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70's chassis, vs. 80's chassis

 
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AdamtheWayne



Joined: 09 Jul 2018
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PostPosted: Mon Feb 25, 2019 1:42 pm    Post subject: 70's chassis, vs. 80's chassis Reply with quote

I'm the guy, that can look at something that's supposed to represent a certain something and go "That ain't right". I can walk into a room and instantly point out everything that isn't level, even if it's just a hair off. So I'm good with the bodies. (I annoy people and I know I do, I can't help it)

However, I'm sitting here looking over a couple recent buys, attempting to grip what's going on with the chassis. Two Monogram kits, one Grand Prix, one 83 T-bird. The mid section, is nearly identical.

I know Ford returned to full frame in the early seventies, but here's my thing.

When it comes to the Monogram chassis the floor plate is not in doubt. They were VERY accurate as far as GM. How far retro (into the 70's) can that chassis go and still be accurate? Same for the Ford? Did Mopar use the same mid-section pan? AMC?

When did NASCAR mandate that the front forks would be box tubing and the trunk area home built?

If you can, provide photos of 70's and 80's NASCAR chassis for Ford, Chrysler, GM and AMC if at all possible. Having trouble wrapping my head around some of this stuff.
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Tom M.
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PostPosted: Mon Feb 25, 2019 9:22 pm    Post subject: Reply with quote

The Monogram (and AMT, since most of the '70s bodies it would be mated with are 1/25 scale) Ford chassis is the most nearly correct for a '70s Banjo or Hutch build. There are some differences, for example the side rails weren't allowed to be fabricated until '78 or later but most surface plate GM and Ford chassis in the '70s used the Ford style front suspension and the long truck arms in the rear.

The GM style front suspension was only used by Bobby Allison, the DiGard cars that Donnie Allison drove, Allison customer cars, and some homebuilts. Those cars typically used modified factory frame stampings in front, not the rectangular tubing. So the Monogram (and AMT) GM style chassis is incorrect for anything raced in the '70s that I'm aware of.

The way I recall the rulebooks reading back in the late '70s, it was legal to build a 4 coil chassis under a Mopar but I don't believe any were built that way until new chassis were built for the downsized cars in '81. I believe all the Mopars in the '70s were Mopar floor pan chassis with rear leaf springs and front torsion bars.
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Firefly



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PostPosted: Mon Feb 25, 2019 10:50 pm    Post subject: Re: 70's chassis, vs. 80's chassis Reply with quote

AdamtheWayne wrote:

...When did NASCAR mandate that the front forks would be box tubing...?


On this point, I don't think it was a mandate, but was an allowance of fabricated front clips, as factory Galaxie mid-'60s clips would be becoming more scarce. I believe around '69 or '70.

Those more knowledgable may correct me here...
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AdamtheWayne



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PostPosted: Tue Feb 26, 2019 4:13 am    Post subject: Re: 70's chassis, vs. 80's chassis Reply with quote

Firefly wrote:
AdamtheWayne wrote:

...When did NASCAR mandate that the front forks would be box tubing...?


On this point, I don't think it was a mandate, but was an allowance of fabricated front clips, as factory Galaxie mid-'60s clips would be becoming more scarce. I believe around '69 or '70.

Those more knowledgable may correct me here...
Okay because that's part of what I was wondering. I had heard somewhere, that the big Mopar K members were removed because in a crash they could come off due to their weight. This forced all the teams to do likewise. Don't know where I heard this.
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Tom M.
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PostPosted: Tue Feb 26, 2019 3:53 pm    Post subject: Reply with quote

The big Mopar K-members were eliminated because they limited how low you could get the nose, and they restricted what you could do with the oil pan and headers. The factory assembled the engine and most of the suspension to the K-member then dropped the unibody down onto it. The race cars didn't need to have as much function built into a removable part.
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AdamtheWayne



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PostPosted: Tue Feb 26, 2019 4:45 pm    Post subject: Reply with quote

Tom M. wrote:
The big Mopar K-members were eliminated because they limited how low you could get the nose, and they restricted what you could do with the oil pan and headers. The factory assembled the engine and most of the suspension to the K-member then dropped the unibody down onto it. The race cars didn't need to have as much function built into a removable part.
Well that makes much more sense! Any idea about when they started doing this? One would guess right around the time the dry sumps came into play?
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Firefly



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PostPosted: Tue Feb 26, 2019 9:16 pm    Post subject: Reply with quote

AdamtheWayne wrote:
Tom M. wrote:
The big Mopar K-members were eliminated because they limited how low you could get the nose, and they restricted what you could do with the oil pan and headers. The factory assembled the engine and most of the suspension to the K-member then dropped the unibody down onto it. The race cars didn't need to have as much function built into a removable part.
Well that makes much more sense! Any idea about when they started doing this? One would guess right around the time the dry sumps came into play?


The Nichels story linked below (and also in the sticky in the Darkside section) shows fabbed K member on a 1969 car. This story is a good narrative of the of Mopar front end structure and suspension evolution from '66-'70.

http://www.superbirdclub.com/InsideNichels.html
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AdamtheWayne



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PostPosted: Tue Feb 26, 2019 10:49 pm    Post subject: Reply with quote

The Nichels story linked below (and also in the sticky in the Darkside section) shows fabbed K member on a 1969 car. This story is a good narrative of the of Mopar front end structure and suspension evolution from '66-'70.

http://www.superbirdclub.com/InsideNichels.html[/quote]

Very interesting. Now I gather this is one team, but is this typical of most mopar of the era, and does it differ from GM and Ford? Or were GM and Ford doing the same just in differing styles per team?

I've noticed that from at least 1970 on, all stockers have the same rear third setup varying only slightly, but they all have the fuel cell, box frame and two pockets either side. Most seem to have similar tubs as well.
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AdamtheWayne



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PostPosted: Tue Feb 26, 2019 10:52 pm    Post subject: Reply with quote

Fantastic article by the way! It looks as though most of the front end parts are found in the Johan torino. I noticed also, the construction was quite similar to the lost Allison Charger.

Where did the AMC cars get their chassis, and how close are the ones in the AMT kit?
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Tom M.
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PostPosted: Tue Feb 26, 2019 11:03 pm    Post subject: Reply with quote

The original boxy Matadors were framed up at Holman&Moody and used the Ford front snout tied to reinforced rocker panels like the Torinos. The AMC used rear coils from the factory so the race cars had to use the same, I suspect the setup was done very similarly to the H-M '65 and '66 Galaxies.

The '74 and up Matadors were generally built at either Banjo's or Hutcherson-Pagan and were similar to the AMT and Monogram Ford chassis.
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AdamtheWayne



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PostPosted: Thu Feb 28, 2019 1:35 pm    Post subject: Reply with quote

Tom M. wrote:
The original boxy Matadors were framed up at Holman&Moody and used the Ford front snout tied to reinforced rocker panels like the Torinos. The AMC used rear coils from the factory so the race cars had to use the same, I suspect the setup was done very similarly to the H-M '65 and '66 Galaxies.

The '74 and up Matadors were generally built at either Banjo's or Hutcherson-Pagan and were similar to the AMT and Monogram Ford chassis.


VERY good information, thank you! I'm just starting to get together a bunch of kits and learning what goes best where. In my younger days, if you put it in front of me I'd paint it and put it together no questions asked. Now... I ask questions. For the longest time I took it on faith the kit makers were doing it right or best as could be. But I'm an accuracy nut so this is now my go to site for NASCAR info.

SO... to summarize, Up until the late 60's everything was pretty much "stock" as far as the frames of the cars went. Then they started building box frames for the rear for the fuel cells and new framing for the fronts for the shallow pans used in the sump systems.

In about the mid 70's, the Monogram style of chassis became the norm for GM and Ford while Mopar struggled with factory plates until the last of them were gone, early 80's.

The mid 70's AMC's had Holman/Moody style Ford frames.

Am I at least close? Confused
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Tom M.
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PostPosted: Thu Feb 28, 2019 1:51 pm    Post subject: Reply with quote

No tubing frames in the rear until '74 or '75. No tubing side frame rails until '80 or '81.
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AdamtheWayne



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PostPosted: Thu Feb 28, 2019 2:02 pm    Post subject: Reply with quote

Tom M. wrote:
No tubing frames in the rear until '74 or '75. No tubing side frame rails until '80 or '81.
Now I'm confused. So when did the fuel cell start?
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Firefly



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PostPosted: Thu Feb 28, 2019 7:41 pm    Post subject: Reply with quote

AdamtheWayne wrote:
Tom M. wrote:
No tubing frames in the rear until '74 or '75. No tubing side frame rails until '80 or '81.
Now I'm confused. So when did the fuel cell start?


Around 1965, and were incorporated into the factory rear frame.
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Tom M.
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PostPosted: Thu Feb 28, 2019 7:50 pm    Post subject: Reply with quote

Late '65 or '66 on fuel cells. They were mounted into a box in the regular trunk floor.
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R.J.



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PostPosted: Thu Feb 28, 2019 9:31 pm    Post subject: Reply with quote

This thread is a great one for a sticky.
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R.J.



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PostPosted: Thu Feb 28, 2019 9:31 pm    Post subject: Reply with quote

This thread is a great one for a sticky.
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AdamtheWayne



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PostPosted: Wed Mar 06, 2019 1:40 pm    Post subject: Reply with quote

Tom M. wrote:
Late '65 or '66 on fuel cells. They were mounted into a box in the regular trunk floor.
Okay, this is a lot of awesome info. Now that I have this info I think I'll line up a couple builds and get the rust off me. Very Happy
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DoctorLarry



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PostPosted: Tue Jan 07, 2020 2:20 pm    Post subject: 70's Chassis versus 80's Chassis Reply with quote

There is a page from the NASCAR Handbook circa 1973 on Cotton Owens' web site on chassis construction.[/img]
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George Andrews



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PostPosted: Tue Jan 07, 2020 9:36 pm    Post subject: Reply with quote

Worth mentioning that what is referred to here as " the GM chassis " is the front - steer design, where the tie rods & steering linkage is ahead of the spindles. Until the great NASCAR down - sizing in 1981, few teams used the front - steer " GM " chassis; the 1965 Ford Galaxie front suspension design was almost universal except among the Mopar teams. Even smaller builders such as Speedway Engineering & CSC offered the Ford front end design stock car chassis, as well as the front - steer design that was widely used in lesser stock car series. As noted above, Bobby Allison was the biggest proponent of the GM front - steer design, as it pulled the right front tire into the turns on oval tracks, as opposed to the Ford design that pushed the RF tire.
The GM front - steer design chassis, with an all - fabricated roll cage and side rails, would become more popular with the smaller 110" wheelbase cars ( and their smaller engine bays ) of the 1980's, partially become of the superior handling and also because it allowed more room behind the front crossmember for a lower engine & headers. The Ford teams stayed with the 1965 Galaxie - based rear - steer set - up a while longer, as the Ford engine oil pan had the oil pickup in front of the front crossmember, where any front - steer tie rods would have interfered. A new design Ford oil pan would later cure this issue.
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