Frame strength help...
 

Hi,

Would a 1963 C20 frame be strong enough to handle a 4wd conversion (np205), Dana 60 front, 14 bolt rear, 6” lift and 37” tires?

Thanks for the help!!

Re: Frame strength help...
 

yup

Re: Frame strength help...
 

I called a bunch of restoration and body shops and they all said absolutely not. Frame needs to be boxed from transfer case forward. Only the rear portion would be okay, but 4wd torque, lift and weight of 37" tires are too much for a '63 2wd frame.

Re: Frame strength help...
 

Bunch of hooey. If I understand correctly, there isn't much difference between the frame rails of 2wd and 4wd. Once you remove the front crossmember, I would really look into a crossmember to tie the frame back together under the engine mounts but that might be about it. My '63 has never had a crossmember in that area and although Ive always wanted to install a support there, Ive never really seen the need for it even with the new suspension, drivetrain and big block. Boxing the frame IMO, while cool looking and very labor intensive, is completely unnecessary in most cases.
Stock frame in mine has seen thousands of towing miles, many loads in the box that were well over the trucks capacity without any indication of fatigue.
Im not sure why an honest restoration / body shop would recommend welding plate to the inside of the frame. Ive seen several instances where frames are not supposed to be welded on due to the alloy that they are made of. Not sure if our old truck frames would be affected. Just saying it would be good to research completely on your own before asking a barber if you need a hair cut.

Re: Frame strength help...
 

I don't know much about this subject but the one thing that I do know is that you should at the very least reinforce the steering box area of the frame otherwise it will crack and rip out with those big tires up front.

Re: Frame strength help...
 

After thinking about it a little more, for the cost of boxing a frame on one of these, Id bet that you could find an original 4x4 truck. They're not super common, but not extinct either. Just another angle to think about.

Re: Frame strength help...
 

Hooey or not its a good thing such places like this forum exist where one can get a bunch of different answers and ideas.

It seems most folks who convert to 4wd on a 2wd frame don’t off-road and ‘63GENII isn’t running a lift or big wheels so there is likely less stress on the frame. Nice truck btw!

I agree with Ryan...extra support isn’t a bad thing. It may not be necessary but its peace of mind.

I have not found any K20 trucks or frames...it seems we live in a world of mostly '60-63 C10/C20's.

Thanks for the help guys!

Re: Frame strength help...
 

The k frames aren't significantly different than the c frames. Do you plan on rock crawling or speeding over whoops? Then you may want to reinforce any factory light duty Truck frame. Driving offroad trails, fore roads and around town? No reinforcement necessary. It also depends on other factors. Have nice flexible suspension? Less stress on the frame. Have super stiff aftermarket lift springs? More street on the frame.

What power plant do you intend to put into it? SMall block, big block, LS, 6bt?

Re: Frame strength help...
 

Has anyone compared frames from an early 60s to a modern frame? Granted braces, crossmembers, funky bends and what not, but these frames are thick. Back when they built trucks, I wouldn't hesitate running the frame as is. Now if you do plan on serious off-road, 800+ horses, towing doubles then maybe want to box the frame.

Re: Frame strength help...
 

I have compaired my 63 K20 4x4 frame to my 93 dodge w350 and it is comparable.
Not enough difference to remember or worry about.

Re: Frame strength help...
 

Welcome back there Jason. Didn't you have some plate cut up to box Big Ugly at one time?

Re: Frame strength help...
 

It is hard to compare new and old frames. The metallurgy is different and most new truck frames have boxed sections. This gives them more stiffness in twisting and bending. Also they vary from generation to generation aND between capacity. The 73 k20 frame I robbed parts from was thicker and seemed harder to cut through than my 66 k10 frame. And the 83 k30 frame was thicker still.

Re: Frame strength help...
 

Hey Chris. I did persue boxing my frame. But I abandoned it when I moved 4 years ago because I had to get the truck reassembled and had no space where I was moving to.

There are several things that I'd do differently if I had it to do over again. But i think it'll be a long time before I build another truck. Too many other things to do in life

Re: Frame strength help...
 

Probably a 350, not sure what tranny yet. No even sure if it will be manual or auto. The lift will be full spring with Bilstein B8 5160 shocks.

No rock crawling or mud bogs for this build, but I will take it off road on trails, potential deep snow through pastures, some mud, definitely steep hills and lots of pavement.

I have since spoken to a few people who suggest either boxing from transfer case forward and leaving the back alone, to just adding a crossmember or two. I have noticed online lots of people converting C10/20's to 4wd seem to prefer Suburban chassis swaps, but I hate the way it looks. I'm going for a factory look minus the lift.

Re: Frame strength help...
 

A small block and mild offroad: I wouldn't worry about boxing the frame. Just make sure you have good crossmembers located at spring and shackle hanger locations. You should be good to go. 37" tires seem a bit big for your intended use, but should work.

Re: Frame strength help...
 

I've got 35's on all my other trucks and have wanted to put 37's on something, so I thought this might look cool and different. All the '63 C10/20's I see are stock looking. Just want something a little different.

Re: Frame strength help...
 

Dont know if this helps but 67-72 c20 frames are actually stronger then their k20 conunter parts. The gvw of a k20 is way less and also the fact I've looked into a k20 of this era is basically a k10 with stiffer springs and axel. Also some c20s came with Ho72 to handle the higher gvw. Know I dont know if there is any specific bracing that a 4x4 has but I would say a c20 will be fine. A c10 might be another issue.

Re: Frame strength help...
 

This is an older thread, but the GVW is less on a 4wd prolly cause of the front axle. I'd imagine the frames are the same thickness, but the front axle would be the weak link.

Re: Frame strength help...
 

Do not think the front axle is a weak link. The weight of the front axle is more and it just takes away from the overall GVW.

Re: Frame strength help...
 

SS Tim provides great information and comparisons in this thread(post #9)... a must read for you.

http://67-72chevytrucks.com/vboard/s...d.php?t=659340

I would run the frame you have, beat it like a rented mule. If(IF) the frame ever cracks... repair it by bolting on flitch plates or an inserted piece of channel iron. Never weld your frame when you can do otherwise. The K frames were designed to flex, in lieu of cracking under stress.

Another two cents... worth the price paid. :chevy:

Good luck!

j

Re: Frame strength help...
 

This is exactly the truth, longbed K trucks in 67-72 used the same identical frame. I’d imagine the 60-66 trucks are similar. Spring and axles were the difference between 1/2 and 3/4. 1/2 short and blazer used thinner gauge frames, suburban used a variation of the longbed frame.

It’s the same in the square body years for the 1/2 and 3/4 trucks, the K30 frame in the sqaure years is 100% different and 100% beef lol.

I doubt this post is still relevant to the OP but I would have used the original frame and not thought twice.