[RicksGTO]

thanks for posting the figures from the recent races Dennis! Very interesting, especially Weymouth's times between his RAIV and 455HO as his engines would be blueprinted and tuned to the same level and suspensions set up in similar ways. The 12.25 to 1 compression allowed on the earlier 400's is a definite benefit to their times. I'd love to see what the HO's and SD's in this class would run with just that one additional change in compression.

[Formulajones]

The SD's and the HO's also got the compression change. It's the same change allowed accross the board, 1.5 points above advertised ratio. So you have to work with what ya got

[1971455HO]

So would I!

[transam1972]

I give a lot of credit to anyone investing time and money into this so we know what these cars are really capable of!...1971455HO is that you with the RA IV cam!?...nice!...I am sorry but Trans Ams were meant to be white!!

[70RAlll]

Originally Posted by RicksGTO

thanks for posting the figures from the recent races Dennis! Very interesting, especially Weymouth's times between his RAIV and 455HO as his engines would be blueprinted and tuned to the same level and suspensions set up in similar ways. The 12.25 to 1 compression allowed on the earlier 400's is a definite benefit to their times. I'd love to see what the HO's and SD's in this class would run with just that one additional change in compression.

I agree..12.25:1 compression seems to be pushing it. Definitely race fuel vs the HO @ 9.9:1 compression could still run on readily available fuel... to me,and disclosure..just my opinion, not trying to start a fight here, I think that is a bit of a stretch. I get the 1.5 increase in compression on all engines from advertised , but when you take an engine from running on pump gas to racing fuel, well I just think you have lost the spirit of STOCK racing.. would love to see numbers of cars with original stock compression engines. Bet the difference ,especially with the RAlll would be glaring... I have always wondered how stock racing produces such numbers vs what these cars did in period tests..And RAlll getting 12.25:1 vs RAIV getting 12:1?? again, seems like the RAlll got a little benefit that makes its performance look better than it ever did against the RAIV,HO or SD's....

[transam1972]

I do have to say we are really no longer stock vs. stock...however I can appreciate things being changed to get more out of your stocker...but it does get confusing as to modifications...when do you stop?...I am looking forward to a nicely set up carb. and uni. dist. on my 58k stocker!

[SD455DJ]

Originally Posted by 70RAlll

I agree..12.25:1 compression seems to be pushing it. Definitely race fuel vs the HO @ 9.9:1 compression could still run on readily available fuel... to me,and disclosure..just my opinion, not trying to start a fight here, I think that is a bit of a stretch. I get the 1.5 increase in compression on all engines from advertised , but when you take an engine from running on pump gas to racing fuel, well I just think you have lost the spirit of STOCK racing.. would love to see numbers of cars with original stock compression engines. Bet the difference ,especially with the RAlll would be glaring... I have always wondered how stock racing produces such numbers vs what these cars did in period tests..And RAlll getting 12.25:1 vs RAIV getting 12:1?? again, seems like the RAlll got a little benefit that makes its performance look better than it ever did against the RAIV,HO or SD's....

70RAIII, '69 RAIV's also can go up to 12.25:1 compression since their advertised compression ratrio is 10.75:1 vs the '70's 10.5:1. When I rebuilt my RAIV motor the heads had been shaved by the previous owner down to 66 cc's. and without decking the block and the pistons .003" in the hole, the compression came out to 10.95:1 with .039" head gaskets. My goal was to keep the compression as low as possible and this is what I got with flat top pistons. I could have used a small dish, but I didn't. I'm sure this was the third time this engine was rebuilt. On the dyno it did 445 hp and 475 tq. In my '70 Judge it turns 12.80's @ 109 mph weighing in at 4050 lbs, original 3.90 rear and Turbo 400 trans and its 13" factory convertor. I'm sure with some 4.33's and some minor suspension work it could run in the mid 12's fairly easily.

Dennis

[SD455DJ]

Originally Posted by Formulajones

You are probably right, I know Mahoney had some jaws dropping on it's debut, but I'm not up to speed on how close he was to the record, but yeah from what I've seen he was running right there with the L88's. Scott Teimann who restored the car does alot of the driving with it I think.

I can post still pics but they don't stay long as you can see already, I have a setting wrong with either photobucket or my computer that I haven't found yet. Unfortunately when I was running the car often years back, I didn't own a video camera at the time.

ET's varied a couple tenths depending on the weather. Best ET was 13.26, and it would go 104-105 mph.
I'm sure the ram air III cars competing nowadays have picked that up quite a bit since.

Formulajones,

It would be great to see you bring your '70 Formula to our race in September. We haven't had a '70 RAIII Formy yet at the race that I recall and your car runs really well. I tech most of the Pontiacs at the Pure Stock Drags and am a stickler for original casting numbers and suspensions.

Is the car a 3.73 4-speed?

Thanks, Dennis

[71HOT/A]

I'm very partial to blue myself but wouldn't mind a white one for contrast. I just tore my engine down for a once over. Still std. bore, even has the original bearings. The old TRW L2423 pistons and SD rods still look great but I'm going with a lighter piston and rod combo. Had a Crane RAIV cam and good lifters and the bottom end was lightened and balanced. Ran like a raped ape but that stuff is old and I don't want to risk a #s engine so it's time to upgrade.

[SD455DJ]

Originally Posted by transam1972

I do have to say we are really no longer stock vs. stock...however I can appreciate things being changed to get more out of your stocker...but it does get confusing as to modifications...when do you stop?...I am looking forward to a nicely set up carb. and uni. dist. on my 58k stocker!

transam1972,

Some people really get caught up on having a fast pure stocker, while many others are satisfied knowing their car is truely factory stock and learn how to make it faster with tuning and driving technique. Don't forget that drag strips are prepped much better than back in the day with glue for the first 330', so you shave a bunch of et with a proper launch and 60' time. It's still possible to spin, but with some control and practice, 2.1 second 60 foot times (and better) are possible, which are alot quicker than the 2.5 or higher back when our cars were new.

Stock RAIV's and 455 HO's/SD's will run 13.50's @ 105 mph regularly after proper tuning and good driving.

Dennis

[Formulabruce]

Originally Posted by Formulajones

The SD's and the HO's also got the compression change. It's the same change allowed accross the board, 1.5 points above advertised ratio. So you have to work with what ya got

So basically 2.5 to 2.75 ABOVE real static CR..

sounds like "stock" to me !

[Formulabruce]

"fast" for a T/A should be measured at the Silver State classic, not a 1/4 mile. It's not a drag car...

[transam1972]

it does have that stripe the length of the car,...seriously though the Pontiacs that are run...does it end there with the last of the roundports the 74 S.D.s? maybe some 455s...any later Trans Ams?

[2manyT/A'S]

1977 & 78 W72 4 speed T/A's have some performance potential.....the HP #'s actually started increasing in those years ...after declines in 75 and 76....

It would be interesting to see what one would do in the Pure Stock drags...but they were burdened with a restrictive cat & lame camshaft,due to emissions regs...

[68bird400HO]

Originally Posted by SD455DJ

Just to continue this fun debate, at the Pure Stock Drags at Mid-Michigan every fall, the best times for the following:

455 HO is 12.76 @ 109 mph (Mark Weymouth's '71 TA optimized to the rules 9.9:1 compression);

RAIV is 12.31 @ 115 mph (Mark Weymouth's '70 Judge optimized to the rules 12.0:1 compression) Bruno is right there as well;

455 SD is 12.57 @ 112 mph (John Glasgo's '73 Formula optimized to the rules 9.9:1 compression);

RAIII is 12.95 @ 108 mph (Todd Kozak's '69 Judge optimized to the rules 12.25:1
compression);

RAII is 11.54 @ 121 mph (Rick Mahoney's '68 Firebird 400 optimized to the rules 12.25:1 compression) Jim Mino is pretty darn close as well at 11.70's, Rick Watson has some 12.10's

RAI is 12.32 @ 116 mph (Jim Mattison's '67 Firebird 400 optimized to the rules 12.25:1 compression)

These are the best et's for each car and usually happened on Saturday morning warm-ups prior to the match-up racing in the afternoon. It seems that most of the HO's, SD's, RAIV's, and RAII's run together in the 12.50 to 12.70 range quite commonly with the few exceptions above, despite the body/chassis type.

Dennis

Interesting comparison. Just to add another dimension, what are the rear end ratios of each of these cars? Also, I thought I saw Dan's Gold T-37 turning 12.50s. What are the specs on his set up (compression and rear end ratio).

[2manyT/A'S]

Originally Posted by 68bird400HO

Interesting comparison. Just to add another dimension, what are the rear end ratios of each of these cars? Also, I thought I saw Dan's Gold T-37 turning 12.50s. What are the specs on his set up (compression and rear end ratio).

Lets add curb weight into the equation,as well......

[Formulajones]

Originally Posted by Formulabruce

So basically 2.5 to 2.75 ABOVE real static CR..

sounds like "stock" to me !

No sir, it's 1.5 points above the "advertised" ratio. So most of your performance pontiacs that advertise 10.75:1 are allowed up to 12.25:1 compression.

That's why you are seeing your HO's and SD's peak at 9.9:1, because you start with an advertised that is so low to begin with. The increase is uniform accross the board, so as far as "stock vs stock" comparison, it's still about as real as it gets considering it's been 40+ years.

[Formulajones]

Originally Posted by 68bird400HO

Interesting comparison. Just to add another dimension, what are the rear end ratios of each of these cars? Also, I thought I saw Dan's Gold T-37 turning 12.50s. What are the specs on his set up (compression and rear end ratio).

I'm sure Dan's car is using the max allowable compression, and for an HO that would come in around 9.9:1.
On rearend ratios, You are allowed any gear ratio you want to run. I'm betting he's running about a 3.73 in that car.

[Formulajones]

Originally Posted by Formulabruce

"fast" for a T/A should be measured at the Silver State classic, not a 1/4 mile. It's not a drag car...

LOL, they are all drag cars, that's what the whole muscle car movement was about, big engines in smaller packages.
Just because the T/A was name was offiliated with the SCCA doesn't mean (for most of us) that it's only good for that. Besides, pontiac never built the car for production to fit the SCCA rules package anyway so it's a moot point (unlike the 67-69 Z28 and Boss 302's )

It's all good Bruce. Most of us just enjoy seeing these cars out doing something rather than sitting in a garage collecting dust.

[Formulajones]

Originally Posted by 70RAlll

I agree..12.25:1 compression seems to be pushing it. Definitely race fuel vs the HO @ 9.9:1 compression could still run on readily available fuel... to me,and disclosure..just my opinion, not trying to start a fight here, I think that is a bit of a stretch. I get the 1.5 increase in compression on all engines from advertised , but when you take an engine from running on pump gas to racing fuel, well I just think you have lost the spirit of STOCK racing.. would love to see numbers of cars with original stock compression engines. Bet the difference ,especially with the RAlll would be glaring... I have always wondered how stock racing produces such numbers vs what these cars did in period tests..And RAlll getting 12.25:1 vs RAIV getting 12:1?? again, seems like the RAlll got a little benefit that makes its performance look better than it ever did against the RAIV,HO or SD's....

Even 9.9:1 is pushing the pump gas limits with a cast iron head and stock HO/SD camshaft. I can tell you I'm at 10:1 with mine and it only likes pump gas if I'm conservative on the timing curve. It's needs a mix of race/pump at the drags.

I know what you mean about the compression and wishing to see stock ratios for stock racing, but as I explained earlier, and as Dennis is also explaining, it's not really possible on a 40 year old engine that's been rebuilt multiple times unless you start changing other dynamics of the engine like installing dished pistons (that don't have good flame travel), or ridiculously thick head gaskets (that kill quench )
So now you would be changing other aspects of the engine that will kill performance and again, technically it wouldn't be stock, would it
When you have to overbore, shave heads, shave blocks, all of which are normal rebuild procedures, compression ratios change. Just the nature of the beast. Hence the reason for the allowable change.