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Torque setting for sump bolts

Postby David Worthington » 24 Nov 2017 17:36

It seems a simple question but I can't seem to find a definitive answer - what is the recommended torque setting for the sump to engine block bolts on a factory MGB GT V8? There doesn't seem to be a value printed in the V8 Workshop Manual Supplement and different websites state different values going upwards from 6ftlb. There also seems to be a suggestion that the rear bolts should have a slightly higher setting. A couple of the bolts on my V8 appear to be finger tight only and may have loosened off after an engine rebuild a few thousand miles ago. There is a slight oil leak at the moment which wasn't there a few months ago.
I have read the notes about adding strengthening bars and the use of different sealants but torque setting are rarely mentioned.
Any help/advice would be gratefully received.
Regards to all Bulletin Boarders,
Dave.
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Re: Torque setting for sump bolts

Postby Victor Smith » 24 Nov 2017 18:37

The sets of V8 Workshop Notes include a manuals folder in which there is a copy of V8 Engine Overhaul Manual Part No RCL 1996. (Information, Torque settings, page1). A copy is attached below.

The MG RV8 - V8 engine overhaul manual - AKM7154ENG - has the torque settings for the sump bolts. The page is Engine, Torque wrench settings, page 1. A copy of this manual is on the RV8 Technical Information CD available from B&G.
http://www.v8register.net/subpages/v8wo ... anuals.htm
http://www.v8register.net/subpages/Band ... infoCD.htm

You will see there is quite a difference in the settings in those sources.
Attachments
V8 Engine Overhaul Manual Part No RCL 1996.pdf
(700.32 KiB) Downloaded 32 times
171124-V8-sump-bolt-torque-settings.pdf
(128.73 KiB) Downloaded 29 times
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Re: Torque setting for sump bolts

Postby Bob Owen » 24 Nov 2017 19:17

There are different sump gaskets available. There are cork gaskets and rubber gaskets with at least some of the rubber gaskets with metal spacers in the fixing holes. The cork gaskets would have low torque fixing but the rubber ones with spacers would have relatively high torques as you are tightening against the spacer and the gasket then has a defined compression. I don't know if this latter type were ever original equipment.
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Re: Torque setting for sump bolts

Postby Nic Houslip » 28 Nov 2017 22:36

David
I find it very helpful to make sure that the pressed steel sump mating faces are flat, lay a 12 steel rule along edges and see that the area around the bolt holes is flush or under flush. I use a largish ball bearing on top and a small socket on the under side and with the aid of G Clamp or a vice, slightly dish the metal downwards. Tricky job, needs about 3 hands! Using a hand held countersink bit, de-burr the edges of the holes in the sump and the engine block. Use any new gasket, but smear joint faces with Original Hylomar blue joint sealant [not the silicone based one] before assembly Rimmers have a neat sump bolt for later LR engines that you can use that have [a] a captive washer and [b] a spot of blue thread locker compound on the thread that helps keep them tight. Scrupulous cleanliness is important, degrease before apply Hylomar and DO NOT overtighten the bolts. Ever.
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Re: Torque setting for sump bolts

Postby David Macadam » 29 Nov 2017 09:20

Like David I had read the useful material on the V8 Register website and was aware of the two types of gasket. I had also seen the information in Tony Lake's note but again like David it is a definitive answer to the question what is the recommended torque setting for the sump to engine block bolts on a factory MGBGTV8 I hoped to see. The care Nic describes in preparing and fitting the gasket is very good but does anyone have the settings used for either type of gasket?
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Re: Torque setting for sump bolts

Postby Tony Lake » 29 Nov 2017 17:45

The SAE grade 5 mounting screw (3 radial raised lines on the screw head) must have thread engagement length of at least 2 times screw diameter, .625" when used in aluminium, this is after allowing space for flat and spring washer and flange thickness. The sump flange is relatively flimsy and easily distorts. The big unknown is the stiffness and compliance of the gasket materials on the market.

Published data for screw torque in aluminium is inconsistent, in a sample of six it ranges from 80 lb ins up 150 lb ins or say 7 to 13 lb ft. One recommendation is to lubricate the threads; another for dry assembly, four others don't say either way.

My belief is that the Rover development engineer knew the sump flange was weak so was cautious about using a high torque to avoid high local load under the screw which then decays almost to nothing mid-way between screws; a sure recipe for oil leaks. The sump is a passive part in that there is negligible cyclic load on the assembly so the bolt has an easy life in terms of keeping the sump in place.

I would say use 7 to 8 lb ft, well lubricated screw thread, under the head as well, oil associated washers too. This should work with both the simple gasket and the controlled compression design. Anything higher will likely distort the flange.

Weak flanges are a killer for oil leaks, modern engine designs just don't leak because flanges are really stiff and load distribution between mounting holes is pretty uniform. You can support the V8 flange and even out load distribution by adding a stiffening piece along the length of the sump on each side. Another improvement is just use a plain washer and omit the spring washer under the screw head, multiple washers cause variation in axial load because friction between relatively soft parts is inconsistent.
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Re: Torque setting for sump bolts

Postby Victor Smith » 29 Nov 2017 19:09

Tony,
That information is useful. I think your torque settings are equivalent to 9.49 to 10.84 Nm which compares with 10 Nm on the torque settings page of the earlier of the two manuals I posted as attachments to an earlier post.
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Re: Torque setting for sump bolts

Postby Nic Houslip » 01 Dec 2017 21:40

David
My apologies, I forgot to go look up the torque figure, the only one I can find in my RV8 manual of 10 NM and the bolt size is common to all Rover V8s. My MGB Manual doesn't list it but my Rover 3500S list as 11 NM or 8lb ft.
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Re: Torque setting for sump bolts

Postby Nic Houslip » 01 Dec 2017 21:41

And they do require tightening occasionally.
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Re: Torque setting for sump bolts

Postby David Worthington » 05 Dec 2017 11:38

Thanks for all the replies and comments about the torque settings for the sump bolts. I went under the car this weekend and the oil leak was not as bad as I thought. The front of the sump was dry and the only evidence of oil was at the rear next to the bellhousing. I nipped up all of the bolts a little so that they all felt of equal torque although none of them reached 10Nm, which was the lowest setting on my torque wrench. So on the basis that it is best to have the lowest torque that results in no oil leaks, I think I will leave it there and monitor the garage floor!
Thanks again for all the replies. It proves to me again the value of the Bulletin Board and the advice available from more knowledgeable V8 colleagues.
Best wishes, Dave.
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