MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - Torque wrench settings

Here's an old chestnut. The reason for bringing it up again is my fear of getting it wrong.

How tight should e.g. the seven backplate/engine block bolts be? No value given in the Haynes Manual.

Are they just nipped up tight using human forearm power (no shoulder) and a proper half-inch spanner?
Nick and Cherry Scoop

Ideally, you should look for a similar fastener into a similar material i.e. the 5/16" timing cover bolts (screws) which are 14lb/ft.
Dave O'Neill 2

Nick

I can't remember if a tightening sequence is in the manual, if not I would be tightening in stages and doing this across opposite sides working my way round to ensure even tightening across the backplate (I.e. similar approach to wheel nuts and cylinder heads). Clean the threads of bolts and the threaded holes, but don't put any oil or thread locking compound etc on them.

I expect you were going to do this anyway.

Cheers
Mike
M Wood

I agree esp if your usimg the cast iron back plate if you get differnt torque values that backplate will crack faster then am indian head massage artist can manipulate your spine

Id focus on a consistant torque for all the hardware over a specific torque setting

Prop
1 Paper

Hi Nick
I torque em at 22/24lbs/ft
Peter
Peter Burgess Tuning

Thank you, Peter. Thanks everybody. I notice that the flywheel bolts, which are only 3/8" dia - 20% greater than these 5/16" ones (though 44% greater c/s area), demand a torque of 40lbs/ft. Are they made of tougher steel?

Mike, I know that some people put oil or grease on fastenings, to make it easier to dimantle in five years' time. I would do it for things that get wet and muddy, like fuel tank flange bolts, but for the engine my rule is oil while cleaning up threads, then wiped clean before using.
Nick and Cherry Scoop

Nick

Flywheel bolts are high-tensile, due to their application. They are also going into steel, rather than cast iron.
Dave O'Neill 2

I've just mounted the clutch - again with no torque value given. Nipping them up with a 1/2" spanner, I got them pretty much all the same, and my torque wrench clicked at 18lbs/ft when I tested them afterwards.

The plate was supposed to say "flywheel" on it according to Manuel, but it didn't. Mind you, when I put it the wrong way it jammed into the flywheel centre and stayed there quite securely.
Nick and Cherry Scoop

Hi Nick, I do the cover assembly set screws at 22/24 lbs/ft as well.
Peter
Peter Burgess Tuning

Hey Peter - it sounds as if you're going with Prop here:- "consistant torque for all the hardware".

Thanks again.
Nick and Cherry Scoop

I just tend to torque 5/16ths at 22/24 lbs/ft, the figures are from MGB units so I use 'em on A series, which should be ok unless the A knows it isn't a B :)

Peter
Peter Burgess Tuning

Without suggesting it's anything like exhaustive, here's a handy mug's guide. One of squillions out there - Google knows everything.

By this guide Peter is on the button for HT 5/16"UNC screws/bolts, (as I would expect of course from Peter).

But it's not always about the fasteners; we need to consider what material the fastener is screwed into, shear values for steel, cast iron, aluminium etc all being different as any fule kno. I've seen loads of alloy parts wrecked by steel screws racked up too hard, which of course is where helicoils are a godsend.

But in practical terms I'd expect this guide to serve well for steel in steel or steel in CI. And I reckon it would be fine also for BSW/BSF in the same sizes. Even near equivalents in metric should be okay I think. Like 6mm - 1/4" or 10mm - 3/8". Because there's a 50 to 60% safety factor built in with respect to the material shear torque value as I understand it.

BTW never retorque titanium screws once they've been torqued to the max. That gets expensive pretty quick. (Thank you Schilling Robotics for teaching me just how expensive).


Greybeard

Correction on my part...let me rephrase what i wrote

I meant to say have a "consistant" torque value for each section of the engine

If the flywheel is 44lbs then make them all 44 ftlbs

If the back plate is 22 ft lbs then make all the hardware for the back plate

Im just saying its more important to have the consistance the same then the actual torque value ....but thats a general rule, and works for intake manifolds engine plates yet will not apply to crank shaft bearings and connecting rods where you want an exact spec

As to the thread lube and oiling threads.... NO this is NOT for easy disassbly in 5 years

Oil and thread lube acts as a hydrolic and reduces the amount of torgue needed to fasten 2 parts togather there by reducing the strain on the threads of the hardware and part for longer longgivity and reduce chance of stretch over time that looses torque value

Arp has its own specific thread lube but general hardware can use various wieghts of motor oil... to which gray can provide better info... i want to say a good basic alround oil wieght is 30w and ithink the oil has to be non detergant based motor oil, so hard to find ... but you might be able to use motor cycle fork oil for this as it comes in various wieghts and i think maybe non detergent... research it ... dont trust what i say

Prop
1 Paper

This thread was discussed between 30/06/2017 and 02/07/2017

MG Midget and Sprite Technical index

This thread is from the archives. Join the live MG Midget and Sprite Technical BBS now