Difference between '70/'71 and '72 Cylinder Head

[lm71z]

What's the difference between them? Is the '72 head a lot better? I'm asking this because I have a 70/71 240z and a '72 cylinder head sitting in my garage. I might have the engine rebuilt and I'm wondering if I should put on the '72 head.

[Kathy & Rick]

The only difference I'm aware of is a reduction in compression

ratio from 9.0 to 8.8. Anybody else?

All Z Best,.............Kathy & Rick

[mikemerkury]

http://www.zcsd.org/tech-articles/power-quest2.php

[Carl Beck]

First - are you certain that the "72" cylinder head is a "72"? The reason I ask is because cylinder heads from 73 and the 74 260Z's were also cast with the E88 casting numbers, but their combustion chamber design is quite different. The 73/74 heads are designed to meet the stricter emissions standards of those years... not for the best performance.

You can see the difference here:

http://ZHome.com/ZCMnL/tech/E31andE88Heads.htm

The combustion chamber design is the same on the 70/71 E31 and 72 E88. The E88 combustion chamber has a 2.3cc larger volume. {42.4cc vs 44.7cc}.

The E88 has slightly redesigned intake and exhaust ports. The radius of the curves in the ports was changed to improve the heads breathing. So with slightly lower compression but better flow though the ports the E88 produces the same HP as the E31 when mounted on an otherwise stock L24.

The exhaust valve seat casting was changed slightly in the E88 as well. The E31's suffered from cracking around the exhaust valve seats. If you plan to use the E31 be sure to have it checked for fine line cracks in that area. Any good head shop can weld them up if they are otherwise good, but it isn't cheap.

Since you have both - I'd have a good head speciality shop inspect them both - then use the one that is in the best condition. Consider the condition of the valve train at the same time.. New rockers and cam's aren't inexpensive.

good luck with the rebuild...

FWIW,

Carl B.

Edited October 7, 2009 by Carl Beck

[Rich1]

Exactly when was the '73 cylinder head introduced? Was it introduced during the final months of the 72 cars or did it make an appearance after the beginning of the 73 model year?

[Carl Beck]

As far as I know - it was used only on the 73 Model Year vehicles. I don't believe it would have been legal to use it on the 72's without certifying it with the EPA for 72... and that would have been a time consuming and expensive process, that Nissan would have wanted to avoid.

BTW - that chart that Jim Wolf put together lists the 73 E88 as N33 and the 74 E88 as N33/P50. The 72, 73 and 74 heads all have E88 cast into them externally - I think Jim used N33 and P50 as references to the Nissan Part Number for them - so that they would not be confused with the casting numbers..

FWIW,

Carl B.