Help - 1974 Head Casting Numbers

[ernie d]

Hi guys, am having a little confusion here about the correct spark plug for my motor. Engine is a 1974 Chevy 454, not positive if from a Chevy Corvette, Truck or passenger car. (Car is a 1969 with a 1974 BB engine).

Anyway, LH head casting number is 346236. Can someone please look it up and give me the info on the motor application, but most importantly, the right spark plugs for it?

The plugs that I just pulled out of the motor are approximately 1/4" shorter than what the Champion plugs application book would seem to indicate. :confused

Of course, there are implications either way on using the wroing plug, so this is an important issue I need to resolve!

Thanks for your help.

Ernie

 

[Tom B Hargrove]

My book shows that head number to be from either a 75-76 pass car or a 75-87 light truck. Both being 454 applications. The casting date should help narrow it down. Can't help you with the plug info. Tom

 

[JohnZ]

AC-Delco R44T (without HEI) or R44TX (with HEI) are correct for use with those heads; forget Rapidfires - they're a waste of money.

 

[ernie d]

John, looks like I do indeed have a 75 motor (head casting date is "A1475"), this means Jan 14 1975, right?

Looking in Tune Up specs, my book shaows R44T is for 1974 454 motors, with .035" gap. Same book shows R44TX for 1975 and later, with .060" gap.

Do you agree? This would mean that for my engine, based on above date code, I should use R44TX, correct? Note, I do NOT have HEI>

Thanks!

 

[JohnZ]

If you don't have HEI, use the R44T, gapped at .035"; the 1975 tune-up chart listing for the R44TX with .060" gap assumes HEI, which was standard from 1975-on. The .060" gap never worked out, and GM later issued a TSB to reduce the specified gap with HEI from .060" to .045" anyway.

 

[ernie d]

Thanks John.......I assume both the R44T and R44TX are the same length? Don't want plugs crashin' into any pistons!


Thanks