N42/47 head on '83 L28, problems?
 

i found the site talkin about modifying the P79 headwork. it also suggests using the N42/47 heads for ppl on a budget, but says the design has flaws for the combustion chamber. if your gonna use 91+ oct gas, wouldn't this prevent any knocking that he was talkin about?

http://www.geocities.com/zgarage2001/head.html

Well first off the big deal about the n42/47 heads were the size ofo the compresion chamber and the valve size. N42 being the most sought after! It would raise the compression and it would breath a little better. then you had too worry about clearence in conjunction with the cams if there aftermarket! The only problem then is the spark plugs pr7/8 depending on the weather. Now if your turbo charged this would probly not be the best set up.
Brian

I've heard it both ways. someone said they have that setup and it pings all the time. If they use 91 octaine it only pings a little bit at full throttle in the mid rpm range.
The closed chamber design of the P79 resists pinging a little more than open chambered designs. (comparing both you consider each one has the same compression)

You have to shave the P79 quite a bit to raise the compression up as it is already made to be used with flattop pistons. After the shave its up to you how you want to correct the timing chain slack. I would just advance the cam sprocket to #2 and replace the chain at 100K miles.

I actually have not heard of anyone having problems with higher lift cams causing the valves to hit the piston. If you have a super long duration and advance your cam 6+ degrees then maybe you can think about that... but the clearances in the L28 engine aren't really that close. Its a fairly long stroked engine.

I didnt go into detail before but this was my setup N42 head 2mm shaved deck 2mm copper spacer under cam towers to adjust chain slack, new lash pads to compinsate, 2mm metal head gasket to yeiled close to 9:1 compression, 90 mm domed pistons (fj90) L16 conrods and a deisel crank lightened and balanced everything matched and balanced with harmonic balancer and os twin plate . I ported and polished the head and intake to match, the head was also ported also ported to match my stainless kakimoto equal lenth header. Thee inch kakimoto exaust no cat. with three 50 pie Sollex carbs Mallory distributer blaster coil Producing a 3.2liter

i just came from having the car checked out by a Z shop here, & asked a few questions. he said his favorite motor was the '82-3 motors. all he did was swap in a cam & ppl were shocked at how different it was. & swapping in this N42 head would actually make the motor run hot, not good for TX ppl. but in the end there is nothing really wrong with it, but just not his kinda route.

i'm gonna do it anyway, then after awhile i'll swap a cam in the P79 head & put it back; then sell the N42 by next year.

I wish I could afford a performance cam. The 81-83 motors are the 8.8:1 compression from the factory motors. They use larg cc closed chambered heads, but flattop pistons. The same idea is used on almost every late model car.

Previous L28 engine were said to have 8.3 or 8.5:1 compression depeding on the source of the info.

Bleach,
I am running the N42 head N42 block . It was rebuilt and it is
only about 8.3 to 1 compression. I could probably run it on toliet water :) Ignition system is the key to running the 10 plus compression on low octane fuel. A good adjustable ECU will
retard the timing while running 91 octane fuel. Then when you slap the good gas in it dial that baby back up.

The one web site that Steve has listed isn't exact science either.
He even states that he thinks that certain combos work or don't work. He has tried them all.

Personally I think the 280ZX F54 and P combo is probably the best set up in the long run. Nissan had a few more years to get
it right.