#17 heads originally came on a '68 350 2-barrel engine. They came with small valves & press-in studs. Most head ID sites show 'em to have 72cc chambers. Lots of guys have used 'em in modern day builds.
Most put in bigger valves, and many will port 'em, or pay to have 'em ported. The chambers can be opened up, or they can be machined to reduce chamber size. There are all sorts of upgrades that can be done, for high performance engine builds. With flat top pistons, & a zero deck height, on a 455, they produce too much CR for pump gas, IMO. I feel that combo would require more octane than pump gas 93. If I had to run that engine, I'd use Torco Accelerator octane booster. Some would mix in some 108 octane race gas, or something else to increase octane.
https://www.summitracing.com/parts/t...EaAh5_EALw_wcB
Using the Wallace CR calculator, a .040 over 455, with flat top SP pistons, 72cc heads, .045 x 4.3 head gaskets, & zero deck height, has aprox 11.65 CR. You'd need dish pistons to get the CR down to a pump gas safe level, IMO.
http://www.wallaceracing.com/cr_test2.php
But, Cliff Ruggles and others who know how to build & tune Pontiac engines have reported running high CR, on pump gas. So, it all depends on who you ask, and the exact combination of parts, specs, & tuning.
The RA4 cam you mentioned has long been very popular in high compression Pontiac engines. I ran that cam, along with Rhoads lifters, in most of my 455 bracket cars. Produced a goof enuff idle to launch from an 800rpm idle, using a stock 13" converter. Most of these cars had between 3.55 & 3.73 rear gears, with 13' x 30" slicks. The very few times I tried street tires, just for testing, the traction was basically zero. Nothing but smoke.
Don't know if any of this helps or not.
