big block sparks plugs
 

I have a 68 gmc with a 396 (which i think is original motor) it had r44xls plugs, i put a hei in it was going to change to the r45ts but they dont have a long enough throat or enough threads, should i stay with the 44xls and regap to 45 or is there another plug i should be using thanks Ron

Re: big block sparks plugs
 

Could you use, say a later model 454 plug? I'm not sure but don't HEI's gap to .060" ?

Re: big block sparks plugs
 

you can use the same plugs

Re: big block sparks plugs
 

the later model plugs have shorter threads and dont even thread in the holes, why is this

Re: big block sparks plugs
 

use the stock pn plugs and regap to at least .045

Re: big block sparks plugs
 

I understand the GM dealers and some after market are now selling a simple part nnumber for the AC delco plugs 1-6 changes the heat range.
I understand the #4 plug is an ideal street plug for the big block.
All that being said I just bought the R44XLS plugs for mine and gapped them at 45

Re: big block sparks plugs
 

I've been told to go with a R45TS plug, it's a little longer and helps resist fouling on older engines.
This was for a 72 402, iupdated with HEI

Re: big block sparks plugs
 

longhorn man, i tried the R45TS they dont have enough threads to even screw in, but it sounds like i can go with the R44XLS, are the older big block heads casted different than the newer big block heads? Thanks for all the input Ron

Re: big block sparks plugs
 

I have no idea. Thiw will be my first big block chevy

Re: big block sparks plugs
 

I ran into the same problem recently.

Had to go with the R43XLS's which is 1 step colder than the R44XLS's (I did this because my motor is pretty built) If you have a stock motor the R44XLS will work.

Just gap to .045 - that's what I did, and I have an HEI