Small block chevy cast block weld

Is the tab broken all the way off, or is there meat all the way around that you can weld onto?

I can't comment on stainless vs. nickel, other than to note that you already know how to use nickel so why not stick with what you know?

I'm not sure that you're headed for happy-ville here anyway -- I would expect that if you want something better than "hold it together long enough to sell" you need to strip the thing down to a bare block, weld it, then re-machine any mating surfaces that are close by (which is presumably the bellhousing: I can't visualize a SB chevy well enough to know if you'll be getting into the oil pan mating surface).

Is it something too rare and special for you to just get another block?

The problem is that his weld will be hot , The thermal mass of the block will keep the tab quite low . When the weld cools it's going to pull away from the cast - no matter what he welds with . The only way I can see getting around that is to weld short beads parallel to the length of the hole and let them cool thoroughly before doing the next . And I use braxing rod , and only fill it enough to use a permanent insert because the brass filler probably won't hold a thread for long . And I can visualize that block , is it the upper or lower hole ? Lower has a higher chance of success IMO . Hmm , almost has to be the upper , doesn't the bolt come from the rear on the lower ?

It looks like this pic

except mine is wallowed out larger till there is not much meat around the end at all think I'm best to weld it up solid and drill/tap a new hole I know about preheating and peening the weld on cast If there were any threads left I would thread a peice of carbon and weld around that I have the block out and stripped bare, so now it the time might find a new block for around $500 but this one is good except that little problem thanks for all the quick replies :-)

I would bore out the hole then install a long solid wall insert. Then V out the cracks and braze them up. The insert will extend the grip into the better iron. The brass will stabilize it.

Last week I needed to repair a transom clamp on a Johnson outboard. The original 5/8-11 threaded hole was stripped and there wasn't enough material for even a Heli-Coil insert. So I tapped the hole 3/4-16 but used a drill much larger, relatively, than the normal minor diameter of the thread. I then made an insert on the lathe tapped 5/8-11 and threaded 3/4-16 on the OD. The 3/4-16 thread was really only about 50% because I made the minor diameter only .003" smaller than the hole I drilled in the transom clamp. To do this I set the compound on the lathe parallel with the Z axis. Then after single point threading until I got to the minor diameter I wanted I used the compound to advance the treading tool .002" per pass and widened the thread until the pitch diameter was correct. So the insert ended up with shallow threads with a really wide root. Finally the insert was installed with Loctite so that any clearance between the insert and the part was filled. I made the insert from stainless because it was for an outboard motor. In your case I would use any easily machinable steel you have laying around. Ledloy would be plenty strong enough. 303 SS would be a good choice as well as 17-4 or 15-5 SS. Though the PH stainless steels are not that easy to machine they do finish nicely. I would not use mild steel because it tears so easily. Eric

I might comment that I once welded a cast iron cylinder head using TIG and probably 308 rods and the weld was hard enough to take the end off a HS end mill. If you will need to machine the repair it might be something to think about.

Isn't NI 55 considered non-machinable? It's been my experience that it is not... pdk

">> I might comment that I once welded a cast iron

I will use good (expensive) nickel 99 rod, think I still have some UTP I think around 55,000 PSI tensile strength it machines well should make stronger threads than the cast iron by far as I have at least an inch of thread length. will preheat, peen, and cool it slowly wrapped in insulation of some kind You guys have helped me tackle this with more confidence thanks everyone.

Is this a valuable vehicle with a numbers matching block or something?? What version of SBC? Surely canot be that hard to find a bare block since you already have the old one stripped. Personally I wouldn't waste the effort fixing the damaged block.