The Stovebolt Site Forums The Shop Area Engine Shop Spark plug size

I was shopping around for plugs for my 70' 292. I usually go to Napa cause they have an old school parts guy named Rob. Stuff I ask for isn't in the computer so the parts guys have to go to the "book". I love it! So the book calls for AC R45's. I get home gap em and now they don't fit in the spark plug hole. The R45's are 13/16". The ones I pulled out were AC R44's which are 5/8". Am I going nuts? About half a dozen parts houses give the same plug size.

AC/Delco changed a whole lot of stuff around 2002 or 2003. One of the things that changed was the size of their spark plugs. I used AC exclusively for years and years. All of a sudden I started burning plug wires on the headers. Seems that the "current" R44TS and R45TS (the ones I was using in Chevy smallblocks) were longer and caused the plug boot to contact the header pipes.

I contacted AC/Delco customer support and the best answer I could get out of them was that it was my fault and their products worked fine. They never would admit to having changed the plug length.

So I made up this web page to illustrate the problems:

http://www.chevyasylum.com/acdelco/

Their oil filters changed, too.

The last time I got plugs for the 292 in my 64, I had to use Champions (not my first choice by a long shot, but they've been fine.) I've also had to put Champions in my Model A due to the lack of available alternatives.

As far as plugs for V8s, I've been using Bosch Supers and I'm happy with them.

Btw, I went to AutoZone to get the plugs for the 292.

Good luck with it.

You must have a latter head. Chev. changed the plug type back then on those engines. Get plugs for a 71 up model. R44TS. or r45ts if you need a hotter plug.

As of the end of June, DELPHI (formerly AC Delco) will no longer be in the spark plug business. If you have not already noticed, about a year ago they stopped making EVEN number plugs (ie 42, 44). So if you have an old parts house better buy out their stock or use e-bay

I may try Motorcraft next time. Champions break real easy & there is nothing inside of them. I,m serious it is hollow from the term to the shell.

I guess the era of the once quality made AC plug is over. Time to adapt. I have had pretty good luck with Autolites on my small blocks. I assume they would work ok on my inline. A little trivia TooMany, F___d used a Quadrajet on their Boss 429 to meet federal emissions. And Pontiac used a F___d top loader 3 speed in the late sixties as their standard tranny. Sorry folks got off the subject.