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MG MGA - Re torque Head

I took the car for a spin this morning and now want re-torgue the head bolts. The outside temperature is around 85F, the engine is taking forever to cool down.

Should the engine be in the 50F or 60F temperature range or does it matter when re torgueing the head bolts if the engine is about 85F?

Ray
Ray Ammeter

Ray-
I do them hot, always for CI heads, alum heads cold. Some people say cold, but 50+ years exp and very many heads says hot. In reality, it makes little difference on CI heads.
FRM
FR Millmore

Since both the studs and head and block are all iron / steel, it makes no difference if all the parts are the same or nearly same temperature. A "hot" engine is only 200F max, which is nothing.
Art Pearse

Thanks for the comments. I re-torgued the head yesterday and adjusted the tappets. The engine was at its 500 mile mark after a rebuild.

Now today I wanted to take it for a long drive and the dang rubber grommets that mount the float bowl to the carb are leaking. I find one in my collection of parts.

OH for a good supplier of rubber bits.
Ray Ammeter

When you retorque the studs, do you loosen them fist and if you do, do you loosen them just a turn or get them really loose? The reason I asked is that I was told to loosen them first then retorque. Doing this caused water to get into the oil sump. I had to change the oil anyway but it was something I wasn't expecting. Thanks and have a good day!

John
John Progess

John,

You do not need to "loosen" the nuts only to turn enough to break the "stiction" (i.e. just to move) before retightening. You only need to do this on those that do not move when being tightened. The purpose of this is ensure that the stud is being tensioned (a known amount measured through the torque) rather than by the nut being "stuck" by residual friction (stiction). The reason this is not always mentioned or recommended is that there are no prevailing torque devices (star washers, lock washers, nylock etc.) in the joint, so less chance of stiction. Also the retorque is normally done before there is chance for corrosion on the nuts/threads outside the rocker cover.

Hmm, not easy to put into words! Does this make sense?
Neil McGurk

John-
Standard recommendation is to loosen each nut in turn, and in the normal tightening sequence, "about" 1/6 to 1/4 turn and pull smoothly up to torque. The loosening is such that there is a definite easy motion as it tightens, rather than a bare wriggle or no motion. Only one nut at a time is somewhat loose. You never loosen all the nuts at once, since you then have the water leaking problem, which means that the sealant on the gasket is now contaminated with coolant.

In any case where you need to loosen multiple nuts for any amount of time - like if you need to remove the rocker assembly but not the head, the procedure is thus: Loosen all nuts in reverse sequence, about 1/4 turn at a time. When each nut in turn is actually loose, tighten it back to about 15lbft. Again only one nut at a time is loose, this keeps the gasket sealed. Then remove the 4 nuts to get the rocker assembly off. When you put it back, snug up the 4 nuts to about the same as the rest, then torque all in the usual manner in sequence and by stages.

FRM
FR Millmore

This thread was discussed between 04/07/2009 and 06/07/2009

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This thread is from the archive. The Live MG MGA BBS is active now.