Hi everyone I have a 1989 C3 that I recently put a née frame under because the original was rusted beyond repair, now my problem is the engine didn’t fit it’s a 350 I have to big block mounts on it just mount on the frame my power steering pump now won’t go on and I just found out that my firewall is sitting on the right side header.
Im at a total loss so I went to the local corvette specialist garage and I was told I had wrong frame I was told I had an a 70s big block frame
now I thought they was same again I’m lost someone please help me I don’t know what to do at this point

 

Welcome to the forum. I am going to move this thread to the C3 Tech section where hopefully you will get some assistance.

 

 

Your post is confusing.
I realize you have a 1980 but you typed 1989 and then state a 350 but big block mounts.
Can you clarify the part about mounts?

 

Agreed that the post is most confusing. a early 70's frame could cause a number of fitment issues. but engine mounting I would think would be the least of them.

 

There were changes to the frame over the years, but it's probably best to start with trying to identify what frame you have in your car.

The link (http://www.71corvette.com/frames.html) shows some frame changes between 63 and 82. It's not comprehensive, but there are a few important changes that will help:

in 1975, the rear of the frame was modified to accept shock absorbers for the rear bumper. If your rear bumper is mounted (as it should be) using shock absorbers (you can see them from under the car. The shocks are held into the frame by bolts in all four corners), then your frame is newer than 1975. Last big-block corvettes were prior to 1975, so if this is the case, the term 'big-block' frame is a non-starter.

Next place to look is the rear end type and mounting. In 1980, GM switched to an aluminum rear end which was mounted using a large aluminum 'batwing' Previous rear ends were cast iron and mounted using a large flat steel steel cross-member. This link (http://repairs.willcoxcorvette.com/1...-instructions/) shows what an 80-82 rear end would look like. If you have this rear end in the car, and the supports are on the chassis you either have a real 80-82 frame, or whomever did the swap moved the mounts.

I believe the 80 chassis also brought one more change that's easy to spot. Prior to 80, the transmission cross-member had pass-through holes on each side of the transmission in the cross-member for the exhaust pipes. If memory is correct, that cross-member was redesigned in 80 to have a single indent on the passenger side because corvettes had not had dual exhausts in many years. If your frame does not have these pass-through holes (as shown in pic below), it should be at least a 1980 frame.

https://4.bp.blogspot.com/-CwGo6Eneh...0/IMG_7712.JPG

The C3 frame was modified in 1980 as part of an effort to reduce weight. The changes included making it out of thinner material, swapping in the aluminum rear end (and also thinner glass BTW). I think I read they saved about 250 lbs with the redesign.

Hopefully this helps you in identifying what you have. Any pics you might have would also be helpful to folks on the forum.

 

sorry fir the confusion. I have a 80 vette
for some reason the 350 engine is not fitting
In my new used frame It’s sitting slightly turning to the right extremely tight fit we had to buy big block motor mounts in order to get it to fit like it is So now the power steering pump will not fit
no room for the pulley it hits the frame but we put the body on anyway and noticed that the right side header the body is sitting on it at the fire wall
I looked over all of the comments and it seems that I do have the correct frame but I’m at a loss with the way the engine is sitting in there
Any help would be greatly appreciated
thank you all

 

Did you buy a bent frame? A 350 is a 350, doesn't matter what year C3 frame it is the fit is the same.

 

well I don’t think so it came with the car when we bought it so I’m not 100% sure

 

Well first off you shoud not have had to buy "big block motor mounts" for a 350 to fit, and the fact that you say it is sitting turned to the right suggests a bent frame.
You need someone to check the frame for 2 things: 1. is it really a 1980 frame? 2. is it straight? No point in going further until that is done!

 

Thanks for your reply. So based on your answer i believe I have the right frame. I have the bumper shocks. I have the”batwing” aluminum rear end. And I do not have the exhaust holes in my crossmember. For clarification, originally we could not fit the motor with original 350 mounts so we bought big block mounts. We were able to bolt it up, but it’s twisted hard to the right and seems too far back. Then the transmission had to get pryed to the right for the mounting hole as well. So with it twisted we can’t get the power steering on and the right exhaust header rests on the firewall, will not allow for the exhaust to hook up. All other body mounts and everything seems to line up perfectly
Also before we got rid of the old frame and had all this happening, we tried comparing measurements and everything seemed to measure the same distances from old to new frame.

 

Post some pics of what you have run up against.

 

Interesting information. I'm curious about details of the lighter weight of the later frames. Lighter weight stuff always catches my attention. Anyone know what the weight difference is, allowing for the obvious difference in the rear differential mount design?

 

I don't have any exact figures. But it could not have been too much as the list of items that was lightened was pretty long and varied. The below article mentions some of them:

http://www.superchevy.com/features/1...nd-of-the-line

I'll save you the time, here's the relevent excerpt:

"McLellan’s team refreshed the 1980 Corvette on a shoestring. The most obvious visual differences were the new front and rear bumper covers, with an integrated air dam in the front and a rear spoiler with an aerodynamic Kamm-back design. The hood profile was lower and the hood, doors, and lift-out roof panels were made of thinner and lighter material.The refreshed body didn’t just look swoopy—it was swoopy. The previous body design wasn’t as slippery as we imagined, with a drag coefficient of 0.503. The new bumper covers got the Cd down to 0.443. While that doesn’t seem like much, road tests reported there was noticeably less air resistance.

Also, the ’80 Vette got a 250-pound weight reduction from the ’79 model thanks to the lighter-weight body panels, along with a new aluminum rear differential, aluminum front frame crossmember, and the L82’s aluminum intake manifold replacing the standard L48 cast-iron one."

The frame thing may just be an urban legend, while I can't find any hard references, here's a thread from the forum that seems to indicate that the weight came from areas OTHER than the frame.

BTW to the ORIGINAL POSTER -- The below forum discussion has pictures with dimensions for the 68-82 frames. This could help you determine if you have a bent frame.

https://www.corvetteforum.com/forums...iffereces.html

On the other hand, here's a link that references a lighter frame

https://corvettestory.com/1980-Corve...egulations.php

It's the Internet, pick whichever you WANT to be true and then click on that link

 

Thanks for the additional info.

I've always been curious about the frame wall thickness over the years, but I didn't see anything mentioned anywhere, so I'm assuming that Chevrolet didn't change that aspect of the frame design. About the only obvious area of frame weight reduction in the '80 model year looks to me to be the deletion of the crossmember above the differential.