Way back when, in the mid/late 1980's, there were no local drag strips in the So Cal area that were accessible, or in a venue that was available for a weekly program,so I got interested in NHRA Stock Eliminator. We could at least run the Winternationals at Pomona, and the Finals in the fall if we did well.I bought a typical '70s vintage stocker to start with, a 66 Bel Air 2 door sedan, 283, Powerglide trans, 5.57 geared 12 bolt, and all. It fit P/SA, a 16 pound per horsepower class, at 220 horsepower. 3690 pounds minimum weight with driver. Not a lightweight. The class index was around a 13.64, I never went quicker with this car than a 13.68. It had the #520 283-327 heads, a very restrictive #457 intake, a Rochester 4 jet, flat top pistons, an.040" over 283, and an NHRA legal camshaft that featured .398" lift on both valves. It sounded outrageously radical and the car left pretty well, with 1.78 60 foot times on bias ply slicks, the radials weren't out then, and a whole lot of the current amenities that make stockers fly now weren't being done then. The cam in the car when I got it had a maximum duration rule, restricting max duration to the OEM duration, even valve spring pressure had to be OEM. NHRA blueprint specs at that time carried all these specs so a racer or an engine builder could comply. That cam sounded nice, but the engine was very fussy about the shift point. You needed to turn the engine all you could, but you had to get it into the next gear in time to avoid valve float. that called for a 6800 RPM gear change. Any putter out the intake or exhaust slowed the car down a bunch. 327's from 62-66 used the same cam. They didn't need to be rpm'ed as much,so they actually made better use of the cam. The rules changed in '88, any valve timing as long as the lift remained OEM, and any valve spring tension. That is why those cars today have 200 pounds on the seat and 400 over the nose, That 283 today would be turned about 8000 RPM in the lights. With the later 327 '68 Chevelles, that incarnation of 327 has a .390 intake lift and a .410 exhaust lift. The #462 head has 10.5 to one C/R, the 250 horse has 1.72" intakes, and 8.75 to 1 CR. Same short block and camshaft. It's possible run H,I, orJ/stock with the 275 horse engine, or J,K,or L with the 250 horse combo, and the only difference is the cylinder heads. Kind of a neat set up, but the 250 horse won't turn the RPM the higher horse motor does.
This story in a nutshell proves that valve lift isn't necessarily the only thing in creating a maximum power effort. I've gone as quick in my Chevelle as 12.20's with the 327/250 horse engine, but the 275 horse engine has gone 11.78 at about 5 miles per hour faster with no other changes. When laying out an engine combination, the first thing you need to do is determine exactly what level of horsepower you are after, then determine how you are going to get it without outrageously excessively extreme parts to do it with.
