Pontiac 455 hp reduction

[Glenn Briglio]

Originally Posted by oldskool

Sorry, but that makes absolutely no sense to me at all.

I can name several Pontiac engines that were increased by NHRA, then later reduced by NHRA.

So, are you trying to say that once NHRA has increased the hp, they can't later come back & reduce it ?

If a racer causes the hp increase then no it can't be reduced. If Nhra increases hp before it is introduced into their classification guide then yes it can get a reduction. Hope this is correct from what I was told by Nhra.

[SUPERFTAN]

So if the combo is deleted because GM never made it how is it that the Yenco Nova withe 350 LT 1 IS in the Guide Book

[Glenn Briglio]

Originally Posted by SUPERFTAN

So if the combo is deleted because GM never made it how is it that the Yenco Nova withe 350 LT 1 IS in the Guide Book

Good question......above my pay grade

[GUMP]

Originally Posted by SUPERFTAN

So if the combo is deleted because GM never made it how is it that the Yenco Nova withe 350 LT 1 IS in the Guide Book

Are you saying that Chevrolet didn't produce a COPO Nova with the LT1 350 in 1970? I'm pretty sure that one is well documented.

[Jeff Stout]

Originally Posted by Glenn Briglio

If a racer causes the hp increase then no it can't be reduced. If Nhra increases hp before it is introduced into their classification guide then yes it can get a reduction. Hope this is correct from what I was told by Nhra.

My Olds 307 in Cutlass did not get reduction because of being hit. In my wagon I received 3 hp off. G body to B body platforms.

[DG]

NHRA used to provide the run data base with averages for each combo. It made it easy to understand their decisions. I wish they would post the date base and averages again.

[ss3011]

Back in the early 80's we ran a 73 GTO in Stock with an NHRA factored Hp at 350 non ram air and 355 with ram air . There was some confusion on the factory HP rating which originally came out at 310 , but was later reduced to 290 . Pretty hard combo to run because the parts are so rare .

[oldskool]

Originally Posted by ss3011

Back in the early 80's we ran a 73 GTO in Stock with an NHRA factored Hp at 350 non ram air and 355 with ram air . There was some confusion on the factory HP rating which originally came out at 310 , but was later reduced to 290 . Pretty hard combo to run because the parts are so rare .

Yeah, I've never understood that. I've read that the 310hp rating engine was never actually released to the public. Pontiac decided to put a smaller cam in it, so that it would better meet the emission requirements, at the time. This cam change reduced the advertised hp to 290.

Sorta like SS&DI using an SD455 powered GTO as their cover car one month. Called it "Car of the Year". From everything I've read, the SD455 engine was released to the public ONLY in Firebirds.

https://www.hotcars.com/1974-pontiac...-sd-455-facts/

But, for some reason, NHRA allows the '73 SD455 engine to be used in Lemans, Grand Am, & Grand Prix models. John Clegg actually put one in a GP. And Russ mentioned running one in a GTO. But, as he said, the required factory parts are just too rare & expensive to race, for most Pontiac racers. They're highly sought after by collectors.

I suppose that for the non-Pontiac guys here I should mention a few of the most famous SD455 cars. The 1st is the Herslow & Morlock '73 T/A. It set records in both Stock & SS. Then Phil Szupka raced it for a while. John Clegg bought a new '73 SD455 Formula, & won the D/S class @ Indy with it that year. Later ran pretty strong in SS with it. J.B. Clegg now runs mid 9's with it, which makes it the quickest reg SS Pontiac.

Bob Michael built a '73 for SS. Later sold it to Don Kennedy. Craig Hendrickson of H-O Racing Specialties bought a new '74 T/A. Built a SS/KA out of it & set the record in '77. A few years ago, J.B. Clegg ran some 9.60's in it. So, at that time it was the quickest reg SS class Pontiac, ever. Could name others. But that's just a little Pontiac trivia for off season entertainment.

[Billy Nees]

Umm, I don't think that he posts on here but Phil Szupka owned an original 73 GP/ 455SD!

[oldskool]

Originally Posted by Billy Nees

Umm, I don't think that he posts on here but Phil Szupka owned an original 73 GP/ 455SD!

Yeah, we've all read about stuff that came off the assembly line that wasn't suppose to. And a variety of VIP's could usually special order something that was not available to the general public.

Here's a quote from an '07 Motor Trend article. Don't know how much research the writer did. And I didn't see every '73 GP that came off the line.

"... no SD-455-powered Grand Prixs were ever factory produced..."

https://www.motortrend.com/news/hppp...ac-grand-prix/

Pic #4 is of an H-O Racing Specialties newsletter with John Clegg's '73 GP on the cover. It says that he ran it @ Indy with SD455 power, although it don't say that it was an original SD455 equipped car. But it does show that NHRA allowed the SD455 to be used in a '73 GP, from the early years. So, maybe that's the info that Pontiac gave NHRA, at the time.

Mick Leiferman ran a '73 GTO. I've read that it had SD455 power. If that's true, don't know if it came with the SD455 or he swapped it in. For the non-Pontiac guys who don't know Mick Leiferman, he ran a '71 GTO that was a 5-year nat record holder & who was Stock RU @ Indy 3 years straight.

Here are pics of his '71 & pics of his '73, with 2 different paint jobs.