I am going to be building a high performance over-stock engine for my 240z. The donor engine will be from an 81 280zx. Its a flat top piston motor, with a P79 head. My current engine has dished pistons and the E88 head. I'm wanting to stay as cheap as possible on my engine here, so I was wanting to work with what I have got. I want a high compression, good flowing, best head I can get. I have access to do all the shaveing, valve jobs, and porting work myself. What Head should I use? What will give me the best performance? I was thinking E31, but I see that it doesn't flow the best, valves are small, although it has the best compression ratio. Can it be fitted with larger valves? I was actually wanting to keep the stock valves, so I don't have to spend much more money on this engine then I can possible get by with. What are your thoughts? Thanks

The L28 block from an 81 is a good base to start with. The E88 does have the best compression 10.8:1 if I remember correctly. With this combo you might have problems with pre-detonation (pinging) if you use pump gas less than 94 octane. The E-88,N42, & N47 will give you 10.4:1 (if the head has not been shaved). Like you said the E-88 does not flow the best because of the small valves. And I do think that most of the power comes from a properly designed head. If you use a head with larger valves you would have a good "base" to work with ie.. porting & polishing. All the heads pretty much flow the same.

Is the E88 a large valve head?

Also, I have some questions on the N42, N47 heads. I read that most people prefer the square exhaust ports. Why is this? Do they flow better, larger, what? I see that the N42 has the square ports, but bronze valve seats which will sink over time. Is it possible to have a different type of seat installed on my head? How much would that cost me, for seats and labor to install them? I'm just looking for a rough idea of how much money I would be looking at if I go with an N42 head. I want the best flow, so if the square exhaust ports flow significantly better then the round then I will definatly go with square. What are you thoughts here? Thanks!

One other thing, I want high compression, and I always use high octane gas in all my cars, so thats not a worry. 10.4 would be fine on this engine. But I do plan to shave the head, just to get a good flat surface, not exactly to raise compression. How do I have to adjust my cam/timeing setup to accomadate a shaved head? Since I'm only going to shave a little off do I really have to worry? Thanks again