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Thread: E-31 head, whatch'all think?

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    Registered User siteunseen's Avatar
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    Default E-31 head, whatch'all think?

    I got this a couple of years ago and am ready to get the cam kit for it. I've read go wild not mild to prevent detonation problems, but cam specs are all over the place so advise me please. Can't decide whether to put it on top of an L28 with flat pistons or the L24. It's got the big intake valves and steel seats, also teal colored valve seals. All new a few years ago, never been bolted down. maybe I should use the N47 I have.
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    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    Semi-retired admin Arne's Avatar
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    Big intakes on the L24 will likely require fly-cutting the block, unless it has already been bored .040" over. Save it for an L28.
    Arne - Former owner, HLS30-37705, 7/71, 905 Red
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    Registered User LeonV's Avatar
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    Besides the bigger valves, it looks like it might be ported. Are you sure the installed cam is stock?
    2/74 260Z

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    Look familiar
    Except mine is a E-88.
    Sure the exhaust wasn't upgraded also. I'd see if those aren't 35mm.
    Clearance would need to be checked for sure, or just unshroud everything including the cylinder bores.
    I would mic the cam to see where it comes in at. Maybe you do have something there too!
    L28 block would put you at about 10.25 I think. That's my next step. I already have the flat top block sitting on a stand
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    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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    You might measure combustion chamber volume to see what your CR will be. You might find the flat-top L28 puts you at 12:1 or something.
    1976 280Z, with some minor modifications

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    Registered User Walter Moore's Avatar
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    It looks to me like the exhaust valves are oversized also. Those are the ones that hit the block on an L24.

    I have big intake valves with stock exhaust valves on my engine, and they didn't cause any problem on my stock diameter L24. Somewhere here there is a thread where madkaw (Steve) shows a view from the bottom of the cylinder that illustrates the problem with big exhaust valves better than it could ever be explained in words.
    '71 240Z, Because any fool can drive fast in a straight line.

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    Not sure what pic you are refering to Walter, but the one above shows how I clearanced the bores. My block is .040 over , but I did it for breathing reasons.
    I'm pretty sure the engine calculator shows 10.25:1 with stock chamber size on a L28 flat-top.
    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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    Registered User siteunseen's Avatar
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    Default Which Isky regrind for my E31 head?

    I'd like to run SUs now and a Weber triple 40s set up I have for later. If it was your car which would you get? Stage iii or the competition? F54 with flat pistons

    Type intake exhaust duration

    stage iii .490 290 242
    competition .530 306 264

    Information from here, http://www.iskycams.com/pdfcatalog/2004-05/page176.pdf
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    Supporting Member Diseazd's Avatar
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    I have the Isky Stage III in all of my Z's. It's a really nice regrind......good duration....no ping, but I run the P79 heads. When you install a regrind, install new rockers (IMO) and you'll have to geometry the cam ( wipe patterns centered with the correct lash pads). If you run flat top L28 pistons (P79), your compression ratio may be high enough to ping with the early E31.......not sure about that, but if you over bore, it'll be even more of a potential problem. The Isky Stage III makes nice power for me......I love it and Isky is great to work with. Sounds really nice at idle too.....that's important.
    Last edited by Diseazd; 07-10-2014 at 11:14 AM.
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    On a related note, I'm in need of new valve seals, and probably could use a clean-up and valve job on my 72 240z (E88 head). Would it be worth me just purchasing a $400 head from Datsun Parts LLC which is already reconditioned, or should I take my existing head to a machine shop to have it rebuilt? Also, what is everyone's opinion on valve seats...should the be replaced to accommodate unleaded fuel?
    Dave
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    Registered User siteunseen's Avatar
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    Everything I've read says get the bronze out and replace with steel. If you can find a local machinist that is familiar with our engines I'd go that route, Datsun Parts LLC, from what I've read isn't too concerned about quality control, it's more about moving products. Start at post #44,http://www.classiczcars.com/forums/m...tml#post459944
    The full monty, http://www.classiczcars.com/forums/e...lve-seats.html
    Last edited by siteunseen; 07-10-2014 at 01:37 PM.
    1972 240Z #918 New Sight Orange
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    Valve guide seals can't be stock with that size cam so check that.
    Unshrouded combustion chamber will lower CR a bit.
    So the competition cam will clear pistons okay?
    Steve
    71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
    3.90 Subaru STI LSD

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    Supporting Member Diseazd's Avatar
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    Good point Steve......Felpro makes a short valve seal that I use on my E31 head with the .490 lift Isky Stage III cam. It is supposed to handle up to .500 inch lift.

    Improved L6 Valve Stem Seals - L-Series - HybridZ

    You can use the stock valve seals on an .080 inch shaved P79 or P90 head because the valve springs are shimmed up .080 inches with the longer early L28 valves when you use the Isky Stage III (.490 lift) cam though.
    Last edited by Diseazd; 07-10-2014 at 06:08 PM.
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    Registered User Walter Moore's Avatar
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    My apologizes to everyone, it was Blue who posted photos showing the exhaust valve interference with big valves to the stock L24 block. I don't know how I got so confused.

    See post #4 in this thread:
    http://www.classiczcars.com/forums/e...240-block.html
    '71 240Z, Because any fool can drive fast in a straight line.

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    Registered User siteunseen's Avatar
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    Well I can hardly wait to measure the seals that are on there now. They're the same blueish green color as the Fel-Pro # SS72686 recommended in the hybridz link. The head came from a knowledgeable Z guy it seemed. His Dad was big into Zs and held onto this E31 head and the Weber 40s for his son who unfortunately had to sale the project, lucky for me though. The only thing I'm doing different than his plan is using flat pistons instead of the dished ones that came with the deal. He too was saving for the cam kit when his new paint and body shop's bills jumped to the front of the line. Life happens.

    Thanks guys for the help, I can't read or buy y'all's experience.
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    Registered User siteunseen's Avatar
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    Quote Originally Posted by madkaw View Post
    So the competition cam will clear pistons okay?
    I'll be searching for the right head gasket thickness and if that lowers the compression too much I'll go with the stage III.
    Hybridz here I come. I'll have to take a Valium though, those guys can be intense.

    Maybe I'll just be safe and get the stage III like Dizeased suggest, I'm not going racing.
    Last edited by siteunseen; 07-11-2014 at 03:20 AM.
    1972 240Z #918 New Sight Orange
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    1972 240Z #110 Persimmons Red

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    From all I have read-don't go with a thicker gasket to lower compression. Keep the squish tight to fend off detonation. So far good luck with my Nismo 1.25mm
    Steve
    71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
    3.90 Subaru STI LSD

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    Quote Originally Posted by madkaw View Post
    From all I have read-don't go with a thicker gasket to lower compression. Keep the squish tight to fend off detonation. So far good luck with my Nismo 1.25mm
    So you have a stage II? Which company? and do you like it or wish you had gone bigger? I've watched your videos and enjoyed the chirp into 3rd gear.
    Thanks,
    Cliff
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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