Dan Baldwin

How much power are you making now? How much power do you want/need? If you do go turbo, FI is the only way to go.

Ditto John on the 1 5/8 primaries Nismo header. Don't get me started on N42 vs. P79/P90... long-short: The quickest, fastest, most powerful NA L6 engines I know of all have N42 heads. NOT saying the N42 head is better at all, just that I have seen ZERO evidence that the P-heads are inherently superior. I have read/heard a lot of talk about how the P-heads chambers *LOOK* "better" for performance I wouldn't hesitate to use either the N42 or P90, personally.

A few potential negatives: Looks heavy. Included valve angle quite large. Chambers look to be huge, pop-up pistons likely required for decent C.R. not good for the shape of the combustion chamber. Are the intake and exhaust valves really the same size? I honestly wouldn't bother with it if it were available to me. Still, it would be cool if somebody *does* get it working!

Check the springs for the mechanical advance weights. I bet you're missing one or both of them.

Looks a lot better than the VQ35 intake. What's wrong with an LS1, anyhoo? Well over 300rwhp STOCK! And undoubtedly MUCH lighter than this gargantuan Nissan motor. I'd rather have the LS1 under the hood of my Z.

zredbaron, I got the high rpm numbers from one of zbear's posts. I don't plan on running mine that high. 7500 would be my absolute limit, and only for a limited time, like at the drags, or for a 3-lap time trial run.

Red Baron, The vent tube on top of the cam cover isn't meant to see manifold vacuum, just filtered ambient-pressure air. Stock goes to the air filter, if you don't mind drilling a hole you could run it to one of your filters. I'm just using the itty-bitty K&N. It's the tube in the side of the crank that wants to see vacuum. I'm currently running that to a PCV valve to a balance tube setup on top of the manifold runners. I might try something goofy like eliminating the intake runner balance setup and have a PCV valve for each runner to a vacuum canister, from there to the crankcase and brake booster. I'm running a fuel return line. Sould help keep the fuel a lot cooler. I have no heat shield between the header and the carbs, never have any vapor lock issues. Billyzbear, I don't think Zredbaron was really trying to be harsh on ya. John, on the other hand... Just kidding, it's one big love-fest here at hybridZ. Just don't take anything personally. I've got the Sunbelt setup as well, one spring per valve. I limit at 7200, but the valvetrain should be good for a lot more, at least 7500. You really run to 8500+?! I'm not that brave. I don't think my bottom end is good for any more than 7500, max, and I don't see myself going that high with a stock diesel crank and 240 rods.

Are you consistently losing coolant? What do the plugs look like? If you're just getting little oil slicks in the coolant, but no coolant in the oil, you might try just retorquing the cylinder head. A few years back I got the same symptoms, and this fixed it, believe it or not. Certainly worth a shot...

I've got 165 mains and 190 air jets. Still have a big rich spot in the midrange, very localized around 4500rpm, I suspect reversion. Up top it's a little lean. Anyway, should be a good starting point.

Here's a search on his username: http://hybridz.org/nuke/index.php?name=PNphpBB2&file=search&search_author=norm%5BT12SDSUD%5D Norm's results for a NA, pump-fuelled, SU-carbed L28 are, shall we say, atypical. Norm driving the car is probably worth .5sec, 1-2mph. Having Norm tune the car is probably worth a like amount. Figure his basic setup in the hands of your average competent driver/tuner would be in the mid-high 13s at ~105. Norm's basic setup: L28, LD28 crank, shaved L28 pistons, shaved ported N42 head, ~10.6:1 CR(?), modded bored SU carbs, custom tranny ratios, etc. etc... Maybe he'll pipe in with more specifics.

With a good cam and headwork, you could conceivably get to 100 crank hp/liter even at at pump fuel friendly CR levels. I'm almost there (255 rwhp, 3.1 liters, maybe 95 crank hp/liter?) myself. 12sec Norm is close as well, at 107.x mph in the 1/4. John Coffey is most definitely there, at 13.5:1 cr using race fuel. My engine is a 3x2 carbureted 3.1 liter, shaved/notched KA24 pistons, LD28 crank; Norm's is a modified SU carb 2.9 liter, shaved L28 pistons, LD28 crank; John's is a fuel injected 3.0 liter, forged pistons, L28 crank. Your proposed setup won't work, as even with .5mm shaved off, the pistons will be ~1.5mm above the deck. Even with a 2mm gasket, that leaves only ~.020" piston/head clearance. I'm not sure how much Norm had to shave off his L28 pistons, on the order of 1.5-2.0mm I think. You can get there with or without the LD28 crank. 5% is 5%, though, IMO you may as well get it. You then can overbore from 3mm to 4mm over and use KA pistons, if you're not going too wild on CR. I would guess that at somewhere around 12-12.5:1 you'd want to go forged. I believe LD28 cranks are going for ~$250 these days. I bet you can build an engine like mine for ~$6000. John's into 5 figures I'm pretty sure. Norm probably only spent 50 cents on his engine As far as "old-tech", dohc multivalve isn't much newer tech than SOHC 2 valve. Also, if you're unlimited as to what mods you can make, turbo or v8 will beat the absolute crap out of NA L6 in terms of power/engine weight (which is really more important for performance than power/displacement). But going either of those routes you won't get nearly the stunned respect of the big-inch or turboed machinery you beat the crap out of at the track with an NA L6!

SUs on a 3.1 makes a KILLER street motor. I drove mine that way for years, LOVED it. Mash throttle and GO. At the track it hit a wall at ~5500. A hotter cam pushed the wall up to ~6000, and going to 2" SUs moved it up to maybe 6500, in my case. Going to triples totally eliminated the wall, and peak power is at 6500 now. Still makes good torque at the7000 rpm rev limiter. Long-short, I would highly recommend a 3.1 with SUs, then you can build it up for track usage if you like, or not. IMO, the added cost of a diesel crank and KA pistons ($40/ea from Lynchburg Nissan, ask for Riley) isn't that big a deal if you're rebuilding anyway. DO IT.

I wasn't trying to say that a stock-type radiator is all anyone needs, or that more rows in a copper radiator is better than flat tubes in an aluminum radiator. That's why I said "FWIW"! Just a data point. I know a good aluminum radiator would be lighter/better, but it might be good info for some that it's not required at or below my power level.

You guys are all nuts (but you knew that)! The idea of restricting the flow of the radiator to increase the amount of time the coolant is in there seems misguided. If it's spending more time in the radiator getting cooler, it's also spending more time in the ENGINE getting hotter! Also, the faster the fluid flow, the greater the convection, in the engine and in the radiator. As for 16x the pressure theory, with half the tube area, and twice the length, wouldn't that be 4X? FWIW, I'm using a parts store 3-row 260Z radiator, stock plastic fan, no ducting. No problems!

Be aware that going to the larger 15/16" m.c. will increase the effort required at the pedal for a given level of braking by 15%. I put the 7/8" MC back in my car, I could feel the firewall flex under the pedal effort required at the track with the ZX m.c. I do have smallish (stock z and ZX) brakes, though.

Sorta ditto what Jon said. There are people (Norm, Scott Bruning, Sunbelt) who can make killer hp with SUs. Then there's the rest of us. I too put off 3x2s to the very end (actually a good policy, imo, do the rest FIRST). They far exceeded my expectations. On the track, the Sunbelt headwork and cam was next to worthless without the triples. Prior to the head and cam, with 2" SUs and a Schneider grind I got 190 lb-ft and 180hp. After the headwork and prior to 3x2s, the engine still didn't want to pull hard up top at the track, and the midrange was now suffering. No good at all. Installed used triples (had been run on a 3.1 liter in Japan) Thursday, went to the dyno Friday and put down 235 to the wheels at 6500 rpm. At the track that Sat/Sun the car was fundamentally transformed above 5500rpm. WHEEEEEEEE! I would bet that the headwork without the carbs might've gotten me 10-15hp, and I'd bet the carbs without the headwork might've gotten me a 15-20hp. The two together, though, gave 55hp!

Part of the quote you attribute to me is from John. Don't *totally* agree with the part about reciprocating mass affecting throttle response more than carburation or injection. If the carburetion or FI are spot on, throttle response will be good, even if you have large rotational inertia (not the same thing as reciprocating mass, but what I *think* John *means*). Poor carburetion or FI setup and throttle response will suck, even with a formula 1 engine. Back to the main topic: If you can afford it, and are eager to learn how to tune fuel injection, you should go for it. Carbs are a big compromise. I went with them cuz they were (relatively) cheap, and I didn't have time to figure out FI. I installed the carbs on Thursday, was at the dyno of Friday, and at the track on Sat/Sunday, where the ~30 hp gain was partly responsible for me beating 2nd and 3rd in my class by less than a tenth of a second! The only car faster than the three of us that day was a Formula Ford:) My hp curve sucks, though, and parts are in Japan. I can't just program in a different fuel map.

Jon, Sunbelt did the cam setup, they didn't reuse the Schneider stuff. It only now, two years later, occurs to me I should've asked for it BACK, they still have it (or threw it out). When I was running the Schneider kit, I didn't machine anything, just replaced the stock stuff with their stuff. The Schneider cam card listed 0-lash lift as .503", not .490". Weird if they have two L6 cams that close together, huh? One note about Schneider cams, my first one wiped out a lobe just over a year after I bought it. They were great about it and sent me a new one after they got mine back. I checked the dribble holes on the new one, and lo and behold one of them wasn't *quite* drilled all the way through! I only barely caught it. I blew compressed air in to see if it came out at all the dribble holes, which it did, but the air coming out of that one hole felt like just a *tiny* bit less than the others. I'm sure that's what happened to the one lobe that got wiped out on the first cam from them. When using the internally oiled cam, check each dribble hole! Sunbelt set it up for internal and spray-bar oiling, btw. I *think* lift should be as good or a better indicator of whether reliefs are needed, but either way it should be mocked up and the clearances (of intake AND exhaust valves!) checked. When I took the head off and sent it to sunbelt, there were very slight dings from the intake valves on the tops of the pistons. From the .503" cam, and a couple of stuck throttle overrevs to 8k(!). So I guess I'd say .490 is probably getting in the neighborhood of where it needs to be checked for sure.

Valve reliefs are required for .550" lift! When I first installed the Sunbelt cammed head, I ran the cam a little retarded to get decent intake valve clearance (.040"), which I checked with a lump of clay. Unfortunately I didn't check the exhaust side. A year later when the motor had to get rebuilt, we found deep dings (~.080") on each piston from the exhaust valves! That was with a 2mm gasket. Abacus Racing did the rebuild, and did the valve reliefs in the new pistons. Chuck at Abacus is GREAT, very conscientious, and experienced in building serious (GT2) L-series race motors. He checked all the clearances and mocked up the assembly a few times to get close to the CR I wanted. VERY tight, even with the reliefs.

Mark, Regarding fuel injection, you *could* open up your wallet and go with 3x2 50mm throttle bodies and have all of the sound and fury of triple carbs. But since you already have the 40s, as you say, that's surely a good place to start. I'd try 36mm venturis. You'll have to experiment with your own particular setup. For 40mm carbs, a W.A.G. would be ~145 mains, ~160 air jets. Emulsion tubes, I dunno... My carb setup is very crude, nowhere near optimized, though it probably is giving pretty close to as much peak hp as I can expect. The big dip is killing the midrange, though. And it won't pull clean on the dyno below ~3000. I've got work to do... Jon, I did run the stock cam for years, with something over 10.2:1 CR (depending on how much the head had been shaved), sometimes inadvertently running over 40 degrees of advance! The only times I got pinging was when I tried to continue running 18 degrees static advance after the initial 3.1 build (which had me at ~43 total, STUPID!), and when one of my advance springs disappeared I got run-on pretty bad. I have no preconceived notions that any head is better than any other, at a given level of CR and with the same size valves. Nor do I know how high you can go with the CR for the different heads. The data just isn't out there for comparison (at least I haven't found it). All I have are a very few data points, from which only limited conclusions can be drawn. One of which is: "The N42 and the N47 are probably at least OK cylinder heads". Another one is: "Most likely, so are the P90 and P79".

Jon, I don't think I'm undercarbed, I'm only saying that Mark, for his purposes, *would* be with 40s. The dyno chart you're referring to was done with stock 240Z points, as the 280Z (280ZX?) distributor module failed on me the day before I went to the dyno! I blame Bobby. The Pertronix runs are clean up to the rev-limiter (currently 7200, old run limited to 7000 here: http://www.classiczcars.com/photopost/showphoto.php?photo=2274&size=big&password=&sort=7&thecat=500 ) Not an issue for Mark if he's going crank-triggered, just clarifying my results. I never said I don't believe in the importance of "quench". What I don't believe is that the E31, P79, P90 chambers are much much better than the N42/N47 chambers just because they *look* like they should have "better quench". I'm running 11:1 on 93 pump, at 34 degrees max advance. It made the same power on the dyno at 38 degrees, I'm conservatively running it at the least advance I can without losing power. My conclusion: I don't *think* I'm giving away much if any CR by using the *supposedly* detonation-prone N42. FWIW, my KA pistons were shaved flat and valve reliefs were machined in them, 2.7cc worth (maybe .050-.080" deep?). This was done at Abacus for the rebuild done last Winter/Spring. Pistons are .003 - .004" below deck. The head was shaved .010" by Sunbelt, and they said it had been shaved before. No idea how much, but it is still definitely an "open chamber" head. Head cc is 40.6. Some of the volume reduction compared to stock is due to Sunbelt running the valves a little proud in the chamber. Head gasket is .046". I would never say the N42 is superior, I have no basis. I just don't think anyone else has any basis for saying the P-heads are superior. When/if evidence is presented, we'll ALL know more. Until then, I think my, John's and Norm's results at the very least show that the N42 shouldn't be ruled out for serious performance applications.

Ditto what JohnC said re Sunbelt. My cam from Sunbelt is something like .550"/305 or 310 duration. Those guys probably know more than anyone else about building up high-perf NA L-series engines at the moment. That said, I do have a big torque dip at 4200 rpm. I dunno if this is strictly due to the cam though. It goes way rich at that rpm, looks like multiple carburetion. Extremely difficult to get parts for my Japanese OER carbs. I'm sure John's FI motor has no such issues. No regrets going somewhat big on the cam. I don't street race or fool around on the highway, and though the bottom end torque is ragged on the dyno, I just never drive the car that way (never full throttle below maybe 3500 rpm. The car is light enough and the displacement big enough that streetability is actually pretty good, since nothing over half throttle is called for. If you want the BEST, and you're fiddling with high octane anyway, I'd just go ahead with the full race compression ratio (~13.5:1?) and not bother with mixing with pump fuel. Cost of fuel is high, but why even bother with it at all if you're not going to take full advantage? For my application (I drive as far as ~500 miles to get to track events), I went with a CR of 11:1 to run on 93 pump. For what you SEEM to want, bigger carbs may be in order. My torque begins to drop off at ~6000, peak power is at ~6500, with 45mm carbs and 38 or 39mm chokes. Actually, you really want fuel injection. You should be able to get whatever CR you want with whatever head you go with. I.e., you don't need an E31 for high compression. The 2mm HKS head gasket can be modified by removing sheaves from it to tailor the CR. My engine's head gasket has two .33 thick layers and one .5 layer for a 1.17mm head gasket.

I bet 99% of engineers do know how to SPELL "metallurgy";) (ok, probably more like 80%) Best of luck and godspeed, but this doesn't seem to be realistic. Is it really possible to acquire two KA heads, cut them, jig and weld them together, machine the weldment, for $120? Aren't the bore spacings on the KA kinda goofy, like 96, 98, 96?