TimZ

Ummm, okay... So how were you measuring your speed again?

I hate to say it, but I'd be surprised if the problem was in the head. If possible, try a leakdown test before you take it apart...

As I recall, the Fidanza will work with either clutch. I just saw in another post that you were also looking for a clutch. Why stick with the 225mm clutch? The 240mm will have more holding capacity, and it will package the same.

...Was there a reason that you need a Centerforce? There are plenty of better options available, especially for the money. Do a search.

Hold on a minute here... How are you determining that you are going 65mph? If you are using the speedo, then the rpm to indicated speed relationship will be exactly the same as before the swap, since the diff and tires are after the speedo pickup in the trans. Also, was this a manual or an automatic trans? According to this transmission calculator, 65mph should happen at about 2500rpm in 5th with the combo that you stated, assuming an '83 manual trans. Note that this is actual speed, not indicated speed.

You know, a small exhaust gasket leak can sound remarkably like valve clatter...

I've been thinking along these lines lately, too. Mine seems to run the best with coolant temps around 195 degF. I've also noticed that many manufacturers are letting the coolant temps run considerably higher than 210. I don't really think that running temps at 200 to 210 is going to hurt anything as long as you don't boil over - meaning the system must maintain adequate pressure, and you must use some amount of anti-freeze in the mix (probably the minimum required for these temps). That said, my coolant temps have been running over 200 and sometimes as high as 210 after a hard run on a warm day, and I still cringe a bit when it does it. I'm still trying to get it to stay down around 195 more reliably. It doesn't have much problem staying cool at idle, though. Also, I'm with James - I've never much liked the idea of not running the pump when cold, and for all the reasons he already stated. It doesn't take that long for it to warm up with the pump running, so why risk things with the added complexity? Have you checked the voltage at the pump? If the pump isn't getting full voltage, this could be contributing to the problem... ...BTW, this is the thermostat that I've been using - I'm pretty sure it was the #301. Here is a bit more detailed description.

I've never really bought into this argument' date=' and I think it has been discussed here before. Yes, slower moving water [i']will[/i] absorb more heat, but this means two things - it will be hotter when it exits the engine, and you will see a larger temperature delta across the engine(i.e., the front of the head will be hotter than the back of the head, and by a larger degree). I'm 99.9% sure that the real reason for adding restrictors in the cooling system was to add some backpressure. The reason that you want backpressure is that it makes it harder for the mechanical pump to cavitate at high rpm. Slowing the pump down with an underdrive pulley will also make it less likely to cavitate. Cavitation = no water flow = bad. Since the electric pump no longer changes speed with rpm, cavitation should no longer be an issue. I went the other direction and installed the lowest restriction thermostat that I could find with my CSI pump. This seemed to help marginally.

Not that odd - if the PCV system is still connected, bad rig lands could easily blow enough oil through the intake to register on all six plugs.

Well, I hope I'm wrong, but IME, a sudden increase in blowby usually = ring lands. Did you say you had checked your compression? I'm trying to think of a way that a blown head gasket could leak pressure to the crankcase itself... At any rate, try re-torquing the head first, then check the compression. Good luck.

No one said it was mandatory I don't believe but' date=' it is a good idea. Especially with a motor that is being leaned on by it's owner. [/quote'] I'm having trouble believing this too, although I agree it won't hurt. If you do this, you will want to go buy a bottoming tap (they aren't very expensive) and clean the threads in the block thoroughly and all the way to the bottom of the hole. You should be able to thread the stud all the way down by hand. Know what is mandatory, though? Re-torquing the head bolts periodically. I can't believe nobody has mentioned this yet. When was the last time you re-torqued? Use the factory tightening sequence (check any service manual), and ONLY do it on a stone cold motor - let it sit overnight. Back each bolt off 1/8 to 1/4 turn and retorque to spec, one at a time. IIRC, the turbo bolts are spec'ed for 65 lb-ft. Finally, if you go with the metal headgasket, you will want to clean it thoroughly and coat it with something like copper gasket spray or hylomar spray. Also, make sure that the head and block surfaces are absolutely clean and smooth.

That's a good general equation. Note that it assumes that the engine is operating at 100% volumetric efficiency. It's interesting to note that if your engine has less than 100% VE (i.e., it doesn't breathe very well), your resulting boost pressure will be higher than what the equation predicts. So, you should be able to use your measured boost pressure to give you a rough idea of what your VE actually is. Also, note that with this type of setup, for a given supercharger displacement and pulley ratio, the less boost you make, the more power you will have, since this indicates that the engine is breathing better, and the supercharger doesn't have to compress the air as much to achieve the flow rate dictated by the pulley ratio and blower displacement.

Yep - don't even worry about losing any power from the reduced gap. You won't be able to tell the difference, except it might stop misfiring. Misfiring will cost you MUCH more power... I generally run 0.030".

Just found this: http://www.crank-scrapers.com/products/Datsun%20-%20Nissan.html Anybody tried them? I've always wanted to try a crank scraper, and for $50, I figure it's worth a shot... Not expecting any miracles, but it seems "directionally correct"...

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: 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.

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...

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

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?

Damnit - now you've sucked ME into this mess.... This is simply not true. The intake ports are in exactly the same place on both heads, as evidenced by my ability to use a P-series manifold gasket on my n42 head (yes that's right - I use an N42 on a high boost TURBO setup with no problems - granted it's modified a bit... ) So, given that the valve sits 0.100" HIGHER in the head on the P-series, the P-series has the smaller short side radius. Geez , guys, as far as I can see Dan is the one that is voicing the apparently heretical opinion that there are more options that just the P-series, not the other way around. HE'S ONLY SAID EXACTLY THAT IN ALMOST EVERY FREAKING POST. Get over it. Oh - and ALL of my dyno numbers were on 94 octane pump gas, not 100+ race gas.

Yeah, the smaller plug gap is intended to help misfire problems at high cylinder pressures, as you would find under high boost. If you have a misfire at idle, it's almost certainly something else.

In the meantime, I wouldn't worry a bit about gapping at .030". The power you are losing through misfires will far outweigh any power loss from the smaller gap. FWIW, I generally run at 0.030" on NGK BPR8-ES plugs, any nobody has accused me of having an inefficient setup .

You would have noticed if you had gone to 20:1 at WOT and 12psi. Period. Probably would have seen a big fireball out the exhaust from the abrupt rich/lean transition. As others have mentioned, you really should consider some sort of instrumentation now that you are cranking the boost up. Regardless of whether that shop's wideband was bogus, you really need to have some idea of what's going on with your AFR. Does your EFI already have a narrowband EGO? If so, at least consider getting a cheap gauge for that. Narrowbands aren't as good as widebands, obviously, but they are still FAR better than nothing.

I think the issue with the SDS is not so much it's ability to fine tune - it's more about the fact that it's really hard to know what to tune it to. Without datalogging capability, you are mostly just guessing.