Spark plugs for 365 hp 64

[John F.]

The 64 I just bought has a 365 hp 327. As far as I know, it should have the AC-44's. It currently has AC-R43S. What do you think?

[Joe R.]

Re: Spark plugs for 365 hp 64

43's are too cold for the 365 in my opinion. Use 44's or 45's. If it's old and using a little oil use the 45's.

JR

[John F.]

Re: Spark plugs for 365 hp 64

Thank you Joe!

[Ed P.]

Re: Spark plugs for 365 hp 64

45"s here standard tip

[Duke W.]

Re: Spark plugs for 365 hp 64

AC heat range "5" or equivalent heat range in another brand is best for ALL production engines in normal road service including long freeway trips at 80 MPH. The non resistor AC 45 for small blocks is long out of production, so the best choice in the AC brand is the R45 resistor plug. If your car is not being judged, NGK and Denso offer non-resistor plugs equivalent to the old AC 45, B4 and W14-U, respectively.

[John F.]

Re: Spark plugs for 365 hp 64

I have a NOS set of AC 44's that I picked up on ebay. Any problem with these?

[Duke W.]

Re: Spark plugs for 365 hp 64

They may have more tendency to foul in typical vintage Corvette service, but since the 44 was OE on all C2 small blocks, they are less likely to have any judging deductions than any other plug.

[John F.]

Re: Spark plugs for 365 hp 64

I am going to give them a try. What a PITA to put in and take out the old with that goofy shielding. Thanks Duke!

[Gene M.]

Re: Spark plugs for 365 hp 64

try the ac44s with extented tip

[Jeff S.]

Re: Spark plugs for 365 hp 64

Gene, Duke, et al
Can the 'S' suffix, extended tip configuration AC plugs (or equivalent) be safely used on domed piston/solid lifter small-block engines? Thanks,
Jeff

[Duke W.]

Re: Spark plugs for 365 hp 64

Over the years there have been reports of ground electrodes being bent from piston contact, but it's probably not an issue unless the block and head surfaces have been excessively machined.

[Gene M.]

Re: Spark plugs for 365 hp 64

If you have all stock engine and components they should clear just fine. As noted with modifications all bets are off.