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19USMC69

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When did NASCAR team's transition from factory sheet metal and suspensions? We're factory suspensions and sheet metal abandoned simultaneously? Did all the team's transition at the same time?
 

Charlie Spencer

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How are you defining 'factory sheet metal'? Race cars that started as factory production units and were modified for racing? Race cars that purposely built for racing in private shops but still closely resembled their showroom counterparts?
 

19USMC69

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I realize my question and an answer is/would be subjective. Referring to sheet metal, for the sake of this conversation, I’d say factory doors and only mild mods to the leading edge. I’m figuring mid 70’s?
 

Formerjackman

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As far as bodies, until the early 70's bodies were basically stock cars (bodies in white) put on a much modified stock chassis and a roll case welded in. By the mid 70's until the mid 80's it was factory sheet metal (stripped of it's inner support structure placed over top a purpose built racing chassis with an integral roll cage. It was not uncommon in the early 80's to see where the teams made little sheet metal plates to cover up the recessed door handle openings in the door panels. The panels may have been heavgily massaged, but they started out as factory body shop metal. The first cars I remember that had to be allowed to start straying from this was the 1986 Buick Lesabre and Olds 88s. These were front drive cars and most of the side sheet metal would not really work in anything remotely close to stock form. I beleive that the roof, deck lids and hood still had to be stock metal, and as had been the case since at least the Monte Carlo SS came out in 1983, the nose cone had to carry an approved factory part number. The next car I remember that required even more fudging of the factory sheet metal was the "GM 10" cars like the 1988 Pontiac Grand Prix and 1989 Lumina, Olds Cutlass and Buick Regal. By then the nose and tail pieces carried factory part numbers, but were custom made for racing and would not fit a street car. I can't remember the exact evolution of the Ford sheet metal. It wasn't until MUCH later that not one piece of the body would fit a street car.

Chassis: Until the early 60's they were 100% stock. Slowly they were allowed to be beefed up for racing, but had to be stock. I believe the first BIG change was about 1965 when Ford wanted to run their new intermediate cars that were basically unibody cars with no actual forward frame. Ford teams tried really hard to make this work to no avail, and they were finally allowed to graft their old style perimeter frame forward sections to their newer cars. When the similarly built Chrysler cars hit the track, they were allowed to use steel tubing to build a forward frame section. As late as the mid 70's NASCAR required that at least the middle section of the frame had to be of stock origin. On a GM A body car of the 70's the part of the frame under the door would be stock and the rest would be 100% fabricated. Finally NASCAR relented on that and allowed 100% fabricated construction.

Suspension: All of stock design well into the 60's, but often with heavy duty components. Until the very late 70's cars had to run a suspension design similar to the stock setup, meaning that Mopars had to run torsion bars in the front and leaf springs in the back. GM had coils all the way around, and I think Ford had leaf springs first and then was able to transition to coils. The Ford intermediate car rear steer coil spring front suspension with a single mounting point lower control arm became the standard for all Fords AND GM cars clear up into the 1980's and beyond. The GM A and G bodies were all front steer from the factory, so I don't know WHY they were allowed to run rear steer. Bobby Allison basically pioneered the front steer chassis, copying the GM A body design, and was an ardent advocate of it, but it took a LONG time to become the universal standard. I believe the fact that front steer allowed the engine to sit lower in the car, allow better oil pan design, and didn't interfere with the headers is what FINALLY killed off the rear steer, but it took about 20+ years to do it. I'm not sure when tubular control arms were first allowed. but even into the early 2000's there were ARCA (former Cup) cars that had the fabricated steel Holman Moody style single point mount lower control arms instead of the all tubular two point mount lower arm.

Drivetrain: It was not until the mid-1970's that NASCAR allowed engines from ANY corporate division to be used, basically meaning that ALL GM cars of the late 70's could use a Chevy engine. Around that time all makes were then allowed to use a Borg Warner T-10 style transmission, and all cars were allowed to use the Ford 9" rear axle.
 

Ford 222

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Thanks. Great info.
I agree....love the insider perspectives. Doesn’t seem to have been that long ago that they talked about the cars requiring the hood, roof, and deck to be factory but I distinctly remember when the Monte Carlo came back in 95 or so the rear was too narrow so it did not fit some of the stock templates so NASCAR allowed them to modify it so a spoiler would fit across it. Still irks me.....lol
 

Formerjackman

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I agree....love the insider perspectives. Doesn’t seem to have been that long ago that they talked about the cars requiring the hood, roof, and deck to be factory but I distinctly remember when the Monte Carlo came back in 95 or so the rear was too narrow so it did not fit some of the stock templates so NASCAR allowed them to modify it so a spoiler would fit across it. Still irks me.....lol
Over the long history of NASCAR, EVERY manufacturer has had the rules twisted like a pretzel to suit their particular situation at the time. There is no purity in this regard. It's kind of the price NASCAR pays to keep as many brands as possible in the game. The Thunderbird was the last car model that had ANY sense of purity to it, being a two door rear drive pushrod V8 powered car. On the other hand, Ford was probably the first to be allowed to stray very far off the reservation with the full frame chassis grafted onto a unibody car OR Chevy being allowed to campaign an engine (The 427 Mystery Motor) that was not even available to the public. Of course Chrysler did the exact same thing the next year with the Hemi.
 

Ford 222

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Over the long history of NASCAR, EVERY manufacturer has had the rules twisted like a pretzel to suit their particular situation at the time. There is no purity in this regard. It's kind of the price NASCAR pays to keep as many brands as possible in the game. The Thunderbird was the last car model that had ANY sense of purity to it, being a two door rear drive pushrod V8 powered car. On the other hand, Ford was probably the first to be allowed to stray very far off the reservation with the full frame chassis grafted onto a unibody car OR Chevy being allowed to campaign an engine (The 427 Mystery Motor) that was not even available to the public. Of course Chrysler did the exact same thing the next year with the Hemi.
Good stuff thanks. The Monte Carlo debacle occurred during my prime viewership years so it stands out in my mind. I saw where NASCAR let Ford run a completely illegal Galaxie with Junior Johnson to woo Ford back after they threw a tantrum back then and quit.
 

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And when NASCAR tried to ban the Hemi, Chrysler took their toys and went home, leading Richard Petty to his partial season as a drag racer. When attendance numbers hit the skids, NASCAR relented and allowed the Hemi back in, but I think with the stipulation that they start offering it in production cars, which they started doing for 1966.
 

OldTimer

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Manufacturer specific body panels through 1991...but there was a migration of racing specific body components during the period between 1985 to '91.

As much as the principle of using a stock body of a manufacturer was attempted in theory, in actuality, some in NASCAR got fairly creative even back in the mid sixties.

Junior Johnson's yellow banana comes to mind...the creative body massaging of Smokey Yunick...the chassis streamlining and belly pans coming out of the Petty stable.

Even H&M did some unique techniques to assist in higher speeds...they had a couple of not so light, large women sit on the unsupported (from the center of the front wheel wells forward) nose of the car....changed the aspect slightly. Take a look at some of the pictures from '64. '65, and '67...on their speedway cars the front wheel wells bellow out on top a bit...because the nose is pushed down a bit. Creative bending so to speak.

Short track bodies did not get altered much other than cutting for clearance.

As far as chassis, stock factory full frames up until 1966. Then Nascar allowed grafting on a factory front stub to unibody cars. But it had to be a stub of the host manufacturer. Therefore, a Ford full size front stub on the Fairlane chassis. Since Chrysler did not have an adaptable stub, they were saddled with the "K" frame integrated into their "U" channels (which they plated ending up with with basically tubing). This actually was still being used up through the years that Petty Enterprises still ran Mopar. GM had a front stub, but with the advent of the Nascar Sportsman allowing the Nova (and also the Camaro in the Grand American series) they had to allow for grafting the GM stub to the unibody (remember Camaro, Nova, Firebird, and the little GM alternatives only had separate front stub bolted in the back to the floor pan of the unibody) This was the reason that NASCAR allowed H&M to do the same with the Ford (a year earlier to see if it would work). So that is how the intermediate Fords ended up with the '65 Galaxie type stock front stub. But...the front stubs had to be "stock" manufacturer front stubs.

Interestingly, Bud Moore built 100% unibody Mercury Comets in '66 and '67. He was actually successful with them too. But, a fender bender would put them in the junk pile as they were too costly to repair.

In 1972, the Ford Torino came with a full frame from the factory, so now both GM and Ford could have used their own complete chassis as a base. But, in the spirit of competitiveness and safety (Both Ford and GM chassis were now integrating "crush space" into their front stubs) they allowed for fabricated chassis with the purpose of using the '65 Ford Galaxy dimensions and design(but fabricated out of square tubing)for all makes. Banjo and a few others manufactured these. They were pretty much the same from one to the other, with the primary option of whether or not you wanted front steer or rear steer.
H_M Kit 1970.jpg

1970
 
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OldTimer

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but it took a LONG time to become the universal standard. I believe the fact that front steer allowed the engine to sit lower in the car, allow better oil pan design, and didn't interfere with the headers is what FINALLY killed off the rear steer, but it took about 20+ years to do it.
Beadle's cars ran rear steer up until they closed up shop...believe that is the late '90's. Almost all teams had one or two rear steer cars in their stable. Probably for those few road race events. Once the dry sumps came along, it did not matter as far as pan clearance and since there has been a minimum crank center line height rule in all branches of NASCAR since the Midwest boys (believe it or not that is where Allison got most of his ideas from...specifically the CWRA boys that he knew when he worked for Kiekhaefer) came down and cleaned the NASCAR racers clocks in the open races during the winter hiatus up north. Those boys figured out how to get the bottom of their oil pan a little better than an inch off the track....when someone told them that they had to have 5" clearance....they thought that was the center line of the crank to the ground!

Back to rear vs front steer. Rear has inherent natural Ackerman... easier to put the steering center point on the pivot point of the rear axle (Two lines following from the lower ball joint, through the center of the tie rod end on the spindle side, and then coming together where the roll couple point on the rear end. Therefore, rear steer cars are able to transition turning both left and right with the correct Ackerman related to the roll couple in the rear. Front steer cars have to compromise when on a road course...generally they will bias towards a right turn because most drivers have a natural tendency to feel more comfortable turning left, they are not afraid of the push turning that way. The other advantage of rear steer is that they have less tendency to scrub the front tires. Back in the bias tire days, this was a big deal. Did not bother you too much for qualifying or half way through tire wear....but once it started, the front steer cars faded quickly. But there were plenty of yellows to help even the score.

Once the radials became the predominate tire configuration, the sidewall flex was enough to hold off the scrub factor long enough for the car to pivot in the corner. So scrub was no longer an issue. The other big change that was fortuitous for front steer configurations was the use of the long truck arms in the rear. This moved the center point way forward almost within the reach of the Ackerman of the front steer.

Just FYI....if you have a short arm rear suspension, the rear steer would probably be more accommodating for low budget teams as they allow for more roll steer. Which front steer cars hate.
 

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Thought I would show how low they could go....this is a mid '70's picture of Tom Reffner....he tied Dick Trickles 67 feature mark in one year (Dick actually had 72, but they were not all asphalt I believe, five were on dirt). Keep in mind that the #1 spark plug had to be within one inch front to back of the upper ball joint.
Tom Reffner.jpg
 

Formerjackman

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Beadle's cars ran rear steer up until they closed up shop...believe that is the late '90's. Almost all teams had one or two rear steer cars in their stable. Probably for those few road race events. Once the dry sumps came along, it did not matter as far as pan clearance and since there has been a minimum crank center line height rule in all branches of NASCAR since the Midwest boys (believe it or not that is where Allison got most of his ideas from...specifically the CWRA boys that he knew when he worked for Kiekhaefer) came down and cleaned the NASCAR racers clocks in the open races during the winter hiatus up north. Those boys figured out how to get the bottom of their oil pan a little better than an inch off the track....when someone told them that they had to have 5" clearance....they thought that was the center line of the crank to the ground!

Back to rear vs front steer. Rear has inherent natural Ackerman... easier to put the steering center point on the pivot point of the rear axle (Two lines following from the lower ball joint, through the center of the tie rod end on the spindle side, and then coming together where the roll couple point on the rear end. Therefore, rear steer cars are able to transition turning both left and right with the correct Ackerman related to the roll couple in the rear. Front steer cars have to compromise when on a road course...generally they will bias towards a right turn because most drivers have a natural tendency to feel more comfortable turning left, they are not afraid of the push turning that way. The other advantage of rear steer is that they have less tendency to scrub the front tires. Back in the bias tire days, this was a big deal. Did not bother you too much for qualifying or half way through tire wear....but once it started, the front steer cars faded quickly. But there were plenty of yellows to help even the score.

Once the radials became the predominate tire configuration, the sidewall flex was enough to hold off the scrub factor long enough for the car to pivot in the corner. So scrub was no longer an issue. The other big change that was fortuitous for front steer configurations was the use of the long truck arms in the rear. This moved the center point way forward almost within the reach of the Ackerman of the front steer.

Just FYI....if you have a short arm rear suspension, the rear steer would probably be more accommodating for low budget teams as they allow for more roll steer. Which front steer cars hate.
I understand what you are saying about the dry sump pans, but I remember the topic coming up in the late 80's during a technical piece on one of the racing shows and the "expert" being interviewed stated that the front steer cars gave them more options with the oil pan configuration. Take it for what its worth. In my reletively limited amount of time working on race cars, I never even SAW a rear steer car, let alone work on one, so I have to relyy on the small amount of photographs out there to learn about the details of these cars. I HAVE worked on rear steer street cars. You sound like a rear steer advocate, and I know there are/were many, but there seemed to be an awful lot of people who were convinced front steer was the way to go, and for whatever reason, they won out.
 

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@Churchkey ... Your posts above are very well done.

Thanks for taking the time. The forum is lucky to have you as a member and as a resource.
 

Churchkey

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@Churchkey ... Your posts above are very well done.

Thanks for taking the time. The forum is lucky to have you as a member and as a resource.
Thanks however if you do not mind I'll pass that torch on to new member OldTimer he has the tech data bases covered now I have given up on posting tech data here.
Take care.
 

OldTimer

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You sound like a rear steer advocate,
Depends on the circumstances, rear suspension...if it has to retain stock configuration, then rear steer is more accommodating, providing you have to maintain stock engine set back. If you are running bias ply tires....rear steer is more forgiving and does not wear out the right front as much. But, if you are allowed to have long arm suspensions in the rear, then front steer is generally more acceptable, if you are running radial tires and long arm type rear suspensions....front steer again is more agreeable.
 

aunty dive

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Thanks however if you do not mind I'll pass that torch on to new member OldTimer he has the tech data bases covered now I have given up on posting tech data here.
Take care.
LOL

I flubbed that up badly, didn’t I? Most humble apologies to both of you.
 

Formerjackman

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Depends on the circumstances, rear suspension...if it has to retain stock configuration, then rear steer is more accommodating, providing you have to maintain stock engine set back. If you are running bias ply tires....rear steer is more forgiving and does not wear out the right front as much. But, if you are allowed to have long arm suspensions in the rear, then front steer is generally more acceptable, if you are running radial tires and long arm type rear suspensions....front steer again is more agreeable.

I mentioned it earlier, but the more I think about it, I'm REALLY perplexed given the rules at the time otherwise, why the Chevy teams were allowed to run rear steer which was never on the 1968-1977 A body cars, and why they were they allowed to run truck arms, which were NEVER on a Chevy car?
 

Ford 222

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I mentioned it earlier, but the more I think about it, I'm REALLY perplexed given the rules at the time otherwise, why the Chevy teams were allowed to run rear steer which was never on the 1968-1977 A body cars, and why they were they allowed to run truck arms, which were NEVER on a Chevy car?
Because they were Chevy....;)
 

OldTimer

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I mentioned it earlier, but the more I think about it, I'm REALLY perplexed given the rules at the time otherwise, why the Chevy teams were allowed to run rear steer which was never on the 1968-1977 A body cars, and why they were they allowed to run truck arms, which were NEVER on a Chevy car?
GM promoted this chassis at the Speed weeks in 1971 as a prototype for the '72 season. This was a display outside the quasi GM (the supposedly were not into racing at the time) hospitality tent. Please note the rear suspension...that was a no go from the start. Allison had already came to the conclusion of eliminating one of the upper links in his own builds because of the bind it caused. There was a lot of politics involved to get the truck arm suspension, believe NASCAR saw that has a compromise between GM and the Ford faction...the Chrysler's still had leaf springs, which surprisingly were still very competitive, in fact in some ways superior. But that was also still the bias ply era.
1971 GM Nascar rear suspension.jpg
1971 GM Nascar Chassis Front.jpg
 

Formerjackman

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GM promoted this chassis at the Speed weeks in 1971 as a prototype for the '72 season. This was a display outside the quasi GM (the supposedly were not into racing at the time) hospitality tent. Please note the rear suspension...that was a no go from the start. Allison had already came to the conclusion of eliminating one of the upper links in his own builds because of the bind it caused. There was a lot of politics involved to get the truck arm suspension, believe NASCAR saw that has a compromise between GM and the Ford faction...the Chrysler's still had leaf springs, which surprisingly were still very competitive, in fact in some ways superior. But that was also still the bias ply era.View attachment 49202View attachment 49203
A LOT of interesting stuff in those two pics. Anybody who has owned and worked with this era of A Body GM intermediates knows that the suspension as built had quite a few shortcomings. The four link system CAN be made to work on the street, but usually the better cars replace the stock upper arms with adjustable pieces and boxed lower arms with a sway bar added (if not already present). The REALLY fast cars throw it ALL away and start over. I see they made the upper links adjustable with multiple mounting holes, and that the rear axle appears to be the older style GM front loader type generally not used after about 1964.
 

Formerjackman

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I also notice that the springs have been moved to in FRONT of the rear axle instead of on top as the stock ones are. The shocks also appear to be more upright instead of more tilted outward and backward as the original.

On the front, the two big differences I see are that the upper control arm mount has been raised SUBSTANTIALLY from the stock location, and of course the shocks moved from inside the coil spring to behind the control arm. Once again, those that know the street cars know that these cars were built for bias ply tires and to accommodate manual steering, and are VERY positive caster deficient, which make them a LOT less stable at speed than they otherwise could be. Raising the upper control arm should allow huge improvements there. The solution on street cars is to run custom tubular control arms. Some guys used a special tall ball joint as a crutch, and the ultimate street solution is coilovers. I also see that the frame is a fully boxed unit and looks factory, so it is likely either a convertible or an El Camino frame. Looking further, it appears the engine mounts have been modified to move the engine back in the chassis.
 

OldTimer

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so it is likely either a convertible
It was the convertible frame...but most of us used the standard frame and boxed it in. Just flat plating the channel on the standard "A" intermediate frame reduced flex better than the reseam welded convertible frame. For NASCAR/USAC, since weight was less a priority, we actually used a reversed channel and boxed the factory frame in. If I recall correctly...we used .083 wall, with one inch lips on 3' rail, sent them over to AO Smith (where over half of every domestic auto manufacture had their frames stamped and welded) and the boys would make mirror image pressed rails that would be formed to fit the inside of each factory rail. They would press the rails channel up, that way the new left would be molded to the inner part of the right factory rail, and vise versa. All we had to do was weld the overlapping seams. We did the same with the '65 and up Fords too. Did not have to do that with the '64 and older cow belly framed Fords...they were probably more stout (minus roll cages) than a modern bare frame in NASCAR today.
H_M Cowbelly chassis early 60s.jpg
'62_64 H-M Ford Nascar Frame.jpg
 

OldTimer

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and are VERY positive caster deficient
Gotta love those grocery cart specifications. We always started out with a half a degree or so back on the left and about 1.5 back on the right for any track a mile to about a half mile. Back then you could get enough stagger to adjust, now days, you have to lay the left back a bit more to accomplish the same natural turn in.
 

Formerjackman

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The preferred setup for hot street A bodies with power steering and radial tires is 5.5 degrees positive, but 90% of cars with stock components won't let you attain more than about 3 degrees, sometimes less depending who welded the suspension mounts on that day. That's why the guys that really want a superior road feel go to tubular A- arms.
 

OldTimer

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I also notice that the springs have been moved to in FRONT of the rear axle
An attempt to use the axle torque for the purpose of weight transfer. Looking at it from the drivers side of the car, when power is applied, the rear tires rotate counter clockwise but the axle housing tries to rotate counter to that twist...or clockwise. The springs in front of the axle push up against the weight of the car in front of the axle.

Leaf springs do this naturally as their fundamental spring function is between the center of the axle housing and the front spring mount. Behind the axle leaf springs have the pivoting hanger, so that makes the leafs behind the axle not as much part of the weight transfer function. If you have ever seen a drag car with leaf springs and traction bars launch...the rear of the car actually rises...this is the force transferred from the clockwise rotation of the axle housing vs. the traction of the tire and the resistance of the spring against the weight of the car.

The truck arm suspension takes this even further, the same principle, but the front arm mounts try to transfer weight much further forward. The lift would be more central which sometimes causes the car to squat in the rear slightly has it hooks up.
 
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