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I'm putting together an engine and have options as to what head is the best. I'd like high compression, but not so much that I can't use pump gas. Everywhere I read they point out the P79 as being the best head other than the E31. I can get an E31 from my friend but he really wants to keep it, but he has several E88 heads. If I've done my research right, the E88 will get almost as high of compression as the E31 (this is on an L28 FlatTop block.) The valves are smaller than the P79 valves, but can't you get a machine shop to put the bigger valves in - thus having a high compression head that flows like the P79 that is more readily available than the E31? Is there some downfall to the E88 that I'm not finding? Let me know your thoughts. Thanks,

Matt
 

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You are absolutely right.

It is indeed entirely possible to install the bigger valves in the E88 head. A properly ported/polished big valve E88 will flow just as well as any other head. The main difference is in combustion chamber shape. Some say the shape of the P79 offers some anti-detonation benefits. This may well be true, but unless you're running over 11:1 compression, I wouldn't worry too much. Keep compression around 10:1 for 92-93 premium gas. Anything higher will cause you problems.

I ran a E88 on my L28 flat top, and now have a big valve E88 on my 3.1L. No complaints whatsoever.
 

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RE: Thank you very much, That's good info!

Thank you, I've been asking everywhere, and everybody hails the P79, but when it comes down to it, most haven't heard of or don't know about the E88. This info is very useful. I don't know why that's not a more readily given suggestion for people wanting to know what head to use. Typically they just say just use the P79 and shut up about it. Thank you to everyone who knows what they're talking about and gives good advice to those of us that are wanting to learn more.

Matt
 

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RE: Thank you very much, That's good info!

Can you guys clarify what these heads are? I have a 82 280ZX, which head would I have? Can someone list them out IE

1982 280ZX E88 Head?

As an example, I will eventualy like to build another engine for my car, and will be shopping for parts soon.

Scott Milella
 

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Allot of folx recommend the N-42 on the flat top L-28. It has square exaust ports and no inserts like the P-79. It does not have the high swirl combustion chamber like the P-79, so detonation may be more pronounced. It is my understanding that to get the compression out of the P-79 some additional machining must be done.

Ken
 

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Head differences...looonnnggg

This can be a sticky subject for some. For some reason, people are bent on certain heads, under the impression that they perform better than others. Some of the reasons may be true, but not to the extent most claim.

Basically, the differences between the heads can be traced to combustion chamber design and size. Valve size should be somewhat irrelevant, since you can install bigger valves on any head, so if you spend some money(which you should anyways, since these heads are old to begin with)the valve size becomes a mute point.

In regards to design:
Head Design is better seen than written, but here's a brief description.

All of these relate to the basic shape of the combustion chamber. Some are a 'pentroof' design. Another style is the 'clover' style, and yet another is the 'peanut' shape. Get a cylinder head book if you want to better understand this. Basically, because of the design, some heads resist detonation better than others, hence the reasoning to use them in high compression engines. But, those that have anti-detonation designs, don't necessarily have the optimum head volume in mm or cc. This is the problem with the P79. CC's are what you should be concerned about when calculating compressin ratio, which leads me to part 2.

CC's are important to produce a desired compression ratio. Basically, the less cc's a certain design holds, the higher the overall c.r. the engine will have. So, having said that, a P79 will have to be shaved to obtain the same cc's as an E88, but doesn't need bigger valves. On the other hand, the E88 doesn't need to be shaved, but needs bigger valves installed. Other than combustion chamber design, Z heads can be modified in infinite ways. Just decide on what chamber design you think works for you and go for it. But, keep in mind, that these differences will be minor unless you have a highly modified engine.
 

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RE: Head differences...looonnnggg

SOOOO,
If I get bigger valves in my E-88 and have it extrude-honed, it will be about as good as anything else I could do and not spend a fortune?
 

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<b>RE: Head differences...looonnnggg</b>

So what about the e31. If i wanted to run a 10:1 cr would this be a good choice. Of course the valves would be changed. But my concern would be detonation.
 

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Exactly Mike...

Once you start modifying the head, the 'factory' differences become less and less important. Like I said, I've run E88's on my L28 flat top and now my 3.1L. I don't have any flow problems whatsoever. So long as you install the big valves (which really isn't that expensive, since you need to install new seats anyways), you'll have no problems. And, just for conversation, the design of the E88 combustion chamber is quite good, so I wouldn't worry about detonation too much.
 

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The E31 works well as well Moore...

It should be safe up to 10:1. Figure it this way, they've run up to 12:1 and even 14:1 in racing form, so I'm sure 10:1 is workable. Personally, I try to run about 9.6-9.8 with pump gas. Then, I still have a little room to play with timing and such. Remember, when you have high c.r., you're engine is more susceptible to timing changes, and doesn't have much room for error. The slightly lower c.r. offers a little more room for error and tuning. That is worth .2 c.r. points in my opinion.
 
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