Technical shortening a rect. tube frame?

I want to shorten a t bucket frame a few inches between the engine mounts and the front crossmember. What would you say is the best technique?

 

Why not just chop it where you want it and then weld the cross member on?

 

Because the frame is nicely finished and I would have to redo the whole front crossmember section.

 

step cut frame ..remove desired amount with same step cut ..drill(4) 3/8 holes on inside , outside of both sides of original frame to look like dice pattern , and insert tubing inside 4 inches on one end total of 8 inches so 4 will extend into opposite end ..of course line everything up straight and square . level and diagonally true...rosette welds on both sides..finish welding stepped cuts...good to go...you could add plate on inside rail as is wont be visible for good luck..seems like over kill because it is..

 

I'd guess by the time you section out a piece & put it back correctly , you'd be time & money ahead do as Flathead Dave said , is the frame tapered ? Some are .

 

The proper way is to remove the front crossmember and move it back the desired distance and weld back it.

 

Most of us are "visual" kind of guys. Post a few pictures so we know what you're dealing with.

 

You are. The frame is not painted. The frame has nice fit and finish welding. If I cut the crossmember out, I have to do way more work.

 

In my opinion you should chop off the front cross member, shorten the rails the desired amount, then reinstall the cross member.

The only other option I would entertain would be to shorten both rails at the kick-up then move the engine mounts (and trans mount) forward. The second option would not be my first choice based solely on the wording of your question and the fact that no pics have been provided.

I (me personally) would not section the rails between the engine mounts and the cross member.

 

Understand now. Having done a fair amount of Frame work and not seeing your frame at all I might suggest simply using a hole saw in the correct location on the inside wall of Sq Tube and litterly installing a new front tube. Then cut and wrap the ends at that point. Sectioning Sq Tube and keeping everything correct without a frame jig is a ton of work and generally includes a fair amount of Luck.

 

^^^^^^^ditto

 

pist-n-broke has a great suggestion. if you have the clearance......i did that using a tubular chevy motor mount ..phasing and side to side adjustment too...once the engine and trans was phased i just buzzed it in place....

 

Thanks for all of your input fellas

 

just put in a longer engine!!!

 

Would it be easier to move the motor/trans mounts forward and shorten the frame in the middle where it can't be seen ?

 

This thread could be condensed to these couple of posts, and then a third that simply said "Thank you".
You asked for the best technique. You were given the best technique. End of............

 

He's said he doesn't want to cut the suspension off.....and being a stevedore I would have no problem cutting 2 feet out of the center of a rope, because I know I can braid it back together just as strong.

 

BIG truck frames are cut & either shortened or lengthened ahead of the rear axle regularly , its common practice . That way neither the front or rear suspension is disturbed & in general , cross members are left intact . Doesn't really matter what's done , as long as the process is done correctly !

 

...The longer engine comment is hillarious....lets poke fun now....if you hit a wall doing 50 wouldnt that shorten it...Ha ha ha

 

Damn right.!. a 302 12 port GMC…

 

Is this a running and driving finished car with a big gap between the engine and firewall or one with that big gap that is partially finished with a painted frame? Meaning can you slide the body forward on the frame and take the cut in front of the kickup so you don't have a splice in the middle of the frame?
Someone showed one on FB the other day that you could see most of the trans bellhousing in front of the firewall with about an 8 inch gap behind the back of the block and the firewall.
This isn't the one I was thinking of but hot rod wise there are too many big empty spaces between the engine and other pieces.

 

Would it look goofy to extend the cowl?

 

Pics of said ride.
But measure and cut the section out. If you don’t have a piece to fit inside, use the removed piece. Slice it into a sleeve. Drill some plug weld holes on each end of the frame. Insert the sleeve, plug weld one side of the sleeve, attach the front frame section, measure and square it. Welder up

 

mitch-- if you are just shortening the frame, cut the tube at a diagonal and butt weld back together. weld in fish plates on the inside and bottom, smooth the top and outside rail and be done with it

 

How about moving the body forward and getting a longer pickup bed?

 

Getting to just " building a new car "would be simpler ....

 

People are over-thinking it.

A cut and weld has no less strength than the welds in the kick-ups in the rear of the frame.

I would do what you're proposing....But the frame rails need to be parallel or there will be lining-up issues.
If you can find some tubing that neatly slips inside the rails ,it would be easier. Plug weld the tubes, then fully weld the joins.

Also keeping a longitudinal twist out of the frame will be a challenge when shortening it.

 

Back when I was building the roadster, I had to extend the 2"x3" frame. I cut out half of each tube then flipped it over on itself. Rosette welded some 3/16" plate inside the cut sections then finish welded the whole thing. That was a few years and a couple thousand miles ago. Never had an issue.

 

That's exactly how I did a friend's frame when he wanted the length altered. Plug welds, plates, and offset cuts.