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siteunseen

E-31 head, whatch'all think?

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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. LOL

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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.

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Besides the bigger valves, it looks like it might be ported. Are you sure the installed cam is stock?

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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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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.

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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.

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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.

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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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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.

Edited by Diseazd

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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?

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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/misc-s30/52438-steam-powered-z.html#post459944

The full monty, http://www.classiczcars.com/forums/engine-drivetrain-s30/51401-bronze-valve-seats.html

Edited by siteunseen

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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?

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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.

Edited by Diseazd

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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.

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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.

Edited by siteunseen

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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

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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

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

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