Board index Flathead Power-Technical Questions, Answers, and Suggestions K-Models striped crack drain plug... :(

striped crack drain plug... :(

Post Wed Jul 25, 2012 12:23 pm

Posts: 334
Location: north central Ma.
Hey gang.
My 52K has allways druled from the crank case drain plug. As it's not a daily rider and don't have a check valve in the trany cross over passage I took the advice of my age old dealer and any time i park it i pull the drain plug and push a drain pan under it.

Well wanted to go for a ride last weekend and low an behold the plug just kept twisting by hand pulled it back down and the complete tread was on the bolt. :cry:
I was able to unscrew the thread but theres nothing left in the hole.

The way i see it i've got three options.
1) Helicoil , reuse OEM bolt plug deal with leaks...
2) Tap for 3/8 pipe plug. Good to stop leaks but as it taperd and gets used it will work its way deeper over time or split the case..
3) Drill and tap for SAE / AN stright thread and use O-ring sealed plug. I belive a -6 thread is 9/16 x 18 thread so i shold be able to do that as OEM hole was 1/2x13.

So what have you done? what would you recomend I do?

"Smok'in the competition NOT Tobacco"
"Transplant organs, Don't bury them!"
Why dwarf? 5/8 scale race cars!

Post Wed Jul 25, 2012 5:39 pm
Pa Site Admin

Posts: 6069
Location: Ohio USA

Try a rubber expansion plug. They are available in many sizes from vendors such as MSC Industrial Supply. If the size you need is not listed, you can fabricate your own with a section of rubber hose, two washers, a bolt, and a nut. I would tack weld the head of the bolt to the one flat washer so the bolt does not spin when you tighten up the nut. Bolt head goes inward. Nut faces out. As the washers are squeezed by the bolt, nut and slightly smaller flat washers than the hole, the rubber expands to seal up the opening. Just a thought if nothing else works out. Pa

Post Wed Jul 25, 2012 8:42 pm

Posts: 1212
Location: Ojo Caliente,NM,USA
I would go with the straight threads and o-ring Its good enough for Cat. If you dont have a way to cut the taperd relief for the o-ring in the case search the industrial supplies I used to buy washers with o-rings cast on the inside.

Post Thu Jul 26, 2012 11:21 am

Posts: 200
Location: Middle England UK
If it's in the side like a 45,I'd use a Time-Sert.Put a little sealant under the flange before screwing in,and as Dusty said,a Dowty washer under the drain plug. ... sult_group

Post Mon Jul 30, 2012 10:03 am

Posts: 334
Location: north central Ma.
It's right at BDC. I've got a straight 9/16 thread plug on the way. Think its the best solution and will look closest to stock.
"Smok'in the competition NOT Tobacco"
"Transplant organs, Don't bury them!"
Why dwarf? 5/8 scale race cars!

Post Thu Aug 02, 2012 8:00 pm

Posts: 334
Location: north central Ma.
Got a nice steel plug from one of my favorite places to shop. Surplus Center. I was able to slowly turn the crank and find a spot where the crank check was not in the way and drill the hole out. Tapped the hole and plug fits nice and tight and ring sealed it up. Will see if it weeps hopefully ride it to work in the AM.
even looks stock except it needs a 11/16 wrench not the 5/8.
"Smok'in the competition NOT Tobacco"
"Transplant organs, Don't bury them!"
Why dwarf? 5/8 scale race cars!

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