Welding on a frame

[1940Pipercub!]

Hello all! I have a question that I am hoping folks on here may have more experience than me regarding welding on these squarebody truck frames. I am aware folks weld on these frames during thier builds and they don't think twice about how GM stressed relieved or perhaps normalized the frames after the stamping process. Has anybody ever thought or seen these frames crack around a weld repair due to the natural twisting/flexing these trucks encounter on the roads (not rock crawling)?
I have a 1985 K20 that has some pretty good pitting on the lower flange of the frame rail (about 3 foot in length). My concern is that welding on a doubler may affect the frame's heat treatment and develop cracks. Am I overthinking this? I would also like to add I am a competent welder. Thank you.

[Ziegelsteinfaust]

The frames are pretty basic mild steel more or less. GM never stress relieved the frames, and the way they were riveted togather does not induce much stress if at all.

I have shortened a frame that held a 496 BBC with getting on to about 600hp/tq on tap. It never cracked its frame when I dragged it or hauled trailers.

Do not weld the frame in 1 giant bead. Do several 1/2 sections to stop warping. Then do not quench the steel let cool down naturally.

Also when done put a fish plate over the welded area. Some people are good enough to get away with out putting one, but I don't want to check my skill level so hard. I will just put the fish plate on the inside, and live in shame.

Steel is very forgiving, and easy to play with. Before to bevel the edges or leave a 1/8 gap to fill with weld. Use a 220V mig or Arc welder for good penetrating welds.

I even did one with a oxygen acetylene torch kit to flip the bird at some neighbor who always made fun of my tools.

[1940Pipercub!]

Thank you for posting a reply. We can both agree your truck probably sees more hardcore twisting due to racing and towing than any daily driver. Your response helps me. I tend to overthink things. LOL.

[hatzie]

I welded plates on several 70's & 80's squarebody truck frames back in the early 1990's. They spent too much time in Upstate NY. Salt Central. Vehicles are white after one spin on the roads regardless of paint color.

I wouldn't worry about welding it up. I would make sure the side is not thinned as much as the bottom of the C rail.

[1940Pipercub!]

Thank you for replying. I too agree the vertical portion of the c-rail is probably more critical than the upper or lower flanges, in terms of load bearing. A fellow co-worker gave me the same response as you!

[KQQL IT]

My 68 has been welded since 74 hasn't cracked yet.
Had a slide in camper and pulled a racecar trailer for years.

[hatzie]

Originally Posted by 1940Pipercub!

Thank you for replying. I too agree the vertical portion of the c-rail is probably more critical than the upper or lower flanges, in terms of load bearing. A fellow co-worker gave me the same response as you!

I was not clear.
Weld it up and don't worry about it. Make sure the side of the C is not too thin.

[sweetk30]

My current k30 plow truck frame was a crewcab . I cut 33" out of the middle and welded it back up . I fish plated the inside just incase . Been almost 4 years now no problems . And i run a old scho fisher speedcast plow setup . My 9ft blade is almost 950 lbs on the front end . Clean it good / burn it in good and run it . Also dont grind down the weld unless you need to . Welds are strongest left alone .

[1940Pipercub!]

Thank you kind folks for your responses!