Head gasket...AGAIN!

[timmo]

Head gasket went again...only just changed the blown one. 1st time it went between 3 and 4, changed the gasket torqued it down (45lbs) gave it a run, then torqued it down again...when cold, is this correct? This time it blew front end on a water way. The gasket came in a set, i wondered about the quality of the gasket at the time.

Can someone please confirm the correct way ..(when hot/cold, after how much of a run, how much torque etc) when re tightening the head nuts

Cheers Tim

[mike.perry]

I would check that the faces of the head and block are flat and that the gasket is sitting flat on the block. I don't know what A Series gaskets are like these days but there are some poor side valve head gaskets around.
Are you tightening the head bolts in the correct order? Torque setting is Cylinder Head 40lbs.ft, Small Rocker Shaft Nuts 25lbs.ft (BMC workshop manual).
Fit head gasket and head, rocker shaft etc .
Tighten nuts just tight with socket and check that the head is sitting flat on the block
Torque down to 30lbs in correct order
Torque rocker shaft nuts to 25lbs
Torque down to 40lbs
Finish all assembly work, adjust tappets etc and fill rad with tap water.
Run engine up to operating temp and check for water leaks.
Torque down all nuts again and go for a drive
Check for leaks and check torque settings again
When you are satisfied that there are no water leaks drain off some of the water in the rad and top up with antifreeze. (No point in wasting antifreeze on a leaky engine)
Keep checking the torque settings until there is no movement

[alex_holden]

The Payen head gaskets are better quality than the cheap ones.

[timmo]

Yep, faces are ok. Torqued down as you said etc. I took car for a drive up to temp, but let it cool down before re torquing the nuts or should they be done while the engine is hot? I thought with expansion the nuts would be done when cold not hot??..This was Wedsnesday, drove it about 30 miles untill today, went about 60 miles running very good. Then when letting throttle off going down a hill...big smoke cloud behind me!!

Need to know when to retighten..and when its safe to stop checking the torque.... i'll be paranoid now ..be checking them every day LOL

[alex_holden]

Re-torque after it has cooled down. I would keep tightening until you have been round them all without any of the nuts moving.

[MarkyB]

Are the studs in good condition?
Marks from Mole grips etc might be bad enough for the head to hang up slightly.
Also heavy carbon deposits should be cleaned off.

Worth having a look at how it sits on the engine without the gasket.

[bmcecosse]

I retighten when it's hot. 45 ft lbf is fine - but don't go any higher - unless you change to the later Mini studs and the nuts with built-in washer, which are good for 50 ft lbf. Are you sure about the torque wrench ??? MOST unusual to blow into a water passage - check very carefully for faults on head/block/gasket.

[timmo]

Too be honest Roy i did have my doubts about the torque wrench yesterday when doing the head nuts...so did a search and found this

http://www.ehow.co.uk/how_5635877_verif ... rench.html

http://www.ehow.co.uk/how_5622566_calib ... rench.html

So going to have a go testing the torque wrench and see if its a long way out! Im sure thats the problem

[bmcecosse]

You could just throw it away - and tighten the nuts until you feel the studs 'yield' . I did this for many many years without any problems - however it's a fine line between 'yield' and 'oh dear it's stripped/snapped' !

[timmo]

I did do them by feel in the end....Did the tests on ths torque wrench, worked out to get 45 foot lbs needed to be set at 51.3 or something like that LOL Tried them on the head nuts and the wrench clicked so left them as they are..Will check them again in a few days...Fingers crossed wont have anymore trouble

[PSL184]

Sounds like your torque wrench has been left at a set value. You should always wind the torque setting back to zero when you have finished using them. This removes the problem you have seen of it under reading.

[timmo]

you could be right there

[mike.perry]

Important point by PSL. Not winding the torque wrench back to zero stretches the spring, leading to inaccurate readings

[MarkyB]

EEK!
I think mine is wound nearly to the max so it fits in my tool box