TimZ

SCE - you mean the copper gasket people, right? Do I take this to mean that SCE has a copper head gasket for the L-series? I did not know that. If this is a solid copper gasket, I'd be really surprised if it blew due to detonation - it ought to be pretty strong. I'd be more inclined to think that the problem could be more in the area of the mating surfaces not being perfectly flat - the metal gaskets are much less forgiving about that. Did you have the head and block checked for straightness? Were both surfaces (head and block) perfectly clean before you installed the gasket? The copper gasket ought to be reusable, too (you should confirm this with SCE first) - you might try reinstalling it with clean mating surfaces and the afore-mentioned copper gasket sealer applied to both sides.

BTW, if they did forget to stake the chain, I'd put up a really big fight if they try to charge you for the labor involved (pull radiator, all accessories, timing cover, etc.). This is a very well known and documented procedure, and there is no excuse for a professional shop screwing this up. Like Lockjaw said, if you've done this a few times, it can be done in an hour or so. I'm not sure what the flat rate is for this, but I would guess it's four hours or less.

DOH - That's right. forgot about zero...

The first guess was right - 1 = +3deg 2 = +6deg 3 = +9deg A = -3deg B = -6deg C = -9deg D = -12deg

Well, it's not much of an issue for manuals (like God intended ). I'm not a big expert on automatics, but I would have to guess that it has very much to do with the characteristics of the torque converter. Are they able to lock the converter for the dyno runs, maybe?

Bob Bondurant School of High Performance Driving...Great place to learn road racing skills. Bridgestone Winter Driving School...great compliment to the road race stuff, this course concentrates on low coefficient of friction driving - 1 mile course, 9 turns with changes in elevation, all snow and ice covered, top speed of around 70mph . Pro Rally style driving techniques (lots of driving sideways). Plus, it's in Steamboat Springs, CO. ASET Evaluator Training Course... this was a company-sponsered (not available to the public) course for training development engineers to correlate subjective driving impressions to objective measures.

You guys know that James is running an automatic, right? It's my understanding that it's not that uncommon for automatics to get funky results on inertia dynos - my guess is that they don't load the torque converter properly, and it slips more than it normally would. This could also explain the weirdness with the RPM calibration - the dyno was calculating RPM, based on what the wheelspeed was when the calibration was done at 3000 engine rpm. In fact, now that I'm thinking about it, it all makes sense - the engine pulled to 7000 on each run, but the wheelspeeds only equated to ~5000rpm, due to TC slippage.

It might be a good idea to be there during the training session...

Did you follow the bedding in procedure for your pads? This will make a big difference in how well the pads 'bite'. If you haven't done it yet, I'd do it ASAP. Also, some of this could be due to the stock proportioning valve - it's setup for a drum rear, so it is most likely not sending anywhere near enough pressure to the rear brakes.

Well, almost. 1 atmosphere is 14.7psi, 1 bar is 14.5 psi. Don't ask me why. The other thing is that often, when gauges display in bar, they are in units of absolute pressure, instead of relative pressure. Relative pressure is the pressure difference between atmospheric pressure (~14.7psia) and the manifold pressure. This is what 'boost' is measured in. 18 psi of boost means the manifold pressure is 18psi higher than atmospheric pressure, or ~14.7 + 18 = ~32.7psia. The easy way to tell which kind you have is that absolute pressure is always positive, so if your gauge reads a positive number at idle (say ~0.5), then it is reading absolute pressure. If it is a negative number (say -0.5), then it is relative.

As a couple of others have mentioned, the 2000gt came first, so actually, the Z was a 2000gt look-alike, not the other way around. ...And BTW, are we getting a little too sensitive to people having friendly disagreements? I didn't see anybody slamming Lockjaw for his opinion - I don't think that he needed anybody to come to his rescue here.

Pressure loss from a larger pipe? Why? I'll buy possibly a very slight increase in lag due to the larger system volume, but the 2.5" pipe should result in a lower pressure drop between the compressor outlet to the intake manifold.

Sorry Aaron, but I think you already answered your own question. There are way too many variables involved to say what the best postition is. Really - that is exactly why they make them adjustable. See the recent thread about what is the best head for Mikunis for more details. The only approach that I can recommend is to start with the sprocket at the stock setting, and start going 3 degrees in either direction, until you find the spot that works the best for you. Keep in mind that depending on what FI system you are using (especially if it's a speed-density setup like most of the aftermarket units use), you will very likely have to retune the fuel delivery each time you change the cam timing. Personally, I think that the people that sell the adjustable cam sprockets are a bit irresponsible, in that they don't point out how much work is involved in finding the right settings. They can be a very powerful tuning tool, but I would be willing to bet that 90% of the people that buy these don't have them set properly. It's bad enough with our single cam motors - I have to laugh every time I see some kid with a Honda with two adjustable sprokets and a fart can exhaust. Which sprocket did you get? Was it the Nissan comp one with the eight adjustment holes, or was it one of the vernier types (Unorthodox Racing, etc)?

That is a very nice piece of work. I think AFCO use to carry 180 degree headers - I only managed to find one reference in their online catalog, with little info. You might give them a call... http://www.afcoracing.com/

I agree - I was going to suggest that, but was in a hurry when I wrote the last response You will have a very difficult time finding a compressor that will flow enough to pressurize the intake manifold while the valves are open. Okay I had a bit more time, and looked up some typical numbers. Here's the deal - even the stock cam has 108 degrees of overlap, so there are only three 12 degree wide slivers of crank rotation where none of the valves are in overlap. The mild turbo cam that I use has 124 degrees of overlap, so in my case there is no position that I can put the crank in to stay out of overlap. Agreed.

I'm pretty sure that this will not not work on a 6 or more cylinder engine. The reason being that since there is a firing event every 120 degrees of crank rotation, it would be very difficult to find a spot where you were not in the valve overlap period of one of the cylinders. Maybe you could get this to work, but you'd need a cam with very small valve overlap, and you'd have to hunt around for a while to find the right spot. This is possible on a 4 cylinder, since the firing events are 180 degrees apart, and it's easier to find a spot where you are not in overlap. It might even work out that the engine's compression would force it to stop in a position that was not in overlap by default - but I'd have to think about this...

aluminum doesn't rust.

I can't think of any valid reason to do this. Increasing the flow of oil to the head will result in a decrease of oil flow to the main crank bearings, which is much more critical. If your head is properly assembled, the stock oiling system will do just fine there. The main bearings rely on a film of oil for the crank to ride on and prevent metal-to-metal contact between the bearing surface and the crank journals- if it is not there, serious problems will result.

I don't use the SDS, but this problem is generic enough that I think I can comment. Most likely what is going on in your case is that you are running rich (probably too rich) immediately before you let off the throttle. The resulting unburnt fuel in the exhaust by itself will not cause any popping, because if you are running rich that by definition means that you have used up all of the available oxygen, and still have fuel left over. Now, when you drop the throttle and the fuel gets cut off, suddenly you are dumping a bunch of air into the exhaust. The newly available air allows the unburnt fuel in the exhaust to burn, and you get your backfire, or popping sounds. The solution for this is to either fix the rich condition that exists before you drop the throttle (requires some tuning expertise), or disable the fuel cut function.

...Oops - missed that part. I agree.

Yep - I agree with this. Some of this most likely depends on the cam design, and definitely on the other variables previously mentinoed, but my experience has been that retarding the cam timing should move the torque peak to a higher rpm, not lower. The optimum cam timing setting (again, depends on lots o' stuff) can be fairly peaky (i.e., power falls off quickly on either side), so it's quite convievable that when you advanced the timing to the #2 hole, you brough it back into the 'good' range. Maybe. Who knows? One final illustrative anecdote... I did try a few different cam designs a while back. I had my original Isky cam dialed in at zero degrees to start with. New Cam Number 1 was a regrind that should have been a bit more aggressive. Ran like ass when I had it installed to the same timing settings (on the sprocket only) as the Isky. After some experimentation, I found that this cam needed to be retarded by 6 degrees in order to run equivalently (not better, BTW) to the Isky. New Cam Number 2 was a regrind that should have been more aggressive than New Cam Number 1. It also had a different base circle than New Cam Number 1. New Cam Number Two ran like ass when I had it installed to the same timing settings (on the sprocket) as the Isky. This cam, however, needed 6 degrees of advance to run almost as good as the Isky. At this point I put the Isky back in, and never looked back. Anyway, in both of these examples, the cam timing marks appeared identical to the install with the Isky, which had been properly dialed in. The main thing here was the base circles were different enough to cause an apparent 12 degrees(!) of timing offset between them. Or maybe the cam grinder was drunk, I dunno. Either way there was a ~12 degree discrepancy between the two cams that did not show on the timing marks at all. This, BTW, was how I learned all this stuff about cam timing and head setup...

I would contend that the cam timing could easily make a bigger difference than the head design. This, of course depends on a lot of things, but that was EXACTLY my point. There were way too many uncontrolled variables in your experiment to make any conclusions as to which series head is 'best'. Even the anecdote about four different heads consistently being better - if they were all shaved, then they all had modified cam timing. Who is to say that the N-series head wouldn't have made more power with the same cam timing? BTW, the head saver shims can correct the timing shift due to the chain slack, but they also raise the cam centerline relative to the valves, which, you guessed it, effects the cam timing. Just to be clear on this - nobody was saying that there was anything wrong or inferior about the P-series heads - obviously several people have had very good results with them. What I and others took issue with was the blanket statement that the P-series is always better, followed by some supporting arguments that do not hold water under close scrutiny. Sorry, but that is the way I see it. Bob - my experience with cam timing changes were similar to yours - thanks for mentioning it. One thing, though - I'm pretty sure that the distributor drive is taken directly off the crankshaft gear on the L-series (still a 2:1 ratio though, obviously). So, the cam timing should be independent of the ignition timing in this case. I'm speaking from memory here, so if I'm wrong, somebody please correct me...

For the head gasket, it doesn't matter - in either case one side of the gasket will be 'correct', and the other won't. In all likleyhood, there will be no difference, but you will need to make sure that all of the holes in the gasket line up with the corresponding holes in the head and in the block. If they do not, then you'll have to modify something, no matter which gasket you choose. Now, for the intake manifold gasket, use the one for the N42.

I didn't forget about the cam shims - as I recall, you said all you did was cut the head and swap cams. In this case, the cam timing is different between the two. And I also know that you can fix this problem, if you know it exists, but you gave no indication that this was the case. Also, there are many fine details that can have a significant effect on cam timing - enough that you can't know if you have an apples to apples comparison without actually degreeing the cam. The thickness of the head has a huge impact on cam timing (at least when we are talking about differences on the order of 0.100"), although this one is fairly easy to notice via the timing marks. However, there are many other factors that effect the cam timing that don't show up on the timing marks. Basically, anything that effects the position of the wipe pattern on the rocker will effect the actual valve opening timing. Cam base circle, lash pad thickness, valve length, valve installed height, rocker arm resurfacing to name a few - also notice that there is no guarantee that any of these things will be exactly the same from valve to valve on the same head. And since all of these effects take place "after" the cam sprocket, they will not show up on the timing marks. You can only detect this by degreeing the cam. Being able to assemble a head and have it run without destroying itself does not necessarily mean that you know what you've got.

Why are you running a 2mm head gasket with the stock turbo block and P90? That combo gives a 7.4:1 CR with the stock gasket. By my calcs, the 2mm gasket should yield about a 6.9:1 CR. This might be part of your problem.