How far gone is too far gone?

[71Newp]

Hi,
I am probably going to go look at a 79 Volare. The current owner says there is rust in the passenger side frame rail. I have looked at the caps from "autorust" but I can't tell from the drawing how much they cover. Is there a measurement that can be done or a rule of thumb, to tell how far gone is too far gone? Anyone have pictures of their f-body with the caps? Thanks,
Tim

 

[old yellow 78]

I think it is somewhat more common for the drivers rail to rust, but if one is gone, probably the other isn't far behind. I've never used the caps, but I think a lot of people have. There will be someone on this site who will be able to help you out. Good luck!

 

[old yellow 78]

You might want to check out Deconstructor Jim too! He has just about any parts you might need including full frame rails from rust free cars! Frame rails, front and rear F,M and J

 

[Jack Meoff]

I've never used those caps myself so I'm not sure how thick the steel is.

I think the general idea is if the lower half of the rail is toast you could probably get away with a cap. But if it's shot right up to the floor pan then you might be looking at welding in a whole new rail.

 

[F body Deconstructor Jim]

Frame caps are OK but more expensive (about 2x, $300) than a clean rust free used rail. IMO installation is the big deal for a lot of folks. Theres a lot of metal surface prep to install a frame cap. Frame rail requires cutting about 25-30 spotwelds and some parts removal.

https://www.autorust.com/product/front-subframe-full-fjm-body-mopar-art-038-r/

 

[Aspen500]

Unless they improved the caps in the past few years, I'd find another way and save your money. My car had the typical left rail rot and I cut out the rotted parts and welded in patches and THEN put the caps on. Even though the right side was solid as can be, put it on for reinforcement. They were the ones that go from the back of the rail to the point where it's horizontal again, not full rails.

I ended up basically remanufacturing the caps. They were ROUGH and poorly welded together and had none of the openings. Rewelded, ground them smooth and cut the round and oval holes to match the stock rails and then fully welded and filled so you can't tell anything was ever done.

The material was maybe 3/32"(?) but as I said, they were poorly cut and and the welds were almost a joke. At that time they were like $125/pair. In hindsight, I should have just made patterns and built my own, which is darn near what it ended up being anyways.

Just my experience with the caps. Better way is parts from Jim. If I'd have known about him at the time, that's the route I'd have gone with.

I had assumed the caps were die stamped pieces, not flat steel torched and roughly ground and then half-assed welded together. Almost sent them back to be honest. Looking at the pics, kind of what the full rails appear to be.

 

[71Newp]

Thanks to everyone for your input. I will go look at the car. If frame rails are replaced, are the replacements installed using spot welds or MIG'ed in?

 

[Aspen500]

You'll need to MIG them in. You can also "spot weld" with the MIG by drilling holes in one piece to weld through but if fully welded, it'll be much stronger and the chassis will be a whole lot stiffer. All depends on what the car is intended for (show, driver, hot rod........)