Question about spark plug gap

[Jimbotronics]

Not long ago, I installed new spark plugs. I believe by recommendation of the board I gap the plugs at 45. Anyway a few weeks a go I had a shop install my new headers, and the guy says he noticed the plugs were gapped wrong and re-gapped them to 35. I'm getting a little pinging if I really get on it - could this be part of the problem?

btw my engine is an 87 350 w/HEI

[Brainchild]

I always gap the plugs at 45 with an HEI,and 35 with points.Never have a problem.

[Jimbotronics]

Thanks Brainchild - I was second guessing my thoughts. It may not be the problem but I think I'll change 'em back to 45.

[Mudder]

I've always gapped my plugs (hei) at 045 but I was just looking at the spc sheet on my motor and it says 060.

[Brainchild]

Will it run better at 60? Anyone run thiers at 60? I know some of the smaller 4 bangers and stuff gap at 60,I think my minivan is one of them.I might try that one this week if there is no feedback.

[Jimbotronics]

I'm curious to know that answer as well

[70c10]

I would go with .045 unless you are running a higher end coil, wires, module,etc.

[CHEVYE]

i gapped mine @ 60 with an msd 6al, blaster coil and billet dist. on 11.7:1 comp in my race car. you have to have alot of spark to do that though. i always do 45 on a stock engine with hei. they usually come pre gapped right out of the box and i`ve never had a problem.

[cableguy0]

stock hei is .045 a really hot coil or an msd box you can go as far as .060. .035 went out with points except in a few chryslers

[Jimbotronics]

thanks guys!

I don't know what he was thinking, but he thought he was doing me a favor so I can't really be mad + he did an awesome job on the entire exhaust set up.

I'll gap them back to .045 today - question is. could that be cause of my pinging or is that something else. I've got the distributor just loose enough that I can't barely move it. I run down the road pull over and tweak it - get back in and floor it - pull over and tweak some more... can't get rid of the pinging. I've also set it with a timing light but that didin't do the trick either.

[Longhorn Man]

The first year or two of HEI, GM said .060. When they figured out that they were burning up coils and wearing out plug wires too fast, they chainged it to .045.
As far as your pinging....you may well need to fatten up the mixture on the carb. Did you just go from manifolds and singlr exhaust?

[Stocker]

I've always gapped at .035 (points) and .045 since I put in HEI, and I've been follwing this thread to see where it went. Andy, thanks for the info - it's appreciated!

[Jimbotronics]

Thanks Andy! I did a lot of changing at once so it's hard for me to relate the issue to one thing. I changed from a qjet to a dual-plane intake, a 600 cfm holley, and installed dynomax headers and exhaust.

[kwmech]

The change over to headers will lean out your mixture,[less back pressure] thus the pinging, you need to fatten up the mixture.

[Jimbotronics]

Meaning that I need to run a higher octane? I'm only running 87 right now. Even though he said it wasn't needed I'm thinking of installing an H or X pipe, would that help?

[Mudder]

I'm positive mine are gapped at .045. I remember getting into an argument with my ex-father-in-law about it. I just noticed last night that the sheet here in from of me says .060.

[Longhorn Man]

You probably don't need a higher octain...just need to make more adjustments on the carb. Need to richen the fuel/air mixture. Playing with the timing may/may not help too.
If you can't tune the ping out, then go to a higher grade of fuel.

Mudder, what is it you have there that says to gap like that? I was just going through my manual, and it was only in 75 that GM said to do that. 76 & up is all .045.

[Mudder]

Sheet that came with my motor......Gives all the specs. Trying to figure out a way to show ya.

[Mudder]

this is the motor I got from Performance Parts.

12355345 SP 350ci (300 hp)

[Jimbotronics]

Thanks Longhorn Man - I'll start tweaking on them and see what it does.

[cableguy0]

jimbo your best bet is probably to go 2 jet sizes bigger and see if that fixes it. if not go bigger

[tom hand]

I agree on riching the carb cause of the headers...when HEI first came out GM said run .060 but I believe them backed off that because it was killing the coils.....Some NASCAR team did a test and found no horsepower gains at anything over .035

[cableguy0]

i find it hard to believe that there was no gains with a gap over .035 i know one time i screwed up and gapped mine at .035 then when i checked i put em to .050 and it got better mileage and ran a hell of a lot better power wise

[Jimbotronics]

I've changed carbs but never broke into one - how do I change the jets?

[cableguy0]

pull off the fuel bowl on the front 4 bolts. take on bottom bolt out and have a small cup or the cap to a can of carb cleaner under it when u pull the bolt because fuel is going to come out. then you will see the main body of the carb behind it. the jets come out with a straight blade screwdriver they are at the bottom. it will seem simple to ya once ya see it