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Discussion Starter · #1 ·
hey guys. im doing homework on a straight axle onto my 56 chevy. i have done a couple model A's so welding/axle/steering set up is no problem to me. my question is attaching the frame rails. how do i know they are straight? i assume they must be parallel. which means i could verify equal distance with a diagonal intersecting line. or measure equal distance, one rail to another, front and rear? or diagonal line front to rear? i assume the level of the two rails is verified with a leveler? and also wouldnt the leaf spring mount verify straight rails? if rear mount is attached square to original frame, the front mount is easily located on new rails? the wheel opening on the front clip tells me where to locate my axle?

these new rails have to be in the same position as the original? so i can mark/measure of that? thanks guys, any help would be appreciated, even a simple your wrong lol
 

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You can measure off points that are common to the frame rails and behind the firewall. There are things like body mounts and even holes in the frame rails that are very accurate. Take measurements from the existing front rails and a arm mounts prior to cutting the front clip off, and mark the points you'll need later to measure from.
When setting up frame stubs it's always best to level your main frame first, and work off a level floor. If your floor isn't level you can still use a bubble level to level your frame, and then build the stubs to the same level. Once you have your stubs tacked you can then brace them with cross tubes, and then double check the level on the new stubs, and the existing frame.
It's always a good idea to make yourself a drawing when you measure points, so you can refer back to the dimensions you took later, in case something happens and you don't remember when you're at it later. Cross checking multiple ways will ensure it's all good, and not shifting or pulling as you weld.

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Unless you're dead set on cutting off your existing frame front section there are a whole lot of tri 5 gassers out there who used their existing frame and only had to do minor spring hanger fabrication. That way steering hook up is easier, you retain your motor mounts and some other advantages. But, that's just one opinion.
 

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Vall has great suggestions on common points left and right. Steve also has a good point, why not just fab off the original retaining all the factory setup and originality in the car in case you want to revert again later.
What I did on my MG frame was, I made a box with the 2x4's and used that square as my home base to level into the body or in your case the frame itself if you cut it off. Slide in and out to the desired length.
Its not the most skilled method but it worked out in measurement for me.
 

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Discussion Starter · #7 ·
You can measure off points that are common to the frame rails and behind the firewall. There are things like body mounts and even holes in the frame rails that are very accurate. Take measurements from the existing front rails and a arm mounts prior to cutting the front clip off, and mark the points you'll need later to measure from.
When setting up frame stubs it's always best to level your main frame first, and work off a level floor. If your floor isn't level you can still use a bubble level to level your frame, and then build the stubs to the same level. Once you have your stubs tacked you can then brace them with cross tubes, and then double check the level on the new stubs, and the existing frame.
It's always a good idea to make yourself a drawing when you measure points, so you can refer back to the dimensions you took later, in case something happens and you don't remember when you're at it later. Cross checking multiple ways will ensure it's all good, and not shifting or pulling as you weld.

Welcome to the Gasser Forum!
thanks val. when you say main frame level, you mean building the rails onto the main frame at ride height, or lowering frame till level to ground then continue to build rails level to ground/mainframe? all while keeping rear wheels on?
 

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Discussion Starter · #8 ·
Vall has great suggestions on common points left and right. Steve also has a good point, why not just fab off the original retaining all the factory setup and originality in the car in case you want to revert again later.
What I did on my MG frame was, I made a box with the 2x4's and used that square as my home base to level into the body or in your case the frame itself if you cut it off. Slide in and out to the desired length.
Its not the most skilled method but it worked out in measurement for me.
while i thought of building onto original chassis, i like the cleaner look of rails. i have thought of your idea of boxing ends of rails wider to slide into original frame, i know a machinest who can actually widen the ends of the 2x4s. my concern with that is most builds i have seen push the rails inward and down inside the existing frame, not exactly centered. if my guy widens the ends of the rails, the rails would have to be centered. I am not sure if that would work on setting up the axle? Maybe it would?
 

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Discussion Starter · #9 ·
Nice article Tony, thanks for posting.
I have read this article many times along with others. I am going to be calling and seeing if they sell just the sub frame. This could make things easier, but the cost of sub frames rails vs. their frame is probably significant.
 

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thanks val. when you say main frame level, you mean building the rails onto the main frame at ride height, or lowering frame till level to ground then continue to build rails level to ground/mainframe? all while keeping rear wheels on?
When I mentioned "main frame rails" I mean the frame area under the cab or main body area. Those rails should be cleaned off and then you can level them to use as a base to know your frame stubs are level. There should be no reason to offset the rails up or down. Any I've seen or done simply came straight off the original frame after cutting it off. Of course the stub should be small enough to slip inside the existing frame and in some cases I've seen guys cut the top of their stubs down at a slight angle so the stub goes in even further. Not sure that's necessary myself.
I would not finish off the front contour of the frame stubs prior to welding them to the existing frame. Better to make them a few inches long and then trim to length once they're permanently welded in place. You will likely have to make a split or pie cut in the factory rails to allow them to be molded into place so they fully contact the stubs on all 4 sides. You'll find that rectangle box stubs will fit on two sides well, and the other two sides need to be bent in to contact.
I like to drill holes in the existing frame to plug wed them, and then also weld the mating edges. Some guys plate the sides also, and that's fine, but I think they're plenty strong without plating.
 

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Discussion Starter · #11 ·
When I mentioned "main frame rails" I mean the frame area under the cab or main body area. Those rails should be cleaned off and then you can level them to use as a base to know your frame stubs are level. There should be no reason to offset the rails up or down. Any I've seen or done simply came straight off the original frame after cutting it off. Of course the stub should be small enough to slip inside the existing frame and in some cases I've seen guys cut the top of their stubs down at a slight angle so the stub goes in even further. Not sure that's necessary myself.
I would not finish off the front contour of the frame stubs prior to welding them to the existing frame. Better to make them a few inches long and then trim to length once they're permanently welded in place. You will likely have to make a split or pie cut in the factory rails to allow them to be molded into place so they fully contact the stubs on all 4 sides. You'll find that rectangle box stubs will fit on two sides well, and the other two sides need to be bent in to contact.
I like to drill holes in the existing frame to plug wed them, and then also weld the mating edges. Some guys plate the sides also, and that's fine, but I think they're plenty strong without plating.
thanks agian. what do you mean by rectangle box stubs?
 
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