Rocky,
Having co-sponsored the Pure Stock Drags since its start, Bob Boden and I have seen it all, you might say. Also, having owned several 455 H.O. cars over the years, I have an idea what makes one tick, especially in stock form. John Glasgo, and his brother Paul, are both good friends of Bob and I. I'll share with you what it takes to get a 455 H.O. GTO to run that good.
In two words, not much! The 455 H.O. was probably one of Pontiac's best street engines - ever! No other engine, right off the showroom floor, offered so much torque and driveability, and on low or no-lead fuels. They were cammed perfectly with the good old 068 grind that originated in the '65 Tri-Power engines. This cam was small enough to allow the engine to build lots of low-rpm cylinder pressure, yet had sufficient duration to make power up to 5000 rpm. The combination of cubes, cam, port flow, aluminum intake, higher cfm Q-jet (on '71s - due to no booster venturi in the primaries), and good exhaust manifolds just seemed to click.
But if there is one thing that the 455 H.O. craves for (and any other Pontiac engine for that matter), that's more compression! With a combustion chamber of approximately 111 cc's, the actual compression ratio of an untouched H.O. is more like 8.0 to 8.1, not the 8.4 as advertised. However, if you mill the heads down to the NHRA minimum of 96 cc's, the actual compression jumps to about 9.5! That alone is worth up to 30 ponies! This is a modification that is allowed, but not encouraged, at the PSMCDR.
With higher compression, you can improve output further, perhaps another 10 horses, with a slightly bigger cam, and still maintain the engine's original smooth idle characteristics. Since we can't check everybody's cam at the race for duration and lift, we check all cars for idle smoothness. We sometimes check vacuum if need be. We know that the 455 H.O. has a smooth idle, and that's all we ask for. On the other hand, we expect a Ram Air IV to have a rough idle.
In the case of John's GTO, he has probably done both of the above, in addition to optimizing the air/fuel mixture, recurving the distributor, and installing a free-flowing exhaust system.
To put things in perspective, I have a stock '71 455 H.O. GTO to compare with John's. Both cars are equipped the same with automatics, manual steering, and manual brakes, so weights should be pretty close. My car is still running the original compression of around 8.0, but I've optimized the carb, distributor, and exhaust system. The only other big difference between our cars is the gearing. John has 3.73s, and I have 3.07s!
I have managed to turn 13.34 at 102+ mph on two different occassions! Both times were at the Mid Michigan Motorplex, which is where John did his 12.98 at 106+ mph. So we can rule out the track and topography as variables.
For stock cars, as a rule of thumb, every tenth of a second, and every mile-per-hour, requires an additional 10 horsepower. Well, John's GTO is approximately 4 tenths and 4 mph faster than my car. That's the 40 horsepower I discussed above. Given time, I know John will improve his e.t. further, especially since he is geared much better!
I hope that addresses your questions Rocky. I also hope that you can make it to the next race!
Dan
|