TimZ

When you say "vacuum pressure -7inHg", do you mean that you are running ~3.5psi of boost? That's a really confusing way to refer to manifold pressure - too many negatives.

Yep - I used to use it when I had the triple Mikuni's

Relisted these (again): Cobra Racing Seat - Bolt in for 280Z Boyd's Billets 16x8 "ProSport" wheels with Kumho V700 Victoracers 245/45ZR16 And I've added these: BumpSteer Spacers Gunson's ColorTune

Me too... http://forums.hybridz.org/showpost.php?p=508457&postcount=12

If you know where your torque peak is RPM-wise, it's generally beneficial to ramp some timing back in after the torque peak. Start small, say 0.5 degrees/1000rpm from the torque peak up to redline. Assuming that helps you can try a bit more - I'm currently adding in a little under 2 degrees/1000rpm from 4300 rpm to 7600.

DB37? Man that's ghetto - I could've made a connector that was better than that. :mrgreen:

...and when you dyno it, they'll say you fudged the dyno calibration to make it read an extra 300hp. ...Ask me how I know:mad::mad:

I agree - why would you want to do anything else? If you aren't looking at the engine's response to your tuning, you might as well be changing jets in a carb. The problem you mentioned first could also be fuel tank venting (or lack thereof), btw. In other words, if the tank isn't venting, you could be creating a vacuum in the tank which would make it harder and harder to pull fuel from it the longer you drive. An easy test for this is to loosen the fuel tank cap and see if the problem goes away.

...and of course I think we all left out the weight of the valves themselves. I think that that would definitely need to be included in the mix.

I know you're just joking, but all I was advocating was adding the simple step of dividing the number you got for each spring from the scale by two. There is a solid engineering reason to do this, and it will give more accurate results for the exact same amount of work. That's all. As 1fastZ pointed out, this will only be completely accurate for linear rate springs, but that's what mine are, and that's what dragonfly showed in his pics. And yes, the whole argument is probably academic anyway, but if you're going to go to the trouble...

True for variable rate springs, but these appear to be constant rate, and thus should be symmetrical. They sure look symmetrical in the pics above.

I'm pretty sure that all you have to do is just weigh the whole spring just as you did, and divide that value by two for use in your calculations. The springs are concentric with the motion of the valve and they are constant spring rates, so I don't think it needs to be anything trickier than that. The reason you want to measure the rocker the way you did is to try to accommodate the fact that the weight distribution of the rocker is not constant. In this case it makes sense to get the overall weights the same, as well as the "levered" weights. This ensures that the rotational inertia for each of the rockers ends up essentially the same (they do travel in a small arc about the pivot point, so rotational inertia is appropriate).

I just took the time to read through this article in detail, and it is a really interesting procedure - I hadn't really considered trying to mix and match the components - very thorough. I did notice one thing, though (and I kinda hate to even mention it, considering how much time you put into it)... When coming up with the balance figures, I believe that you should only consider half the weight of each spring, as one end of each spring is always stationary - this is the same rule that you use to figure the spring's contribution to the unsprung weight in your suspension. Also, same reason that you use the "levered" weight of the rocker. Sorry to bring this up, but I figure if you're gonna be anal, you might as well be really anal...

Wow - much more info than I thought I would get - thanks again. Interestingly, I was thinking along these same lines, but had not yet formulated a plan - this is very helpful.

Also really helpful - thanks guys! It's really nice to hear this stuff, and not have to have that nagging feeling like maybe I shouldn't have done that...

Thanks - that's good to know. I can't imagine what you're talking about... Really there isn't much else for me to be doing right now - the head is at the shop, and the rockers were here - wanted to feel like I was doing something.

For me it depends on the ambient temps, and the running conditions. Since I went back to the shrouded mechanical fan, on an 80 degF day I don't often seem to get to 195, unless I'm driving aggressively. I've only seen it go past 200 once or twice, and that was in the 'paddocks' at an autocroos between runs on a 90+ deg day. The lower than setpoint temps for me appear to be attributable to the "drilled" thermostat. Stewart Components

No debate here - as I said, I had to touch them up anyway and one thing led to another. I have no illusions that I'm going to see any measurable results from this. Getting rid of possible stress riser starts seemed "directionally correct", that's all.

This is pretty consistant with what I have heard (and experienced), too. I've generally noticed that I tend to run a leaner AFR (i.e. more complete burn) at 190 to 200 degF, and the engine just runs more smoothly there. FWIW, I run a 195 degF thermostat - it's one of the high flow Stewart Components ones that has been drilled for some amount of bypass flow when cold. One side effect of this is that the engine often runs cooler than 195 - all of my 600+hp dyno pulls were done with the coolant temp right at 185 degF.

Cool - I was hoping maybe somebody else had done this successfully. So it also sounds like the nitriding idea is not necessary, and possibly not even desirable - that's ~$100 that I don't have to spend...thanks! Dragonfly - those look pretty similar to what I did (I'm going to do one more "fine" cleanup pass): You went quite a bit more aggressive on the tip radius than I did - it's nice to know that that worked -I'll try the same - thanks for the pics.

Okay, so this is what happens when I have to wait around for the machinist... My head is off to the machinist getting its new valvetrain, and I've been going over the rest of the pieces here. As it turns out, there was some amount of interference between the rockers and the valve spring retainers - the "lip" around the lash pads was a bit too high for the pad and left witness marks on the underside of the rockers. Nothing horrible, but the marks were there nontheless. I started out by just polishing out the marks, but I just can't stand to do anything halfway, so I went ahead and deburred and polished the entire rocker (yes, I stayed away from the contact surfaces). I have heard of this being done before, so it seemed like a good idea at the time. Of course, now I'm second-guessing myself. Specifically, I'm concerned that I may have polished away any surface hardening that might have been done on the rockers. Originally, I didn't think that these parts were hardened, and it certainly didn't put up much of a fight to my dremel, but now I'm not sure. Anybody know whether these things were surface hardened? I checked with a local outfit about nitriding the rockers, and that wouldn't be terribly expensive, but they were concerned that this would make the rockers too hard. Soooo - two questions... 1) Were the rockers originally surface hardened (aside form the contact pads)? 2) Regardless of 1), is it a good idea to have these rockers hardened via nitriding?

How about 12 motorcycle turbos, 2 for each cylinder, each pair plumbed sequentially for better response... OOOH -OOOH! ...then you could convert to diesel, and then run all of that into a second stage turbo for higher boost levels...

Relisted these: Cobra Racing Seat - Bolt in for 280Z Boyd's Billets 16x8 wheels with Kumho V700 Victoracers 245/45ZR16

That is what I did. The log in this pic sums the vacuum signals from all of the runners, and is used for the signal for the MAP sensor, FPR and boost controller. I built a second log into the plenum and use it for everything else, like the brake booster, idle controller and HVAC stuff. I wanted to keep this isolated from the MAP, just to try to keep the signal a bit cleaner.

Relisted the 300zx 5lug hubs... 300ZX 5 lub converson for first gen Zs