Hello FABO,
Getting ready to pull the heads off a 69 340 motor with stock original X Heads and I wanted to rebuild the heads to go back on the motor with a 400-425 HP street/strip target. I wanted to take my time, do it right, and employ all the tricks of the trade to get the most out of this motor. Had a few questions about valves, valve jobs, and eventually some street porting.
Let’s just start with valves
http://www.moparmusclemagazine.com/techarticles/engine/mopp_0001_360_engine_head_porting/index.html
- Has anybody had any experience cutting a 30 Degree face angle like in the below Mopar Muscle article?
Now, I know the stock tulip valves will not work, but I was considering changing the valves anyway to a flat head style with 5/16 guides like brand X guys use. The article says that you can only do this if you are changing the valve size, so if I go from a 2.02 to a 2.05 would that work? Also I plan on installing hardened seats so would that allow me to switch to the 30 degree angle?
11/32 +.100 over standard small block chevy valves are a common upgrade and the valves are cheap. The guides 'since already needing done' will be changed to a bronze press in style ..and NO u do not have to go bigger than the 2.02 head diameter u have now. As for the 30% seat angle , that is supposed to fatten the low lift numbers from actually giving more area between seat/valve at the same lift as a steeper 45* cut...but they say a 30* seat does not last...i think from the way it's hammered with a poorer cleaning ability in comparison to a 45*..so it go's away faster. something to google...i remember pontiac liked to use 30* cuts.lol
2. Assuming I could cut a 30 degree angle on the valve seat, what would be a good flat head style 5/16” stem valve? I would like to run a solid cam with adjustable 1.6 rockers and still fit under stock valve covers, so would I need a valve longer than the stock unit cut the stem to the same install height? I was thinking like something below:
http://www.summitracing.com/parts/PAR-8483/
Now I know changing from a tulip to a flathead valve will increase compression. Also the 5/16 stem would flow better than stock tulip 3/8 stem. Would there be any other advantage? And does anybody think for a 400 hp target is all this worry about the valves worth it? Or should I just get a traditional 3 angle job at 45 degrees and reuse the stock valves and get on with the next step in the build...
Thanks All!