Sump bolt length

[falcott]

Hi all, can someone tell me the length of the sump bolts please? My sump bolts have been tapped to 5/16" and fitted with 1/2" long cap screws -- not by me, I might add. When I was inspecting it for leaks I found that two of them have departed. I'm wondering if they are supposed to be longer (3/4"?). Thanks.

[Chris KC]

Do you have a standard "tin" sump or a cast aluminium one?

[falcott]

It's a tin sump.

[falcott]

These 5/16" bolts have spring washers under them. I'm thinking of ordering the oval sump washers from the Seven Workshop. If they are fitted with a spring washer also, wouldn't that, in theory, entail a slightly longer bolt to allow more purchase on the threads?

[Ian Williams]

The oval washers were std fitment so std length bolts will be perfect

[falcott]

Okay, but my sump is fitted with 5/16" cap screws and spring washers. What I want to know is what was the length of the original bolts, because my thought is that 1/2" length isn't quite enough when the thickness of the flange and the washer is taken into consideration. Also, were spring washers fitted as well as the oval washers? Thanks.

[Howard Wright]

Hi Geoffrey

A standard 5/16” BSW nut is 1/4” thick so as long as you have at least that depth of contact and don’t torque up too tight (bearing in mind the crankcase is alloy) you should be OK. Don’t make the bolts too long as the holes in the crankcase are blind and it is easy to punch through leading to oil leaks. I know this because some ‘gorilla’ had in the past punctured several sump holes in a crankcase I used recently!

Cheers

Howard

[Tony Press]

And the rear bolt under the flywheel is short if I remember correctly

[falcott]

Thanks Howard and Tony.