An engine break-in question

Re-torque can be done as soon as after the first fully warmed up run, just make sure you get it nice and "hot".

J.

head retorquing is a remnant of the use of compressable head gaskets. If you have those (you do not), then it's not a bad idea. But without gaskets it's simply a waste of time IMO.

Even the compressable gaskets do not sag like they used to, making this procedure mostly obsolete on modern engines.

John Aircooled.Net Inc.

On this we simply have to agree to disagree, even without gaskets the hardware used(fasteners) will settle in their threaded stays. Might be overkill, but sure would make him sleep better at night, even if marginal, I personally would not go without.

J.

you are right, we disagree. Once the fastener is torqued, it's torqued, since the metal stretched like a rubber band. the only way it can loosen is if the fastener physically moves (loosens up), or the gaskets compress. There are no gaskets to compress on our engines, so re-torquing doesn't help. it doesn't hurt either, but it's a complete waste of time IMO.

John Aircooled.Net Inc.

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Which may be read as saying that re-torquing IS a valid procedure for engines designed in the 1930's... such as the VW.

Other factors include the fact all 'modern' engines are water cooled and never see the temperatures normally found in an air cooled engine. The only air cooled examples we can point to are aircraft engines and none of them use head stays. The heads are a threaded, heat-shrunk fit to the cylinder barrels and the barrels are designed with a thick bolting flange at their base, secured by eight or more studs, presenting an entirely different situation with regard the thermal expansion.

-Bob Hoover

I will add that I do not simply torque the bolts and walk away. When I assemble, I torque the pattern (all 16 ), then loosen up again, and do this one more time, before I'm done. It only takes a few extra minutes to do, and I move up in increments of 5lb/ft approaching the final value.

John Aircooled.Net Inc.

I approach the final value in 3-4 steps. Always using the proper sequence. No loctite. Very light coat of oil on the stud threads, after I wire brush them clean. I overtorque the nuts just slightly. No more than using up the "margin of error". Not saying it's good practise, but that's what I do. I haven't had any problems.

Jan

John C> I will add that I do not simply torque the bolts and walk away. When I

That's the whole idea of using the 8mm OEM studs. Torque them once and forget about it. Never had a leaking head or found evidence of the 8mm studs loosening up. Can't speak for 10mm

RT