I'm in the final stages of finishing my BBC build up. Question is what spark plugs to use? The block and heads are the Gen VI vortec stuff. I'm runnning HEI ignition, not the points EFI style crap. Old Mark IV plugs are gapped at .045 and the new ones are gapped at .060. Which era and gap should I use?

i'd start at .045 and go from there

Larger the gap=more power to jump the gap. Can shorten the lifespan of parts. Unless it was a serious track car I wouldn't worry much. .045" gap.

why would you even need a .060 gap?

thats huge!

Thats what they recommend on the website for the new ones. I finally got off my butt and went to walmart to check out the plugs. The Mark IV are very different than the Gen VI. Now comes the headache of picking the right plug. I'm leaning toward Autolite double platinums.

hey your from boise?
I live over here in caldwell

Actually I'm in Nampa. Do you know of any camaro gatherings around here? There used to be one at the shopko parking lot on Broadway around midnight.

never knew that over at shopco. a friend and I once upon a timeway back in the day kinda held some get togethers

there are a few ppl around here in boise, mountain home, and such that I know of who might still be interested in comming if you want I can try to get in touch with them again

Yeah I haven't been over there in a couple years. Don't know if they still do it or not.

you have any pics of your car? just trying to remembre if I hav eseen it at all.

I haven't been here very long so probably won't recognize it.

Usually they open the gap in spark plugs to increase the fuel burn. Shortening will make them last longer, but the wider gap will promote more efficient combustion with a small increase in performance and fuel mileage. I would go with a platinum styled plug and use a gap of maybe .055 and see if it gives you any start up problems. If it does, then your ignition probably isn't up to the task. I don't think you'll have a problem though. To be honest, the .060 recommended by the factory would probably run without a problem. The bottom line here is, the factory has tested your motor as well as many other motors like yours. They wouldn't tell you to run a gap that would be problematic. They want to make sure your a happy customer, because a happy customer not only comes back, but he or she tells their friends too.

Thats a good point. I'm almost positive it has to do with the ignition set up. The Gen VI engines are TBI with the external coil points type distributor. My setup is using the good ol' internal coil HEI. If you look at the gaps for certain setups you can tell there's a difference between the two styles. My 90 chevy camaro(350) is supposed to be .035, A 70 chevy camaro(350) is .045, 79 GMC 3/4t(454)(350) .045, 96 GMC 3/4t(454)(350) .060.

So I think I'll go with the .055 and see how that works.