The best epoxy/jb weld for exhaust side block externel crack

matthew colgate

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Ok guys as per my previous post I have a crack on my motor block behind the exhaust manifold that has been previously JB Welded obviously it was not prepped right and is leaking again not too bad from what i can see I am contemplating pulling the exhaust manifold and re-prepping and resealing the crack ............ My question is what is going to be my best option on type of epoxy / jb weld / and or sealer to use any and all advice and help is appreciated ............. THANKS GUYS
 

JWebber

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Re: The best epoxy/jb weld for exhaust side block externel crack

From what I used JB weld on in the past years that crap don't hold up to heat very well at all. As you can see! maybe pull the head and get a new one. Your call! I know it's not the answer your looking for.
 

matthew colgate

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Re: The best epoxy/jb weld for exhaust side block externel crack

Right well all i wanna do is get it through this season and maybe next because i know i can get a new long block for $1500 which is a pretty good deal considering I only have half that in the boat and trailer
 

matthew colgate

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Re: The best epoxy/jb weld for exhaust side block externel crack

Wow this is suprising 70+ views and only one reply ? surley im not the only one that has faced this problem
 

JWebber

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Re: The best epoxy/jb weld for exhaust side block externel crack

Based on where the crack is on the block, are you loosing fluids, oil, water, or cylinder pressure??
 

Joshua Nichols

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Re: The best epoxy/jb weld for exhaust side block externel crack

JB weld if that how ya wanta fix it.. Prepped well.. It will hold for a long time.. I would use the good ol regular kind.. The kwik is crap...

It won't hurt nothing to use it on a external crack.. Good Luck
 

Howard Sterndrive

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Re: The best epoxy/jb weld for exhaust side block externel crack

On the manifolds I repaired , I mixed regular JB weld with fiberglass. I just bought a piece for auto body repair and pulled it apart into strands... cut it up and mixed it into the epoxy. dremel'd out the crack - drilled the ends and cleaned with brake clean.
Those manifolds lasted many years.
 

matthew colgate

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Re: The best epoxy/jb weld for exhaust side block externel crack

not losing any fluids and compression is all good the crack is in the block behind the manifolds and i dont have any oil in the water
 

zbnutcase

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Re: The best epoxy/jb weld for exhaust side block externel crack

Marine-Tex far better than JB for fixin cracks...
 

tswiczko

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Re: The best epoxy/jb weld for exhaust side block externel crack

not losing any fluids and compression is all good the crack is in the block behind the manifolds and i dont have any oil in the water

Be sure to stop drill the crack first or it will continue to crack!!


and if you are not loosing water, oil, or no water in the oil or vice versa then prep the area and use the high temp product. Most epoxies get soft over a couple hundred degrees if they aren't designed for High Temp. applications
 

matthew colgate

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Re: The best epoxy/jb weld for exhaust side block externel crack

it is leaking water out the crack I can see where it has been repaired before I assume it wasnt prepped properly looks like it was just smeard on there lol
 

Joshua Nichols

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Re: The best epoxy/jb weld for exhaust side block externel crack

J B weld is suppose to handle 500 degrees... It should be able to handle it..

You should drill the crack
 

rickryder

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Re: The best epoxy/jb weld for exhaust side block externel crack

I have had good sucess with JB weld in the auto industry... Like posted end drill the crack on both ends to prevent it from spreading,V grind the crack,clean it well with acetone,blow it dry with compressed air, rough up the surrounding area and apply your weld. I've found thin layers are better than a big thick coat.....if you need to build up.
 

matthew colgate

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Re: The best epoxy/jb weld for exhaust side block externel crack

DRILL ? THE BLOCK ? WOW now im nervous sweating bullets over here how big of a drill bit and how far do i drill into the block ?
 

Bondo

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Re: The best epoxy/jb weld for exhaust side block externel crack

Ayuh,... Just drill an 1/8" or 3/16" hole into the Very End of the crack to stop it from spreading....

I agree with the above posters,...
JB Weld in/ on a Cleaned up block will work just Fine...
 

Joshua Nichols

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Re: The best epoxy/jb weld for exhaust side block externel crack

Small drill bit.. Just drill a little to stop the crack...
 

matthew colgate

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Re: The best epoxy/jb weld for exhaust side block externel crack

ok so drill a hole completely through or just enough to interupt the crack ?
 

Bondo

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Re: The best epoxy/jb weld for exhaust side block externel crack

ok so drill a hole completely through or just enough to interupt the crack ?

Ayuh,... Through into the cooling jacket, not Through the whole block....
 

rickryder

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Re: The best epoxy/jb weld for exhaust side block externel crack

Bond-O got to it first:D
 

StevNimrod

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Re: The best epoxy/jb weld for exhaust side block externel crack

Marine Tex or JB is like Coke or Pepsi. Mostly just personal preference.

I ran fine, idled fine, etc. on a cracked cylinder,although that was a 8 cyl. The compression numbers were actually a little high on the bad hole. But I wouldn't get milky oil until I ran the engine under a load - when the block started flexing and opening up the crack.

Also, how are you checking for water in the oil? If the boat has been sitting it might not show up on the dipstick since the water would be at the bottom of the pan.

But if you are 'ell bent on a putty repair do make sure to pin hole the ends of the crack as suggested. Some cracks under certain conditions stop growing, but putting holes at the end (actually you should put the holes just past the ends) is a good way to be sure.
 
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