flyinghc

I have a 2001 Z28 with 145,000 on it. I don't have much history on the car but decided to change spark plugs. Plugs on car were AC Delco 41-110.
I put Autolite Double platiniums in (with great difficulty I might add, now the car runs like pure crap. I used .054 gap. Any suggestions?

Injuneer

I believe there was a technical service bulletin (TSB) that changed the recommended plug to the AC Delco 41-110 iridium plug, gapped to 0.040". The gap is set at manufacture and should not be changed, or it can damage the plug.

Do not confuse this later TSB with an earlier one, which had recommended ACDelco 41-985 gapped to 0.040"

Not sure that using the plug you selected, in place of the recommended plug would cause a noticeable change in engine performance ("runs like pure crap" isn't very specific). I would check for wires not fully on the plug, cracked plug insulators, plugs not torqued to spec.

cars3

Ok, first of all I do not want to hijack this thread. I'm thinking of changing the plugs in my 01 ss which are original. What one of the plugs that you have listed do I need. I'm thinking the z-28 and ss used the same plug right?

I am not interested in anything but stock as you can see by my sig on all of my cars.
Thank you!

Injuneer

The TSB applied to all LS1 engines. The engine in the SS is no different than the engine in the Z28. HP differences are due to external factors.

akwa

The Change to the plugs is ONLY for Iridium plugs and changes to .40. The Platinum plugs are still .60.
Make sure the plugs are torqued correctly and are not backing out.
Use the spark plug seal only on half the threads.
Check the wires continuity and fit.
.56 shouldn't matter but if you set them yourself you might run into trouble from damaging the tops. They might of given you the wrong ones because they are supposed to come preset from the factory but that's not always true. compare the old length to the new ones

Suprabuilder

Autolites are crap get those out of there.

Nothing better than the factory delco plugs if you are stock or maybe a few mods. If heavily modded try an ngk v power.

WhiteHawk

Sounds like you have a cracked one. I would check the ceramic for cracks - especially on plug#8. Also, when you re-seat the wire on the coilpacks, make sure they click twice.

-Geoff

DrRuckus13

As these cars age the rubber / plastic breaks down. If you have not already, follow Injuneers recommendation and buy the cheap house brand plug wires and slap them on. The rubber breaks down over time and on a 12+ year old the inside of the wire likely broke when pulling it off. Its about $45 for house brand wire-set from autozone.

I personally have never noticed a difference for street driving between premium and house brand spark plugs wires. you can always buy a fancy pair from one of the sponsors if the cheapies bother you.