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LA Light Six engine setting torques

Culbu
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LA Light Six engine setting torques

Post by Culbu »

Good evening Guys,


Happy New Year dear DLOC members. I hope that you're in good health (that's the more important, according rich people !).

This question has probably been already asked but I didn't find the answer into our forum. It's time for me to re-assemble my Lanchester Light Six engine and I have no information about the different setting torques (crankshaft main bearings, connecting rod caps, ,cylinder head).

Anyone can help please ?

Kind regards,

Julian

grahamemmett
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Re: LA Light Six engine setting torques

Post by grahamemmett »

The only thing I've ever seen printed:
Image1.JPG
But I always use 40 Pounds/foot for the head
Graham Emmett ¦ DLOC Chairman ¦ chair@dloc.co.uk ¦ 07967 109160
Northwich, Cheshire
DB18 1949 LCV522 (Yes that one with the P100s)

Dobbinridesagain
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Re: LA Light Six engine setting torques

Post by Dobbinridesagain »

And these are dry torques, no oil.

Ivor

Culbu
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Re: LA Light Six engine setting torques

Post by Culbu »

What do you mean by "torque dry" ?!?

Culbu
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Re: LA Light Six engine setting torques

Post by Culbu »

Dry torques !

JT7196
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Re: LA Light Six engine setting torques

Post by JT7196 »

I believe , Ivor is asking whether the Threads of the Studs are lubricated, I would and actually do, lightly lubricate the threads , this will prevent binding on the threads which in turn, “May” cause an incorrect Torque being applied .

Cheers Al 👍👍

Ps , I torqued the Cylinder Head Nuts down on my LA11 to a Torque of 40 Lbs / Ft

Culbu
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Re: LA Light Six engine setting torques

Post by Culbu »

I always lubricate the thread of all the studs I screw, specially when I rebuild an engine. But to be honest with you, I didn't know that it could prevent an incorrect torque. Thanks for the tips !

Dobbinridesagain
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Re: LA Light Six engine setting torques

Post by Dobbinridesagain »

At the risk of taking issue with a distinguished contributor, all torque figures for any vehicle should be regarded as DRY - no oil!

If the threads are bad, then a loose die should be run down them to clean them up.

The torque wrench is in effect measuring the frictional load on the thread, plus the bottom washer if any, and if one adds oil, this results in a reduced friction. This leads to overtightening.

The only car manual I have seen this specifically addressed is the shop manual for the Rolls Royce Silver Shadow, where it states that if a fastener is oiled and cannot be cleaned, the stated torque should be reduced by 25-30%.
Some people would say that a 30% reduction is not enough, and it should 40%.

It is true that a lubricated fastener will give more consistent results in terms of the load on the fastener for a given torque, unfortunately this is also influenced by what oil is used, so to be on the safe side, manufacturers always give a DRY figure.

Ivor

Culbu
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Re: LA Light Six engine setting torques

Post by Culbu »

Very interesting post Ivor, which makes sense, even if all the mechanics with whom I worked add some grease on the threads before to tighten them, without reducing the given setting torques...

Dobbinridesagain
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Re: LA Light Six engine setting torques

Post by Dobbinridesagain »

Culbu wrote: Thu Jan 13, 2022 5:44 pm..all the mechanics with whom I worked add some grease on the threads before to tighten them, without reducing the given setting torques...
Well I've done that in the past.
I had to do it last year when retorqueing the heads of my Rambler... some of the head studs were oiled and I could not dry them, so I reduced the torque about 30%. The others I tightened to the dry torque. Or I could have oiled all of them and reduced the torque uniformly which would probably have been a better solution, well it's an all-iron engine and so far I am OK.

But on a stressed fastener, lubrication and overtightening comes with risk.
Strip or distort the thread, snap the fastener, or more insidiously stretch the fastener beyond its yield point.

My LA10 used regularly to blow its head gasket. After many many replacements, I took out all the block studs and found that one of the threads in the middle of the block had pulled up a little so the head was not able to sit down properly. I stoned it flat - took a long time - but afterwards I never trusted that stud and did not torque it the full 40lb. Doubtless at some time someone had pulled it too hard.

The question when lubricating and consequently overtightening a fastener, is... do you feel lucky?

Ivor

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