Best setup for PSMCD '70/W66
 

I just perused the results for the 2015 PSMCD, and I thought that I might start a fun little thread here;

First the link:
http://www.psmcdr.com/17.html

I was wondering if anyone would chance speculating at the best manual transmission & engine setup for me.

My car was built as a 3.55:1 geared, L78/Muncie three speed car with nothing that I can think of to add weight (besides PS & PB).

I have the option for this even to run as either a L78 or a L74 car;

• L78: 067 cam, "log" manifolds, dual snorkle air cleaner (I have it all).
• L74: 068 cam, 'ram air' manifolds, 'ram air' aircleaner (functional through hood of course; again, I have it all).

I can run either a Muncie three speed, a wide ratio, or close ratio muncie four speed - all were optional (and I have them all).

• 3 speed: 2.42/1.58/1.00
• M20: 2.52/1.88/1.46/1.00
• M21/22: 2.20/1.64/1.28/1.00

(I am thinking that the Muncie three speed is a close comparison to the TH350; th350= 2.52/1.52/1.0)

Any differential gear set is permitted;
I am inclined to run 3.90:1 after a brief ride in a '68 RAI Firebird (I have the correct speedo adapter already).


My experience so far:

I have never run either of those cams;
I believe my car had a 066 cam in it when I bought it as a RAIII (less carb; YZ engine, #12 heads, ra manifolds) car;
When I rebuilt the RAIII, I went straight to the (illegal for this event) 744 cam.

I have only run a close ratio muncie in my car c/w 3.55:1 gears - which I have been told time and again is a bad match;
I have only spoken to three people who have run Muncie three speeds, and every one of them said that it was faster than a four speed.

I will likely setup my car with the numbers & date correct engine once I get the body work ect finished. Then around the time that I build a second engine purely to run at the PSMCD, I will get a second 12 bolt setup with 3.90's - so I have ample time to ponder the specifics of my combination...

I am understanding that the 067 cam is better suited for more low end torque versus the 068...

I understand that the 1970 D-port Firebird RA manifolds offer much less of an advantage than one might think...

I am seeing that the highest "hp" cars aren't necessarily the fastest - it seems to be more about setting up the car just right.

I realize that I would be at a disadvantage by keeping the manual transmission (I haven't raced much, so I will be my own worst enemy on consistency vs my dial in) - but I'm ok with that..

I am thinking that the first of these three combinations might be the best setup:
Thoughts?

cam gear trans
 

068 cam 4:10 gear and m20 will net high 12 s once you learn to drive it like you stole it

what I'm seeing is this;

L74+4.10*+M20 = lousey 60'

* = not the gear set I am inclined to run, because it makes it that much less streetable. I planned on driving there...

But, lets take your suggestion, and to simplify the variables, lets remove the differential gearing from the equation;

I would think that the L74, with slightly less low end torque teamed to a lower first gear ratio with an already low differential gear set, would essentially multiplie the torque to where I would have to either bog it off the line, or I would have a high two second 60';
I was thinking that:
A) with more torque, a lower first gear and low differential gearing, that I'd get a better lower rpm launch and avoid bogging - then hook up faster...
OR
B) with less torque, a higher first gear and low differential gearing, that I can launch at a bit higher rpm, hopefully not immediately incinerate my tires, and get up to speed faster.

I would be concerned that unlike a higher winding motor (like say a small block Ford, or a '70 LT1, putting too low differential gearing might have me need to do an extra shift just before the traps...
(it's been a while since I've really run my car, I cannot recall if one would have to be in top gear before hitting the traps, or if you would be able to remain in third while going theough the traps.)

Am I totally off here?

I have read of '70 A-bodies running L78(067) cars especially well...

The A bodies can run better because the rules allow 'hop stop' bars for them.
The leaf spring cars aren't allowed any mods except straps on springs basically.
(the 67 Firebird would work better with their radius rods)

Lots of straps on springs and possibly add the upper hole on front of spring mount, could help the launch.

The 3 speed would require the 1st shift to be the problem for it.
Getting through the 'H' part at the critical 1st shift may slow the shift and the car's acceleration.

I would probably use the TH400 with the shift kit and smallest and highest stall allowed.
Mod the governor to shift at 5500 RPM (or whatever wanted) and leave it in drive.
(with kickdown still hooked up)

This is basically a bracket race where consistency wins.

I would also use the 068 cam setup.
Not sure it said anything about 1.65 rockers?
(they probably wouldn't know the difference?)

With the right tires, moderate launch, let the Pontiac eat!

:)

i can't use 1.65 rockers.

that's some good stuff to ponder

I am going to bump this thread in the hopes for a little more help;

I may have found a decent deal on a replacement camshaft, but now I am starting to question if it really is that great of a deal.

Can someone please help me decipher who makes 067 & 068 replacement camshafts, and their part numbers?

I found this link;
http://www.pontiacpower.org/PontiacCams.htm
This page seems to have the shotgun effect on me;
there's alot of information blasted on the page - so much, that I am having a little trouble in figuring out what qualifies as a replacement 067/068 camshaft other than the (discontinued) HO-Enterprises "k" cams.

I downloaded the comp cams catalog, but I can't make heads or tails of their offerings...
I have also perused summit (LINK), but again, am havign a tough go at it.

Thanks!

I was under the impression the 067 was no longer made. Seems like there is always some cam suggested which is "close to" or "like" an 067. FWIW, I've used both the 067 and 068 in 350's and 400's and definitely like the 067 more in the 350.

I know that for a while it was NLA... it appears to now be available.

He's already figured out how to drive it like that. :drive:

/\ /\ well, thank you very much :D

Normally I only get ridicule for this - I'll take compliments any day of the week.

Yes, they do :-)

scrap the idea of a replacement 067/068 cam. Get a custom designed cam near those specs. work with someone who knows cams. They cost the same as those replacements and will work much better.

for years I've really been thinking of a RAIII bird. I could just find a donor car, swap in my engine/trans setup (with RA manifolds of course), at least 3.90s, or maybe 4.33s and run mid 12s. However, I have enough projects as it is

Get yourself a back copy of HPP Aug 2008 issue the article is Pure stock Prep school. It goes into drivetrain and suspension and what makes them run.

/\ /\ I have that issue - there are not many from the last fifteen or so years that I do not have;
But setups like that aside, I haven't yet totally nailed down my actual configuration that I should be running - which is why I'm looking for any advice that can be offered.

:D

3.90 with what tire height?
I would choose a 3.73 gear with the 3 speed stick if the tires are under 25 inches...
Just my opinion.....
You are on the right track!

according to the information I found;
F70-14 or 225/70/14 are a 26.5" tire - who knows if that's based on a 6" rim or not - and my car having 7" rims might shorten up that diameter a smidgeon.
I believe that 235/60/14 are permissible, but they offer an extra 1" of tread width, at the cost of over an inch shorter tire (25.1") - so I am inclined to run either a repop bias ply F70/14 or a 225/70/14.
(aren't first gen Firebirds running on a tire at least as skinny as an F70/14?)
http://www.psmcdr.com/7.html

My choice of 3.90's is based on the 67-69 RA cars all(?) coming standard with that gear set;
I had one brief shotgun ride in a legit '68 RAI car;
(It had headers, and an unknown cam, but the factory 3.90's, with the #'s M21 - and that gear set REALLY made the thing launch!)
I figure if I'm going to try to replicate early RA car performance, I need to start with an even playing field - and that necessitates at least 3.90's. :D
Also, 3.90's are still a little more driver friendly than the 4.30's that I was strongly encouraged to go with from a Pontiac racer I respect.

Now, 3 speed versus 4 speed(s) comes down to opinion/consensus;
I am inclined to believe that the guys who are having positive results from using lower gears with the wide ratio stick does point to the Muncie three speed being a winner (less shifts, and the few I have spoken to with this gear box say it seemed noticeably quicker than the four speed they had to compare it against);
I understand that not everyone goes through the traps in fourth gear - and that might be a matter of gearing & delays from shifting ect - but combine this with the Muncie three speed being geared similar to the TH350, and I am thinking that with a little more gear that factory, that I should be in top gear by the time I hit the lights at the end of the track...

Two possible strikes against running the Muncie three speed are:
1) very hard to find parts - if it needs servicing/repairs, I'd be better off running a four speed.
2) if I get some good info that suggests I shouldn't run the Muncie three speed...

:beerchug:

hmm...
It looks as though I misinterpreted the rules regarding tires;
If I show up running either a 14x7" steelie, or a 14x7" rally, my OE tire size is F70-14;
The rules allow me to go up one size - but they require that I retain the aspect ratio - which means I can run a G70-14.

I found this:
F70-14
Dia: 26.45"
Tread: 6.55"
Sect: 8.75"

225/70R14
Dia: 26.4"
Tread: 6.7"
Sect: 9"

I just found this (same link as F70-14):
G70-14
Dia: 26.81"
Tread: 6.9"
Sect: 8.9"

I am guessing that a 235/70R14 is the equivalent size, but these appear to no longer be manufactured.

Just came to this thread from your other link. I don't race Pure Stock, but I do run on the little tires…

Best combo in my mind, especially if you're intent on keeping a clutch pedal, is one that would have less torque and more top end power. Any 400 is going to have enough torque to get you off the line smoothly. Too much torque, though, and you're fighting wheel spin all the way through first gear.

Also- I'd set it up with log manifolds. They weigh a good 20 pounds less than RA manifolds and run just as good if you use mandrel bent 2 1/2" down pipes. Look at Chris (gloryrestoparts) results in his signature.

I would go with the G70-14 tires. The bias ply works way better than a modern radial off the line.

thanks for offering your thoughts!

std manifolds = 'L78' trim = 067 cam = 430tq @ 3,000 rpm
RA manifolds = 'L74' trim = 068 cam = 430tq @ 3,400 rpm

http://i303.photobucket.com/albums/n...irebird-15.jpg

I don't recall the exact rule, but they do allow you a little room on cam design at the PSMCDR. Use that leeway to your advantage.

there is a tiny bit of leaway, it is a rule which was created to accomidate people who cannot get an original pattern camshaft any longer.

I did get one lead, and reached out to it, but never got a reply.

http://www.psmcdr.com/12.html

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...

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

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.

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

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

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...

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.

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

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.

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

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.

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.

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

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

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

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.

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!

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

It has to stay within 1% of advertised so not a lot of wiggle room there.

Chris, We limit duration to 1% deviation at .050" as well as the lift. You can move the lobes around all you want.

Dennis

Must be in the FAST class then - from what I understand the lobes look like rectangles. ;)

I have both laying here I could weigh.

I run a complete 4 speaker AM/FM stereo in mine, it's a driver first, fun track car second. That's also why I kept compression at 10:1 and didn't take advantage of that rule, and also why I'm still not running any gear to speak of in the car either. So pretty happy with how it's performing.

Dang...Tree'd by FJ!

Yeah the FAST class is pretty much unlimited, solid rollers, you name it. It just has to look stock on the outside, that's pretty much it.
That class gets EXPENSIVE in a hurry. LOL

Kind of why I like the stock class, it keeps costs down, parts breakage is almost nil, and it's still a whole bunch of fun.

I got some practice on the tree this weekend :D

FJ - Your Formula is running very strong to pull 13.0's at 104 mph at altitude. It would be an easy 12 with good air. That 400 is a torque motor with only 3.31 gears...very impressive!

Dennis

Thanks Dennis, I advanced the cam a bunch. Motor seems pretty much done by 5,000 or 5,200 but I did accidently go to 5700 on one upshift when I wasn't paying attention. It didn't speed the car up, it actually slowed down a bit.

But the car does need more gear. 3.73's would be sweet. On the video of the runs you can tell it kind of lugged off the line and the engine was flat for about 30 feet before it really started to move pretty good.

To be fair, I was running drag radials on the car just for giggles. I wanted to see what the car was really capable of without the tire being a variable. The tire was taller than I wanted too (28") I normally run the stock 26" tires on it. So I hurt the gear a bit.

I'd like to go back with the 26" tires and some better air and get that magic 12 sec time slip.

And being the type of person I am that likes to tinker and always thinks there is more to be had, I can't help but think the MPH could be better.

It could be the gear holding it back, maybe the taller tire, or maybe the cam position, or a combination of all the above, but I may give the fuel system another good look over too. I'm still running the same 20 year old AC large body pump on it. I almost changed it but it still seems to work good.

Or maybe I'm looking for something that just isn't there, lol.