I am currently rebuilding a set of 291 double hump heads with the following:

bowl porting
threeway valve job
copper guides
valves are int 1.94 exh 1.50 manley street pro valves
springs are:
Number of Springs Per Valve: Single
Outside Diameter of Outer Spring (in): 1.254
Coil Bind Height (in): 1.150
Spring Rate (lbs/in): 417

This will be on a 68 327 engine with an Edelbrock air gap intake, qjet 750, stock cam, and 1.6 roller rockers. What should be my expectations of how much horsepower I will get.

Probably about like a stock, 300hp/327 if your CR matches that motor?

Maybe 10hp more?

Should be a dandy running motor imho..

Switch to onna these hy-cams and gain probably 35 to 40 more hp!!

CC 268HE and 270 Magnum;

Crane/Cam Dynamics 272/272 Energizer; and

Isky 270 Mega...

Nothing fancy cam-wise, but all in all, these are STILL darn good running older cams!!

pdq67