"Baby" P79 head

[DAW]

I found an N47 head in my garage while spring cleaning and it is not the same as the N47s I have from 280Zs. I think it's probably from a Maxima L24. It has 35mm ex. valves, 42mm int. valves, and the peanut-shaped combustion chamber of a P79. My question is, what is the cc volume of this head? I don't see how it could be equal to the 53.6cc volume of the P79 because with flat top pistons, the L24 would have to have a much lower c.r. than the '81-'83 L28 (8.8).

Anyone know the cc of the Maxima N47 head, or the c.r.?

DAW

[Bob_H]

People who have measured the Maxima N-47 head claim it is in the 39-41cc range. CR of course depends on dish size, etc..

-Bobby

[DAW]

Thanks. 40cc must be about right, working back from the Maxima c.r. of 8.9:1 and assuming flat top pistons. Looking at the chambers next to E31, N42, & P79 heads it appears closest in volume to the E31. Actually, it looks most like a W58 L20B combustion chamber (40cc) in size and shape. The Maxima N47 looks like an excellent choice for updating a 240- 260Z, given it already has hardened valve seats and L28-sized (35mm) exhaust valves (but means must notch the top of the cylinder bore on L24s, L26 comes notched from factory), and if converting to f.i. later, it's a bolt-on to this head. The drawback is it's got round/liners vs rectangular exhaust ports. Also, must get rid of Maxima cam, it has reduced intake lift vs Zcars. If using on L28 & larger, L28 intake valves (44mm) would need to replace Maxima (42mm). There are some strange finds at some of the Japanese engine warehouses. I have a rectangular port "N47" on one of my cars that is essentially an N42, and I've seen P90 heads on na stock L28 f.i. engines from Japan, so I wouldn't be surprised if there are f.i. L24s from Japan with the Maxima 40cc head but with rectangular exhaust ports. DAW

[Bob_H]

I have had discussions with many people about how I have found N42 heads on early turbo motors and other oddities like that. Most don't believe. You have obviously seen that. Anyways, the exhaust liners are not really a bad thing. Check out Paul's comments on my head page.

http://www.geocities.com/row4navy/head2.html

It is a myth that Bryan Little and I helped to perpetuate far too much. Yes, for 100% performance, i.e. race motors, they are not good. However, most of us are building for street use, with the occasional race.

Just food for thought.

-Bobby

[DAW]

I think round ports are more of a problem re no abundant round port headers vs square ports. Also, if one is using cast iron manifolds, there are much better square ports than round, including turbo manifolds. I have removed liners before and it's a pain. I found a round port ceramic-coated header in a JY and I'll leave liners in for that one, but I want to use a square port manifold on another round port head and it appears that the porting for manifold gasket match will be better without the liners there, both for machining and flow. Any experience adapting round port head to sqare exhaust? DAW

[Bob_H]

DAW,

Pulled this up while doing some research. I never responded to the last post.

First, there are round port headers out there,(how good they are? who knows). And I think NISSMO has a round port header in their 3-2 racing header design. The main drawback of course being the $300 retail price tag.

And my experience adapting a square manifold to a round port head? Minimal. But, I discussed with two people who had done that, (one ran a square port header on a round port head and the other person ran the square stock manifold on the round port head). They never considered removing the liners, so the square port was larger in all areas, and the match was fine.

And your last question, adapting a round to a square? Absolutely no experience. I would think that with the round port being smaller in size than the square port, you would be blocking/impeding flow out of the exhaust port. Where putting the square on the round port has the lip away from the chamber, vice in the way,(that doesn't sound real clear, but I think you understand).

Sorry for the long dealy in a reply!

By now you have likely figured it out. Shoot, I just thought about that diesel oil pump question we talked about a few days ago. I meant to look into the actual part number for the diesel oil pump. You know, it wouldn't surprise me if it turned out to be the same as the "competition" pump for the L6....

So have you adapted the Maxima N47 to a motor yet?

[Guest LIghtningZ]

I did the N47 head to 2.8L block swap like DAW recomended for better Perf. and had to use the stock manifold (Money problems, no money thats the problem) I,m getting ready to fire it soon i'll let you know how it goes.