Let me start by saying that my current engine was my first exposure to aluminum heads. I called the head manufacturer to ask them which spark plug was correct. They ended up telling me that I could use a tapered seat plug, as the heads had a taper cut into them. So, I had been running AC Delco R43TS plugs. When I had to tear the engine down due to the builder using the cheapest head gaskets on the planet, I did some more checking & found out that the correct plug is the Autolite 3924 (ended up getting a full set of those for only $0.88 due to a mistake by the rebate company - they told me to go ahead & cash the check).
My question relates to performance/emissions. With the proper spark plug now installed, will the engine burn the fuel more completely, resulting in slightly more power & lower emissions?? The R43TS plug only had a 3/8" reach, whereas the 3924 plugs have 3/4" reach. I am imagining that the shorter plug had the spark shrouded up inside the spark plug threads on the head. I am running an HEI with an MSD 6AL, so it was probably the stronger spark that enabled it to run.
Also, is there a possibility that it will have higher vacuum now?? I was only getting about 5 inches at idle, which is way too low. The engine is a 9.8:1 377, with 64cc heads, & a Comp roller cam that specs out at .510/.520 lift - 230/236 duration - but actually specs out at .544/.555 with the 1.6 rocker arms. I was never able to get the carburetor to completely smooth out either - it would occasionally backfire (Speed Demon 750VE - the Holley Street Avenger had the same problem). Any input will be greatly appreciated. Thanks in advance.
P.S. If anyone has trouble getting the number 6 spark plug installed with straight plug aluminum heads & Flow Tech headers, the answer is an O-Ratchet. I had to slightly cut the 5/8" socket down in a lathe (outer diameter of the socket), but it installs the plug with no problem now (the number 4 plug has to be out, as you have to come in from the front side for it to work).
My question relates to performance/emissions. With the proper spark plug now installed, will the engine burn the fuel more completely, resulting in slightly more power & lower emissions?? The R43TS plug only had a 3/8" reach, whereas the 3924 plugs have 3/4" reach. I am imagining that the shorter plug had the spark shrouded up inside the spark plug threads on the head. I am running an HEI with an MSD 6AL, so it was probably the stronger spark that enabled it to run.
Also, is there a possibility that it will have higher vacuum now?? I was only getting about 5 inches at idle, which is way too low. The engine is a 9.8:1 377, with 64cc heads, & a Comp roller cam that specs out at .510/.520 lift - 230/236 duration - but actually specs out at .544/.555 with the 1.6 rocker arms. I was never able to get the carburetor to completely smooth out either - it would occasionally backfire (Speed Demon 750VE - the Holley Street Avenger had the same problem). Any input will be greatly appreciated. Thanks in advance.
P.S. If anyone has trouble getting the number 6 spark plug installed with straight plug aluminum heads & Flow Tech headers, the answer is an O-Ratchet. I had to slightly cut the 5/8" socket down in a lathe (outer diameter of the socket), but it installs the plug with no problem now (the number 4 plug has to be out, as you have to come in from the front side for it to work).
