Patching an engine block- what's better than JB weld?

[donwhiteside]

Hi- engine is Mercruiser 325 (basically a big block 427 chevy) in a '73 Cruise-a-Home. Raw water cooled, running in fresh water now, but a history of being in salt water.

The heads are off and at the shop for a valve job. Looking at the short block, and cleaning it up for re-assembly, I discovered some old repairs from a previous owner. At several points at the perimeter of the "deck" (where the heads will be bolted and mate), there are corroded spots that have been filled with what seems like JB weld. This was used to bring the deck up to flush, so the head gasket would seal the water passages. I need to re-repair these spots as they lost surface area as I cleaned the mating surfaces.

Is JB weld the best of doing this? I'm familiar with it and know how to use, shape, and get it the right size. I heard that there is a "high temp epoxy" made for diesel engines, maybe Catepillar brand?

I welcome all constructive suggestions= thanks in advance and HAPPY NEW YEAR!

Don

 

[farmboy]

Re: Patching an engine block- what's better than JB weld?

I really like Belzona 1111. www.belzona.com The problem is its cost. JB weld is much less expensive but the supermetal will run performance circles around it. The 1111 has a working heat range from -40f to 392f dry and 200f wet. No matter what product is used for the repair, surface prep for proper adhesion is critical as is a post cure with heat to allow the patch to develop maximum strength.

 

[JustJason]

Re: Patching an engine block- what's better than JB weld?

hmmm.... sometimes you can get by epoxying (or jbwelding) the sides of the block (coolant jackets). It's a common repair for a DIYer, but most shops won't do it... liabilities and all. However, Id be weary about doing it to any kind of gasket mating surface. You may want to post some pictures or bring the block to the machine shop to say what they say. Some shops are able to melt metal (like those alumarod's) into small voids. The last thing you want in a marine engine though is 2 disimilair metals. Hunt around and see what you can find for 427 cores.
Good luck

 

[JCF350]

Re: Patching an engine block- what's better than JB weld?

Being old school I would heat the entire block and use brass.

 

[donwhiteside]

Re: Patching an engine block- what's better than JB weld?

Thanks all. I understand there are much better ways to do this, but practicality and budget are big factors here. The engine is in the boat, the boat is in the water (all 8 tons of it), and removing either gets to be a "too expensive" proposition for an old boat. Plus, I admit it, I love figuring out solutions for these things.

And, just FYI, these old 4-bolt main 427 blocks are worth a FORTUNE to car hot rodders, and the chances of finding one are VERY slim.

Don

 

[whywhyzed]

Re: Patching an engine block- what's better than JB weld?

I second the Belzona kudos. That's what we used at the Cat dealership. (we would never do block work like that though with it, we did "stitch" some cracked blocks)

If the block is worth hot rod $, sell it to one of those moneybaggers and get a smog-era 454 or something - just another option.

 

[HT32BSX115]

Re: Patching an engine block- what's better than JB weld?

Yeah.... And I know this just doesn't help either....I'm even more "OLD SCHOOL"

I'd too replace it with a newer 454/7.4L engine. (and put closed cooling on it and eliminate the freeze problem once and for all) Either way the engine HAS to come out. There's a LOT of 454's out there in engine land.....

Thanks all. I understand there are much better ways to do this, but practicality and budget are big factors here. The engine is in the boat, the boat is in the water (all 8 tons of it), and removing either gets to be a "too expensive" proposition for an old boat. Plus, I admit it, I love figuring out solutions for these things.

And, just FYI, these old 4-bolt main 427 blocks are worth a FORTUNE to car hot rodders, and the chances of finding one are VERY slim.

Don

 

[donwhiteside]

Re: Patching an engine block- what's better than JB weld?

Thanks again all. Luckily the local Belzona distributor is about 4 miles from my house. I'm going to pick up a "sample" (still $50!!) later this afternoon.

Just so you don't all think I'm crazy, the block is NOT cracked. There are low spots in the surface due to corrosion that need to be brought up to flush. This is not a structural repair. There will be no shear and very little compression stress. If the JB weld held for what might be 20 years, I think this better stuff will last the life of the boat. We'll see...

And, as far as pulling the engine, I might do that next year. This is a '73 boat, with the 325 Mercruiser engine, and uses a big 72C transmission driving a Mercruiser III drive. It's a big deal to get all that stuff out of there...

 

[HT32BSX115]

Re: Patching an engine block- what's better than JB weld?

Hi Don,

I just looked at a PLETHORA of Cruise-a-homes!

Those are VERY COOL!!

I would love to have one on Shasta, Trinity or Oroville!!


Hope your project goes well!!


Happy New Year!


Rick

Thanks again all. Luckily the local Belzona distributor is about 4 miles from my house. I'm going to pick up a "sample" (still $50!!) later this afternoon.

Just so you don't all think I'm crazy, the block is NOT cracked. There are low spots in the surface due to corrosion that need to be brought up to flush. This is not a structural repair. There will be no shear and very little compression stress. If the JB weld held for what might be 20 years, I think this better stuff will last the life of the boat. We'll see...

And, as far as pulling the engine, I might do that next year. This is a '73 boat, with the 325 Mercruiser engine, and uses a big 72C transmission driving a Mercruiser III drive. It's a big deal to get all that stuff out of there...