Anyone had SBC thrust surface welded and repaired? I have a 4340 Cola crank 4 inch stroke 350 rod bearing, it's been sitting on the shelf for a few years, don't even remember where I bought it. I got it out to wipe down and re-oil and found several cracks in the thrust area that may go down into the journal. Is this headed for the s**** pile or has anyone gotten damage like this repaired. Sorry no pics, they all came out blurry and the crank is 2 hours away. Any idea on cost if repairable.
I always considered a cracked crank a big risk in racing. Have you had a reputable machine shop look at it? Cracks are all different. Like where they are ect... A cracked crank is never a good thing. Is this out of a street engine? If so I would call the mfg.. JMO In a street engine it may be ok, but for a high performance engine, make a lamp stand out of it. Lippy
on the big diesels we would get them x rayed to see how deep the crack went if it was less than .120 then they would rod then spray weld them and re grind them , but your talking a crank that has m***ive journals and cost $3-5000 , so spending 2500 was worth it , you have to see how far the cracks go with RT and UT to see if its just on the surface or deep into it . the place that used to do it is in Iowa near Des moines they do tractor cranks .
We often weld up worn thrust surfaces. I would have the crank checked first for cracks. We use Rhyne Compe***ion Engines in Gary. If its ok, figure 300 to 400 to test and repair.
Thanks for the feedback. I don't have much in it. The crank has been cut to clear a 5.85 rod, when I bought it I was thinking a 4 inch stroke in a 350 block with a partial hardblock fill. Its been balanced before but i don't know the bobweights, lot of plugs in it already. Pretty much a street strip "fooler" engine. RPM would be around 6000 max, so a mild enough cam, keep the torque peak low. I just threw it on the shelf 10 years ago and kinda forgot about it. I'll get it checked over and get some estimates. See if it's worth messing with. $3-400 to repair it may not be worth it, I could just go to a 383 instead and not have the expense of balancing up a Frankenstein rotating ***y.
Quit while you're ahead. SBC parts are so affordable that it really isn't worth your time or trouble to repair it. Buy a new crank and just go 383, you won't regret it.
I wouldn't weld it and I'll weld about anything. If the cracks get to the journal I would think that it is done. Unless you get the journal welded up and turned then it is still a **** shoot. But it would make a neat piece to hold the mailbox up.
Years ago I run 426 style Hemi bracket racing . Every crank I had was cracked numerous places. All the smart guys just said run em, I did ,never had any problems.
Thanks guys, I think it will become a decoration. There are several cracks in the thrust surface and they do extend into the journal. It is a really cool "looking" piece. Big slugs of mallory.
For a while in the '80's I had an older guy doing machine work for me. He said if it p***ed the ring test it was useable. He remove the timing gear, stand the crank up on it's end on a hard surface and hit the front counter weight with the handle of a ratchet. If it rang he would use it if it made a thud it was junked. He would even use one that didn't p*** a mag. test if it rang.
I dont know where guys are getting the idea that a good quality american made 4340 crank is so cheap. Maybe they have a lot more money than I do, or maybe they figure a cast steel chinese crank is "just as good". As described, the crack will run right through the journal fillet, and a 4" stroke wont have much journal overlap to speak of, so its inherently weaker than a crank with a shorter stroke. I wouldn't run that on a bet. A buddy of mine had a Callies come apart in a 540, took pretty much everything with it. Balancing the damage it will do if it comes apart against the risk of it breaking, I wouldn't touch that deal with a ten foot pole.
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