hey guys i have #5 heads on my engine do you know what size the valves are?

 

1.875" int. and 1.562" ex. I've got the same heads on my Cutlass. They're good heads that flow quite well. I consider the intake valve diamater a bit on the small side, but apparently it doesn't really matter unless you're building some 500+ hp monster.

- GoldOlds

 

are those the only size that came in these heads?

 

I believe the W31 had a 2.00" intake, not sure about the exhaust size. It makes sense that you could cut the valve seats out and install the larger valves. But the chances of finding a factory set of W31 heads is pretty low. John

 

Correct. The #5 heads used on the 68-69 W-31 were cut for big-block sized 2.000 intakes and 1.625 exhausts. Pretty much any SBO heads can be cut for the same. The #5s do not have hardened seats, so cutting for larger valves is easy.