In the process of stripping down and wire wheeling my 72 Cutlass engine bay and frame, I discovered a large crack going around the passenger side shock mount/upper control arm area. Before moving forward anymore I am trying to figure out if this is fixable? If safe, I could have a local mobile welder to come repair it.

 

Yes, it's repairable by an experienced welder. I would inspect the entire frame before proceeding to see if there are other problem areas.

 

^^^This. The frame is just mild steel. It was welded at the factory and it can be welded again. The thing to be aware of is that less-experienced welders just want to add plating to "reinforce" the area. If not done correctly, that will add a stress concentration that will cause another crack. Proper reinforcement must use tapered "fish plates" that gradually spread the thickness change to avoid a stress concentration.

 

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Are there any typical stress points known to cracking that I should pay attention to?

 

I would think you would also want to pull it together to try and get everything as close to original spec as possible. Maybe have both sides of the front on stands to keep it level?

 

Good time to measure the frame for bends etc. as part of an evaluation it may need to go to a frame shop anyway. Get the specs from a factory manual and start measuring.

Good luck!!!

 

I had a local welder tell me $300-400 depending how it looks when he sees it in person.

I know another welder that would do it for much less but he is a couple hours away. When I showed him photos this morning he said he would slice into it and then weld back properly and would take a couple hours.

Joe mentioned it needs a tapered fish plate. Is that the only way to go about it?

To measure if it is twisted or warped...it would be measuring from the floor to the base to the frame to make sure they are at the same height?

 

Ive seen other threads w frame cracks on here. Many of the cracksare around the front upper and lower control arms and their mounts, try a search.

also ive seen a frame dimensions spec on here that may help you as well

edit frame dim link https://classicoldsmobile.com/forums...-frame-146230/

 

Honestly, 69-72 frames are dime a dozen. If you can spare the downtime and have the means, find a nice virgin frame and give it some PC/coating then slap it under.

 

Thank you for the link.

I would go that route if I had a lift. Originally I was going to pull the engine and just change the oil pan as it was dented then it snowballed into stripping the whole front end and sanding/wire wheeling it down to bare metal so I could repaint it. Thats when I discovered the crack. I dont have tons of room or cash either.

 

Im doing a frame off 64 in my garage without a lift. It can be done!

 

I am considering it. If I do end up committing I will build a wooden a stand like this that will allow me to roll it out from under or put the whole thing on casters.

 

Just get the frame repaired. Save the headache of swapping a frame. That's a very easy fix. Shop around for other welders or get yourself a cheap welder yourself and have at it.

 

$300-400 to fix that sounds like a bargain to me. Think through the logistics and procedure for a good half day repair on that. Get it in the air, take some measurements, likely pull it tight, recheck measurements, clean it, fab plate, rig welding blanket, weld it (really fun, easy and quick to weld upside down under a car), grind it, coat the inside….

Thats if no internal fish plate, if even feasible, which then additionally involves trying to clean clean inside as reasonable, drilling holes through frame, maybe a few slots to get the plate edges, some plug welding of the plate, then welding the seam, more finish work…

I would jump on that estimate, I wouldn’t have touched that in a CT body shop for less than double that. My estimate would basically have been losing a frame guy for a good part of a day when he could have been leapfrogging 2 other jobs. Around here you’d be lucky to find someone that would even bother with it but that varies geographically and situationally.

Just my observation & opinion.

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While I am not a fan of fixing something that isn't broke. But I think a duplicate set of plates for right and left side of the frame could be a good idea. The frame has been stressed on the opposite side due to the break.
What does Joe P say ?

 

Read the GM Best Practices manual about frame plates and welding.

 

Bringing this thread up once again as I am getting closer to finding someone to repair it. After researching I found some threads on Chevelle forums of cracks in the same area and the repair photos I saw just involved drilling and cutting the crack then filling it in. I did not come across with plates in this specific area. Is plating it going to be required? If so, where exactly would the plates go considering the bulk of the crack is on the lip area where the spring sits.

 

I was taught by an old-timer years ago that you should drill a hole at the end of the crack to eliminate the stress riser, then weld it from this hole outward. To get a strong weld you will also need to clean the metal, that crack is under the engine bay so there may be oil or grease residue that needs to be cleaned out before the repair.

Rodney

 

I'll add that heating the area with a torch goes a long way towards burning off oil and grease. If done properly, the weld should be as strong as the parent metal. Sadly many are not done properly and the scabbed on plates are even worse. When done incorrectly, a plate can create a stress riser that increases the likelihood of a new crack.

 

I would not recommend buying a MIG welder and doing it yourself. I have a MIG welder and with my limited welding skills there is no way I would attempt that. I have a strong enough welder to weld that but the smaller welders would not handle that thick of a metal. I would look for a guy with a welder mounted on the back of his truck. He will be wearing jeans, long sleeves and leather boots. Those guys know how to weld.