Spark Plug Recommendation

[Jack C.]

My 68 427/400 used 43N's (currently 43xls) as the factory plugs. Any recommendation for a plug that I should use today which would be better suited for the limited amount of driving that I do? Thanks

[Clem Z.]

Re: Spark Plug Recommendation

My 68 427/400 used 43N's (currently 43xls) as the factory plugs. Any recommendation for a plug that I should use today which would be better suited for the limited amount of driving that I do? Thanks

R-45XLS plugs will work great

[Jack C.]

Re: Spark Plug Recommendation

Thanks Clem.

[Domenic T.]

Re: Spark Plug Recommendation

Jack,
Years ago a good friend of mine was running a small block at the strip and decided to dyno it.

He also changed plugs to see if they made a difference.

The outcome was Autolite, champion, then AC.

He said champions ran great till the plating wore off.

I did good with the autolites then their #s changed and I didn't know if the replacement was the same.

DOM

[Jack C.]

Re: Spark Plug Recommendation

Thanks Dom. Considering Clem's experience, I'm going with the AC's.

[Paul H.]

Re: Spark Plug Recommendation

R-45XLS plugs will work great

I agree with Clem. I have a 68 427/390 and have tried all of them. For street driving the R45XLS work the best.

[Douglas C.]

Re: Spark Plug Recommendation

I agree with Clem. I have a 68 427/390 and have tried all of them. For street driving the R45XLS work the best.

I have a 69 L68 with a hotter cam than stock. For street and some highway would you go with AC 44XLS?

And, so many engine builders today seem to lean towards NGK plugs, I know not the correct brand, but any thoughts on their BP5ES or GR5 plugs as a cross reference to the AC?

[Claus S.]

Re: Spark Plug Recommendation

Not long ago i sold a Porsche 911 twin turbo that ate spark plugs when you did "around in town driving"
I used the plugs Porsche recomended which was Bosch Platinum. They was just as bad as any other plug.
So i bought NGK spark plugs and installed them and what a difference. I did not have to worry about spark plugs after that. Use spark plugs that is made for high temperature

[Duke W.]

Re: Spark Plug Recommendation

Spark plug heat range selection is a function of average engine load, not peak power. For normal city and highway driving any Corvette engine, OE or modified, operates at low average load, and AC heat range 5 appears to provide the best foul-free performance for all small blocks and big blocks. The equivalent NGK heat range is 4, and Denso is 14.

If you're road racing or hot-lapping race tracks, a colder plug should be used - AC heat range 2 or 3 or equivalent in another brand.

Duke

[Clem Z.]

Re: Spark Plug Recommendation

another thing to remember is after driving around town and you want to open it up a little bit don't just nail it wide open right away. take it up in RPMs just on the primary side of the carb to clean the carbon off of the plugs. if you go wide open throttle right away you will bake the carbon deposits onto the plugs

[Joe R.]

Re: Spark Plug Recommendation

Clem,

Let me ask a dumb question, how many RPMs would that be to stay on the primary side of the carb?

Joe