The Racer Brown ST-12 was 'super impressive'. Launched at 5700 RPM's, and it pulled like a 'monster' out of the hole.
The 273 'screamed' right up to the 6800 RPM 'Red Line'.
Great pull thru Bottom-End and Mid-Range.
Valve-Springs {268 lb.. Load-Rate} were a touch 'shaky above the 6500 RPM range.
The Valve-Train 'peaked' about 100 feet from the Traps.
Camshaft #8
Crane 'Zip 488' = .488"/.488" Lift ~ 300*/300* Duration ~ 76 * Overlap = (328 HP} = 12.40 @ 108.36 MPH
We switched Valve Springs from;
Crower #68305X1 {95 lbs. Valve Closed ~ 250 lbs. Valve Open}
to
Compu-Cam #926 {130 lbs. Valve Closed ~ 316 lbs. Valve Open}
The Crane 'Zip-488' was a popular Camshaft back in the early 70's, and was a 'Screamer'.
This Camshaft with the 'higher' Load-Rate Valve Springs let the 273 pull right up to 7000 RPM's with
ease.
Was a real strong power-pull from 4500 RPM thru 6500 RPM.
The 273 pulled amazingly strong from Bottom-End all the way through Upper Mid-Range.
We are running with a Carter #3447 AFB {600 CFM}, but this engine now could easily handle
a bigger Carburetor.
