['ol Pinion head]

Interpretted lift @ valve within 2% of NHRA spec, not @ .407 valve lift.

[unruhjonny]

Originally Posted by 'ol Pinion head

Interpretted lift @ valve within 2% of NHRA spec, not @ .407 valve lift.

oh... I guess I'm going to have to recheck what is NHRA spec...

[bird72]

can you remove sway bar in front for run per rules? also I agree on 3.73 post for max....

[Formulajones]

Can't remove the front bar, has to stay attached and functional.

Unruhjonny,

I have my 70 RAIII formula setup to run PS.

For sure run the polyglass tires for this class, don't even look at the modern radials in the equivalent size. Those bias tires work very well at the track and will 60 foot better than one might think. On a side note, the Firestones work a little better than the Goodyears

If you're content to run a manual trans, I go for the M-20 wide ratio every time. The first 3 gear ratios are steeper than an M21 and will accelerate you down track quicker for the first 800 ft or so. The rpm drop in 4th at that point is inconsequential because you have momentum on your side. Also much easier to control wheel spin and recover quickly the first 60 feet.
M21's are more crucial when it comes to rear gear choice to find that happy spot between bog and spin. Not as forgiving from my experience. How you have the secondaries setup on the Q-jet play a roll here.

I'd personally start with 3.73's and the M-20, then you may want to change the rear gear from there (possibly) to suit the car/driver better.

On the cam I like the Melling stuff. Seems to be the most accurate when checking lobe lift and duration specs. You can go the custom route if you want to take advantage of the slight gain in lift and duration the rules allow, but I don't bother. Keep in mind nothing in the rules tell you where you have to install that cam. You can move it around to suit your car, traction, or the lack there of. Might look into retarding it a degree or two if worried about 60 foot times driving a stick shift with a lot of gear multiplication.

Behind the engine I run the original 400 turbo in mine, never opened up or rebuilt and still running it's original converter. So no tricks here. I run a 3.31 gear in the 12 bolt because it's primarily a driver first, fun track car second. So I give up some ET with it but I've still gone low 13's at 106 mph and it will cut 1.8 60 foot times.

Suspension is very basic and simple. Installed new front control arm bushings, well lubed, slightly modded and move somewhat freely. Front shocks are oil filled shocks, not gas. Gas shocks are too stiff. Rear shocks are gas shocks, stiffer to control the rearend a little better (my theory). My front sway bar has poly bushings on the frame mounts that are honed out and greased up to allow the bar to twist freely and not limit front end rise so much but end links all still hooked up and functional per rules.
Rear springs and bushings are bone stock factory issue (47 years old). I left it alone because the car just flat works. I've tried clamping the front of the leaf springs (allowed in PS) but it did nothing but hurt my 60 foot times with this car. Mine seems to like being setup kind of "loose" and has never had any spring wind up or wheel hop issues.

Are you going to take advantage of the 1.5 compression bump the rules allow?

I never did that either, I run mine on pump gas so I built the engine with 10:1 (another compromise I made with mine)

Mine weighs 3690 without driver. Has PS and PDB. Even with the compromises I made (gear, compression, cam, converter) I'm still close to the 12's. I think 12's would be very easy to do with one of these cars when building it to the rules. If that's your plan you should get there no problem.

[unruhjonny]

Great reply!
Thanks for taking the time to share all that!!

[SD455DJ]

Unruhjonny, Formulajones and OPH are correct regarding the legal allowable cam lobe lift for the 066/067/068/744/K Pontiac cams at 2% over NHRA allowable of .425". So we would accept up to .434" max. lift with stock stamped 1.50 rocker arms. I'm sure a few Pontiac racers have substituted stamped 1.65 rocker arms on a stock lift cam to get to the max. lift assuming .010" of flex(No roller rocker arms). This is acceptable as we look at the total valve lift and vacuum minimums as our guide rather than tear down and physically measuring the cam. When we used to have the "Certified" option, we did a pre-race tear down inspection to confirm complete compliance to the rules. It was a lot of work for us and the car owners, but it was a badge of honor and cool to see how fast these cars would run 100% legal. The owner would get a nice "certified" jacket and decal for the window.

I think Goatless is on to something regarding running a 330 hp engine and M-20 trans with the 3.73-4.10 rear end. A 400 with the stock manifolds along with a 067/068 style cam will run amazingly well (Chris Smetana's '70 GT-37) and is more of a torque producer than horsepower. I would expect mid-12's from of a well sorted out car stripped down to manual steering and brakes, no options weighing about 3600 lbs. with driver (little guy or gal).

You can run any gear combo inside your M-20 box, but the factory gears seem to work well with the torque output of the Pontiacs, except the RAIV's. We've seen several RAIV cars switch from the close trans to wide with negative results, primarily from the 3-4 rpm drop of 1.47:1.00 vs. 1.27:1.00 being too great to overcome. A custom 2.52 1st gear with M-21 spread for the 2nd/3rd would be great for RAIV's. For the lower hp 400's and 455's, the M-20 seems to work well due to the low end/mid-range torque they produce.

For tires, either the Firestone or Goodyear G70-14 is the way to go vs. any radial tire for drag racing, not to mention they look better too. Clamping the leaf springs is a trial and error exercise as well as Formulajones suggested. Most cars with leaf springs that run in the 12's and quicker do due to wind-up, but each car is different and needs to be experimented with. That is the fun of the Pure Stock Drags, trying to get the most out of your ride with one change at a time.

And, yes, the front sway bar needs to be in place, but can be shimmed to loosen it up for quicker rise on launch.

I'm happy to answer (or try to) any questions.

Dennis

[unruhjonny]

Wow!
I keep getting more and better information!
Sweet.

I had never thought that the 2-3 shift in an M-20 might hurt the E/T - then again I have (gasp) never driven an M-20 car, only M-21 & M-22.
I have had some time to chew on it, and the more I think about it, the more I like the idea of re-degreeing the camshaft... That had never occured to me, and for some reason I figured that was a no-no...

1.65 rockers huh...
I had figured that was a definite no-no, as it works out to something like 10% extra lift...
I might have a set of stamped steel 1.65 rockers...

[Formulajones]

Originally Posted by unruhjonny

Wow!
I keep getting more and better information!
Sweet.

I had never thought that the 2-3 shift in an M-20 might hurt the E/T - then again I have (gasp) never driven an M-20 car, only M-21 & M-22.
I have had some time to chew on it, and the more I think about it, the more I like the idea of re-degreeing the camshaft... That had never occured to me, and for some reason I figured that was a no-no...

1.65 rockers huh...

You mean the 3-4 shift......Dennis mentions this being a factor for the RAIV cars. They are a little more high strung, like more rear gear etc...and will need that rear gear to get the car going with an M-21 (2.20 first gear) They like RPM and seem to make most of their time up on the back half of the track. On our 400 RAIII stuff you may find the M-20 is your friend.

May want to ask Dennis, I can't remember but there is also a spring seat pressure limit to keep guys from running a ton of pressure and gaining advantage. I can't remember what it is, might be 110 or 120 lbs. I'd have to check.

I have my 69Z setup for PS as well. High strung and likes rear gear, most likely will run better with an M-21.

[SD455DJ]

Formulajones, 130 lbs max seat pressure, unless came from factory with stronger springs and you'll need to show us the proof, but you should run the least pressure springs for the most horsepower, so it is not uncommon for the racers with the fastest cars do a lot of testing to find the minimum pressures they can get away with to maximize power. It's a fine line with some cams and a reason to run cams with slower ramps like Cliff suggests. It works at the Pure Stocks.

RAIV's, like SBC's like a lot of gear, 4.33's work great, 3.90's slow your 60' by 2 tenths along with your ET. The Z's at the race seem to gravitate to 4.88's as the favored gear. 4.56's are OK, but not enough for them there no-grunt hi-winders. The tighter you can keep 2-3 and 3-4 shift points, the better these cars seem to run.

The RAIII's are a different animal and the M-20/3.73 combo is a great starting point.

Dennis

[Formulajones]

I already have a 4.88 rearend here setup and ready to go

Thanks for the update on the spring pressure. I couldn't remember what it was and I just went through this last summer. Getting old, lol.

[unruhjonny]

Originally Posted by SD455DJ

...I would expect mid-12's from of a well sorted out car stripped down to manual steering and brakes, no options weighing about 3600 lbs. with driver (little guy or gal).

Personal diets aside, what are these cars generally weighing in at?
IIRC the official weight rating was 3,450, which is why the highest official engine option was rated at 345hp...

I would think that a non-AC car without too many options should be able to come in under #3450...

Maybe a work out regiment, and cutting back on the burgers is something people do before the PSMCD's?

lol

[Formulajones]

I've never seen a second gen that light, even a no frills version. If they are that light at the PSMD then someone went through a lot of trouble to make it that way. Then I start to raise an eye brow.

I've done absolutely nothing to lighten mine. The only weight bearing options it has is PS, PDB, and 400 turbo. Nothing added, nothing missing. You can say it's basically a no frills version, no AC, no other power accessories. It scales at 3,690 lbs. without a driver. Take out the PS and PDB's, put in a 4 speed that would lighten it some, but it still won't be a sub 3500 lbs. car. If you find a 70 Formula lighter than that, then someone has taken weight out where you can't see it As far as I'm concerned, that's starting to flurt on the edge of fishy, then I start to scrutinize the rest of the car.

Generally the Formulas are lighter than the TA's too. But I can tell you those fiberglass hoods sure aren't that light either. I've picked up steel hoods that didn't weigh that much.

1st gens are another matter. A 400 firebird or 396 Camaro (stock weight) shouldn't have a problem seeing 3400-ish lbs. I haven't scaled my 69 Z yet but I fully expect that one to come in right around 31-3200 lbs. I did nothing to remove weight on that one either, I left the factory sound deadener in it etc... matter of fact I added weight, my wife wanted power steering (originally a manual steer car) so I added a complete factory setup.

Edit: just to add to this, I float around 205 lbs. So my Formula is pushing close to 3900 lbs. going down track. These things aren't featherweights that's for sure, or maybe I need to lose a few lbs, lol.

[Formulajones]

Add to that the 70 and probably 71 models are among the lightest of the 2nd gens to boot, so look at the weight of my car, then compare. I believe shortly after impact regulations set in, and later models have reinforced doors with side impact beams that add weight. I also know the front noses got a little heavier. I have a couple of spare noses here, a 71 and a 73 and when I scaled them the 73 weighed a few lbs. more. I suspect it had some impact upgrades by then. Probably other small details that add weight like the core support bars (70 never had them) etc.... and likely more small things.

In a nut shell, for example, if you find a 73 model (that is heavier than previous years) and it's lighter than my 70 Formula that has very little weight adding options, then you know someone put that car on a serious diet.

[SD455DJ]

Formulajones, the lightest 2nd gen Firebird at the Pure Stocks was Steve Coulter's '71 Formula 400 a couple years ago with a TH400 and 3.73 gears (ran low 14's/98 mph) weighed 3700 lbs. John Glasgo's '70 RAIV TA auto weighed 3800 lbs. I think Steve's Formula had power steering & brakes, center console, radio, etc. If you pull all the sound-deadening (only lightening that is legal), ran just a half tank of fuel and devoid of all options, it's conceivable you could get one down in the 3450 - 3500 lb. curb weight range (no driver). 1st gen Birds are 250 - 300 lbs heavier than their comparable 1st gen brethren in Formula form and 350 - 400 in TA form.

Dennis

[Formulajones]

Thanks for that Dennis, those cars are right in line with mine.

[unruhjonny]

Well, it's been about a year, seems like a nice time to bump this one...

I think i noticed a new rule, or maybe a change;

Cast-iron exhaust manifolds are mandatory and must be correct for the year, model, and horsepower claimed.

Internal modifications to the exhaust manifolds are NOT allowed.

For someone thinking of running regular 'log' manifolds, that's a bit of a bummer...
This thread had inspired me...
http://forums.maxperformanceinc.com/...d.php?t=630943

[Formulajones]

Not a new rule, that's always been in place.

I finally ran mine over the weekend. With a 3.31 gear it went 13.10 at 104 mph best with DA on that run at 2,079 ft. It corrects to a 12.79 at 106.

For giggles I put it on the scale while there. I had aluminum wheels on it as the only change. 3625 with a full tank of gas. I scaled all the wheels, and between the rallys and the aluminum, I removed exactly 50 lbs. from the car. So technically the car normally would weigh 3675 according to that scale, not that far off from the last time I scaled it at 3690.

Race weight this past weekend was 3840. Just a 70 RAIII formy with the only weight adding options of PS and PDB, and the automatic trans.

[unruhjonny]

any idea how much a TH400 weighs compared to a Muncie four speed?

Mine's got ps & pb, and I have no plans of removing them.
The only type of optional equipment removal I had considered was leaving my car as it was built with a single front speaker... but a dual cone one

that's pretty awesome!

[SD455DJ]

Originally Posted by unruhjonny

Well, it's been about a year, seems like a nice time to bump this one...

I think i noticed a new rule, or maybe a change;



For someone thinking of running regular 'log' manifolds, that's a bit of a bummer...
This thread had inspired me...
http://forums.maxperformanceinc.com/...d.php?t=630943

Jonny, Yep, as Formulajones said, that rule has been in place since the early 2000's when we were finding extrude honed intakes and exhaust manifolds, not to mentions many other 'enhancements'. Our ban on all that craziness was the impetus for the cheaters to start the FAST organization. We allow some leniency, but after all, we are the 'pure stock' drags.

Dennis

Dennis

[The Boss]

The trick with the cam is duration I believe - the lift is limited but the duration is not.