E-31 head, whatch'all think?

[siteunseen]

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.

[Arne]

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.

[LeonV]

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

[madkaw]

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

[Zed Head]

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.

[Walter Moore]

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.

[madkaw]

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.

[siteunseen]

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

[Diseazd]

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 July 10, 2014 by Diseazd

[Jarvo2]

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?

[siteunseen]

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 July 10, 2014 by siteunseen

[madkaw]

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?