Newbie seeking advice - what is the best L engine/head combo

[Drax240z]

So far everyone has kept this civil and even though opinions differ they have been differing in a professional and respectful manner... Let's not begin down the path of name calling guys.

[Doug71zt]

Proud - It comes up in that context in translations from Chinese and Japanese fairly frequently. It made me scratch my head the first time I came across it.

 

In theory - How close do the piston and head have to be to get good quench action? In my 3.0l, the pistons are flat-top, but a little way down the bore to achieve 8.5ish:1 ratio with the P90 head.

 

Doug

[JMortensen]

From the chevyhiperformance.com link on page 2:

Savvy engine builders know that minimizing the piston-to-head clearance in this quench area to less than 0.040-inch dramatically increases the amount of turbulence created in the combustion space between the piston and the chamber.

 

EDIT--with respect to JohnB's "prouder" thing when I bought new valves for my head on the last rebuild I went from valves that were cut too far to valves that were brand new and much prouder, and lost 2cc in chamber volume!!! Also the original Nissan valves had quite a bit more dish in the end of the valve than my new ones did. Point is that can really affect compression ratio.

[Doug71zt]

So, on a low-compression turbo engine with a P90, you don't stand much o f a chance of getting good quench with flat-tops anyway, especially on a stroked and overbored 3.0l. The chamber volume would be too small to get 8-8.5:1 without putting in a 2mm HG, or doing the same thing by putting the piston down the bore. Even if I open up the head diameter to 87mm (my bore size) and notch the bore, I don't think that I would be able to get the chamber volume required to bring the piston that close to the head. Theoretically, the N-series head would be worse for this application, as the chamber is even smaller.

 

I welcome anyone's theory on this.

 

Doug

 

PS-jmortensen - Thanks for the quote.

[JMortensen]

So, on a low-compression turbo engine with a P90, you don't stand much o f a chance of getting good quench with flat-tops anyway, especially on a stroked and overbored 3.0l. The chamber volume would be too small to get 8-8.5:1 without putting in a 2mm HG, or doing the same thing by putting the piston down the bore. Even if I open up the head diameter to 87mm (my bore size) and notch the bore, I don't think that I would be able to get the chamber volume required to bring the piston that close to the head. Theoretically, the N-series head would be worse for this application, as the chamber is even smaller.

 

All true, but with a turbo you just retard the timing and turn the boost up to get your power. The timing and the high compression ratio isn't nearly as critical.

[JMortensen]

Maybe I spoke too soon. Check out the semi-dished piston:

http://www.chevyhiperformance.com/howto/47075/

[Dan Baldwin]

speaking honestly and candidly, I think you have an aggressive, inflexible, know-it-all approach to presenting your point of view that doesn't serve you well

 

Yeah, I can get pretty heavy-handed, I'll work on that. Just so you know, none of it's meant personally. And your "flat earth" comment, while it might've pissed me off, I didn't take it personally either (bringing it back up was meant in fun, hence the ).

 

Obviously we strongly disagree on the relative importance of both r/s ratio and the P vs. N L6 cylinder heads. On that we can surely agree!

 

Peace love and understanding,

[TimZ]

On another subject' date=' this has been bugging me:

I use an N42 on a high boost TURBO setup with no problems - granted it's modified a bit...

Unless you're running flat tops Tim you're not getting the benefit of the quench anyway, so that is not a very good argument for an N42, plus you say you've modded the head, which pretty much throws it all out the window.

 

...So it bugs you that I said it, or it bugs you that I've been successful with that setup?

 

My point was that I have not had any detonation problems with this supposedly "detonation prone" head. I mentioned the fact that the head was modded just to be fair, but the chamber modifications were not particularly extensive - the chambers were smoothed to eliminate hot spots, and they were ceramic coated (which is surprisingly inexpensive - this cost ~$150, as I recall).. The main work/expense was in modding the ports for flow and verifying on the flow bench.

 

As far as good arguments go, it was at least as good as G-tech results on an E31 head with dished pistons (where was the quench in that setup?)

 

Now this has been bugging me...

As far as Dan having a "aggressive, inflexible, know-it-all approach to presenting your point of view that doesn't serve you well", if it bothers you that much to be fact-checked, perhaps you should refrain from making unsubstantiated claims.

 

Dan's argument all along has been crystal clear:

1.)Regardless of what "should" work better, there has not been, to date, ANY evidence presented that even suggests that this P-series superiority bears out in practice.

 

2)Although there is also no evidence saying that the N-series is superior, there IS plently of evidence that it works pretty darned well.

 

3) Therefore, use whatever is readily available and allows you to get the CR you want and is affordable.

 

He has never swayed from this position, and so far NO ONE has offered a logical argument to refute it.

 

Why is that so hard to understand?

[JMortensen]

Sorry for the formatting issues. Copied and pasted from IZCC email from a couple days ago. The name is withheld to protect the innocent...

 

It would appear that this guy had the same basic builds we're talking about, N42/N42 and F54/P90 shaved. Looks like the P90 was good for about 9hp. Now there is the issue that these were not the same engine with a different head on the same dyno on the same day, but two totally different engines presumably on different days and who knows if it was the same dyno.

 

Even so, his pinging experience backs up the P head theory. Call that "not evidence" if you want. Call all of the articles listed and the hundreds more "not evidence". I'm going with common sense.

 

I would have to say the only "problem" I had was not being able to really put my foot in it without pinging. It was a fresh engine using Euro pistons, Felpro, and total shave of .0012. So, I was probably over 10.5 CR (220~225psi). I was using an E12-80 dist and Z-Therapy carbs. The initial, I believe was about 8 degrees. I experimented with the timing, reducing the initial brought a notable (small of course) decrease in power. I doubt I was running out of fuel either with the SM's. The overall mixture was on the rich side too. No matter how much octane booster + 93 octane gas made much difference. It did run very well otherwise. Now, I'm not saying I wasn't impressed with the improvement over a stock

N42/N42 L28, but that I wasn't impressed with how sensitive the engine was.

How good is the compression if you can't confidently open it up?

So maybe with less compression, say 9.8, it wouldn't have pinged...but

that's with less compression=less power (as I see it). I had a flat-top

short block I gave a friend, and he bolted on an N42 and went with his stock 280z EFI. Yes, it is an improvement over his stock N42/N42 engine. It runs very well, but he too has some pinging issues. Again, how good is the compression if you can't use it?

 

I new it was a common issue when I decided to try the N42...it was an

acceptable risk. Am I saying every N42 on a flat-top will ping? No, I'm

just saying that based on my observation and readings, it can easily be an

issue.

 

I believe the chamber on the E88-N47 heads were engineered for dished

pistons, not flat-tops and the quench characteristics of them (or lack of

perhaps). I forgot where I read it, but it was a breakdown of the

combustion physics involved with the difference between the two different

chambers firing with flat-tops. It basically explained how the shape with

flat-tops encourages detonation over a smooth burn front. I know a little

bit of Physics, PV=nRT, Newton, etc., so it made sense to me. (I got out of Engineering and into MIS, but that's another topic, I digress).

Another thing nobody seems to be able to explain is how the P79/F54 engine gained 9 horsepower over the N42/N42 engine with only 2/10ths increase in CR. Was it intake or exhaust? Was it ignition? Maybe, maybe not. Until someone can explain it, I'll continue to believe it was due to the improved chamber that Nissan spent alot of money to design, retool for, and produce.

 

I have an .080 shaved P90 and a minimal shaved P90. I hope I can do some experimentation with these and try to compare to my old setup (from memory).

 

Yes, the only way to unequivocally solve this is to run a scientific

comparison on the same flat-top block with everything else being the same.

With the increased compression, the N42 just may beat the P79. But if were only by a few HP, I wouldn't be surprised, nor impressed considering thepopularity of the N42/N47.

Holy Cow, sorry for the rant...I've been typing and watching the Miami/FS

game.

This part is my favorite:

Dan, I guess I'm just baffled how you've got that much pingless power out of your N42...and it's a stock N42 that's never had any chamber

modifications? Wow, imagine the power if you went with a modded .080/P90!

(he-he)

If anyone out there has experience with comparing the two heads, please pass it on. I'm a sponge for this stuff.

BTW, it only cost about $150 more at the machine shop to set up the .080

shaved P90 over the unmodified P90.

 

EDIT--Forgot to respond to this:

As far as good arguments go, it was at least as good as G-tech results on an E31 head with dished pistons (where was the quench in that setup?)

 

The answer is you don't need quench when you've got 8.5:1. That motor ran fine at the track in 100+ heat running 87 octane. That post was more railing against Dan's BOW DOWN thing than anything else.

[Dan Baldwin]

KEE-RIPES, Jon, hasn't this gone on long enough without your cutting and pasting ONE SIDE of the same argument (actually, it was more of a brief DISCUSSION there) from the IZCC list?!

 

Suffice it to say that after that discussion, it looks like the original poster to the IZCC who asked about block/head options will be going with an N47 head on an F54 flat-top bottom end.

 

Looks like the P90 was good for about 9hp.

 

He never said that. He said THIS: "Another thing nobody seems to be able to explain is how the P79/F54 engine gained 9 horsepower over the N42/N42 engine with only 2/10ths increase in CR". That's power AT THE BROCHURE he's talking about. Could mean a lot of things, and could mean NOTHING AT ALL. Anyway, he wasn't talking about his motor with an N-head vs. a P-head.

 

Even so, his pinging experience backs up the P head theory. Call that "not evidence" if you want. Call all of the articles listed and the hundreds more "not evidence". I'm going with common sense.

 

He had pinging at what he thought was ~10.5:1 with a stock shaved N42. I did not have pinging at ~10.4:1 with a stock shaved N42. I cannot draw a conclusion as to *why* he had a pinging problem. He said he had euro pistons, and the head was shaved ~.0012 (surely he meant .012"). Anyone know what the "dome" volume an pin height on those is? Could be the CR was higher than he thought? Burrs or other hot spots in one or more of the chambers? Like I said, I don't know.

 

This part is my favorite:

Dan, I guess I'm just baffled how you've got that much pingless power out of your N42...and it's a stock N42 that's never had any chamber

modifications? Wow, imagine the power if you went with a modded .080/P90!

(he-he)

 

Yeah, "he-he", as in he was joking. Of course *I* don't think I'd be making much if any more, assuming I could get to 11:1 CR with the P90 in the first place (I don't think .080 would even come close). Regarding the "baffled" comment, I myself am puzzled at the reports of pinging with the N42. It was never a problem for me, even totally stock (shaved slightly) with the stock cam.

 

EDIT--Forgot to respond to this:

That post was more railing against Dan's BOW DOWN thing than anything else.

 

Of course with the "BOW DOWN" comment I was saying I don't know everything, not the opposite.

[Guest bastaad525]

you guys still at it?? Did the original poster ever check back in even? heheh.

 

 

Dan what about me? I too had really bad pinging problems with a NON shaved, bone stock N42 at what I was told would be about 10.3:1 compression. I had to run quite a bit rich and back the timing off a couple degrees to get rid of it. This was with the ZX EFI and also running SU's on the same motor. After switching to a hotter cam I could run leaner and more timing and never had the ping problem again. This was all tested and tuned on a dyno, so I know that I had to run really rich to get rid of detonation with the stock cam. Dan what cam are you running? Might be why you can run yours w/o ping as well.

 

I know this is really comparing apples to oranges, or ... apples to gorillas, so I'm not really comparing, rather, just asking. For everyone running turbo motors out there with high boost (15psi plus) isn't the actual compression ratio equivalent to something like 13:1 or some really high compression like that? I never understood how turbocharged street cars get away with that on the same octane gas, maybe the P90 has something to do with it I'm assuming that, at the least, the effective compression ratio of my motor running 14psi right now is higher than my N/A motor was?

[TimZ]

He had pinging at what he thought was ~10.5:1 with a stock shaved N42. I did not have pinging at ~10.4:1 with a stock shaved N42. I cannot draw a conclusion as to *why* he had a pinging problem. He said he had euro pistons, and the head was shaved ~.0012 (surely he meant .012"). Anyone know what the "dome" volume an pin height on those is? Could be the CR was higher than he thought? Burrs or other hot spots in one or more of the chambers? Like I said, I don't know.

 

Ummm, yeah...

So I guess modded N-series head results are only acceptable as "evidence" if they don't work well.

[JMortensen]

KEE-RIPES, Jon, hasn't this gone on long enough without your cutting and pasting ONE SIDE of the same argument (actually, it was more of a brief DISCUSSION there) from the IZCC list?!

Tim asked for proof. I thought the fact that his N42 did ping and his P90 didn't at ~ the same compression was a good point, that's why I shared it. That to me is a valid comparison, and probably the best we're going to get.

 

That's power AT THE BROCHURE he's talking about.

I TOTALLY MISSED that. My bad.

 

Regarding the "baffled" comment, I myself am puzzled at the reports of pinging with the N42. It was never a problem for me, even totally stock (shaved slightly) with the stock cam.

I think you're the odd man out there. I know your East Coast gas is 93, where CA gas is 91 and oxygenated in the summer time but that's about the only rationalization that I have for your lack of ping.

 

Of course *I* don't think I'd be making much if any more, assuming I could get to 11:1 CR with the P90 in the first place (I don't think .080 would even come close).

Not sure on this. We already figured out that you can come close to the stock N chamber volume. The P79 and P90 have the same chamber, and the P79 cc'd out at 46cc with a .080 shave. If you shave the crap out of the N, then yeah, I suppose you're right. I don't know if there is a practical limit to the amount you can shave the P. Of course Mack's Max N47 would be the obvious answer to that problem anyway.

 

It seems that you and Tim are never going to listen to reason or accept the "evidence" of car, truck, boat, chainsaw, motorcycle, ATV, and race engine manufacturers, so I'm officially giving up trying to convince you, but hope that OTHERS reading this realize that it is possible to make good power on an NA L series with an N head and flat tops, but it will be easier and more ping resistant with a P head.

 

 

A strange game. The only winning move is not to play.

-WOPR

[TimZ]

For everyone running turbo motors out there with high boost (15psi plus) isn't the actual compression ratio equivalent to something like 13:1 or some really high compression like that? I never understood how turbocharged street cars get away with that on the same octane gas, maybe the P90 has something to do with it I'm assuming that, at the least, the effective compression ratio of my motor running 14psi right now is higher than my N/A motor was?

 

Nope. There is no actual thermodynamic relationship between "effective compression ratio" (whatever that is) and boost pressure. This is another pet peeve of mine:

http://hybridz.org/nuke/index.php?name=PNphpBB2&file=viewtopic&t=16380&

 

BTW - not bitching at you - I know you were just repeating what someone else said, and on the surface it sounds logical. It's just that under the surface, it's not...

[Guest bastaad525]

no prob well that thread cleared a few things up for me while confusing others... anyways was just asking as opposed to really stating, as I still didn't and dont fully understand how all that works.

[Dan Baldwin]

Dan what about me? I too had really bad pinging problems with a NON shaved, bone stock N42 at what I was told would be about 10.3:1 compression.

 

I don't know. It's almost like there's two different kinds of N42 out there, good and evil.

 

Dan what cam are you running? Might be why you can run yours w/o ping as well.

 

Currently running a ~305/.550" cam, at 11:1. But I ran the stock cam for years at your CR level with no pinging problem with 35 degrees advance all-in.

[DAW]

Truce Dan. I've stopped looking at the posts on this, it makes my head spin.

 

John, thanks for the clarification on "proud." I was proud of my valves and my pistons until they collided. DAW

[Dan Baldwin]

Tim asked for proof. I thought the fact that his N42 did ping and his P90 didn't at ~ the same compression was a good point, that's why I shared it. That to me is a valid comparison, and probably the best we're going to get.

 

You're talking about a "comparison" that never happened. Read it again. He says: "I have an .080 shaved P90 and a minimal shaved P90. I hope I can do some experimentation with these and try to compare to my old setup (from memory). "

and

"If anyone out there has experience with comparing the two heads, please pass it on. "

 

NOWHERE does he mention running a P90 (or P79) at the same CR. You continue to misrepresent his story to fit your argument! I'm sure you're not doing it on purpose, but surely this brings into question your ability to look at the evidence without bias or prejudice. You're subconsciously altering the story in your own mind to fit what you WANT it to be, or what you THINK it should be!

 

regarding my not having pinging issues:

I think you're the odd man out there. I know your East Coast gas is 93, where CA gas is 91 and oxygenated in the summer time but that's about the only rationalization that I have for your lack of ping.

 

Quite a number of Z's over the years have gone with the flat-top piston + N42/N47 head setup without pinging issues. The 164rwhp ZCCNE club race car is just one of many. Only a few cases I know of where problems cropped up, and certainly they're worth mentioning when the subject comes up.

 

The P79 and P90 have the same chamber, and the P79 cc'd out at 46cc with a .080 shave.

 

My head is at 40.6cc. Figure you'd have to take at least another .040" off the P-head to get there, maybe? Total of .120", 3mm. I couldn't say if that'd be practical or not, that's a lot.

 

Of course Mack's Max N47 would be the obvious answer to that problem anyway.

 

Yeah, that'd work, you'd want the larger L28 intake valves of course. But of course that's not a "P" head

 

It seems that you and Tim are never going to listen to reason or accept the "evidence" of car, truck, boat, chainsaw, motorcycle, ATV, and race engine manufacturers

 

Fitting that you put "evidence" in quotes. Engine development is NOT based on what SHOULD work. If it works it works. The N-heads DO work very well for myself and others. No evidence I have found indicates the P-heads work any better. Maybe they are better. Maybe not. Maybe the difference is negligible.

 

, so I'm officially giving up trying to convince you, but hope that OTHERS reading this realize that it is possible to make good power on an NA L series with an N head and flat tops, but it will be easier and more ping resistant with a P head.

 

I'd have no problem with the statement of your point of view above if you change "will" to "might" or "could" or even "is likely to". It is a statement of what you BELIEVE to be true, don't present it as a statement of FACT.

[JMortensen]

NOWHERE does he mention running a P90 (or P79) at the same CR. You continue to misrepresent his story to fit your argument! I'm sure you're not doing it on purpose, but surely this brings into question your ability to look at the evidence without bias or prejudice. You're subconsciously altering the story in your own mind to fit what you WANT it to be, or what you THINK it should be!

 

All right then. I need to put down the crack pipe when I'm reading. I guess I totally misread that post. I thought he was saying that he had an n42 with the Euro pistons that pinged like crazy, and changed to a P90 shaved and made 9 hp. Maybe I had a glass of wine before I read that. I don't know. You are correct Dan. That apparently is not what he said.

 

Yeah, that'd work, you'd want the larger L28 intake valves of course. But of course that's not a "P" head

 

Doesn't matter if it's a P head or not. The idea is to get the quench. It could be an early E head, a P head or the Max N head. All are going to have the same innate advantage that the Z N heads do not.

 

Engine development is NOT based on what SHOULD work. If it works it works.

 

I agree, but engine developers don't start from scratch every time. A good engineer should be able to see the merits of a good design and use it to their benefit (remind me never to hire you). You and Tim seem to be the only ones stating that this MIGHT not work. And the abundance of evidence (no quotes this time) from V8s, V6s, I4s, V twins, single cylinders, 2 strokes, 4 strokes, etc, etc, etc is overwhelming. I KNOW that I can't make you open your mind. I'm sorry about that, and I'm done arguing. I just made this post to tell you that you were right and I was wrong on the other guy's story.

[Dan Baldwin]

A good engineer should be able to see the merits of a good design and use it to their benefit (remind me never to hire you).

 

You couldn't afford me, anyway

 

You and Tim seem to be the only ones stating that this MIGHT not work.

 

What, putting a shaved Phead on a flat-top motor? Of course it'll work.

 

And the abundance of evidence (no quotes this time) from V8s, V6s, I4s, V twins, single cylinders, 2 strokes, 4 strokes, etc, etc, etc is overwhelming.

 

And all of those have shaved Phead combustion chambers, right? I'm just saying that I think there are enough subtleties in chamber shape that you can't just say the Phead is inherently superior or the Nhead woefully INferior just because it LOOKS that way to you. It hasn't been demonstrated to be superior. And good results have been achieved with Nheads. I wouldn't hesitate to recommend either head, and in fact that's what I did in my first response to this post. That's all I'm saying. I don't see anything that's been presented as "overwhelming evidence" one way or the other.

 

I KNOW that I can't make you open your mind. I'm sorry about that, and I'm done arguing. I just made this post to tell you that you were right and I was wrong on the other guy's story.

 

Open my mind? My mind is fully open to the possibility of the superiority of the Phead. I see no reason to decide that this is absolutely the case until there is some FREAKING EVIDENCE. STILL haven't seen any.

 

I would feel very differently about this if I hadn't been able to run ~10.35:1 with the stock cam, and 11:1 now, on pump gas. If I'd felt seriously compression ratio-limited with the N42 I would HAVE a P-head (or Max N42) on my engine, for all the reasons you've given, it *should* be better. Maybe my cylinder head (and Tim's, and the ZCCNE club car's) are blessed by God Almighty while others are cursed or something, I don't know.