re-torquing heads - Team Camaro Tech
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post #1 of 5 (permalink) Old May 3rd, 11, 07:15 AM Thread Starter
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RICK
 
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Question re-torquing heads

I am putting together a 400 sbc with AFR heads. Planning on using felpro gaskets. Some say they do not need to be retorqued, some say they do. My question is that on some of the head bolts there needs to be thread sealer because of going into the water jacket. Now after the first time being run, do I back off the bolts one at a time, then simply retorque. What about the sealant for the bolts that go into the water jacket? Do I do them one at a time and take completly out and put new thread sealer on or just back off and retorque. Some say put a film of moly lube on the head of the bolts so they slide easily on the head to keep the torque more equal from bolt to bolt. What does anyone think is the best procedure to go with.
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post #2 of 5 (permalink) Old May 3rd, 11, 08:13 AM
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Re: re-torquing heads

Don't back off the bolts. Just check the torque. If any are off just tighten til torque is reached.
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post #3 of 5 (permalink) Old May 3rd, 11, 10:02 AM
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Thumbs up Re: re-torquing heads

It may just be the "Old's-COOL" mechanic in me (or the fear the guy I apprenticed under might hop back out of his grave and wack me 'up-side' the head for not following good procedures ) - but ... I always run an engine to heat soak and break-in internals and then allow to cool before re-checking all the torque setting (heads, manifolds, fittings & etc.) and then go test drive or dyno it.
I know the majority of composite gasket suppliers say 'it's not necessary' - but what can it hurt?
Besides, I've ran into way more than one that a bolt or two DID move some while going through torque pattern again!
As stated, no need to back them off - just set your torque wrench to recommended setting and run the bolt pattern again to check the final torque.

The Sealer you use on the bolt ends should be a non-hardening type - in other words, it should not dry hard and should be somewhat pliable even after it is 'set-up' (even years later when the engine is disassembled again).
Permatex 'Aviation Form-A-Gasket' #3 liquid in the small can is a great product for use in this area, as well as most of the wet contact seal areas (like the coolant gaskets, timing cover seal outer edge and other seal mating edges).
GM also sells a very good product, but it is only available in the 'large-economy' size, so a can would be a lifetime supply to most ...

Truthfully, the SBC design (along with many other truck/fleet engines) is so robust and forgiving, that even if you didn't re-torque steel-shim gaskets (GM didn't ) it would probably still lead a long and healthy life unless severely overheated or abused.
The shop I apprenticed in in the early 60's had a "Flat-Rate Freddie" mechanic that only liked to work on the fleet trucks and buses for the city and county - because no-one opened the hood when they picked it up to check the quality of work you did ...
He only had one 1/2" impact gun, a set of deep impact sockets - 1/2" drive, maybe 5~6 wrenches (2 - 9/16" I think ) and some really beat up "Pry-Drivers" (screwdrivers that seldom saw a screw in their life, just used to 'pry' $hit apart ...) and a couple other tools, all that could double as ' the hammer of Thor' when needed ...
He had a surprizingly (to me anyway) low 'come-back' rate
He NEVER torqued ANYTHING! He removed and installed heads with an impact
This guy would knock an engine apart with his mighty impact, smack the retainers off the valves, grind the valves and seats and reassemble - without EVER touching the rocker(s) or their adjustment! - then just reassemble and re-install ... and only touch the rocker adjustment if the lifter had a noticable tick Watched him do it hundreds (literally) of times and 99% of them he never adjusted anything before signing the card and turning it in - they never seemed to have problems and seldom came back on him - still don't know why ...
He rebuilt huge truck rearends - with an impact - no dial indicator!
He did hundreds of manual trans overhauls - same impact ...
Never cleaned a part, painted a part or wiped grease off a door handle or steering wheel in his life.
Hardly ever used any gasket sealant - just slapped them on dry - said " if they needed sealer the parts store would have sent it " - or something like that.
And he told the raunchiest jokes I've ever heard
He was hardly ever allowed to do regular customer work
(I did all the carburetor, electrical, performance and high-dollar stuff - you know, any work that required being clean, detail oriented or painted before the customer got to see it or get it back )

So anyway ... long story to illustrate how forgiving an engine can be ...
But, don't follow his example

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post #4 of 5 (permalink) Old May 3rd, 11, 01:09 PM
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John
 
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Re: re-torquing heads

fwiw....ONLY check torque value while the bolt/nut is MOVING. Checking torque on a bolt that doesnt move is misleading. The bolt could be threadlocked, frozen, bottomed out, galled, crossthreaded, whatever, and not exerting the correct pressure on the surface as intended. I always throw this in because I have seen too many blown gaskets, cracked mounts, etc, because of improper torque procedures.

Quote:
Originally Posted by Vintage 68 View Post
It may just be the "Old's-COOL" mechanic in me (or the fear the guy I apprenticed under might hop back out of his grave and wack me 'up-side' the head for not following good procedures )
I know my mentor is watching from above! I am in fear of getting smacked (for not saying anything) since this was his pet peeve!!!

......Jb

Beat it to Fit, Paint it to Match!
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post #5 of 5 (permalink) Old May 3rd, 11, 02:06 PM
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Steps
 
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Re: re-torquing heads

Quote:
I know the majority of composite gasket suppliers say 'it's not necessary' - but what can it hurt?
Exactly...I have always rechecked torque after a couple 100 milesIn the old days yeah sometimes changed others times not...modern times...doesnt change...but hell I prefer to checkanyway..u dont know if have say a weak thread on a hole or bolt or whatever
Called peace of mind.
Anyway u are going to re check tappets, so re checking head/ inlet/carb bolts is no big deal.
Called peace of mind.
Sealer..I put on all the bolts..that way u dont accidently miss one that should have had sealer on.
All of the above require a toque wrench....now things like water pumps, sumps, timing chain covers...again torque is very important epec with cork type gaskets.

When was the last time (or ever have) any of you have practised the feel of diffeent torques with different spanners/sockets/drives...or even refamilarise your selves with the correct feel... or check the torque of your air gun?
If not I hae to think of all those threads that have been stretch, distored....and then ppl wonder why things go wrong, have leaks.

My Spelling is not incorrect...it is creative

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