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Hot tightening cylinder head nuts?
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08-03-2021, 10:15 AM
Chris KC. Just let’s just agree to differ on this point. I have been tightening cast iron head hot for the last 60 years without problems and at 76 I am not going to change. I don’t re check tightness either after doing further runs out in the seven. I agree with Terrytuned about alloy heads tighten cold.
John Mason.
Would you believe it "Her who must be obeyed" refers to my Ruby as the toy.
08-03-2021, 12:20 PM
Seeing as the coefficient of thermal expansion of steel and cast iron are roughly similar, I don’t see it makes a lot of difference. I’m struggling with the concept of getting an engine hot to fit a cylinder head, however. I’d always choose to check it cold simply because cold is a stable condition. Hot isn’t.
Alan Fairless
08-03-2021, 12:32 PM
I agree with Alan. If you are fitting a new gasket, and intend tightening the studs when the engine is hot, that must mean that you are running the engine up to working temperature with the head nuts less tight than they should be, with coolant in the system as well. I think this could lead to coolant entering the cylinders. I would tighten the head down to the correct torque by degrees when the engine is cold, before filling with coolant. Give it a run up to temperature, let it cool down and then check the nuts again.
08-03-2021, 02:21 PM
Alan and Malcolm, you are not understanding how I tighten the head down possibly I didn’t explain things correctly. I do everything the same as you do fitting the head to correct tightness filling with coolant and then running the engine to running temperature. I then do the final tightening whilst hot. I don’t let it cool down before the final tightening.
John Mason.
Would you believe it "Her who must be obeyed" refers to my Ruby as the toy.
08-03-2021, 03:40 PM
(This post was last modified: 08-03-2021, 03:45 PM by Steve Jones.)
(08-03-2021, 02:21 PM)John Mason Wrote: Alan and Malcolm, you are not understanding how I tighten the head down possibly I didn’t explain things correctly. I do everything the same as you do fitting the head to correct tightness filling with coolant and then running the engine to running temperature. I then do the final tightening whilst hot. I don’t let it cool down before the final tightening. For steel heads, I do exactly that and have done for many years. For aluminium heads I always let the engine cool down before tightening. For both I re-check the head nuts regularly over the next few days at 20 ft lbs until they stop taking any further torque. Malcolm and I know someone who usually forgets the last bit and who regularly experiences head gasket failure!!  Steve |
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