hi need gap information

[historyg]

Somewhat nubbie, but what is the right gap number for spark plugs for my 307 motor 1986 cutlass supreme. I have a haynes and it says .060 in. I am using stock replacement ac delco plugs. Sorry, for the newbie question, but i want to make sure. thanks. 😀

 

[84GP455]

That sounds correct, i gap mine at the same .060 though my book says .045 but that's because it is a 1974 block which had a points ignition distributor. So i looked up a motor with HEI ignition which has more spark therefore you can go bigger with the gap at .060

 

[historyg]

Thanks I appreciate it.

 

[FE3X CLONE]

One of the reasons the gap is so wide on an engine with HEI is due to the emissions equipment, EGR, etc. If you remove a lot of that, you don't need such a wide gap. .035"-.045" would be fine and less wear and tear on the HEI.

 

[84GP455]

One of the reasons the gap is so wide on an engine with HEI is due to the emissions equipment, EGR, etc. If you remove a lot of that, you don't need such a wide gap. .035"-.045" would be fine and less wear and tear on the HEI.

Well i don't have any emission equipment on my car and i still run a .060 gap and the car loves it. I am sure that because the HEI puts out way more volts than points distributors therefore more spark, you can gap your plugs wider which will give you more spark thus more power. How does emissions equipment rob voltage output of a HEI distributor? I don't mean to sound rude but i've never heard of such a thing, No offense.

 

[FE3X CLONE]

It takes a stronger spark to ignite the fuel because it's diluted with exhaust gases (exhaust gas recirculation). The wider gap provides a stronger spark however the downside is that it can also cause the plug not to fire at all or miss.

Everyone I've talked said there's no need to go over .045-.050 gap on most applications. But if it works for you, great.

Have you tried running smaller gaps?

 

[historyg]

oh man you guys confused me now.... Should i run 0.60 or 0.45, I think i will shoot for the middle i guess at around 0.50... my car still has all the stock emission stuff including the cat, and the electric HEI, so should i run the recommended 0.60?

 

[FE3X CLONE]

Sorry, didn't mean to confuse anyone. I was just pointing out that just because someone has an HEI distributor doesn't automatically mean you need to gap the plugs to the factory .060" specs. Heck, my '76 455 specs were .080" and I ran that for a while until I found out there wasn't any reason to. It ran just fine at .045-.050.

For your stock 307 you can stick with the stock specs but it's not going to be detrimental to your engine if you go to .045 or .050.

 

[adumb]

It takes a stronger spark to ignite the fuel because it's diluted with exhaust gases (exhaust gas recirculation). The wider gap provides a stronger spark however the downside is that it can also cause the plug not to fire at all or miss.

Everyone I've talked said there's no need to go over .045-.050 gap on most applications. But if it works for you, great.

Have you tried running smaller gaps?

i was always under the impression that the more powerful your ignition the more of a gap you can run.

say if you ran a gap of .010 you would not have a very adequate spark to ignite the cylinder. however if your ignition system is strong enough to produce a spark that can span .060 or .070 that would provide more spark to ignite the cylinder.

your explanation of egr needing a larger gap and no other advantages of gapping wider makes no sense to me.

 

[joe_padavano]

It takes a stronger spark to ignite the fuel because it's diluted with exhaust gases (exhaust gas recirculation). The wider gap provides a stronger spark however the downside is that it can also cause the plug not to fire at all or miss.

Everyone I've talked said there's no need to go over .045-.050 gap on most applications. But if it works for you, great.

Have you tried running smaller gaps?

i was always under the impression that the more powerful your ignition the more of a gap you can run.

say if you ran a gap of .010 you would not have a very adequate spark to ignite the cylinder. however if your ignition system is strong enough to produce a spark that can span .060 or .070 that would provide more spark to ignite the cylinder.

your explanation of egr needing a larger gap and no other advantages of gapping wider makes no sense to me.

X2. If the HEI will fire the plugs with the wider gap, this will be a benefit even without the emissions equipment. Of course, the reality is that you will be hard pressed to measure the difference between using 0.060 and 0.045.