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+--- Thread: Sump bolt thread restoration (/showthread.php?tid=9994)
Sump bolt thread restoration - falcott - 10-05-2025
Hi all,
I'm wondering if it's possible to restore the 1/4" threads in the crankcase back from the 5/16" threads that it is currently? I'm thinking of fitting an ally sump, and it will be a shame to drill it out to 5/16.
Or would it be better to change the crankcase?
Ta.
RE: Sump bolt thread restoration - Ruairidh Dunford - 10-05-2025
Fit helicoils.
RE: Sump bolt thread restoration - falcott - 11-05-2025
Do helicoils work for threads already tapped out to 5/16"? I've never used helicoils before.
For example, would these work?
https://nzsafetyblackwoods.co.nz/product/recoil-thread-repair-kit-bsw-1-4-20-457154
RE: Sump bolt thread restoration - Ian Williams - 11-05-2025
No they don't, if the case is already out to 5/16 or above I use bespoke brass or aluminium inserts to plug the holes if the case
RE: Sump bolt thread restoration - falcott - 11-05-2025
Ah, okay. I'll look at getting some plugs made up, I guess. It could be an engine-out job.
RE: Sump bolt thread restoration - bystander - 11-05-2025
How about converting to stepped studs, 5/16" down to 1/4"? That would save an engine out job.
RE: Sump bolt thread restoration - falcott - 11-05-2025
(Yesterday, 07:34 AM)bystander Wrote: How about converting to stepped studs, 5/16" down to 1/4"? That would save an engine out job.
Good point! I never thought of that. Thanks.
RE: Sump bolt thread restoration - Ian Williams - 11-05-2025
Studs will work although they can make sump removal in-situ difficult. I would not recommend undertaking any of this work without removing the engine first.