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

[TimZ]

I agree, but engine developers don't start from scratch every time.

That's exactly the point. We aren't starting from scratch here. Nobody has been aruging that quench doesn't work. Dan, and now I, have questioned whether it bears any measurable or useful fruit as it it is implemented on the P-series heads. This was your original point:

 

Again you miss my point completely. For the 1' date='000,000th time, I'm not arguing that the N-heads are BETTER. I *am* arguing that there is NO EVIDENCE that the P-heads are better. Get the distinction?[/quote']

 

Yep' date=' I sure do. I AM arguing that the P heads are better.[/quote']

 

All the the "evidence" that you have presented addresses why quench is good. We never said it wasn't.

 

NONE of your evidence (except the stuff you apparently made up out of desperation) showed that the P-series is demonstrably better (or worse).

 

Modified or not.

 

At anything.

 

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.

 

Your whole method of mischaracterising what others have said, and then subtly implying that they must be stupid or closed-minded because they don't agree with you is getting really tiresome. I found this last bit to be downright insulting, and it just goes to demonstrate the true strength of your argument. Oh wait - it was Dan that browbeats people and is too agressive and insulting. That's right...

 

For the record, though, a GOOD engineer would be able to follow a premise to it's logical conclusion, and would not recommend spending money on technology for technology's sake, especially when said technology has been the field (the P-series, not "quench", per se) for twenty years and STILL no one has been able to demonstrate any actual superiority.

[JMortensen]

Your whole method of mischaracterising what others have said, and then subtly implying that they must be stupid or closed-minded because they don't agree with you is getting really tiresome. I found this last bit to be downright insulting, and it just goes to demonstrate the true strength of your argument. Oh wait - it was Dan that browbeats people and is too agressive and insulting.

except the stuff you apparently made up out of desperation

 

It's a good thing you're above all that, isn't it?

[DAW]

Hey, check out this guy. Is he out in left field or what? What a hoot!

http://www.kb-silvolite.com/index2.php

 

Sorry, couldn't resist. DAW

[Guest 28]

do you guys ever notice' date=' that every so often some newbie will show up, ask this question, start a 5 page long feud, but that said newbie-thread-starter never even checks back in to get his answer, whilst we just go round-and-round in the eternal debate?

[/quote']

please go on,coz some other newbie(like me) haven't asked a question is studing from these post,just to proof,I quoted this sentence,coz I have read these round n round pagez.

Thanks for everybody's words!Realy helps

I'm in NZ,not many mint 240/260Z's here now,even 280z's become rare!

I just bought a mint 79 280z,original 120Km,but it's a shame it comes with a JDM L20e motor.

[DAW]

Welcome, newbie 028 and thanks for the encouragement to keep going. You can be newbie swither's stand-in (he asked the initial question on this)because I think he probably fled a long time ago.

 

Of all the anecdotal declarations on this topic there seems to be a paucity of accounts from those who have built both open-chamber and closed-chamber head L series performance engines. It's usually on camp vs the other with few who have spent time in both camps.

 

Another pitfall is looking at evidence re detonation tendency from engines with big cams. You might as well compare engines with 8:1 c.r. because the tendency to ping is diminished. This is like comparing two mufflers for their restrictive properties on a 3 liter engine and using different brands of 4.5" mufflers to conduct the comparison.

 

Common sense tells me that in high compression engines with stock cams in place, if one or the other head choice pings more I can extrapolate that the pinging champ is not the one I want to use as the foundation for the engine I'm going to build up and put through the wringer or even use for a performance street engine. I'd assume I'd be able to run more advance and leaner stoichiometry on a street engine and get better mpg (with equivilant performance as the other head choice) if I excluded the foundation from "the engine that ping built."

 

Another misguided notion is that experience from an L4 Nissan doesn't directly correlate to an L6 with equivilant parameters but differing by two cylinders in length, or that 2-cycle, open vs closed-chamber head experience has no bearing. (Hey, I'm talking about my CAR here, not some WEED-WHACKER!).

 

My intent was to teach a newbie the value of reasoning for himself the options instead of accepting rubber-stamp formulas; that time didn't stand still when Nissan stopped offerring the N42 head. DAW

 

 

 

 

 

 

 

 

to achieve equivilant performance but better mpg

 

A basic premi

[JMortensen]

Here I was thinking I was done....

 

If you look at some of the links that I listed and that last one that DAW put up, you'll see that there is an almost universal combustion chamber shape for 2 valve heads. Looks like a heart shape, my 510 buddies always called them the "peanut" chambers. I have seen some heads from the worst of the smog years like the later E88 and the N42/47 that didn't use that shape, but engines made at that time were also some of the lowest output engines in recent history. That's the truth, regardless of what head you used to build your race engine. What's also true is that you can make as much power with the open chamber shape. You can machine your pistons for quench, and they'll end up making that peanut shape in the top of the piston instead of the head. But for those not machining pistons you'll be better off starting with the best chamber shape.

 

My point is and has been that this peanut shape is damn near UNIVERSAL. So when Tim and Dan say that I have no proof because it hasn't been tried on an L series, or the P head in particular, to me that is just like saying (as I mentioned in a previous post) that I hadn't tried upping the compression in my engine, but I did and voila!!! More power!!! You don't need to prove that upping compression is going to increase the power, and likewise quench has been similarly proven. Dan's argument was that you can't quantify the quench, and I think that this is probably an untrue statement, but I don't have any proof that you can, at least not that Dan would accept.

 

This thread has degenerated really badly (first time I've been called a liar), posts here are mostly better than this one unless you're in the Non-Tech Board arguing politics.

 

Do your own research. Don't listen to me, or DAW, and definitely don't listen to Dan or Tim...

[Dan Baldwin]

Another pitfall is looking at evidence re detonation tendency from engines with big cams.

 

Which is why I always include the experience I had with my engine at 10.35:1 CR with the STOCK cam. Still, data with a bigger cam IS pertinent to those who know how cam specs relate to allowable compression ratio.

 

Common sense tells me that in high compression engines with stock cams in place, if one or the other head choice pings more I can extrapolate that the pinging champ is not the one I want to use

 

Of course not. So if you HAVE had detonation problems using a particular head, I can totally understand your reluctance to use it and your advice to others against it. But of course if you see that others have used it at high-ish compression ratios without any problems, you should also realize that your bad experience isn't universal.

 

I'd assume I'd be able to run more advance and leaner stoichiometry on a street engine and get better mpg (with equivilant performance as the other head choice) if I excluded the foundation from "the engine that ping built."

 

With the stock cam, at well over 10:1 CR, I was running rich down low, lean up top, and ran normal (35deg all in) advance. On the street and on the track. With ambient temperatures as high as 95 degrees. Making good power with no pinging. Stock shaved N42 head.

 

My intent was to teach a newbie the value of reasoning for himself the options instead of accepting rubber-stamp formulas;

 

Nothing I can see is wrong with giving a newbie the two most obvious "rubber-stamp formulas" as options for an L6 build: 1) N42/N47 on flat-top bottom end, and 2) shaved P90/79 on flat-top bottom end. Which is what I did in my first post in this thread. Obviously he's going to do better if he can reason things out for himself, but I'm not presumptuous enough to think I can teach ANYONE "the value of reasoning" these days.

 

that time didn't stand still when Nissan stopped offerring the N42 head. DAW

 

Time might not have stood still, but performance sure did. From Zhome.com (I added 180 lb. and calculated estimated hp by HP = weight*(speed/234)^3 [oops, I incorrectly had .333 as the exponent, fixed now]):

 

'75 Z, N42, 81.7 in the 1/4, 2858 lb => ~129hp (avg. of 3 tests)

'78 Z, N47, 84 in the 1/4, 2780 lb => ~137hp

'79 ZX, N47, 82.5 in the 1/4, 2886 lb => ~134hp (avg. of 4 tests)

'82 ZX, P79, 82 in the 1/4, 2825 lb => ~129hp

 

I know those engines are at ~8.3:1 CR and we're talking about the 10:1 range, but if N-headed stock-cammed motors exhibit no ping at ~10:1 (plenty have been built that don't), I think the data is relevant (if not totally conclusive).

[Dan Baldwin]

I have seen some heads from the worst of the smog years like the later E88 and the N42/47 that didn't use that shape, but engines made at that time were also some of the lowest output engines in recent history.

 

The '72 E88 was an open-chamber head. I do know of one successful (i.e., repeat championship-winning) SCCA ITS 240Z that got pretty much equivalent performance out of the E31 (peanut shaped chambers) and the '72 E88 (open chambers), despite the E31 giving higher compression. Word was the E88 flowed enough better to make up the difference.

 

Dan's argument was that you can't quantify the quench, and I think that this is probably an untrue statement, but I don't have any proof that you can, at least not that Dan would accept.

 

Even if you CAN quantify it (there are a couple of schemes that come to my mind, relating chamber volume to quench area), but THAT isn't what is ultimately important. What IS ultimately important, is how high can you go with compression ratio before you run into pinging issues. I mean, that is the primary benefit of quench, right? My point is that there are plenty of flat-top L28s with stock-ish N42/N47 heads on them that are in the 10+:1 range. Pretty good. Could you go higher with a P79/P90? Perhaps. But no one seems to be doing it. Could be it is a practical matter. Perhaps it is just difficult to GET to a CR significantly over 10:1 with the large-chamber Pheads. I don't know.

 

There *are* some reports of pinging problems at around 10:1 with the N42/N47. It's entirely understandable that those with that experience would be inclined to steer others away, and toward the Phead route. I totally understand this. But my N42 experience has been positive, enough so that I believe it is worthy of consideration. It allows the possibility of a simple head swap with NO machining whatsoever, which should be an advantage to some.

[JMortensen]

The '72 E88 was an open-chamber head. I do know of one successful (i.e., repeat championship-winning) SCCA ITS 240Z that got pretty much equivalent performance out of the E31 (peanut shaped chambers) and the '72 E88 (open chambers), despite the E31 giving higher compression. Word was the E88 flowed enough better to make up the difference.

 

I would guess (and it is just a guess) that this has more to do with the exhaust valve size than anything else. Again we would have to have an impossible level of proof to say one way or the other. Could be that the E88 guy had .002 looser main bearings than the closest E31 guy, and the reduced friction in the bottom end made the difference. We don't even know the setup of the car vs his nearest E31 competitor. Racing is what you can put to the ground, not what the engine can produce. Plus neither of these engines is prone to pinging anyway, so the only thing missed out on in this situation is the compression and the tumble of the mixture due to quench. That very well may be made up for by the exhaust valve size.

 

Maybe it was the same engine with two different heads in the above example. Doesn't really matter. The valve sizes being different is a pretty big disparity. BTW--I have one of those open chamber E88s. If you want to buy a "race proven" head, just let me know.

 

So again, no real significance in that one...

[Dan Baldwin]

I would guess (and it is just a guess) that this has more to do with the exhaust valve size than anything else.

 

Nope, same size valves on E31, '71 E88, '72 E88, and '73 E88. The bigger exhaust valve came with the '74 260Z E88 head.

 

Could be that the E88 guy had .002 looser main bearings than the closest E31 guy, and the reduced friction in the bottom end made the difference. We don't even know the setup of the car vs his nearest E31 competitor.

 

I'm talking within the same team, same engine builder.

 

So again, no real significance in that one...

 

Exactly, no significant difference in power outputs between an L24 open chamber head vs. L24 closed chamber head.

[JMortensen]

Exactly, no significant difference in power outputs between an L24 open chamber head vs. L24 closed chamber head.

 

At that compression ratio...

[Dan Baldwin]

 

At that compression ratio...

 

Right. I think 9.4:1 is the ITS limit, probably easy enough to get with the E31, don't know how close they got to it with the E88.

[katman]

The spec line for an ITS 240Z says 9.5:1 is the legal limit, and the engines in question were both at the legal limit.

[JMortensen]

Nevermind. Same compression ratio, same valve size, no pinging, same power output. I'd still think that the E88 might have had an advantage in the combustion chamber shape, especially with the effect of the overlap due to the big sharp ridge between the valve seats that I spent hours getting rid of on my E31 (mine was 1/4" tall in some spots). The E88 I have is perfectly flat there, so the overlap would be a lot more effective.

 

Maybe the quench in the E31 made up for that. All hypotheticals.

[Dan Baldwin]

Thanks, katman!

 

Nevermind. Same compression ratio, same valve size, no pinging, same power output. I'd still think that the E88 might have had an advantage in the combustion chamber shape,

 

IOW, whatever inherent quench advantages there are to the general peanut shape can be overcome by other chamber design parameters.

 

especially with the effect of the overlap due to the big sharp ridge between the valve seats that I spent hours getting rid of on my E31 (mine was 1/4" tall in some spots). The E88 I have is perfectly flat there, so the overlap would be a lot more effective.

Maybe the quench in the E31 made up for that.

All hypotheticals.

 

Exactly.

[JMortensen]

IOW, whatever inherent quench advantages there are to the general peanut shape can be overcome by other chamber design parameters.

 

Damn dude, you are one pig-headed SOB. Just like me...

 

The P heads have the best combo of these qualities. Peanut chamber, flat "deck" where the valves are, and a much smoother transition between the seats and the rest of the chamber. Just like the FIA heads

 

IIRC the N heads have a crappier casting like my E31. Looking at the link below, that is definitely the case.

 

But the casting issue and the small valves are the reasons why I was saying before that I wouldn't have sunk all that money into the E31 if I had known about the P head shaving thing when I built my engine. I spent lots of time fixing the crappy casting in the chamber, and then more time unshrouding the valves.

 

Just take a look at the chamber shape and tell me that it's not better than your N head was before any modifications in terms of sharp edges and blending the seats into the chamber. http://geocities.com/zgarage2001/head.html If you can honestly tell me that you think your chamber was equivalent to that stock P head from the factory then I give up.

[DAW]

I consider the E31 and '71 E88 heads to be in the open-chamber head category. When I refer to closed-chamber heads I'm referring to heads that are flat and except for a discrete combustion chamber (i.e., peanut-shaped, or heart-shaped chambers). In the L4 heads this includes the SSS heads and W53/W58 heads, while the U67 heads are strikingly similar to the N-series L28 heads. The N47 Maxima L24E head is closed-chamber while the N47 280Z head is not.

 

I think people should go with what works for them. I've offered my favorable experience with closed-chamber L4 and L6 heads vs my experience with the L4 and L6 open-chamber heads because I feel it's my civic duty to do so. It's really not to my advantage from an economical standpoint because it means a poorer selection in the JY of W53, W58, P79, P90 and Maxima N47 heads. I have a lot of E31 and '71 E88 heads I acquired when I thought that was the hot ticket and I'd use them if I needed a class-rules engine but otherwise I would definitely use the L24E N47 as first choice in an engine of 2.4 to 2.8 L displacement regardless of f.i. or carbs., but that's just me. DAW

[Guest raddoc]

Speaking up for this noob who quietly lurks here...

 

Briefly, I have been restoring 240s for awhile, and have recently gotten interested in the whole modification thing. While restoration certainly is challenging from a procurement/historical perspective, I enjoy hearing the innovation and original thinking that goes into performance-enhancing Zs, and have really enjoyed the previous discussion (BTW, the flaming was not that bad from an objective viewpoint...)

 

Here's what I think I have learned. Is this accurate?

E31 head from 1970-1971--high stock CR. Good to transplant onto higher displacement engines.

 

N42 head from the 280zx Appears to be a great candidate for NA-related engine modifications. Not sure if it's better than E31. Anecdotally has tendency to detonate at high CR vs. modified P90.

 

P90 head from the 280zx--appears to be the best candidate for an EFI-related engine modification.

 

Is the P90 the better option for Turbo applications?

 

Biggest difference in opinion is N42 vs. P90.

 

Best block--F54 from the 280zx.

 

Questions:

1) Where can I get info on how much modification is allowed for SCCA-sanctioned racing? Went to their website and could only find info re: Pro-level racing late-model cars.

2) Has anyone used these heads with an over-bored L28 to 3.1?

3) I have done a search on "quench," and found it referenced, but without a good definition. Can someone help me out?

4) What are folks thoughts about P90A heads?

 

Thanks for taking the time, folks. I appreciate it.

 

Regards,

Steve

[gramercyjam]

When it comes to SCCA racing, it is best to have a current rule book in hand. Building a car with out a rule book can land you in a class where the car is hopelessly outclassed.

 

What kind of SCCA activites are you thinking about? Solo I, Solo II (autocross)?

[Dan Baldwin]

E31 head from 1970-1971--high stock CR. Good to transplant onto higher displacement engines.

 

I don't think anyone's arguing for that head as a first choice for a 2.8+ engine. It has the smaller intake and exhaust valves, and I believe is prone to cracking between the valve seats(?). But if you have one on ya that's one less expense I guess. Good results have apparently been had...

 

N42 head from the 280zx Appears to be a great candidate for NA-related engine modifications. Not sure if it's better than E31. Anecdotally has tendency to detonate at high CR vs. modified P90.

 

This would be one of my choices for a 2.8+ NA engine. Mine never had a ping problem at 10.35+:1, with stock cam, on pump gas. Plenty have run at 9.8:1 CR with no problems. But some have reported pinging issues in that CR range.

 

P90 head from the 280zx--appears to be the best candidate for an EFI-related engine modification.

 

This would be another of my choices, but I don't think EFI has anything to do with it. The N-heads are also notched as they came on fuel injected motors as well.

 

Is the P90 the better option for Turbo applications?

 

Probably, as the chambers are much bigger, so it's easy to build to low CR levels, depending on what boost you want to run. Good results have been had with other heads on turbos as well, though.

 

Biggest difference in opinion is N42 vs. P90.

 

see above posts

 

And note that the difference of opinion boils down to one side saying "There's likely not that huge a difference in performance potential and none has been conclusively demonstrated either way", and the other side saying "The P heads are inherently and obviously FAR superior!"

 

Best block--F54 from the 280zx.

 

Not necessarily... I've heard it argued both ways which L28 block is "stronger", but for an NA build there's probably nothing between them. Of course the NA F54 total bottom end (block, crank, rods) is preferred as it has flat-top pistons where earlier 2.8 liters had dished pistons. Dished piston bottom end NFG for NA performance.

 

Questions:

1) Where can I get info on how much modification is allowed for SCCA-sanctioned racing? Went to their website and could only find info re: Pro-level racing late-model cars.

2) Has anyone used these heads with an over-bored L28 to 3.1?

3) I have done a search on "quench," and found it referenced, but without a good definition. Can someone help me out?

4) What are folks thoughts about P90A heads?

 

1) Join SCCA and get a copy of the General Competition Rules (GCR), or get ahold of a copy from a member. Also, this forum and the IZCC (Internet Z-Car Club) mailing list, as well as the 240Z (http://www.240z.org) list are all great resources. In road-racing, you've got ITS and EP. ITS allows next to no mods. EP allows tons o' mods. Either way I hope you're rich! And SMART. You might consider just doing track days and/or autoX for a while (if you're a wuss like me...).

 

2) N42 head on my 3.1 (Sunbelt ported and cammed)

 

3) I don't know much if any more than you, but the idea is to have a large area on the head that comes very close to the top of the piston (~.035" - .055") at TDC. Puts all of the charge in a tight chamber underneath the spark plug. Broader, thinner combustion volumes are more likely to experience spontaneous ignition away from the spark plug, aka detonation or "pinging". This kills power and is bad for the engine. That's about the extent of my understanding of it. Specifically regarding L6 heads, I can speak for myself and a number of others who haven't had these problems with the "no-quench" N42 or N47 heads at and well above 10:1 CR. Others have reported problems. Practically speaking, you only have so many heads to work with on the L6. None of them is ideal for a high-performance application. In the end you have to makes your best-informed choice and takes your chances:)

 

4) A lot of folks are turned off by the hydraulic lifters claiming they bleed down at high rpm, but I've seen dyno results with a P90A on a 3.1 making power up to 7300 rpm. Probably not nearly the practical performance build-up knowledge base on the P90A as the non-hydraulic heads, though.

 

Have fun!