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Post by douglasmc on Feb 8, 2021 13:36:55 GMT
My 100 has a very early Le Mans conversion and has the higher 8.1:1 compression ratio pistons and cam fitted
Just putting the head back on after replacing the valves and springs and my standard 100 service manual quotes 65-70lbft torque for the head nuts. Does anyone know if there is a higher torque recommended for the 100M compression ratio?
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Post by bbh on Feb 8, 2021 19:59:22 GMT
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Post by douglasmc on Feb 8, 2021 21:30:49 GMT
Yes. They are standard as far as I know.
Mike’s answer is of course correct - go beyond OEM limits and there is a risk it will go wrong. I saw a narrative elsewhere that someone had used 80 Lbs ft after his 100M head gasket had blown twice. So it’s a choice really: risk some stretch at 80 or risk a blown gasket at 70lbft.
My torque wrench comes with a table that suggests that a 5/8 UNF bolt of the basic quality steel has a recommended max of 81.9lb ft. Higher grades are good up to 167!
Maybe 75lbft will be the compromise.
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Post by douglasmc on Feb 8, 2021 21:49:34 GMT
Or of course, upgrade to higher spec head studs.
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Post by bbh on Feb 9, 2021 20:08:30 GMT
Or of course, upgrade to higher spec head studs. I think that if you want to go above the general figures quoted above, then higher spec (ARP) studs would be the best option. You might want to give one of the professional restorers ( JME / Bill Rawles ) a call, I have always found them to be very helpful |
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Post by douglasmc on Feb 17, 2021 20:01:08 GMT
Thanks for that. I will do. The car came via Bill Rawles so hopefully that will not be too much of an ask.
Cheers
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