The Stovebolt Site Forums The Shop Area General Truck Talk Crack in the block.

Hi all,I need to ask another question. I found my leak in the 51 3100 original 216, it has a crack behind the manafold in the #3 cylinder(outside of the block). It only leaks when it starts to warm up then it stops after it is warm. Some bolters have sugested using J B weld on it to stop the leak. My question is, what kind of preparation do you have to do to the block to get this to work? Grind it out, drain all antifreeze, what else? I am afraid it will not work if the block expands on warm up and opens up the crack, will the J B weld expand with it? I have heard of J B weld, but I have never used it. In the old days if you had a crack in the block you pretty much had a pile of junk, but these old engines are getting harder and harder to find. It is sad the engine was rebuilt by the previous owner and he never started it.It runs fine except for the leak.Thanks everybody.

Cleanliness is key, also must be dry. You have the right idea, VEE the crack using a grinder. If its cold up there warm it up somehow, a droplight nearby if nothing else. I'm pretty sure there is Devcon epoxy made that will also work. Press a piece of sandpaper to the epoxy after it has set but not hard, & it will be harder to see. Brian

Don't you have to drill and pin the crack to keep it from spreading?

JB weld was pretty much made for fixing cracked blocks, that was one of the original advertised applications. Supposedly its coefficient of expansion is pretty close to cast iron.

I used it to fix a cracked dishwasher and it outlasted the pump and motor.

I would drain the block and lightly heat the crack with a propane torch, then let it cool. That will dry out the crack. Then v-groove it, then JB it. I bet it will last a long time.

Im with 4onthefloor. JB weld is duct tape and bailing wire all in one package.(well,two) That stuff fixes anything. I keep it in my small tool pouch in my truck,the 15 minute stuff is great for quick fixes.
Marty

I have never seen anything work like JB Weld. However when I was a snotty nose kid the word at the shadetree garage was, cook up a few gallons of potato soup and empty the radiator and fill it with the soup. Run it through the engine for a few minutes then drain it all out; let the engine cool and refill the radiator. This, they always said would seal any holes in both radiator and engine.
Probably an urban myth...

i fixed a 350 in a 2500 chevy truck and drove it for years the block froze and split i ground it to bear metal jb welded it painted it and drove it

It won't hurt to put in a sealer also.I've found that powered aluminum works great.Up here in Canda it's called "Alumaseal"

My youngest brother had a '87 chevy pickup that had a crack in the engine block. He used JB Weld on it and drove it for about a year, then he sold it and the JB was still holding.

As was stated, you should grind, clean and dry before applying to make sure it gets a good surface to stick to.

Yea, you have nothing to loose, putty it up, or use a sealer on it. If the first sealer don't work, try another. I know that the JB weld will work. On tractor engines I do drill both ends of the crack so it does not spread, v it out, and spread it on. The sand paper sounds like a great Idea, I put duct tape over it to texture it (remove it when dry), same idea as the sand paper.

KB

Me being a welder,I better look for another line of work...LOL

Thanks for all replys. I will have to wait for it to warm up,up here before I can work on it.You are all right what have I got to lose. The engine runs too good to just throw away. I will have to patch it up and see what happens. Again thanks for all help.This is a great site.

I cracked my exhaust manifolds, which water runs through, on my brand new boat back in 1987.I ran the motor in March on a warm day 60 degrees, not thinking it would fall below freezing again, but it did.I used Marine-Tex which is probably similar to JB weld and they're still holding 20 years later. I think it will work on your block with no trouble.
Joe

I've got a question on this matter, and a crack on the block of my own 216. Why not drill all along the crack, allowing the JB weld to really push through the crack? How about 1/2 inch between each hole?
Karl

I am with the folks that say drill both ends of the crack and "V" it out.You have to stop it from spreading.I prefer Marine-Tex over J-B Weld.
OR....you can talk Beaver53 into a road trip to pin it and weld it up.I heard he is so good he can weld the crack of dawn lol.

The jb weld will probably work but if it fails a REALLY good welder can weld it. I can not but I have seen blocks thae were done this way.

jbit and forget it

As long as the engine doesn't freeze again, the crack shouldn't get any bigger. There is not a whole lot of pressure on the cooling systems on those. Brian

Good luck getting it fixed.The problem with repairing a block is the expansion and contraction of the cast iron.Back yrs.ago my dad had a Packard with a cracked block.He tried everything from sealers to having it welded,and never did completly seal it.Of course this was before JB Weld,was available.A lot of good ideas posted here,like drilling at each end of the crack to keep it from spreading.hope the JB works out for you.

The old time engine builder/machinist(70+y/o) here in town swears JB Weld is the best invention known to modern man. He routinely repairs blocks w/it that are made of unobtainium, like ancient firetrucks & uncommon tractors or just high dollar(like a Merlin 540). Brian

Ok it's warm enough to work on the 51 again. I have got everthing dismanteled so I can get to the crack,and drained the antifreeze. Someone mentioned that you should drill the ends of the crack to stop it from cracking more. If so how deep do you drill the crack? Thanks again for any and all help.

On aircraft parts, we drill all the way through then weld. Have never JB welded an engine block though. Maybe someone else can provide input.

I've just been getting into this kind of repair, too, you'll find a lot of advice in the Engine and Driveline Department under the topis "Mystery petcock."
Karl

clean it and jb weld it, that is your cheapest bet

I'd take it in and have a professional fix it right. IMHO, I don't believe fixing a cracked block with JB weld is the ticket to peace of mind.

Builder-Builder .Where have you been I've missed you. I'm ready for another tripple dog dare project. Gtow thanks for the input I am a good welder 30+ years "V" it and weld or "V" J-B weldit. Grind it to rough up the patch area. Roughfer the better if you J-B it.

Beaver53 - I've been in cease and desist mode for a while. You want another dare?? I need sponsors and the right truck.

Drill right thru at the ends of the crack with the smallest bit you've got. The purpose is so the crack doesn't end abruptly. I agree JB weld should work for you. I didnt see anybody mention this:
http://www.locknstitch.com/

Curt B.

elm I was told how to do the JB thing by a jent that was a machinest at NAPA and a flat track racer [with chev 6's] The JB thing works but you must cleanit very well. The big prob is getting the stuff to stay where you put it, I was told to lay block so you could form a puddle over the crack/ and POUR IT IN PLACE and wider than the crack by 1/2-3/4 inch and about 1/8+ thick [in depth] . then DONT MOVE, TOUCH, SPRED,for a few days. This method is for water jacket rust threw only. not for cracks in areas like main webs or areas of stress.

I know guys that fix hydralic cylinders and they use jb weld on the shafts and machine it to match, never a problem I've heard about. Everything I've ever fixed with jb weld has never given anymore problem. V it clean it, rough it up and jb weld it.