Hello,

I bought a 87 blazer which the owner said he swapped out and put a 400 small block in it. The plugs I pulled out were AcDelco R43TS, are they consistent with the 400 small block? Also, what are the compatible plugs for this engine?

Thanks,
Austin

 

Those plugs should work. Pretty much the same plugs that worked with the original engine will work with the 400. If you are messing around with other aspects of the ignition system, etc, you could try some different heat range plugs, but you typically won't see big gains.

 

Alright. Sorry for sounding so stupid, but I'm still looking for the casting numbers to verify this is a 400. I took off the passenger side valve cover, and saw 2 sets of numbers towards the firewall. They were 333882 and 1K144. Are these the casting numbers or am I looking in the wrong spot completely? Thanks

 

Those heads are run of the mill 1.94" intake valve truck heads with 76cc combustion chambers. They aren't anything special. And that number only identifies the heads.

The block casting number is located behind the driver side cylinder head on the top of the bell housing boss at the back of the block. The block stamping codes are on the cylinder head mounting surface directly in front of the passenger side head. But I've already said that in your other thread! LOL