LeonV

FYI, there are charging system testing procedures in the FSM, without even having to take the alternator out of the car.

Yes, KPI is measured in relation to tire centerline. JM gives good advice. I'm assuming you're trying to use Z struts because of the relative difficulty of getting Skyline parts? Sounds like a 510 or S130 strut may work better, inferring from Jon's post. The PGC10 Skyline has a Macpherson front/semi-trailing rear suspension, more similar in architecture to the 510 and ZX.

Nice work! I've never actually seen a stripped 2+2 until now.

A good thing to do while you're testing leakdown is check your plugs. Check gap and closely examine them for electrode wear. Poor running will cause spark plug electrodes to wear prematurely, so see if there is any degradation or erosion on the ends.

I would hope that you're not referring to my post as "anecdotal", unless you don't understand the reason why down-drafts are at an inherent disadvantage to side-drafts. Like I said, people make it "work". Mark is a good example of that (and knew he'd chime in ) and am not saying that his setup is "bad". I don't deny that max power numbers can approach stock SUs, but as Mark found out, this involves greater compromises in other areas. Here's a quick rundown: (1) When mounted on an inline engine, the air coming in through a down-draft carb must make a 90 degree turn in order to line up with the intake runners. This leads to a pressure drop (loss). (2) The fuel must make the 90 degree turn with the air. This leads to more fuel pooling underneath the carb. This makes tuning more difficult and inefficiencies in transient conditions. (3) The manifold geometry is forced to make the central runners shorter and the outer runners longer. This leads to a more uneven air-fuel mixture distribution and forces you to run a richer mixture in order to get enough fuel to the lean cylinders, while you dump more fuel in the cylinders that already had a good mixture. (4) Because of the manifold geometry, pairs of cylinders are tuned to differing rpm. The middle cylinders breathe better at high rpm, while outer cylinders breathe better at low rpm. This doesn't allow for intake tuning to be as effective. This is an explanation of the main disadvantages. It is not to say that those that use 4-barrel carbs are wrong, or that they should change. Everyone is free to do as they wish. If someone thinks that a 4-barrel is the bee's-knees, then so be it! I find it is good to provide information and let the end-user make their own informed decision. Good luck with your 4-barrel, azkyinc.

Things are going well! Good luck with the project, can't wait to see the Skyline again, looks like it will be better than ever! BTW, I got an S2000!

What is the condition of your transmission and diff mounts?

It would be good to double check, it's quick and easy. Check cold, drive around, check hot. If nothing helps, I'd pick a needle and start setting it at different heights, logging, and seeing the results. If anything, it's an interesting experiment!

This will increase your "kingpin inclination angle". This will make low-speed steering a bit heavier, but it doesn't look like the angle changes much (have you measured it?) so you may not notice it at all. It'll also give you more positive camber on the front, which adversely affects front grip. Again, if the angle change is minor, you likely won't notice much. This can be alleviated by camber plates, or the cheaper method of slotting the shock-tower holes. EDIT: As you can see, higher kingpin inclination angle is not beneficial. As I've said, if the measured difference is minor then you shouldn't notice much. Why the new struts? Are you ditching the coilovers? Leon

I was thinking the same...

Welcome! Look for an orange Z driving up and down 19th Ave, or around CCSF once in a while. My Z visits the city usually once or twice a week (when it's nice out). See you around!

Well there's your problem! Down-draft carbs don't belong on an inline engine, especially one with high-performance in mind. Some will be drawn to contradict me because their's runs great, but that setup is just inherently inferior to proper side-drafts. Slap on some SUs (or triples) and be done with it. People make the 390cfm "work" but that 600cfm Holley is probably no where near jetted correctly for your engine. Oh, and there is a rev limiter on the L24, it'll stop revving once you see a piston flying through your hood! An SU-equipped L24 will rev to 8000rpm just fine, just ask Greg Ira.

What I'm thinking is happening, is that your horn is shorted. When you turn the wheel, the copper contact that comes from the steering column touches the contact ring on the steering wheel and sounds the horn. I'd look at that copper contact first and see if it's touching the ring at all times. The horn circuit is very simple and there are a lot of good posts about it on this site, if you search.

It's conceivable, and I've been thinking all along that it's ignition-related. However, Zed has done quite a few tests to eliminate most variables in that scenario. The only other ignition stuff I can think of is poor grounds, but I think that's been covered as well. We should note that the spark plugs are grounded through the block, so the block must be well-grounded. Otherwise, you're robbing power from the spark. With that said, it really sounded like there was not enough advance at part-throttle but it seems as though adding vac advance didn't help, either. At this point, I would do what I can to alleviate the issue. It doesn't matter so much as to why this or that, but what can I do to make it run right. Maybe Zed's engine is not similar to other engines because there are some unknown modifications? Who knows! What I would be doing, with all other options exhausted, is seeing if I can make any adjustments that make it run like I want. I will repeat, though, take a look at your valve lash! Although no one seems to understand the importance of this, valve lash affects valve timing. If you have a tight or loose valve(s), you are putting in more/less air-fuel mixture into the cylinder, the effects of which are most prominent at part-throttle! Uneven mixture distribution can lead to misfires in certain cylinders, the effects of which would be drowned out by the other "good" (compression and valve lash) cylinders. Basically, you may have 4 cylinders firing evenly, but the other 2 are misfiring, giving you problems. An engine with the same setup, but 6 "good" cylinders will not have a problem. This really seems like one of those extensive, time-consuming, head-bashing problems that is being caused by some little, minor adjustment out of tolerance.

This tells me that the needle profile is not correct for your engine. I'd try different needles. If the piston rises more, you will make the mixture leaner because of a diminished vacuum signal. Run a little experiment with stock needles, placing the shoulder at varying heights and recording what happens.

I like using cardboard (or even better, laminated cardboard), it lets you slide around!

Thank you, Jeff! You've saved me from typing this. Stock brakes are just fine, people love to get caught up in "upgrades". I will even venture to say that you'll be worse off with the 4X4 calipers than stock because of added cost, unsprung weight and they may not perform much different than stock. People will say, "it feels so much better" but I haven't seen any supporting data. A bigger caliper will give you more pad surface area, which will tend to have less fade than stock, but this is not noticeable until you hit the track. In Jeff's case, and in the case of many ITS Z-racers, stock has been adequate even out on the racetrack.

Nope, no discernible difference between the two, in that respect. I completely agree.

Ouch, I hate to see something like that happen, especially to a Z in such great shape! Hopefully, you'll have some insurance money and you can buy back what's left and use it in your next Z.

True, but unfortunately I don't have the time to make the trek, and I think my fiancee would kill me at this point.

Damn, I'd pick that up in a heartbeat if it were closer!

Spot on! You'd have to try different needle profiles in order to tailor the carb to a certain engine. This is when you realize that triples are more user friendly in this regard. Take old jets out, put new jets in. Drive. Repeat. Idle, accel, and main circuits can be tuned separately. Time for triples!

That's a parts car.

Booyah! I spend too much time on this stuff...

It opens with Microsoft Excel. I don't have access to it right at this moment, so I can't give you any numbers. I think that distributor has 17 degrees of mechanical (typical ZX unit) and a really large amount of vac advance (30 degrees?).