I just recently acquired a 84 6.9 with cracks by the block heater area, Are there any fixes for this issue? JB Weld?

 

NO.....many have tried but no success.

 

got two old macks with 300 six in them with jbweld holding them togeather some said it wouldn't work but ya never know till you try if it don't then call local machine shop they have ways to fix

 

The parameters effecting the Mack crack (no pun inteded) and the 6.9 block heater cracked area are probably totally different. Many members have used JB weld, slow heating/welding with several types of rod and slow cooling to no avail. Master welders and expert machine shops have all tried, just once I heard of a partial success. The cost to try was more than the block was worth in the end.

 

You interested in buying another motor chowitworks? I noticed you're a member of the NW chapter, and I live in the Seattle area (Kent), and I just happen to have one that may be for sale after tomorrow.

I bought an 86 F250 three weeks ago and it came with a spare engine. I'm doing a compression check on the motor in my truck tomorrow. If it checks out OK, I plan on selling the spare.

 

I think that I will try a combination of KW block sealer and a coat of JB weld on the outside. Will report on success or failure after the fact.

 

When I purchased my 84 6.9 two years ago, I noticed it didn't have a block heater...since I was replacing the stock starter with a "mits" I figured I'd put in a block heater...replaced the starter, put in the block heater and just my luck the block heater didn't work and it's a good thing from what I'm reading!

 

I have never had any problems with the one in my 83

 

So exactly what's the issue? The heat from the block heater causes cracks in the block - or what?

 

in the early 6.9 from 83-84 the casting was weak at the freeze plugs essp at the one for the block heaters ford finally figered this out at the end of 84 and international fix the prob but as i stated earlier in the post sometimes ya never know till ya try had and old macinest however ya spell tell me his secret to success is to find the crack an drill very small holes at all the ends of the cracks this relives the stress points the the fixin begains sometimes ya win some ya don't

 

Interesting - makes sense though. I've seen pretty much the same technique used by windshield repair places to stop a crack.