There's only one "type" of 48. There are "rumors" of one with Ram Air IV chambers, but is still ellusive. We've seen them with chamber volume anywhere from 68 to 74 CCs.
Though Pontiac installed the large-valve heads on 350, we try to discourage the practice. We've found the small-valve heads can actually make more "usable" power with 350. The 2.11" intake valve is restricted ("shrouded") quite badly by the cylinder wall. Using the 1.96" valve allows more air/fuel mixture into the cylinder.
I would suggest 17s or 47s for this. A little port work, screw-in studs, and you're 350 will LIKE it! A Comp XE262H will make it "silly" with good carb (750 or smaller), intake ("Performer" is adequate for 350) and smaller (1 5/8") headers.
Should make at LEAST 350 HP, and over 400 lb. ft. of torque. It really messes with a Chevy boy when you beat HIS 350 with yours...!!! Contrary to popular belief, it CAN be done!
Mr. P-Body, Know of any good head rebuilders, in wisconsin, west side of state, by lacrosse. I know pontiacs are different, than chevys, but alot of buiders do not know. Thanks Fred.
Doubt you'll find any in the area. Best best is to find a builder that has cores. (By the time you buy a set and ship them, it's probably cheaper).
I believe SD has different cores and people that have used their services love them. Not only do they produce good flow numbers, but maintain high port velocity. http://www.sdperformance.com/listProducts.php?categoryID=5 They are also one of the few (if not possibly the only) that can CNC port a Pontiac head.
I have a spare set of '74 GTO #46 350HO heads, small valve, lower compression. I understand these can be good heads with the right combination of parts.
Vikki 1969 Goldenrod Yellow / black 400 convertible numbers matching
