[tbm3fan]

Has anyone ever personally ground out the thermactor boss seen just inside the exhaust port of a small block head? Given how much room it takes up, and how small the port is there would seem to be the opportunity to get a pretty decent gain in exhaust flow by eliminating it. Since I have the needed tools I could handle it. That is as soon as I get my valve springs off. Being double springs my standard compressor doesn't seem to depress them at all.

 

[Bad69cat]

Yeah - if you got the ambition grind away. If you don't want to cough up for new heads, everything you can do will help. Might as well gasket match the ports while your at it. Your not talking huge gains or anything - maybe 3 to 5 HP at best. You should see better flow and smoother torque curves though....

 

[Cougrrcj]

Check out DIYporting.com for some good info on what to do, and more importantly what NOT to do... Lots of information out there to be found with a simple Google search!

 

[tbm3fan]

I found DIY on my own and looked it over.

Instead, at this time, I took the heads down to get them cleaned up. I couldn't get the springs off using my hand operated tool. The shop had pneumatic which works in an instant. After pulling the valves from cylinder 4, since there was some oil there, we both felt the wobble in the exhaust valve. Intake only a little better. The exhaust valve stem had galling high and low on opposite sides. Possibly guide not straight and knurled back in 1974. Valve seats ok. One intake top was mushed on one edge. Cylinder 5 has the same oil contamination.

So they are being disassembled and cleaned but it looks like I'm going bronze guides and viton seals. The teflon around the intake stem kept them too dry. Then powered metal exhaust seats installed. Some valves are fine and a few need replacement. Springs and retainers are ok for the new application.