cij911: "a setup that had more like 400 ft lbs of torque and 550 hp would probably be faster, yet easy and fun to drive casually around town (below 4k rpm) and a hoot to drive like I do (up to 5500 rpm)."
PJ: Not realistic. Pontiac engines come with torque - that's their design. A 550HP can be had with a stroker engine, but be ready to shell out about $10,000. Check out these prices from KRE and note the 550HP build & price:
Tin Indian Performance Pontiac Engine Builder Combinations
Check out Butler's engine - Whaaaaaat? Cast iron heads AND is that a hydraulic flat tappet cam?:
https://butlerperformance.com/i-244...01-cu-in-long-block.html?ref=category:1267471
My guess would be getting 550HP from a 400CI engine would mean higher RPM's to go with all the aftermarket parts needed.
I don't think the '65 tri-power, or even the '66 version would be good for 550HP without some serious rework.
bigD has pointed out the "041" cam which could work with the Rhodes lifters. Here is a quick synopsis of the Jim Hand test cam session:
****Installed 041 cam with 1.5:1 rocker arms; E.T. fell off by 0.1 sec. and 1 mph. Car was all but impossible to drive on the street due to the rough idle and loss of low-end power.
****Installed 1.65:1 rocker arms on the 041. No performance gain, and even worse low-speed performance.
****Installed Rhoads variable (leakdown) lifters on the 041 with 1.65:1 rockers. Quarter-mile performance improved by .15 seconds and 1.5 mph over the 068 with 1.65:1 rockers. Idle quality was excellent, with high vacuum when the engine warmed up. Rhoads lifters cause a ticking noise similar to solid lifters.
****Due to the rpm limitations (5,500) of the 455 engine’s stock internal parts, and my desire to retain comfortable street driving, any new cam I tried would have to provide a smooth idle at 560-580 rpm in Drive with at least 12 inches of vacuum, and develop strong power from idle to 5,500 with the 3.55 gears in this 4,000+ lb. vehicle. The Rhoads lifters were used in all cam tests in order to maintain the 500 to 600-rpm idle capability with adequate vacuum to operate the power brakes.
****The 041 cam was designed for the highest level of power available from about 1,500 to about 5,800 rpm, which was the planned operating range of the 400 engines, for which this cam was originally designed. In our performance tests, the broad power range of this cam is obvious.
****For great street driving with some drag-strip work the 068 with 1.65:1 rockers provides outstanding performance with automatic equipped 455s, including air-conditioned vehicles. The 041 cam is suitable for both the 400- and 455-equipped cars with 4speed transmissions, with or without the Rhoads lifters. The 400 automatics perform well with the 068 and 1.5:1 rockers.
****Both the 400 and 455 respond well to valve lifts of up to about .460″.
****All of the custom cams provided good performance at the strip, but in direct comparison, the 041 provided as good or better quarter-mile performance along with superior idle characteristics (with the Rhoads lifters).
You can read the complete article here:
Building a Strong Street Machine ? Part 5: Pontiac Camshafts | Dallas Area Pontiac Association