Topic: sparkplugs, gaping
in Forum: C3 Engines
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Lanoka Harbor, NJ - USA
Joined: 12/21/2006
Posts: 828
Vette(s): 1975 metallic blue coupe with t-tops,L48, t/t steering, black leather interior. 1990 L98, white/red leather interior, auto,a/c
gap on my 75 with ac platinum plugs is listed at .060. it does have hei ignition. ossw1--- .035 sounds like the gap for distributors that have points. electronic ignition has higer gaps.
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Duncanville, TX - USA
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
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The EARLY HEI systems did have really large gaps, .060"
They found out that wasn't really good for the coils...too much heat involved. The later cars went to a tighter gap, at .045"
That being said, in 1979, I did a tune-up on a friends truck, a '79 Cheby, with over 100,000 miles(he were a Whiskey salesman...). He had a slight miss at idle, but that was it. When I pulled the plugs, I were shocked(no pun intended). There were absolutely NO side electrodes AT ALL on any of the sparkle plugs. NONE! The plugs were just completely worn smooth out, but the truck ran fine!! That was a real eye-opener for me, as far as the HEI systems. I figured if his truck ran that good with no electrodes, then the system must be pretty good.
This was the problem with the larger gaps, tho...it would eventually just arc away the electrodes. The smaller gaps allowed the plugs to survive longer, as well as reducing the amount of heat build-up in the coil.
Go with the .045 gap on your '80 car...
They found out that wasn't really good for the coils...too much heat involved. The later cars went to a tighter gap, at .045"
That being said, in 1979, I did a tune-up on a friends truck, a '79 Cheby, with over 100,000 miles(he were a Whiskey salesman...). He had a slight miss at idle, but that was it. When I pulled the plugs, I were shocked(no pun intended). There were absolutely NO side electrodes AT ALL on any of the sparkle plugs. NONE! The plugs were just completely worn smooth out, but the truck ran fine!! That was a real eye-opener for me, as far as the HEI systems. I figured if his truck ran that good with no electrodes, then the system must be pretty good.
This was the problem with the larger gaps, tho...it would eventually just arc away the electrodes. The smaller gaps allowed the plugs to survive longer, as well as reducing the amount of heat build-up in the coil.

Go with the .045 gap on your '80 car...

Joel Adams
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in Forum: C3 Engines
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