1970 supreme convertible L-74 . does this combination sound like it will work? w-31 cam, 3.91 rear end, high stall converter....and will the power brakes function or will I need to switch ..thanks for any advice

 

Probably need a little more cylinder pressure for the W31's lazy ramps. A dynamic CR closer to 8:1 for better performance. The stock CR for the L74 is around 9.7:1 not the advertised 10.25:1. Flat top pistons and head and or block machining to increase the static CR would help a long way with that cam. A dynamic CR between 7.5-8.5:1 for best performance. Dynamic CR takes into account the cam duration and overlaps, that effect cylinder pressure. Wouldn't develop enough vacuum for power brakes neither. Vacuum booster required.

Check yours http://www.projectpontiac.com/ppsite...nt/view/16/30/

 

A W-31 cam has 308 degrees of duration and 474 lift and is old technology for a street driven car and will not produce enough vaccum to run standard power brakes. You can get a more modern cam with less duration a little more lift that will make good HP and have vaccum to run your power brakes!