chasman414

Has anyone ever filled their heat risers between 2/4 and 3/5 exhaust runners and also welded the exhaust divider between the same cylinders on the exhaust side of C heads? I am told it can add HP although I'm not sure how.I tried to search these topics here but came up with nothing!!!

Oldsmaniac

I have not tried blocking heat passages but heard it can be done by melting an old piston and heating the head in your oven.... As for welding the divider I had mine milled down flat so its even with the exhaust ports. Headers fit better too with that.

VORTECPRO

Yes, its manditory if you want to make good power.

davebw31

take (mill) .125" off the exhaust side of the head and you are done. Adds 8 hp on a NHRA stocker engine. More on a non-NHRA spec'd engine. It shortens the exhaust pluses. Does not effect header/stock manifold fit/clearance.

I did all of my exhaust crossover ports using one Olds piston, using a case iron skillet and a home made forge (copper tubing attached to air line from my compressor) using charcoal. Block off the exhaust crossover (intake side of head) and pored melted alumn. through chamber side.

droldsmorland

If you’re running a cast intake?....I welded the "slugs" into my intake and left the heads alone. I’m running W Z 455 manifolds on a 68 400 with big valve C heads. I also removed the stove flap and bi-metal spring on the driver’s side mani and welded the holes. If your using an aluminum intake then you need to weld the plugs into the heads (iron heads of course). Or find someone to weld aluminum plugs into the aluminum intake.
Yes you can build the divider on the heads but you need to find a welder who knows how to weld on this metal correctly then mill it flat. I actually built up the divider on my manifolds because I didn’t want to mess with the numbers matching heads nor pull them at that time. It works but doing the heads is the better method.
I blocked off the heat riser circuit to remedy my hot starting issue. Problem solved. Cold blooded as hell due to the divorced choke but I only run in the summer.

67 Cutlass Freak

http://72.22.90.30/phpBB2/viewtopic.php?t=85840

chasman414

Thanks to all of you for the advice, I think I will try one of your methods but I,m not sure which one.