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How to select spark plugs

2307 Views 4 Replies 4 Participants Last post by  echristie

After searching the archives, I have not found the answers to the questions. I have a '70 454, automatic, 3.42 gears, 180 t-stat, dual plane intake, Edelbrock AVS 800 cfm carb, Accel HEI, 8 mm wires.

There are Accel plugs in the car, but I found one has a cracked external insulators and there are some light brown colored carbon build up, so it isn't running to bad.

I want to know:
How you know what heat range to use?
What things influence spark plug choice?
Do you always run the recommended gap?
If not, what affect does opening or closing the gap do?
Is there a better brand than Accel? I grew up using Champions for everything, but I know there are other options.

Thanks in advance,

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Bob West said:
I just asked the parts guy what plug is recommended and snip...

want to go one range colder, nitrous a couple ranges colder, gap depends on intended use also, tighter for performance, out to spec for a cruiser. I like AC Delcos too, just don't get the life out of autolite plugs.
Thanks guys for the info. The plugs in the car are Accel 0576S, which cross references to a Delco CR45TS. I got a set of those and will gap them at .035.

I pulled two plugs yesterday to see what they looked like. Medium brown with some build up on the electrode and the ground. I cleaned both and got the build up off. I put them back in and drove the car today. At part throttle, now it surges. Sheesh, I can't seem to even check things without something else happening. It's a tad frustrating. When I had my first Chevelle, I had the 300hp 350, TH350, points distributor, etc. It's been a few years, but I don't remember these kind of issues. When it ran like crap, you had a pretty good idea why. With this one, it seems almost moody. :)

I'm just venting guys, I probably forgot half of the tuning stuff I used to know, so now I have to relearn it. I'm off next week, so I am picking up a new engine analyzer and I will go from there. I will start by changing plugs, tuning the new carb, and once that runs well, I will start making adjustments to the timing to get 'er running smoother. Maybe 454s aren't supposed to run smooth.

Anyway, thanks again for helping clear the spark plug fog.

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