Kohler K 12hp

[Save Old Iron 1,566]

A friend gave me a Kohler K 12 hp engine with a quarter sized hole in the block.

The hole is roughly circular - directly above the bottom end of the oil dipstick tube.

The entire inside of the engine appears in perfect shape - appears the hole was created by a blow to the outside of the case as the hole is tapered to the outside of the case indicating the piece missing was pushed INTO the block and not away from it. Suspect maybe a previous starter removal gone bad ??

In general, would this be considered a scrap block ??

[chazm 413]

Hello- I wouldn't give up on it yet -

If you know a good welder that can weld cast iron , he should be able to rosebud it shut.

Good luck with it

Chaz :scratchead:

[Kelly 1,029]

If it's just a bare block I'd junk it they are easy to find, now if it's a complete engine, fix it, do you have the piece?? get it and the block very clean, carb or brake cleaner, then JB weld it in, I've fixed cracks in car engines with it, as long as it's not a high stress spot should be good.

[big mike 13]

If the block is standard bore,round and in good shape I would try and fix it.I would NOT braze it or JB Weld it.My first choice would be to find a welder that is proficient in tig and has done cast,my second choice would be the same welder that has stick welded cast and if all else fails THEN JB Weld and brazing last.

[Save Old Iron 1,566]

Thanks Guys,

I DO NOT have the piece off the block - just imagine a quarter sized piece slightly above the base of the oil dipstick tube - at the 10'oclock position looking straight on the block - sorry, kids have the digital camera this week.

It seems like a low stress area given the location of the oil tube. Maybe brazing would work seeing as how it would be at a lower temp and stress the repair area less on cool down. I have never welded cast before - I know there is quite the art to it - all concerning the prevention on rapid cool down after the weld.

So I'll look in the local area for a welder who is confident in his ability to weld cast.

Otherwise, the block is complete minus the skins, bore is straight, standard size and little if any ridge at the top of the bore. Internals all look clean and undamaged - maybe i'll check the crank clearances before I go too much further.

Anything else I should consider from a $$$$ standpoint before continuing ??

What would you expect to pay for good used bare block ?

Thanks again for all the advice.

[sorekiwi 761]

I MIG'ed this one back together, and it ran for another year or so...

Everyone will tell you you cant Mig cast reliably, and they are probably right. The experts like a good preheat, and a really slow cool down after welding to avoid stress cracks from the different expansion/contraction rates of the welding rod and the cast iron.

In my case, I didnt have a choice, and I figured I had nothing to lose. I did have to coat the patch with epoxy to stop it leaking oil like a SOB, maybe it developed a stress crack while it cooled down!!

[Save Old Iron 1,566]

Mike, thanks for the reply

My damage is no where near that severe.

Did you ever figure out why your block cracked like that - was it dropped off a workbench ? What finally caused it it fail after it was repaired ?

I'm thinking maybe going in a reverse order here since I really do not have to depend on the engine at this time

- going JB WELD - if that fails maybe brazing due to this being a low stress area - then welding if all else fails.

Any other comments are welcome - thanks to all those who have responded.

[big mike 13]

The main reason I advised against JB Weld or brazing is that once that is done if the repair fails the material is contaminated.

The main reason cast is not usually mig welded is because the wire required(yup,special wire )is VERY expensive and is sold in fairly large quantities.My guess is you used stainless steel wire for your repair?

[sorekiwi 761]

Did you ever figure out why your block cracked like that - was it dropped off a workbench ? What finally caused it it fail after it was repaired ?

I'm not sure I should write this as a "how-to repair a block" reply, it was really just something I tried, and it worked. I'm not sure I would do it again either.

On this one a rod broke and punched out the side of the block. It took out the starter too...

The second failure wasnt really unexpected. I was unemployed at the time I did this, and although the piston skirt was a little damaged I reused it with another rod. The engine had a little knock to it after the "rebuild", but it ran really well, so I kept using it till that poor old piston had enough.

Big Mike - I looked into a special wire for cast, and read up a little on the pre/post -heat process, but in the end just used the normal old general puropse wire that was in the machine. It actually welded surprisingly well, but there were a lot of creaks , groans and pops from the block as it cooled down.

My feeling on the brazing is the same as Mikes - once you attempt this, its very hard to get rid of the brass for a different welding process. Over the years I have seen a lot of engine blocks repaired by brazing, and it does seem to work well.

At work a few months ago one of the guys brazed up a crack in a cylinder block. He put the block in a gas BBQ for about 4 hours, brazed it up, and put it back in the BBQ for the rest of the day. At the end of the day he turned off the gas, and left it in there overnight. The repair worked well in this instance.

Having said that, I'm not sure how you would braze up a hole that size if you dont have the missing piece... :hide:

[Save Old Iron 1,566]

Thanks Mike.

I'm sure the clicking and popping as the block cooled was the weld material shrinking and pulling away from the much less flexible cast iron.

Thanks for the update on the brazing, I never really got much experience with it.

Since this area is on a relatively flat spot on the block away from any internal parts - JB weld may be the first step I take.

Since this block is not really a necessity - i guess it becomes an "experiential piece",

I will update the site when I get my digital camera back and make and test the repair.

Thanks again to all

[TT-(Moderator) 1,131]

Here's some more "food for thought".

I've seen a few non-stress area block repairs that consisted of a metal (brass, aluminum, steel) patch plate bolted over the hole. This is only possible if the hole is in an area that's flat enough to get a good seal. The location of the holes drilled around the perimeter of the patch plate is transferred to the block so they can be drilled & tapped to match. Once the plate is final-fitted, smooth and clean both mating surfaces, apply a good gasket-type sealant, and secure the plate to the block with the bolts or screws.

[Save Old Iron 1,566]

Thanks TT

come to think about it - isn' the block supposed to be under somewhat of a small vacuum condition - I saw a manometer setup in the kohler manual to check block vacuum while the engine was running.

Seems like a "patch" sealed appropriately at the block surface may be a good way to go. Maybe round off the one small angular part of the wound to relieve any concentrated stress at that area - so no further cracks proceed out from that area - and give it a go.

:scratchead:

[WheelHorse_of_course 99]

Here's some more "food for thought".

I've seen a few non-stress area block repairs that consisted of a metal (brass, aluminum, steel) patch plate bolted over the hole. This is only possible if the hole is in an area that's flat enough to get a good seal. The location of the holes drilled around the perimeter of the patch plate is transferred to the block so they can be drilled & tapped to match. Once the plate is final-fitted, smooth and clean both mating surfaces, apply a good gasket-type sealant, and secure the plate to the block with the bolts or screws.

TT,

excellent idea. It also give an "inspection" point :scratchead: