ZL-1 Spark Plug Gap

[Camaro Rick]

I have a spec zl1 engine, just installed TI ignition, and was curious on how far I could go with the gap on the plugs. I started at the factoy spec of .035". After I ran that for about 2 weeks, I pulled the plugs and found they were nice and brown color, but not enough pep in the acceleration. I opened them up to .044", and the engine now winds up quick and lots of power. Am I going in the right direction with this?

[Salvatore]

Sounds like it Rick. Check the timing too.

[Camaro Rick]

Thanks Sam, I didnt know if there was a "sweet spot" for the gap on the plugs, and if there will be harm in the ignition components eg. amplifier, coil. if the gap is too large. It is hard to time the engine at idle as it is all over the place with the rough idle. I have the curve for the distributor and have been setting the timing at a total of 31 degrees @2000 rpm. Does this sound correct?

[Chevy454]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Camaro Rick</div><div class="ubbcode-body">I have the curve for the distributor and have been setting the timing at a total of 31 degrees @2000 rpm. Does this sound correct? </div></div>
For starters, is your timing all in by 2000, because if not you're simply guessing. You need to run it up to 3000 or more and see where your timing is done at, and then you can set your total.

[69SSZL1]

I have been driving my ZL-1 Camaro for over 6 years and have discovered alot about these motors. They like lots of timing advance, they don't like exhaust pipes. Remember that your T.I. ignition retards timing 1 degree for every 1000 rpms. Set your gap at .035&quot; for a stable idle. Add an adjustable vacuum advance pod to the distributor connected to full-time vacuum. Set initial timing to 12* -14*, my vacuum pod adds 11* at idle, total timing is 42* @3000rpm. You probably will need to add a mechanical advance limiter to the distributor to achieve this. The stock exhaust system will dog this motor, and dilute the chambers so much as to lose 100hp or more. Carb: make sure your power valves are rated below your engine vacuum, they can cause eratic idle as well when they fluctuate, Holley power valve blow-out protection is required due to the cam spitting back when cold. I could go on and on, but this is the greatest motor every built by Chevrolet. It works great on the street, but is a race motor that has unbelievable power!

[Camaro Rick]

I had the distributor set up on a sun machine and the mechanical advance curve is set to zl1 specs. The readout of the degrees are on a sheet. I just was going by it. I can tell it likes alot of advance. The 263 distributor has no spot for a vacuum advance pod, but I think if what you are saying about going all in at 3000 rpm @42degrees, i will try that

[Camaro Rick]

Also I did change the power valve from a 6.0 to a 3.5 since the vacuum at idle was about 8. That helped alot. Car has headers and flowmasters and runs strong. The idle is smooth (as smooth can be) even when I opened up the gap to .044. That change really made a big performance difference

[Salvatore]

Rick, take that car to Dave Alosio (DARE) in West Chester and have him do the distributor and set the carb up for you.

[Camaro Rick]

I am close with the tuning. Dont think it warrants taking car to anyone. I was just wanting to get some imput on tweeking that car in. I think I just might need a tad more timing.

[Chevy454]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Camaro Rick</div><div class="ubbcode-body">The 263 distributor has no spot for a vacuum advance pod, but I think if what you are saying about going all in at 3000 rpm @42degrees, i will try that </div></div>
I'm saying you need to check *where* it's all in by...could be 2000, could be 3000, could be 4000, etc...most factory curves were really slow, so you'd have to really zing the engine up to arrive at total timing.

You can definitely go too wide on the gap...you can't get as wide on the stock stuff, as the coil simply doesn't have the pop and the wires can't handle it. The larger gap will result in a better spark, and have more contact with the charge.