go bucks

What spark plugs are suggested for a 63 327 300 h.p.?

Also..... what are the letters at the end of AC Delco mean? For example.....What is the difference between a R45T and an R45TS?

5thvet

R45 or R45S will work fine. The S designation means a slightly longer electrode which will not foul as readily in a stock engine. I believe the difference between a T and a TS is the same ( longer electrode)

JohnZ

The "T" means it's a "peanut plug" with a 5/8" hex shell and a tapered (no gasket) seat; they only work in heads machined with tapered seats, which started in 1970 or so. Your engine wants the old-style plug with a 13/16" hex shell and the square-shoulder seat with a gasket.

bluestreak63

Replaced the AC R43's with R45's in my 327/340. In stock at local NAPA for about 2.15 a piece.

stratplus

I have been using the R45S for years on the 327.

Frankie the Fink

I ran the R45S for years as well; then Autolite 86s for a while.

On a recommendation I switched to NGK-XR4 and have to say, they are a phenomenal plug and work superbly in my dual quad 283ci...which tends to run a little rich in traffic and these plugs burn very nicely with improved idle...
Nobody ever sees them below the C1 ignition shielding anyway..

Powershift

The best and cheapest is AC R45 or R45S. AC 45 plugs (non resistor) are closer to original, and they are now available in reproduction. Not certain about quality, but I would expect that it is good........probably reproduced by an old AC factory and tooling.

If you run unleaded gas, a set of AC 45 (or R45 or R45S) should last you for MANY years. Back in the day, folks often went 12,000 miles or more on a set of plugs. For most of these old cars today, that is 6+ years.

The 45 heat range is ideal for these engines running around town and occasionally on the highway. 44 and 43 heat range are too cold, and will foul quickly.

Larry