Dan Baldwin

Going into Iraq was a hopelessly retarded endeavour. Justification for it was total BULLSHIT. I take no solace in the fact that the administration's hopelessly naive schemes haven't profited them (and CERTAINLY not US) *nearly* as much as they thought it would. It just sucks all the way around, for everybody. These guys are irresponsible ASSHOLES. Kerry may not get my vote [hell, he KNEW Bush was a flake and STILL voted to give him authority to go to into a needless, COSTLY (in human and $$ terms), and totally counterproductive war], but the Bush administration is clearly a bunch of satanic IDIOTS that should be removed. OBL must not be able to fricking BELIEVE it! We spend a relatively meager effort going after him, then spend 100s of BILLIONS making asses out of ourselves in the aftermath of getting rid of someone he probably hates as much as us! The terrorists have evil geniuses, and we have evil retards. Dang. Vote Libertarian!

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... 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. 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. 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. 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!" 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. 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!

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

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.

Nope, same size valves on E31, '71 E88, '72 E88, and '73 E88. The bigger exhaust valve came with the '74 260Z E88 head. I'm talking within the same team, same engine builder. Exactly, no significant difference in power outputs between an L24 open chamber head vs. L24 closed chamber head.

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. 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.

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. 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. 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. 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. 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).

You couldn't afford me, anyway What, putting a shaved Phead on a flat-top motor? Of course it'll work. 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. 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.

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

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

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

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,

Is it just me, or does "strong" equate with "irresponsible, impractical, and totally counterproductive" these days? An administration "strong" on terrorism would've been on top of OBL BEFORE 9/11. And wouldn't have spent/be spending IMMENSE resources fighting a war against what was a NONTHREAT to us (contrast with the comparitavely MEAGER effort against those who actually attacked us, letting them GET AWAY!). All I have to say to those who laud the administrations efforts against "terror" is, WTF?! These guys [the current administration] are immoral, hegemonic IDIOTS.

Check out my first response in this thread, I didn't start it You've given as much denigration as you've taken, DAW, callin' me a flat-earther and all (see "stroker experts" thread: http://hybridz.org/nuke/index.php?name=PNphpBB2&file=viewtopic&t=36580&start=0 ). I been denigrated! Whom EXACTLY are you talkin' about here? When and if I feel I have something to contribute, I contribute. I do admit this particular post is mostly "wasting everyone's time", though...

Take my jetting recommendations with a HUGE grain of salt. Just giving you the first guesses *I* would try, and I am NO expert! Aux. or "booster" venturi size doesn't directly affect power potential and main jetting like main venturi size does. The main venturi size is the total cross-sectional area a cylinder is breathing through, so it directly affects flow velocity: larger => less velocity => less vacuum signal => bigger jets required. It's gonna be kinda tough to get consistent reliable data with a GTech. Best bet is to be good at predicting what you'll need jettingwise and go to the dyno, prepared to swap 'em out quickly between runs. Regarding advance, I was wondering if you had torque curves vs. ignition advance. Better to compare curves against each other than absolute peak torque and hp. My approach is to go with the LEAST ignition advance that doesn't hurt the torque curve in the desired range of operation (for me, 4k-7k) to give some leeway for a tankful of lower-octane fuel. It sounds like you might have done the opposite, going with the MOST advance that didn't hurt you. Agree w/ jmort , 23 initial/43.5 all-in seems very high. Which would seem to imply that compression ratio isn't too high for the fuel you're using (oh yeah, race gas). FWIW, race gas required an additional 4deg advance over pump 93-octane (38deg vs. 34deg) when I tried 'em both the same day at the dyno. And I got similar results over ~6deg range on pump fuel, which means I *might* have seen as much as ~44 not hurting my power on race gas. Which may or may not mean something regarding your setup...

I was thinking more of how you'd get a P90 headed street/track motor with stock pistons up to 11:1. Could be a problem to get more than 10:1 with flat pistons? That might explain why I never hear of them.

The stroker crank increases popup only 2mm, HALF of 4mm. So if the pistons are shaved 2mm, that puts you right back at stock piston height at TDC. Oh yeah, since Norm uses L28 rods, not L24 rods, his r/s is 1.57, even "worse" than mine. Maybe I take that back about trying the 140mm rods if they fit the L28 block... Ah, I might or might not, it remains something I'm not terribly concerned about. Like with the head, I'd just use what was available, what could be most easily put together. Compression ratio isn't the same type of property as quench, compression ratio can be CALCULATED. Total cylinder volume at BDC divided by volume at TDC. You have a NUMBER, a quantity that can be compared. I think that "quench" is a more illusive property, it's not like you can absolutely quantify it. I'm also wondering, how hard would it be to get a P90 head L28 or L31 to 11:1 CR? I'm thinking you might have to use custom pistons with reliefs for valve clearance and popups that protrude up into the chamber shape to get there. Which might explain why I never hear of any particularly high-compression P90 engines, I don't think pistons like that for the L-series are exactly readily available. Also, there's got to be a point of diminishing returns, as such a convoluted combustion chamber shape would begin to work against maximizing compression ratio. Just pondering...

Nothing like those theories, which can be considered "proven" much more so than phead superiority. By observations and EXPERIMENTAL DATA. Norm's setup is LD28 crank, L28 rods, L28 pistons shaved 2mm (putting 'em right back down at deck level), and 2 head gaskets. Or was that 2mm gasket (I don't think so, he'd NEVER spend that kinda money if he didn't absolutely have to!). Bigger rod ratio has been shown in some cases to improve performance *slightly*. In OTHER cases, SHORTER r/s ratios have been shown to improve performance *slightly*. Such performance differences *could* be as much a function of how "happy" the cam is with the piston speed near bdc and tdc. IOW, it *could* be that a cam developed for a 1.6 r/s ratio doesn't work as well with a 1.8 r/s ratio and vice versa, and that might have as much to do with actual performance gain or loss. There is FOR SURE reduced side load and associated piston thrust with greater r/s. Also reduced peak piston acceleration. There is improved angularity/leverage through max cylinder pressure with shorter r/s. 1.60 is definitely the LOW end of what's normally seen. Would I try 140mm rods if I could fit 'em in the L28? Sure. It's mainly the LD28 block I'm railing against there. From what I've read and my own calculations, I don't believe the difference between 1.60 and 1.80 to be huge, but sure, if I could practically do it I'd have used 140mm rods. I'm an engineer (big surprise I know), and I too speculate and USUALLY come out right. But there's just WAY too much subtle invisible stuff going on with combustion chamber design to KNOW just by LOOKING. Looking at a Golf II and a 928, my intuition would tell me the 928 is more aerodynamic. But it's NOT. Regarding the Kameari chain tensioner setup, I too had temporary wood. BUT having thought about it, I don't know if it's such a great idea. Consider that you ALWAYS see curved guides for chains. They prevent the chain from TWANGING like a GEEtahr string. I bet with the Kameari setup you have to apply a TON of tension to prevent serious TWANGAGE. Stock setup doesn't require much tension, as the chain pretty much can't move laterally due to the guide on one side. I'll stick with stock for now... KEE-rist don't go on about how I'm spending $millions vs. your budget build. If I wanted to be an engine builder that's what I would be. Truth is, my setup isn't all that inherently high-dollar anyway, I've just paid proven qualified labor to do a lot of the work. Note: the headwork was done by a shop that has DEVELOPED L6 engines. As in build, dyno, tune, dyno, mod, dyno, tune, dyno, mod, dyno, etc. Upping compression as much as possible before getting detonation is a known and well-proven power-builder. So is upping displacement. Upping r/s ratio to maximize performance is a DIFFERENT proposition. You won't get any indication you've gone too far, like with compression ratio. That said, I don't know if you CAN go too far within an L28 block, but I hope you see my point. If you could go with 280mm rods practically, do you think performance would improve? I think it would be reduced. Look at cylinder pressure vs crank angle, vs rod/crank throw angle. ENOUGH, good night!

And I never suggested that. BOW DOWN BEFORE ME. BOW or receive my WRATH. (for the million and ONEth time) I totally agree that I don't know. Point is, YOU don't know that they DO provide any benefit. You think YOU could get done in fairly short order. To a lot of people that task would be a major undertaking. But the LD28 block idea is offered up as if it's the only logical way to go. Then when fitment is brought up, we get "oh yeah, well ANYbody can put a cowl induction hood on, or cut the hood and use the Nissan hood vent thingie, no big deal" (paraphrasing here). Man, if I had built up an LD28 block based on the advice I've seen here, and then run into having to butcher the hood or use a different hood entirely, or lower the engine, I'd be fricking FURIOUS. Norm is, I believe, at 11.2:1 with 2 Felpro head gaskets, and with 2mm filed off the top of his L28 pistons (done in situ!). I THINK that's his setup. Speakin' of which, how does THAT have "quench" (2 felpro gaskets = close to .100", tops of pistons approximately even with block deck)? Anyway, I'm not really meaning to suggest anyone do this. Ah more theoretical benefits! I can see why you *almost* didn't want to bring it up I can understand how a LOT of things are SUPPOSED to be good for power, but until it's proven out... I mean, you can't just LOOK at a port shape and KNOW how it flows, hotrodding history is crammed with stories of overporting (even some STOCK heads). I'm sure there's flow-bench data out there for the different L6 heads, so we probably have that, but ultimately it's gotta be real world results whether those ports are better. Theory is only ONE side of science. Theory without the support of experimental results remains, well, THEORY. Just because a head LOOKS higher performance doesn't make it so. That's the crux of my problem with people suggesting that the N42/N47 are detonation-prone crap and the P79/p90 are the ONLY way to go. I KNOW I don't know, you don't realize that YOU don't know either. That's the fundamental difference between our positions. The only valid way to develop and tune for performance is to QUANTIFY PERFORMANCE (engine dyno, chassis dyno, 1/4-mile runs, by whatever valid repeatable method), make a modification, QUANTIFY PERFORMANCE, modify, QUANTIFY, modify, QUANTIFY. That is SCIENCE. This will tell you what you're REALLY accomplishing. Saying "this should be better so it is better" is just conjecture, and shouldn't be presented as a demonstrated proven FACT.

Hey, WAIT a minute! I already let you pretty much get away scott-free with STEALING John's and Norm's astounding results from my side of the argument, although they use N42 heads. No way I'ma let you throw in your results with an E31 and say that's any kind of evidence of P-head superiority! NO WAY!!!!! Speakin' of which, if an N42 can be made to have the supposed "quench" characteristics you describe by machining it down the same amount you HAVE to machine the P90 down for an na ANYWAY, then I REALLY don't see how you can argue, from your quench premise, P-head superiority over N-heads in the first place! I've had all I can STANDS and I can't STANDS any more! Where's me spinach?! DAYUM I'm a sucker...

Let us suppose for a moment that you, God of Quench, are right, that quench is a binary type of property, you either have it or you don't, and that my engine does not have it. Consider: 215-220 rwlb-ft from 4700-6100rpm, and 255rwhp @ 6500, from a 11:1 CR 3.1 liter engine running on pump gas, tuned by ME, a RANK amateur. *If all the above is true*, I can only conclude that quench can't be all that important, PARTICULARLY for people asking about what they can do practically, easily, and cheaply to get some extree ponies (see original post). [note: if you get the subtlety of the above paragraph, you will recognize that it is not necessarily an argument against quench ] Looks to me like, with a stock gasket, your L28 flat-top/E31 CR *should* be ~least 10.2:1, or are you saying the GTech results were with dished pistons? anyway: Woohoo! I guess the clutch WAS slipping! I think GTech sez they typically read 3mph high, =>240 at the wheels. ASSUMING Gtech accuracy, AND assuming that is a good rwhp estimate. Looks impressive, particularly if it was with a 8.5:1 motor. Me neither! More Original build was ~$1700, then $1500 for the head modification and cam setup, $600 for carbs, that got me to 235rwhp. Rebuild last year was VERY expensive, mainly because I had the money and the engine was in Virginia, so I just paid $$$$ to have an experienced GT-2 L6 engine builder do EVERYTHING, including machining valve reliefs in the pistons and multiple mock-ups of the assembly to ensure clearance while maximizing CR. No doubt had I had the skeelz, shop space, equipment, and the time, I coulda saved a BUNDLE! FWIW, my motor could be built for WAY under $8k. I'm perfectly willing to tell what I've done, but I've never tried to say that's the only way. And *I'm* saying that in most cases (this post included) *I* think they're better off just plopping an unmodded N42 or N47 on a flattop bottom end. Most of these people don't have machine shops in their basements. Your advice is going to send them to the local speed shop (with only an *inkling* of an idea what they *think* they want), which is as likely as not going to butcher what was a decent cylinder head, while charging them outrageously. All for VERY little gain if any at all (depending on the shop, could be a BIG loss of both power and $$$). Agreed, there might be. I just don't think it's worth monkeying around with an LD28 block. No, but I might ask what you think your time is worth! I also have to question your methods a little, as you apparently don't dyno to see what you've lost or gained, and where. That said, I don't think your doing your own work and putting in the hours is any more wrong than my decision to pay those who already have TONS of experience with the L6 to do most of the work for me. I'll take the GTech results (with a grain of salt, of course!), but the above sentence can't be construed as any sort of evidence of engine performance, IN THE SLIGHTEST. First of all, 2 seconds is like an eternity, there's no telling what your motor being "in a really bad state of tune" REALLY means, he is " SUPPOSEDto have crazy hp"?! Not to mention the HUGE contribution of driver skill and car setup. There's just NO WAY to take your paragraph and make ANY kind of quantitative estimation of your hp relative to whatever "crazy hp" is! Not at all, I *KNOW* I'm not an authority. I just don't think you guys are either! Sheesh, I can understand your reluctance now that I've seen it! The last bit, anyway. I'd call the Buttonwillow "evidence" 1/100th assed! GTech evidence, maybe 2/3-assed. Maybe... Won't get into "butt dyno" reliability, but going from 8.5 => 11:1 should be worth quite a bit. I've never disputed this. My point remains that for just about all intents and purposes, if you wanna build a strong NA L6 the EASY way, flat-top bottom end + N42 or N47 head is pretty much the way to go. And if you wanna build a stroker, the basic LD28 crank, L28 block L24 rod, KA24 piston combination is easy and works pretty damn well, too. Now get to a fricking dyno, it ain't THAT expensive.

Wow, what a thread! I'll just add a coupla minor points: To the original poster, You HAVE 2wd. An open diff does drive both wheels. In fact, an open diff ENSURES that both wheels get EQUAL TORQUE! I have a video of my car doing a SMOKY 2-wheel burnout way back when it had the 3.36 open diff 8) Problem is that both wheels always getting equal torque isn't what you want, 'cuz as soon as one wheel loses traction, the wheel WITH traction is limited to the reduced torque level going to the spinning wheel. One wheel in the air or on ice and you'll just spin that wheel. Thrust at each contact will be limited to the traction at the wheel with the LEAST grip. Spin the inside tire in a turn, and you lose DRIVE. What's happening is that while the TORQUE at each wheel is equal, all the POWER is going to the spinning wheel (power = torque * rpm). Regarding "worn-out" clutch type LSDs, I'm still using mine after 8 years! Breakaway was ~18lb-ft when I installed it, and I've never shimmed it. Before I removed the rear sway bar it would spin the inside rear out of 2nd gear turns, but without the rear bar, no problems:) Even with NO preload you get clamping force from the ramps the pinion shafts are located in. As long as you can get *some* torque to the ground, you're generating clamping force. My setup ain't exactly optimal, BTW. I'm lifting the inside FRONT out of corners! Looks cool and impresses the hell out of observers, anyway

What total ignition advance did you end up with for max power? Do you have the curves to compare run to run at different advance levels? That could give us some insight as to whether your compression ratio is too high for the fuel your using, though if you're using race fuel you should be OK even at 11.5:1. Agreed you're probably *somewhere* between ~10.5:1 and 11.5:1, I suspect it's over 11:1 as I think they usually set up the valves to sit somewhat proud of the chamber (appears that way in my case). It'd be good if you can get cc volume. I think *most* 3.1 builds have the pistons above deck (unshaved KA pistons). My original build they were unshaved (.022" above deck). For the rebuild last year, they were shaved => .003-.004 below deck. LEngine builder is only a tool, doesn't really reflect real-world engine builds, I don't know of any 3.1 builds with -.37mm deck clearance (i.e., KA pistons shaved 1mm). And it's erroneous in it's CR estimation when you shave dished pistons (like the KAs). Doesn't account for the fact that your not removing as much material due to the dish. Just so you guys know. Carburetion: Can't offer you anything on accelerator pump jets or emulsion tubes. But judging from your lean condition 5000-6500, you clearly want bigger mains. And based on the rate at which it goes richer up top, I *think* you want to make a BIGGER jump with the air jets. I'd try going from 130/180 to maybe 135/190 or 140/195 or 200. Hopefully you know someone with a mess of Weber jets to try out on the dyno! You might try 36mm chokes and even BIGGER mains and air jets, maybe 150/210 (based on your current A/F and scaling up the guess to "correct" it by 36/34 squared). But I think you're ultimately going to want bigger carbs.

Jon, DAW, Show us what YOU'VE done. You guys have NO IDEA what you're talking about. I can't believe I have to repeat my basic points YET AGAIN. I should really shut up, as the more sophisticated forum members can clearly see the evidence and draw logical conclusions on their own. But you guys CONTINUE to actively mislead unsuspecting netizens down your misguided path of placing FAR too much emphasis on things you have NO REAL UNDERSTANDING of. Regarding "quench": To illustrate P-head superiority due to "quench", you have to provide evidence for at least TWO points: 1) That "quench" is absolutely critical to make power 2) That the P-heads inherently have or impart "quench", and that the N-heads inherently do not. You've provided indirect evidence for point #1, and I won't argue on a subject I know very little (probably just about as much as you) about. But you've provided no real evidence for point #2. If we assume for the moment that point #1 is true, I say that results indicate that "quench" can be had with the N-series heads, based on SOLID IRREFUTABLE EVIDENCE: A) 11:1 CR pump gas 255rwhp 3.1 liter 10:1 CR stock cam, totally stock head, pump gas 164 rwhp 2.8 liter C) 13.5:1 CR race gas 287rwhp 3.0 liter D) 11.2:1 CR pump gas 2.9 liter 240Z running 12.8x @ 107.x in the 1/4 (this engine *did* have detonation issues at 11.6:1 on pump gas, I must admit!) What conclusions do you draw from this evidence, regarding "quench"? I myself am not too worried about it, and only draw the conclusion that you can indeed run high compression ratios and make GOOD power with the N-series heads. But you continue to argue as if your SUPPOSITIONS on the subject are more important than real-world results! You are WRONG. jmortensen, mocking me : I NEVER SAID THIS. That was NEVER my argument. If we're going to have a civilized discussion you have GOT to quit misrepresenting/mischaracterizing what I've said. Regarding rod/stroke ratio: jmort again: DAMN, you continue to ACTIVELY ignore my point! I'll agree in a second that, theoretically, longer r/s ratio should be better due to slightly higher redline potential, reduced parasitic losses from piston side load. In the real world, there will always be a point of diminishing returns, though. Also, there IS improved rod/crank angle to be had with SHORTER r/s ratios. MY POINT on this issue is that the ACTUAL performance benefits of going from ~1.6 to ~1.8 r/s are most likely NEGLIGIBLE, and CERTAINLY not worth experimenting with trying to fit a taller, heavier, higher-c.g. LD28 block into a Z. In Formula 1, I believe they're over 2:1, r/s. BUT, they can design from a clean sheet of paper, and they'd kill their mothers for another 50rpm up top! I am not too concerned about tens of rpm up top, and besides L6 redline is reportedly more a function of crank harmonics than absolute piston acceleration. Practical real-world results TRUMP the theoretical ramblings of non-experts every single time. You guys don't have JACK. NOW BOW DOWN AND WORSHIP ME

M Coupe, great mix INDEED! I love the IDEA of a Z wagon, but the execution looks a bit awkward. The Z 2+2 should've gone in that direction, though! More like the M Coupe, MGB GT, P1800ES. Ah, what might have been...