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I have an E88 head on my L28 motor. Someone has told me that the hot set up for my car would be with an E31 head. Currently in my 70Z I have an L28 block with the E88 head, 5spd, and a 3.9 diff. I'm running the original '70 carbs on the motor. From what I've read the E88 head has larger intake and exhaust valves, so I wonder does the E31 head have anything over the the E88?
 

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E88 answers

> I have an E88 head on my L28 motor. Someone
> has told me that the hot set up for my car
> would be with an E31 head. Currently in my
> 70Z I have an L28 block with the E88 head,
> 5spd, and a 3.9 diff. I'm running the
> original '70 carbs on the motor. From what
> I've read the E88 head has larger intake and
> exhaust valves, so I wonder does the E31
> head have anything over the the E88?

Because the E31 has smaller combustion chambers (42.4cc), compared to 44.7cc for the E88. It really isn't the hot setup for a street car. The REASON it is the hot setup for racing, is because of the RULES required to race in a certain class. Most stock class rules don't allow the use of the newer heads, or different pistons, shaving the head more than a certain amount, etc.... This is why these guys use the E31. It is a stock item, and will increase the compression ratio, just by installing it, while not violating any rules. The compression increase is worth it compared to the smaller valve size. Remember, the cars running in these classes are mostly stock, except they have hot suspensions, and all motor building is for reliability, not all out hp. Modifications are restricted to try and keep the cars equal. The 240Z running in these races are 2.4L, and they are running SU carbs, so the smaller valve really isn't that much of a big deal.

BUT, on the street, this might not be the ultimate setup. It would work great, but you could probably get more power out of a later head, that was properly ported and polished, with larger valves and pistons to give you a good compression ratio. You are running an almost identical setup to me, except I still have the R180 diff.(soon to be swapped). I'd say stick with what you've got, you won't notice a huge increase just by swapping for an E31.
 
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