Figure $20,000 for that build.

    SCCA GT2 spec 2.4L engines make somewhere around 350hp at over 8,000 rpm.

    If you can make 200 real horsepower on 91 octane pump gas you've done well.
    Last edited by John Coffey; 11-05-2009 at 03:13 PM.

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    Damn fellas, I appreciate all of that good info. Seriously.

    Since I'm on a mega budget, SU's sounds like it will do.

    John, did you ever get a feature in Sports Compact Car or something?

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    Crumudgeon
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    John, did you ever get a feature in Sports Compact Car or something?
    No. I avoid putting my cars or my customer cars in magazines. There's no positive result for me or my business from a feature; just a bunch of useless phone calls from teenagers who want the exact same car in a week for under $1,000.

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    Sorry John. Mistaken you for Bill Coffey which had a feature on the Jan. 2000 issue of Sports Compact Car with a 240z, wide flares, Solex carbs, etc.

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    Quote Originally Posted by OneSimpleZ View Post
    Would you suggest to just buy used carbs? I was just looking at the Triple Weber 45 mm's from MSA's website and it goes for like $1600. is this even something to consider or am I waaaay out of my mind? I need more info!
    Trips are nice when they are clean and synced etc., but sure SU's will do ya just fine. Find a clean L28 and maybe a 4:11 for the rear and go drive!
    j!
    '72 HLS30-cage, 2.8L, 44mm trips, 4:11LSD
    '71 PL510-cage, 2.0L, 45mm ITB's, 13x7-5 Wats
    '03 Z33 Track, stock, ie., daily driver status!

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