Pulled internal threads on motor crankcase

[hard_y_rd]

I'm rebuilding a motor, not a motorcycle engine and as i was cleaning the old gasket off the crankcase, i noticed the threads are pulled a bit on the bolt holes that hold the sump cover on. Just wondering how to flatten them down so they are flush with the gasket surface. I was thinking on putting a bolt in the hole and gently hammer it till they go down. Bad idea? Also thought about sanding them down but didn't want to get into that.

 

[Royboy]

If it was me I'd probably go with a nice fresh mill (flat) file, being careful to keep the mating surface true.

roy

 

[hard_y_rd]

It has 2 locating studs that position the gasket. Don't think they come out. Maybe they can.

 

[gggGary]

+1 I have flattened threads raised above the mating surface with a file fairly often. helps to work across the widest area possible (like across both sides of the opening) to avoid filing a dip or angle into the surface. I'll hit the cover a bit also, common to find the area around the bolts has been squished down.

 

[cra-z1]

How about a stone with a chamfered taper.

 

[TwoManyXS1Bs]

...I'll hit the cover a bit also, common to find the area around the bolts has been squished down.

Ditto. Very important on sheet metal pans.

If your gasket is thick cork composition, probably not necessary to flatten the pulled threads.

If the block is aluminum, a light tough with a new/sharp countersink bit, in a low-speed portable drill, would suffice.

 

[hard_y_rd]

Thanks for the replies guys, some good ideas. Might try the countersink bit trick. Block is aluminum.