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Noticed my Thermostat housing had a leak (427/425 hp - checked the bolts and found one stripped. Checked the Service manual and found "water outlet" 20 ft lbs torque but no spec listed for the thermostat housing. Pls confirm your understanding of torque spec for the Thermostat housing bolt to aluminum intake. Also - I am going to use a stainless steel helicoil for the repair - any experience or hints with this repair will be appreciated
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Re: 66 L72 Therm Housing Torque
helicoil only way to go but use a good sealant when installing the helicoil(permatex or Right Stuff silicone) Stripped threads usually secondary to a knucklehead trying to correct a leaking gasket( oem gaskets notorously poor sealers) also straight edge manifold and outlet and correct if warped(surface manifold and or outlew) then use a good quality paper gasket that has been coated with thin layer of Right stuff by permatex. torgue to about 20lbs/ft sq. good luck, mike -
Re: 66 L72 Therm Housing Torque
Having a fair amount of experience with the all-aluminum Cosworth Vega engine I can give you the following rules of thumb for bolts engaging threads in aluminum castings.
1/4-20 65 in-lb
5/16-18 15 lb-ft
3/8-16 25 lb-ft
Also, shop manuals can have errors in torque specs, and may not not have a provision to account for aluminum manifolds, an unfortunate oversight. If it seems high for the thread size use reasonable standards such as above, and consider the application. For example, the thermostat housing/water outlet is not a structually loaded part, so you only need enough torque to compress the gasket and ensure a seal. In that case about 10 lb-ft should be more than sufficient.
DukeComment
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THX Mike *NM*
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10 ft lb no load
Duke
Excellent point on the 10 ftlb no load comment - that is what I will use with careful application of the sealant.Comment
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Re: 66 L72 Therm Housing Torque
Peter-----
The terms "water outlet" and "thermostat housing" are generally synonomous terms although they may generate some confusion as you've experienced.
For Heli-Coil installation I recommend that the inserts be installed with high strength, anaeobic thread locking compound like Permatex Red. You want these inserts to stay in place through, possibly, many future bolt removals. The Permatex Red will lock and seal the threads. Apply it sparingly since you don't want to use this for the bolt-to-insert interface. The Heli-Coil inserts will provide a much better thread than was present with the original threads tapped into the native aluminum material. For all practical purposes, they're forever.
As others have mentioned, the thermostat housing surface and the manifold surface have to be absolutely flat for a good seal. Also, they have to be absolutely free of remnants of previous gasket material. Some of the newer gaskets have a pre-installed silicone bead on the gasket. The GM #10105135 is such a gasket and it eliminates the need to use silicone sealer on the gasket which always gets "squeezed out" and requires later tedious t*******.
If you're really after positive sealing and your less concerned about originality, then use Fel-Pro gasket #2202. This is a plastic gasket with an o-ring insert. It's made of a blue-colored plastic and it's 1/8" thick, so it is "observable", but this gasket WILL END any thermostat housing sealing problems forever and it's reusuable.In Appreciation of John HinckleyComment
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Re: 10 ft lb no load
I've gotten into the habit of using silicone spray on gaskets - makes them easy to remove and often reusable. In the case of my Cosworth Vega that's a benefit as some gaskets are getting rare and expensive.
As I example, I glue the cam cover gasket to the cover and then liberally wipe down the bottom of the gasket and the cam carrier mating surface. I've been able to R&I the gasket up to about six times for lash checks before the gasket finally breaks and needs to be replaced. It's a conventional paper gasket - fairly thick.
DukeComment
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Joe Great Additional Info THX *NM*
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Re: 66 L72 Therm Housing Torque
I've used the molded Fel-Pro thermostat housing gasket on several other non-judged cars, and they are indeed leak-free and re-usable; great product.Comment
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