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Lotus Europa Forums => Garage => Topic started by: Stuleslie on Thursday,August 16, 2018, 08:55:06 AM

Title: Re-torque the head on a TC
Post by: Stuleslie on Thursday,August 16, 2018, 08:55:06 AM

I have just completed putting the head back on after the gasket blew. I know that in the good old days you should re-torque the head after about a 500 mile run-in. Does everyone agree? Should I re-torque when hot?
Cheers
Stuart

Title: Re: Re-torque the head on a TC
Post by: BDA on Thursday,August 16, 2018, 09:05:54 AM

I agree. I don't think it has to be hot, but I would loosen each nut (or is it a bolt?) a little and then tighten it back to spec. The reason for this is the coefficient of static friction is higher than dynamic friction.

Title: Re: Re-torque the head on a TC
Post by: 4129R on Thursday,August 16, 2018, 09:32:16 AM

Quote from: BDA on Thursday,August 16, 2018, 09:05:54 AM

I agree. I don't think it has to be hot, but I would loosen each nut (or is it a bolt?) a little and then tighten it back to spec. The reason for this is the coefficient of static friction is higher than dynamic friction.

Mostly agreed.

Engine should be cold, or the torque will be different due to thermal expansion.

Title: Re: Re-torque the head on a TC
Post by: jbcollier on Thursday,August 16, 2018, 10:18:38 AM

After fitting a new head gasket, re-torque after the very first warm-up and complete cool down -- I wait until the next day.  Consult the manual as to whether further re-torques are necessary.

Re-torque:

- mark each bolt head for position -- I use a sharpie and mark a line parallel to the engine.

- follow the torque pattern.

- loosen the first bolt a half-turn using a breaker bar.*

- fit the torque wrench and turn to specified torque setting.

- it must at least go back to where it was, preferably further.

- move to the next bolt in the order and repeat.

Engines driven very hard will require re-torqueing even if it is not specified in the manual.  Not sure?  Mark and check the first bolt in the sequence.  Moves further than marked?  Do the rest as well.

* never, ever use a torque wrench to loosen a fastener.  Yes, I know some have a switchable ratchet, or a fixed beam, but don't do it regardless.  It may throw your wrench out of calibration.  Speaking of which, when was the last time you had your wrench calibrated?

Title: Re: Re-torque the head on a TC
Post by: Stuleslie on Friday,August 17, 2018, 12:24:41 AM

Thanks everyone for the advice.
I bought myself a new torque wrench just for this job as I realised my old one was only 40 years old!
Cheers
Stuart