[equidr]

I have a 71 Formula project. Mild pro-touring build. I also have a complete 77 subframe and suspension pieces that have been blasted and powder coated with global west bushings etc. already installed. The 77 project had to be abandoned as severe collision damage and resulting rust were discovered. What hurdles will i encounter in swapping the already done 77 subframe into the 71. I already searched the site and found very little info. Thanks

[78w72]

the actual swap to the body should be straight forward since the body mounts are in the same location. but other little things like trans cross member & motor mount hole locations may be different.

[marxjunk]

they are not the same as far as body mounts..the rears are in a diff spot for the later frames//the fronts are but the 2 most reward are not..it works you have to drill the rear 2 bushing holes...theres actually a post on this..it shows frame specs and the diff...

not hard to do...

has something to do with the catalytic converter location for the later cars

i just went thru this myself...i put a 77 frame under a 70..it didnt matter to me, my car is an esprit and i am building a road race type car

as long as your later frame horns look the same the damaged is a bolt in after you drill the rear holes to accept the bushings

for some reason i though laters had shocks for the bumper mounts.. i cant remember right now

[78w72]

Originally Posted by marxjunk

they are not the same as far as body mounts..the rears are in a diff spot for the later frames//the fronts are but the 2 most reward are not..it works you have to drill the rear 2 bushing holes...theres actually a post on this..it shows frame specs and the diff...

not hard to do...

has something to do with the catalytic converter location for the later cars

i just went thru this myself...i put a 77 frame under a 70..it didnt matter to me, my car is an esprit and i am building a road race type car

as long as your later frame horns look the same the damaged is a bolt in after you drill the rear holes to accept the bushings

for some reason i though laters had shocks for the bumper mounts.. i cant remember right now

thanks for clarifying the info on the rear holes, i knew the bushings were a different part# but thought the frame locations were the same.

do the holes need drilled for the different bushing size or the actual location is different? sounds like it will work with minor mods.

the later year firebirds dont have shocks for bumber mounts.

[Formulabruce]

Here is a picture

[Formulabruce]

And this from Leigh...
SUBFRAME DIFFERENCES


70-74 and 75-81 F-Body subframes are the two basic groups.
The frames are the same physical dimensions in both early and late frame, the difference lies with the location of the rear body mount holes. Starting in 1975, the rear body mounts on both sides were moved forward approximately 2". Along with this change, the gearbox crossmembers were redesigned to mount further forward on the frame rails, ahead of the depression pressed into both upper inner frame rails where the earlier crossmembers had been mounted. These changes were to accomodate the altered floorpans due to the position of the catalytic converter.

Some things I've found.....
1. you can use late frames under an early body (and VV) by cutting new rear mount holes and plating over the old holes.
2. 70-74 body shells require the use of 70-74 gearbox crossmembers, the floorpan does not allow the clearance to fit the 75-81 crossmembers.
3. later frames are drilled for all engine mount combinations, Pontiac (early and late frame mounts), Chevrolet and Oldsmobile.
4. early 2nd gen frames have small diameter lower control arm bolt holes, requiring the use of early control arm bushes only.

I have a late 2nd gen Camaro frame in my 71 Firebird. I use 79 Trans Am control arms and a 71 TH350 crossmember. Other than having to locate and drill the crossmember mounting holes and the rear body mount holes, everything lines up and bolts in fine.

Regards,
Leigh

Sydney, Australia
1971 Firebird 455

[marxjunk]

somewhere here..theres actual frame measurements too..its measured from the cowl bushing to the rear..so you know where to drill

[marxjunk]

Originally Posted by 78w72

the later year firebirds dont have shocks for bumber mounts.

correct..but X bodies have a big bracket that bolts on and the shock bolts to it..73 up...thats what i was thinking about

[Formulabruce]

here are the factory Dim's for 1972

[equidr]

Thanks everyone. This I just the info I needed. Sounds like with a little work I can use my 77 subframe and continue to move forward. Now to get the Chevy small block out from under the hood!

[72projectbird]

I have a 76 Sub Frame on my 71. Like posted above, it's pretty easy to do.

Hell, I have a 76 hood and dash harness too. lol

[NOT A TA]

I have an '80 frame from a Formy under my '70. Some good things about the swap is the later frames appear to be made using higher quality steel, and the welds are better. If using a Pontiac engine you can swap to the better later style clam shell engine mounts and use the bolt holes in the engine cross member provided by the factory. Checker (yes the cab folks) made a lot of the later 2nd gen frames for GM.