[bobzdar]

I had a '77 400 (L78, so 6x-8 heads) t/a with 4 speed. Had the edelbrock 'performer' package - intake, cam and carb. It was a dog, ran 16's at 86mph in the 1/4. I swapped cam to a 744 clone, torker intake, qjet and 4 tube flowtech headers. Cost me about $500 at the time, now it'd be closer to a grand - current prices say melling spc-3, used torker and 1 5/8" flowtech headers come to around $700, add $100 for fluids and gaskets, but assume you already have a qjet. Car went high 14's at 98mph but had bad wheel hop and fuel delivery issues. Carter mech pump fixed the fuel issues and I rebuilt the suspension, which fixed the wheel hop, but I never ran it in the 1/4 again. I assumed I could have hit low 14's at around 100mph if I wanted to drag it, but built it more for road racing. 86mph to 98mph is around a 100hp gain without having to pull the heads. These cars are way undercammed at stock, keep in mind they have the same airflow in the heads as the ra1 and ra3 cars that came with either 068 (auto) or 744 (stick) cam in the '60's. Pontiac also used the 744 (originally 041) in the SD which only had 8.4 comp. It's about moving air in and out.

20k miles later, I swapped to high compression #16's with crower valve springs, along with a cast iron factory intake (per prevailing wisdom at the time, early 2000's) and it didn't get any faster though picked up low end - which was pretty much useless with a stick. It wiped a cam lobe likely due to the higher spring pressures, and cracked the pressure plate at the track, and I sold it in a fit of stupidity.

[Sirrotica]

The 455 SD is a classic example of why you don't gain a ton of power when you increase compression ratios a full point. As you say, moving air is another way to increase power, over raising compression. Moving more air doesn't have the possible drawbacks that increasing compression over your fuels ability to supress detonation does. More naturally aspirated air doesn't break pistons, or rings.

As I previously posted, on a late 2nd gen T/A I would go for full length headers over RA manifolds, because they have the ability to move more air. If you keep the low compression, you have to move more air to compensate.

I had a customer that actually managed to order a 73 SD 4 speed car, removed the RA manifolds and substituted Hooker super comp headers. The car noticably picked up with just that modification. No times, just butt meter readings.

Another customer car, 1976 455 T/A, cam, headers, H pipe, intake. it ran a 13.92 with 7.6 to 1, 455 D port engine, basically the same engine that came in a B body daily driver. The car would run out of gas just before shifted, due to the stock fuel lines. Probably would have run 2-3 tenths quicker without fuel delivery problems.

During the late 70s, early 80s, there was no premium pump gas, if you wanted a quick street car, you had to stay with low compression for the low octane fuel available.

During this time there were tons of older high compression factory heads available, cheap too. If you bolted GTO heads on your late smogger T/A you couldn't get fuel for it. At this time all the premium fuel engines left over from the late 60s were blowing up due to broken pistons, and rings. I wasted a good 65 Bonneville 389 this way.