whats better p90 or n42 head

[Lockjaw]

For what its worth, a Max head was for sale on ebay and its owner said it has round ports.

[DAW]

The N47 Maxima L24E head U.S. market, has round ex. ports with liners.

 

I saw the sq port reference too, and it made no sense. However, I wouldn't rule out the possibility that there is a JDM counterpart with sq. ports (like the N47 sq port L28E head I have).

 

An ardent discussion about these heads, but it's essential that comparisons be kept equivilant. Basically, there are three categories of the L6 heads: "small, medium, and large" combustion chambers. For the "large" chamber heads (about 53.6cc), use is dictated by larger displacements or lower (turbo) compression ratios). There's only two choices, both are closed-chamber design: P90/(a) and P79 (not big cut & shim-modified). P90 is my first choice here due to sq ex ports and mech valvetrain.

 

The biggest controversy seems to be in the "medium" cc chamber range (about 44.7): N42/L28E N47 (open-chamber) vs P90/P79 (closed-chamber) cut 0.80", shimmed towers, & N42 valves (longer) placed ($) vs late E88 (open-chamber). E88 has small intake (42mm) valves and valve seats for leaded gas, whereas the L28 heads have hard seats and larger intake (44mm) valves.

 

If your engine is a smaller diplacement, or you can run a c.r. well over 10:1 with a larger displacement engine, then the "small" chamber series is for you (around 42.5 cc). Most of these are early pre-unleaded fuel heads and will need the valve seats replaced. All are from L24 engines and have smaller 42mm intake valves than the "medium" and "large" heads from L28s (44mm intakes and harder seats). The E31, and early E88s (open-chamber), have small 33mm ex. valves. The L24E Maxima N47 head (closed-chamber) differs from the others in this category as it has the larger, 35mm, ex valve already in it (same size as L28) and has hardened seats that the others lack. The closed-chamber Maxima head is good to go with it's ex valve as-is and this head is my pick over the others in this category as the one to go with, both because it is the later closed-chamber design and especially considering it also has f.i. notches and bolt holes in the intake surface. I'd prefer the sq ex ports ala E31 but there may be JDM L24E head out there that way. You'd need a donor L28 head to upgrade valve size in any of these "small" heads. In the Maxima head you need to have L28E intake seats placed, intake valves and springs transfered, and the L28 cam transfered. In the E31 and early E88 you need to have both intake and exhaust seats placed and transfer all (in & ex) valves.

 

My interest in this discussion is to provide some guidelines for some who may not have experience in putting these combinations together so that they realize that there are some choices that weren't available during the initial evolution of the L6 which may have advantages (like f.i. and closed-chamber heads and hardened valve seats) and that the desired c.r. is the main determining which category of heads to choose from. DAW

[Guest Anonymous]

Good post DAW! Helps alot with my research of which head to replace my N-42, if I decide to. I don't know how everyone else feels abot this but a straight forward head swap that does not have alot of hidden cost is seems the way to go. Just my thought which has probaly been covered already..... just my .02 cents. Jake

[Bob_H]

DAW,

That is the first time I have seen it broken down into small medium and large. I think that is a very apt description and a great way to seperate out the heads.

Thanks for the clarification on the Maxima heads. I may be getting older, but I didn't think my memory was getting that bad. And I need to edit that last post, it was a 280zx turbo that I saw the square port N47. I have mistakenly posted that some early turbo motors had the N42. It wasn't until this discussion that I remembered it was a square port N47 that I found on a turbo that appeared to have never been off the head. Geez, I am getting old.

And we are all in agreement,(DAW, Norm, Z speed Auto, Dan, myself, Lockjaw, TimZ etc..), that unless you specify what your APPLICATION is, then it is a moot point to discuss. And we also all agree that any comparison between heads is only valid in a stock vs. stock configuration. As soon as you change ANYTHING in the head, shave it, bigger valves, port/polish, new camshaft, etc.. ANY comparision is just not valid anymore.

And Geez Norm! That is a TINY combustion chamber! Mine is a full 10cc's bigger.

-Bob

[Lockjaw]

I guess I can agree to that, as long as everyone realizes I am not in the novice category, and nothing I have stays stock long enough to make a comparison.

 

As for Norm's combustion chamber, I can see my P79 is going to have to get another milling. I want more compression.

 

Either that, or I am going to hunt down one of the maxima N47's. I have a partner in crime now, and well will colaborate. HEHE.

 

Nice post DAW, best I have seen to date on a head breakdown.

 

Hey does this mean that the next person that posts a "which head is best?" questions gets a canned answer, or we just tell them to shut up?

[Dan Baldwin]

Once more for DAW and those with short attention spans. There are FOUR E88 heads:

'71 E88 has E31-like chambers, 42.4cc, 42mm intake, 33mm exhaust

'72 E88 has N42-like chambers, 44.7cc, 42mm intake, 33mm exhaust

'73 E88 has larger 47.8cc chambers for reduced compression, 42mm intake, 33mm exhaust

'74 E88 has same chambers as '73, 42mm intake, *35mm exhaust*

 

The '73 and '74 are regarded as undesirable "emissions" heads (whether that means they're nfg or not, I don't know). ONLY THE '74 260Z E88 HEAD HAS THE LARGER L28-SIZED EXHAUST VALVE. The E88s commonly used for performance apps ('71 and '72) both have small intake and exhaust valves.

[240Z Turbo]

And the winner is...............

 

N42

 

Hurray, discussion over!

[Lockjaw]

Wrong, the winner depends on your application and technical expertise.

 

That said, if you want to run an N42, hey I am all for it.

 

 

I'm not gonna yet.

 

Oh and if you have a P90 on your car now, and think you may sell it when you convert, how about giving me a shot at it?

[johnc]

Sometime next year (or maybe 2004) I'll get Sunbelt to build a P90 for my NA 3.0L. Then we should have a viable comparison of a heavily modified N42 vs. a heavily modified P90. Kinda like comparing genetically altered apples and oranges. $10 says we end up with an orange the looks and tastes like an apple and an apple that looks and tastes like an orange.

[Lockjaw]

I think you will find that the P90 is superior. But the results should be interesting just the same.

[Tim240z]

OK, Lets put this whole discussion to bed:

Take the engine out and drop a V8 in. End of story

 

Tim

 

(ps..Don't flame me...just trying to interject a bit of levity here)

Tim

[Bob_H]

So John, the important question is have you gotten to drive yours yet?! I look forward to a "report" of how the car drives with all its crazy stuff, quaife box, sunbelt motor, stripped car, etc..

eating apples that taste like oranges,

-Bob

PS- it would likely be better to put this in another subject.

how did those v8 guys sneak in here?

[Lockjaw]

Hey the V8 guys were in another post too, on this board, so I had to remind them which board they were on.

[pparaska]

Yeah, the evil V8 guys lurk around here too

 

Just for a summary, JUST HOW MUCH of a difference in torque and power will the two highly modified heads have? 10, 20, 30 hp?

[Drax240z]

I believe that on the same engine, good tuning etc. we are arguing about 10hp here... (given CR's are similar, same cam, same valve sizing, same displacement, etc)

[pparaska]

I guess with a strict set of racing rules, that's important, but I think all this attention and fretting for 10 hp is kind of silly.

 

Thank goodness I can go from old Chevy heads to new Vortec heads and gain 30-40 hp OUT OF THE BOX.

 

Just trying to get a perspective.

[Lockjaw]

You have to put that 10 hp into perspective though Pete. If you have a 180hp engine, and pick 10 hp, that is a ton when you are dealing with a 2.8 liter engine.

 

I think there may be a little more difference then that, I was thinking perhaps 15hp, but either way, people have won a lot of races on a less than 10 hp advantage.

 

I will take 10 free hp anyday.

[pparaska]

Definitely an issue if you are racing with that kind of "typical" hp. A different perspective is that I throw away 10-30 hp up top to get better drivability, when parts shopping for a V8 using Desktop Dyno 2000. Of course, it's 460 peak hp vs 490, etc.

 

Sorry, I guess my sense of perspective is a bit skewed

[Lockjaw]

HEy when you have that much HP, I guess you can throw a little away and not sweat it.

[Dan Baldwin]

To further beat a dead horse, I don't believe we're talking about 10hp. Even if we were, we still haven't seen any evidence that it would be 10hp more with the P79/P90 or with the N42.