Technical Should I toss the frame?

I am building a 30 Coupe, fenderless traditional hot rod. I wanted to use the original frame (because it is numbers matching) but is has some issues. There is a sag in the drivers side rail at the rear engine mount. I have tried the bottle jack, chain, and railroad tie method. It didnt work. The deviation is compounded at the front crossmember. Is it time to toss the original frame and start with an aftermarket foundation?

 

If it matters, I am building a late 40’s early 50’s period rod. Not boxing frame. Very mild 59AB flathead.

 

Model A frames are regularly out of whack. I personally think you should use '32 rails. New rails are straight, easy to work with and in the end add value to your A. It looks better on a '32 frame too.

You can straighten the A rails, but it takes a frame table and some work. I "straightened" one when I swept it & Z'ed it... so basically, after I cut and weakened it enough to move it around. I ended up boxing it, but kinda had to. I also had a flatty/3spd.

3blap.

 

It measures square, although the sag is present. If I build the car on these rails as is, will I have drivability issues later because of the sag?

 

Do you have a rosebud torch? Try heating a couple of inches of center of the sag at the bottom of the frame and heating a wedge-shaped section up the side of the frame at the same time. Let it cool and see how much the frame has drawn up. It would work even faster if you were to support the frame next to the heated section with no weight on the ends. I've moved a lot of iron just using heat.

 

Tie it with chains to a big I beam, bottle jack under the sag point, and apply a bit of heat to the top of the rail as you lightly apply some pressure from below. Sneak up on it, don’t go whole hog. Better to require multiple tries than to go too far.

 

If you apply the heat to the bottom of the rail, the heated area will shrink as it cools and take the bow out of the frame. As you said, do it multiple times until you get it where it needs to be.

 

It’s not right fix it now.

 

That's normal for a Model A frame after all these years. Mine was bad enough that I took the entire frame apart and used heat and a hydraulic press to straighten the rails vertically and horizontally. I then boxed it to prevent things from moving again...

 

Simple fix
Heavy beam with a jack in the low area, chain down the ends.
Could try heat
Or flip it over, block up the ends and m***age (whack it with a big hammer) the now inverted high area.

 

I'm probably the wrong guy to ask but I do agree with the consensus, you shouldn't use it as-is, but you should use it, it's repairable. An original frame is an ideal starting point for a late 40's/early 50's period build.

If you try and try and absolutely can't get the bow out of it, I think you could still whack the frame horns/front crossmember off as far back as they are straight, plus re-use the rear crossmember and make the rest out of tubing. But I don't think that's going to be necessary.

 

Almost all A frames are sagged near the motor mount and spare tire mounts....too many holes in that area.
Folks have been straightening them out darn near since new, never heard of one too far gone in that area.

Use a short piece of steel to jack against so you dont wreck the shape of the rail, and pay attention!!! jacks will fly like a cannon ball if it slips out

 

Also, it would not effect handling being sagged there, but you could never get a hood to line up at the cowl

 

You don't need a beam
Flip it upside down. Stand a bottle jack at the sag.
Attach a chain to the frame rail near the rear crossmember, the run it over the jack to the rail near the front crossmember. apply low heat at the sag and gently start jacking.
Remember too, it's going to move while it's cooling.
You may have to chase the sag with a few attempts.

 

Thanks all! I appreciate the knowledge share. I pulled the front crossmember out tonight, because it was holding tension in the rails (I planned to weld in a dropped crossmember anyways). It released a lot of the tension. The problem is still there, but I believe it will be much easier to address the rail individually before installing the crossmember.

 

This 32 rail was way up in front. Buckled behind the steering box area and twisted. The block of wood under the cut front x-member cured that. The previous owner had already cut it.
Having a frame bench gives us a large advantage.
But Ive done the same with a beam underneath the frame.

these old unboxed frames move like ****er compared to new frames.

 

My '31 Coupe frame was bowed bad. I use one of the removable legs from my cherry picker and chains at both ends and a 20 ton bottle jack at the bend. Drivers side is usually worse. I also place a board on top of the frame to keep the chain frame causing damage. Drivers side went easy, with first attemp it was fine. I jack them a touch beyond level figuring it will settle with engine, body and all the rest installed. The p***enger side was much harder! Jack it up and it would bow out sideways. Jack it back in and would sag down again. Went through 3 or 4 times til it was finally right.

My '31 Roadster pickup is as sway backed as an old nag! Had to space the rear hood center pivot up so hood would close. Need to pull the cab and bed off that one someday and straighten it.

Dave

 

Your frame issue is common in most Model A's. A lot is going on in the area you mention, weight of the battery box, steering gear, pedals, weight of the driver, holes punched in the frame, poor frame design and poor road conditions in the 30's and 40's. I have been restoring Model A's since my first one in 1968 and most have a sag in the drivers side footwell area. I have the luxury of using a friends Car-O-Liner and I chain all four corners and use a 20 ton jack to get it level, the last Model A I worked on was 3/8" out of level. I laugh when people are building a Model A and complain when the need 1/2" of shims to align their doors and hood simply because they didn't take the time to level the frame.

 

My frame was not a model A...but this method straightened a sideways bend that I was dealing with...I used a string as a center line/reference point...worked slowly....no heat...had to go past straight so that it would relax/rebound to straight. Brought it back easily. You can do the same.

 

Drivability issues for regular street driving? Probably not.... the buggy suspension makes up for a lot of flexible and out of shape frames

 

It's a Ford Model A, no rocket surgery involved here. That sag would only cause some panel alignment issues, it would otherwise drive fine.

 

I've straightened several Model A frames with a set of jack stands, 12' 4x4, chains and a bottle jack. Jack stands on top of the 4x4. frame chained down, string line from the front crossmember to the rear of the frame and a short piece of 2x4 on top of the jack at the lowest point on the frame. Jack it up until it starts to push the string up, let it off and repeat until the string stays against the frame. I've done two flathead V8 A's on unboxed frames with no problems. I've done three banger powered Model A's and the flathead V8 A's and always check and straighten the frames.

 

Depending on your location, it might be really handy to have the original numbers on the frame when registering / licencing the car (if it's not done already).

 

Thanks! Already ***led in my name.

 

I also vote fix it. You're building a traditional hot rod, use what the car came with.

I'm glad to see all the great tips from other guys, I'm sure I'll need that info when I get going on my ch***is.

 

My 31 Coupe has enough sag that the hood doesn't line up very well at all. On the side panels of the hood by the cowl, it goes from a decent fit to about a 3/4 in Gap.

I would agree with all of the suggestions of cold bending and using heat to get the bow out of the frame rail, but wonder without dis***embling my whole car to get at the frame rails is there enough room to chain and clamp things to straighten the frame on a car that's already ***embled? I must say the hood misalignment really bugs me.

Lynn

 

@lake_harley you just need enough room between the frame and body to get a chain thru it.

Now I've been doing frame work daily for oh over 40 yrs and I use only high-test chain. It's expensive but some days I'm pushing 10-ton rams close to their limit. And I will stall 5-tons often so always be careful of what type and strength chain your using.

Oh BTW those are 5/16" and 3/8" chains that I use. On smaller cars or where space is at a super premium I will use 1/4" chain but I know it's limit and never go past it.

It's all about placement, heat, and experience... gotta listen to the metal when you pull or push it, it will talk to you if you listen...


...

 

I straightened truck frames for 20 years and with a little thought you can straighten about anything. I always did the truck frames cold since they were heat treated steel. When you get it set up right it almost seems like magic.

One thing I have not seem mentioned is peening the area against a dolly while under tension from the jack. Vibration from peening does the same thing as heating in a more controlled manner.

 

And put in the time to learn the language.