EZDUZIT

Whats happen guys, lets look at the pros and cons and see if you guys can help me make a decision. Alright working on my brothers 1974 260Z stock motor with dual Webbers. My delima, we are going to put a cam set, Header, 3-angle valve job, resurface the head, new seals, mabey a little blending on the intake and exhaust ports, The only problem What Head? We can use the stock E-31 that is currently on it, or we have a N-42 and a N-47. I know we are not going to use the N-47 due to the exhaust liners so the battle is between the E-31 and the N-42. The E-31 is supposed to have alittle more compression but I think the N-42 has a larger exhaust valves. Another determning factor is he can still drive his car(daily driver) if we use the N-42 head. I don't know which one flows better nor do I know all of the pro's and con's. I do have a P-79 head but I just don't think we won't to do that much machine work, not a full race application here if you know what I mean. Any feedback would be appreciated. thanks Josh

Bleach

The P79 has close chamber design, but is actually a larger cc chamber so you need to run flat top pistons with it. Does the L26 have flattops? The P79 has exhaust liners, and those aren't that big of a deal. You're not building that high performance of an engine anyway with dual downdraft carbs.

The N42 is good, but if it has the original valves in it, they are a weak point on that head. The N47 has steel valve seats. Those are longer lasting and won't wear out. That is especially important if you are getting tighter valve springs with your cam.

Any extra performance you get from the higher compression E31 will be lost in the high rpms with smaller valves. Get the E31 done with a new valve job. (put in L28 valves) That is your best head but it has got to have the larger valves. Since you are doing the valve job anyway I think that will be your best head.

Make sure you don't overjet those Webers. Each one only needs to flow 1.3L of air. Your primary and secondary jets should be in the range of .100 / .90

EZDUZIT

Thanks for your response Bleech, Yeah I know about the steel seats was going to do that on either head anyway. The P-79 is an open chamber head by the way, found on the 81-83 ZX non-turbos. Yes the L-26 has flat top pistons, as far as the Webbers are concerned they have done their job, we are going to go with the 4 barrell Holly and intake, MSA 6to1 Header. The valve are no problem we have some in other heads. My machinist will do most of the work he does enough for us that he gives us discounts So you think with the L-28 valves and steel seats the E-31 would be the best bet right

Bleach

The P79 should be closed chambered. Yes, it was on the 81-83 as you stated. Compare it to your N47. The N47 should have totally round chambers and the P79 has one side with a slight indent into the chamber with a flat spot facing the piston.