Frame straightening with or without engine?

**Ed S.** · May 18, 2015, 07:39 AM

Re: Frame straightening with or without engine?

Sascha,
I'm not a frame repair expert but think about this. The frame was originally made straight without the engine, body etc on it and when those major components were mounted on the frame it remained straight. It appears to me that if the bare frame is repaired and is "true" it will remain that way when the car is re-assembled. Others with more experience may want to offer comments.

**Patrick B.** · May 18, 2015, 08:07 AM

Re: Frame straightening with or without engine?

You will have no trouble reinstalling the engine on a straight frame. The engine is not distorted. Hopefully the body has not had a major repair like a new front clip installed while the frame was bent. Your biggest problem will be finding a competent shop to straighten a bare frame.

**Jim L.** · May 18, 2015, 08:08 AM

Re: Frame straightening with or without engine?

My concern about leaving the engine in while the frame was straightened would be stressing the block and risking cracking the cast iron.

And if the motor mounts don't align properly after the frame is "straight", then the frame isn't straight.

**Michael W.** · May 18, 2015, 09:10 AM

Re: Frame straightening with or without engine?

The frames were not straight or level to start with. That's why they were individually measured on a rack to determine how many shims were required in order to fill the gaps. It's not rare to see widely varying amounts of shims from one mounting point to the next.

If your car is not having any secondary issues with body and door fit or wheel tracking and alignment, I'd repair the weld and leave well enough alone. The 'while I'm in there' temptation can be a bottomless pit.

**Steve G.** · May 18, 2015, 11:07 AM

Re: Frame straightening with or without engine?

Most, if not all, commercial frame straightening equipment is designed for use with a complete, or mostly complete car. It could be difficult to find a shop willing to take a bare frame and work with that.

There are dimensions and checking points identified in the manuals, I think for the 69 I found it in the AIM. If it were me I would block it up per the diagram on a flat floor and take the measurements. 4 bottle jacks would be best and easiest. A tape measure and a plumb line are typically all that's necessary. The tolerance is indicated in the spec. Go through all the measurements. The diagonals are probably more important than the verticals.

Depending on your shop, you may be able to do minor straightening yourself.

Steve

**Domenic T.** · May 18, 2015, 11:37 AM

Re: Frame straightening with or without engine?

I did the flat floor measurement thing Steve was talking about and could see the twisting the front of the frame, about 1" high on the right side. I also looked from front to back using a parallelogram and could see the 1". I straightened it and sent it off to the powdercoater. When I did the body drop I found that I moved the wrong inch and the radiator support was equally off about 1 1/4 ". Some where I mixed up measurements and made all parallel, but went the wrong way.
Took the engine & trans out and brought the rolling chassis to the frame rack and all was corrected. With the engine out it made things much easier, especially when having to measure point to point on the frame.
It was a happy ending to a stupid mistake.

Dom

**Stewart L.** · May 18, 2015, 12:04 PM

Re: Frame straightening with or without engine?

On the 82 and back ladder frames, + or - 1/8 of an inch is considered within tolerance. So if it is really 1 cm, you may need a correction. On the other hand, I suspect there were a lot of Corvette frames in that era that were 1cm off when they left the factory. The AIM has frame dimension data and I have some Tru Line specs I could send you if you need them. Also is there any tell tale signs of an accident repair?
When I had my body shop, we straightened frames that needed minor corrections all the time with the engine in the car but on major collisions you sometimes need to remove the engine for acess. In your case, it seems like it would be easier to just have a bare frame to move it around.
You need to establish a level datum plane to gauge your height measurements. A tram gauge is most accurate to establish your cross measurements and length. With a bit of internet searching you can probably find some detailed information on measuring frames.
There is a lot of specialty equipment such as tie down chains, rams, clamps and port a powers needed for frame repairs, it may be easier to sublet it out to someone that has the knowhow and equipment if it does need repairs.
Good luck with it.
Stewart

**Bill W.** · May 18, 2015, 12:26 PM

Re: Frame straightening with or without engine?

If you take it to a good body shop with a frame rack and a computorized laser measuring system they will have no problem checking & repairing your frame and can give you a before and after print out . It is best to have a rolling frame for the ease of rolling it on the rack but could be done on a bare frame if needed .once clamped down the laser dont no or care if a body , engine or susp. is on the car .

**Stewart L.** · May 18, 2015, 01:32 PM

Re: Frame straightening with or without engine?

Bill, are any of the Laser Measuring companies supplying data for pre 82 Corvettes? Im not aware of any. It would take some time and a known good frame to establish the data points for a laser measuring system. Also, the weight of the engine will cause a bit of drop in the front height measurements in a ladder frame car. Specs are often noted if they are with the engine in or engine out.
Stewart

**Sascha P.** · May 18, 2015, 03:22 PM

Re: Frame straightening with or without engine?

Thanks for your replies!

Regarding this question from Stewart: "Also is there any tell tale signs of an accident repair?". I'd say "yes". The front cross member (which I hope is the right term) underneath the engine has signs of welding on the RH top of it.

I have driven the car for three years now (well, a few days within that time). I never had the feeling that it would not drive straight or so. But the driver side was always lower than the passenger side and the front suspension has many shims. Now that the body is off I found this crack and did the first measurement.

After all your replies I should probably get the welding job done first. Clean it up, level it, do better measurements and see what is says. I will also look into the list of body shops here (Vancouver/ Richmond BC) and see who may has some experience with that type of work.

I guess each one of you went through some kind of "experiencing" with frame issues. There does not seem to be the "golden" answer :-( I will read through your answers again later to make sure I did not miss anything. And I hopefully will not dream about this issue again afterwards!

**Patrick B.** · May 18, 2015, 04:36 PM

Re: Frame straightening with or without engine?

Originally posted by Stewart Lowe (3422)

Bill, are any of the Laser Measuring companies supplying data for pre 82 Corvettes? Im not aware of any. It would take some time and a known good frame to establish the data points for a laser measuring system. Also, the weight of the engine will cause a bit of drop in the front height measurements in a ladder frame car. Specs are often noted if they are with the engine in or engine out.
Stewart

A drawing of the frame with all the critical dimensions is given in the regular Chevy shop manual (Chassis Service Manual).

**Dan B.** · May 18, 2015, 06:25 PM

Re: Frame straightening with or without engine?

I would be taking a good long hard look at that nose (fiberglass) as well as taking several measurements and cross referencing to factory specs, it might reveal body damage that was repaired to fit a previously bent frame. Better to know now what to expect when you try to mount what you have back on a straightened frame. Hopefully, it will work with the frame changes. Good luck.

**Stewart L.** · May 18, 2015, 10:01 PM

Re: Frame straightening with or without engine?

Check with Corvette Specialities in Surry. If they don't repair frames there he can probably provide you with a reference.
You probably don't need to weld the crack until you establish what corrections need to be made on the frame.

**Sascha P.** · May 18, 2015, 10:57 PM

Re: Frame straightening with or without engine?

Yes, I will speak to them tomorrow. They should be the best address here in this area. Thanks!
And Dan, I will check the nose!

Frame straightening with or without engine?

Frame straightening with or without engine?

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