LeonV

No, care to explain? My post wasn't an opinion piece. A staggered setup (we're talking smaller front tires here) will induce more understeer and decrease braking traction. It's simple vehicle dynamics...

Bad idea, if you care about performance...

Seconded. Those guys saved me from going through a lot of trouble and heartache on my head build.

Excellent, thanks for doing the testing Phil!

I would think that an engineer would base a statement like, "maximum engine braking occurs in gear with the key off at full throttle" off something more than one data point. I also like how your responses must always be condescending, is that how you deal with people face-to-face too? Anyway... If your wife's truck showed that it would go full-throttle under engine braking, then I think it would be safe to assume that it has some sort of variable valve timing. The trapped air within the cylinder acts as a spring when the valves are closed. The main losses of a motored engine are frictional, with the rest being pumping losses past the valves and throttle (ignoring skin friction in runner walls). On an L-series engine, valves have a constant timing and lift profile, so the only thing you can manipulate is the throttle, thus increasing/decreasing pumping losses at the throttle. An engine with variable valve timing can alter when the intake valve closes and exhaust valve opens, thus the exhaust valve can be opened much earlier which would then bleed off the work that was done to the air when compressing it. This would be similar to a Jake Brake in diesel truck applications. It was YOUR recommendation so go ahead and prove it. With your Z this time and not a modern, computer-controlled truck. Personally, I'd be interesting in testing this myself but both of my Zs are disabled for the time being. My hypothesis would be that engine braking is MINIMUM at wide-open throttle. FWIW, here's an interesting tid-bit from Cummins:

Opening the throttle would decrease engine braking...

FWIW, as far as engine braking is concerned, I always leave the car in gear until right before I stop, no matter whether the ground is flat or I'm on an incline. In EFI cars, you take advantage of drop-throttle fuel cut by leaving it gear. This is part of the reason why I can get 37mpg out of my '01 Accord.

Allow me to help a bit then... You pretty much did everything wrong in that scenario and were lucky that there wasn't a need for any panic stops. As soon as the engine cut, you should've pulled over to a stop as soon as it was safe to do so. Without power assist, your brakes work just fine although it will take a lot more force to get the same amount of stopping power. Use two feet on the pedal if you don't have enough strength using one leg. Engine braking could've helped as well, had you put it into say 4th or 3rd gear and slowly let off the clutch (as to not lock up the rears). You've been SORELY misinformed about keeping the car out of gear. Keeping it out of gear has ZERO benefits and more than a few drawbacks. Mainly, you'll get worse gas mileage, wear out your brakes quicker, and don't have immediate engine response to get you out of trouble if the accelerator is needed. The ONLY time your clutch wears is when you SLIP it. An engaged clutch does not wear. I recommend you attend a driving school near you. It would benefit you and those around you greatly. http://www.tirerack.com/features/motorsports/street_survival.jsp

Frankly, that was just plain stupid. If your engine dies pull over as soon as you can, and don't continue hurtling down the road.

Since you're on a time-budget, you should know that you probably won't get those Tokicos anytime soon unless you found a place that had them in stock. Tokico's distributor went out of business so there haven't been any new shocks delivered to the US for a while now, AFAIK.

Ah, gotcha...

Nice, is that Clive's car? Triple Webers, Megajolt, and carbon fiber air horns?

I'm not super familiar with Socal, but try Sunrise Z in Glendale or Beta Motorsports in La Habra (John Coffey is the owner and on this board). I think Pierre Z is still around too, they're in Gardena. Pierre Z did a lot of work for Nissan during their factory restoration program in the late '90s. Not really sure how close any of those are to you since you just list your location as "California"...

Don't tempt me! I don't really need anything, so it would be more of an opportunistic buy than anything. I do like the looks of that header and I'm also on the lookout for some nice wheels, preferably 16".

Thanks for the feedback! Good to know about adjusting the front valence. I really like the fit of 225/50-16s but as you said, it'll require some altering to get those to work with the stock front valence. I have no issues on one Z which has a Xenon air dam but I want to run the stock valence with a lip on the other car. Looks like I may have to go down in size for my next set...

I'm thinking the same thing...

Does that combo work without trimming the stock front valence, i.e. there is no rubbing with the steering at full lock?

Steve makes good points. The cam I'm putting in the L28 I'm currently building is .540" lift and the pistons pop out of the bore .021". I'll be doing piston-head and piston-valve clearances soon and can report back. Pistons are flat-tops and compression should be close to 10:1.

Ha! The original flat-tops are sitting in storage, just in case.

It's not the overlap, but the intake valve closure point that's the important bit. No way to tell your compression ratio from that data. You need to know bore size, compressed head gasket thickness, and combusion chamber volume. The Holley can be part of the issue because of uneven mixture distribution. All it takes is one cylinder, one weak link, to cause knock. The wideband shows average AFR, not cylinder-to-cylinder differences. That engine is begging for triple carbs or standalone EFI. The more control you have, the better chance of alleviating your issues. In the meantime try colder plugs, cooler thermostat, and a slightly richer mixture, in that order. That makes a bit more sense. Sounds like your torque converter lockup changes depending on heat, since the torque converter is a fluid coupling. This has nothing to do with how much power your engine is making.

Your current setup is much more likely 14X6 wheels. Otherwise, I'm not sure how you fit 14" tires on 15" rims! I agree with the rest that those look like 15" Konig Rewinds. As for wheel pricing, I've sold 3 sets of 5-slot mags, with the 14X6 sets selling for $200 and the 14X7 for $250.

Is siteunseen's name Leon, or am I missing something? That isn't the correct way to set timing. The correct way is on a dyno, anything else is just guessing. Seriously, an hour on the dyno will cost you maybe $100. I consider that a worthy investment. Maximum advance DOES NOT equal maximum torque. Read up on MBT (Max Brake Torque) timing.

Sure, tighter lash would leave it open a bit longer but it's not exactly what I was recommending. You can try but I'd go with the lash settings given by the cam grinder. I was recommending retarding the cam (as long as you have ample valve to piston clearance) to drop low-rpm cylinder pressure. You may need an adjustable cam sprocket for this depending on where your cam is currently set. If it's on the #2 hole, set it to #1. That will retard the cam by 4 degrees and may be enough to help. You'll lose a bit of low-end but make up for it in the high-end, if you notice anything at all. That makes absolutely no sense to me. Engine RPM to MPH is controlled by gear ratios, i.e. solid meshing gears that don't have magical temperature-sensitive gear ratios. Could you clarify what you mean here?

If colder plugs and cooler coolant doesn't help at all, I'd really consider going with a more aggressive cam or at the least retarding your cam. My hypothesis would be that the high heat and pressure caused by your current valve timing profile and static compression is causing engine knock. Knock is more likely to happen at lower RPM because it has more time to develop while waiting for the flame front to reach the hot spot. Therefore, you want to decrease cylinder pressure within the zone where knock happens. As far as valve timing goes, this is mainly done by delaying the intake valve closing point. That's a good plan for the future, IMO. An unshaven P79 or P90/P90A with flat-top pistons will get you to ~8.5-9:1. The shaved P90 that's going on my flat-top L28 has 44cc chambers and should give me approximately 10:1 compression. I was hoping for a bit lower but I'll probably be close to the edge of what I can run on pump gas, especially in CA where we get up to 91 at most pumps. I do have access to 100 octane if I need it, but I REALLY don't want to resort to that... You'll be fine, probably even on regular gas. That combo is ~8.5:1.

This escalated above my programming experience very quickly! Great work Lenny, this is a fantastic project.