The Stovebolt Site Forums The Shop Area Engine Shop JB weld on a cracked block?

I have a 1949 3100 with a 1954 235 motor in it which seems to run fine except, I have a small crack on the LHS of the block just above the oil pressure fitting which weeps coolant (water) very slowly. It doesn't leak very much, even when under pressure like last Sunday I broke the fan belt 10 mile from home and the radiaor was venting by the time I got home (7lbs cap?)

Can I clean the block with GUNK and pile on some JB Weld to stop it? Should I try some of those filings you can add to the radiator?

What's your advice (short of a new block!)

Thanks!

I would start with JB Weld..Just make sure it's clean metal and dry..It'll work, and you really don't want to put that other stuff in your cooling system

I have read on here that you may need to drill a hole at each end of the crack to prevent further cracking. Hopefully others will chime in with the details on this.

You can make the JB Weld match the texture of the block by pressing a piece of sandpaper against the JB Weld once it is applied to the block.

Phil

i would definately do this. it helps stop the crack from spreading. drill a hole just larger than the crack at each end. obviously drain the cooling system first. some grease on the drill bit will keep the shavings stuck to it instead of falling into the block. jb weld, let it dry , then fill it back up with coolant.

use brake clean instead of gunk
gunk may leave some residue whereas brake clean should not. scuff the area and wire brush first.

you've been listening to too much paul harvey!

Sounds like it's time for a rebuild. Then you can fix that crack properly.

The JB weld will hold if you can grind the block out a little and clean it very well. did this on a big block mopar and it stayed on for a good while. drain the water out of the block below the crack and clean the block very good and mix the JB weld up and put thin coats on about four each time get the spot bigger and bigger.
Hope this helps

Super250six

I know a guy who had a hole in the side of a 350 block about the size of a base ball he just grond the area smoothe smeared JB weld all around the hole and stuck a piece of 1/8 steel plate over it and believe it or not it worked.they used the truck for 2or3 years to deliver parts for his salvage yard.

Maybe we could get JB Weld to contribute to the SBP

I think Cletis had a craked block and used JB weld to fix. I will suggest the same thing to you as I did to him. Drain the cooling system and then hook up the shop vac to one of the hose fittings (waterpump or Thermastat). This way there will be some negative preasure to draw the jb weld into the crack. Make sure to leave the other end of the cooling system open just a bit, you don't want to suck the JB weld Through the cooling system. But just draw in into the crack. I would make sure you clean the crack out very well.

Good Luck!

I agree with Brian. Cleaning your crack well is very important.

JAAYYY....BEEEEE....WHHHELLLLD....

Guuud day!


I have never used it...but if Paul Harvey sells it...

What we did at the machine shop was to drill the ends of the crack, peen in a small rod, & JB the whole area well after roughing it up a little. Shop owner been building engines since the 50's, swore it was the best invention since sliced bread. Brian

I used JB weld to repair a cracked slate on my pool table. So far so good.

But wouldn't it be better to put a real weld over the crack or maybe even some solder.

do what super 250 said and dont drill holes if its small

i used jb weld to fix a worn valve guide once filled it in and redrilled it it worked