[Rocky Rotella]

I guess this can be directed towards Dan Jensen, but anyone feel free to answer. I noticed that in the current issue of MCR, John Glasgo has a 71 455HO GTO and he ran a best of 12.987 @106.09. What kind of modifications can be made to these cars yet still be considered "pure stock"? His GTO is a great running car in the 12's where most stock (factory built) HO's are in the high, high 13's and low 14's. Please note I am not disputing anything, I am just curious about what is acceptable, not only with Pontiacs, but in general. Thanks Dan, someday I'll attend. Rocky

[Rocky Rotella]

I guess this can be directed towards Dan Jensen, but anyone feel free to answer. I noticed that in the current issue of MCR, John Glasgo has a 71 455HO GTO and he ran a best of 12.987 @106.09. What kind of modifications can be made to these cars yet still be considered "pure stock"? His GTO is a great running car in the 12's where most stock (factory built) HO's are in the high, high 13's and low 14's. Please note I am not disputing anything, I am just curious about what is acceptable, not only with Pontiacs, but in general. Thanks Dan, someday I'll attend. Rocky

[Dan Jensen]

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

[Rocky Rotella]

Dan, Thanks for the input. My dad and I had the pleasure of talking to you at the POCI nats in Moline IL(1996) when you had your 71 455 HO Lemans 3 speed (beautiful car, by the way). You have/had quite a nice collection. My dad has a 72 455HO T/A and its been built some. A little port work on the 7F6's, gasket matched, about 9.5:1 compression, a tuned 71 HO Q-jet, Nunzi 068 profile high lift cam as well as the basic rebuild on the block. I have a 76 T/A that is a 455 4 speed. I have ported 4X's, 1.77 valves, RA III exhaust manifolds and the 068 Nunzi cam. My winter projects are to install the 72 HO aluminum intake, 71 455HO Q-jet, Nunzi 744 profile cam and 1.6 full roller rockers. As the set-ups sit, they are dead even. I am hoping to gain a little with the 71 HO carb and 72 intake. What are your comments or opinions on those two particular items? I saw you on MCC and read in MCR, my compliments to you and Bob. One question in general, I have read much about the difference between the 197 and 7F6 heads. I know the 197 is supposed to flow better, but what is the real world difference (performance) between the heads? I have considered getting into round ports, but I am happy with my d-ports. No use spending some big bucks on a pair of round ports for little if any gain. Thanks again Dan, I hope I am not asking to many questions. Rocky

[Dan Jensen]

Rocky,

Thanks for the comments on the LeMans. It was, without a doubt, the best Pontiac I've ever owned. It did everything well! Actually, I don't own it anymore, but it has remained in my barn since the change of ownership. The current owner, who has never driven the car, is interested in selling it due to personal issues that have come up. Anybody interest? See the June 1997 HPP for info.

I think the '72 H.O. intake and '71 H.O. Q-jet are both good pieces that will add a few horses to your combination. More so the '71 H.O. Q-jet because of its increased airflow - the result of the booster venturies being removed.

I honestly do not know if there is any flow difference between stock 197 and 7F6 heads. It is probably minimal, if there is any difference at all.

About the only advantages over stock D-ports are the taller intake ports, and the fact that the center-two exhaust ports have better separation (not siamesed together) for better header designs. Since you are running the good cast iron D-port exhaust manifolds already, I won't switch to round ports either.

[Forrest]

hey Dan, I own a 72 h/o and have been looking for a carb for mine, and saw your mess. about the carbs, I remembered seeing this in the 72 service man.; the 72 carb also has the second boost venturi removed, and the small boost venturu skirt lengthened to increase air flow, so which carb do you think flows the best? thanx Forrest

[Rocky Rotella]

1972 455HO Q-jets are of the normal 750cfm casting. The 1971 455HO Q-jets (7041267, 7041268, 7041270, 7041273) were the only carbs to have the primary booster ring not cast in. The booster ring delete help curb nozzle drip and increased air flow to 800cfm. That is what makes them so desirable for performance.

[Gerry Charlesworth]

On the primary booster. Is this something a person could mill out of a standard carb ( if you had the big carb to copy) and still be able to get a proper fuel curve? Thanks, Gerry

[Rocky Rotella]

I ground the booster rings out of my 76 T/A carb. It seems to work well, but it was a lot of work

[Judge273]

Oldie but goodie... Back when Dan Jensen was a member, and the guy can build them and write about them too!!

[Lloyd-TX]

Whoa, Mike, LOL!

When I first saw this I thought it was a current thread . . .

[Judge273]

Lloyd, before your first post....Forrest and Rocky had just joined. Took me 4 years before I did.

[Lloyd-TX]

Originally Posted by Judge273

Lloyd, before your first post....Forrest and Rocky had just joined. Took me 4 years before I did.

Yeah I was checking that out too, Mike . . .

[Drew W]

Originally Posted by Judge273

Oldie but goodie... Back when Dan Jensen was a member, and the guy can build them and write about them too!!

I understand Dan is a very knowledgeable fellow. Is there a reason he no longer participates?

[Judge273]

Drew, I think so.

[SD455DJ]

Originally Posted by Drew W

I understand Dan is a very knowledgeable fellow. Is there a reason he no longer participates?

Dan is a very busy guy, but he does lurk and occasionally responds to direct questions. If you have any questions for Dan, I'd be happy to tell him to get on the PY site and answer them. He is always more than happy to help anyone with their Pontaic issues.

Dennis

[Judge273]

Thanks Dennis!

[bulletpruf]

Originally Posted by SD455DJ

Dan is a very busy guy, but he does lurk and occasionally responds to direct questions. If you have any questions for Dan, I'd be happy to tell him to get on the PY site and answer them. He is always more than happy to help anyone with their Pontaic issues.

Dennis

He's been very helpful with my Pure Stock build and very open about what they normally do to their Pontiac engines.