The Ford Barn

Mart · 12-08-2020, 03:14 AM

Quote:

Originally Posted by Lawson Cox

Why would you loosen a nut to re-torque it? Sounds counterproductive to me. Inquiring minds want to know.

While I tend not to loosen before tightening, I can see the logic. you loosen, re-tighten and the chances are it will settle at a point past the original setting.

I might try it that way next time.

Mart.

JSeery · 12-08-2020, 10:19 AM

When a bolt or nut is tight and you check the torque with a wrench it takes a load above it's current torque value to move it. If it moves that would indicate it was well below the desired torque value. By loosing the fastener first you eliminate the initial break free torque issue. This is a lot less of an issue with new threads and new bolts/studs/nuts with everything clean, as an engine built at the factory (I have no idea if they retorque head bolts/nuts). But a rebuild becomes a different issue and it is more difficult to get the torques to the correct values in one operation. Over the years three heat cycles have been found to be a good practice.

Ol' Ron · 12-08-2020, 10:47 AM

I'm not sure what the factory specs are for head bolts? But I do know it's higher than the 45 lbs we now use. Not sure where this came from, but it's part of the learning curve when running these engines in competition. there are allot of things we do to these engines that the Factory might fron on. Like the seals on the intake guides. I've never used them because there was a better wat. i just put a little sealent on the lower part of the guide and install it, and the guide is sealed forever, and easier to remove for the next guy. Most modern engines use much of this stuff instead of gaskets. All things go thru an evolution. Another NEW thing, paint the Aluminum head with some Latex paint and it will not eroad. Never tried it but will next time I installan alu head. can't hurt, might work??

Pete · 12-08-2020, 02:37 PM

Quote:

Originally Posted by Lawson Cox

Why would you loosen a nut to re-torque it? Sounds counterproductive to me. Inquiring minds want to know.

It has to do with static friction and moving friction.
It takes more torque to get a fastener moving than to keep it moving.

12-08-2020, 10:19 AM	#22
JSeery Member Emeritus Join Date: Nov 2012 Location: Wichita KS Posts: 16,132	Re: Headbolt When a bolt or nut is tight and you check the torque with a wrench it takes a load above it's current torque value to move it. If it moves that would indicate it was well below the desired torque value. By loosing the fastener first you eliminate the initial break free torque issue. This is a lot less of an issue with new threads and new bolts/studs/nuts with everything clean, as an engine built at the factory (I have no idea if they retorque head bolts/nuts). But a rebuild becomes a different issue and it is more difficult to get the torques to the correct values in one operation. Over the years three heat cycles have been found to be a good practice. Last edited by JSeery; 12-08-2020 at 10:27 AM.

12-08-2020, 10:47 AM	#23
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,857	Re: Headbolt I'm not sure what the factory specs are for head bolts? But I do know it's higher than the 45 lbs we now use. Not sure where this came from, but it's part of the learning curve when running these engines in competition. there are allot of things we do to these engines that the Factory might fron on. Like the seals on the intake guides. I've never used them because there was a better wat. i just put a little sealent on the lower part of the guide and install it, and the guide is sealed forever, and easier to remove for the next guy. Most modern engines use much of this stuff instead of gaskets. All things go thru an evolution. Another NEW thing, paint the Aluminum head with some Latex paint and it will not eroad. Never tried it but will next time I installan alu head. can't hurt, might work??