Kurt G.

327/356 hp, new AC Delco R43 plugs..... what is the correct gap for these plugs? Should I use a different plug ?? thx.

Donald #31176

AC R 43 is too cool for street use. Heat range 5 is a better choice gapped @ .035".

AC R45
Denso W14 U
NGK B4

stingrayl76

FWIW with Donald.

Kurt G.

R45 plugs even after rebuilding the motor with solid lifters, 30-30 cam, 9.8:1 compression etc ?? Please forgive me, I don't know much about spark plugs......

Hitch

Yes, the 43's are now waaayyy to cold. Use the 45's or you can install the 43's now and then change them to 45's in a few weeks when the 43's are fouled...

Dave

ghostrider20

9.8:1 compression with the 30-30 cam?

Mark

Hitch

Yeah low compression late closing valve hmmm those don't work to well together do they?

stingrayl76

Kurt,

I'm running a 365 bored .040 over with 11:1 compression and a 30-30 cam and have used the 45's or equivalent heat range plug for 15 years and have had no problems.

Youwishtobeme was correct when he stated;

Kurt G.

Thanks guys. I spoke to the mechanic and the compression is right at 10:1.