Hey Folks!

Simple question. Why is the head bolt torque sequence different when using Cometic gaskets compared to what's called out in the Service Manual?

-Dave

 

Because their gaskets are designed and made different from the OEM and the R&D department decided (probably from trial and error) that it is the best procedure and torque value for insuring a proper tension and seal?

 

I use a combination of the HD factory and Cometic torque procedure for Cometic MLS gaskets, the first step for Cometic is 14 ftlbs, torque to 14 and mark the head bolts, continue the Cometic steps, the marks will end up a few degrees past 90 degrees, what this does is give you a visual that the bolts all torqued down correctly, of coarse all the marks should end up very close to the same.

Harley’s torque and turn 90 degrees takes the friction of threads and bolt head contact out of the equation, but Cometic!s procedure draws the head down more evenly, so marking the head bolts does both.

Cometics metal gaskets wouldn’t do well if you nailed down one corner at at time.

 

I use the torque sequence from the book but do a 4 step torque procedure. 14 ft lbs, 22 ft lbs, 32 ft lbs and final 42 ft lbs.. Never had an issue. With this method I've been able to re-use head gaskets with copper coat... Again no issues...

 

last set I bought was copper, had heard of rising copper. I think they call it annealing, heat the gasket really hot and let it cool slowly. But I will do more research if I have to cross that bridge

 

Great discussion. I do believe it's the combination of gasket design, and torque wrench margin of errors that drives each method/sequence. Cometic and James (which have the same sequence) and the Service Factory Manual methods arrive at a 42 ft lbs ending. Since most of us aren't using Harley's gasket, I would use the gasket manufacturer's sequence. I do lubricate the head bolts each time before tightening to get the correct torque.

Now, do you guys re-use your head bolts or get new ones?

 

I always use oil on the studs and on the face of the head bolt where it contacts the cylinder head too get the proper torque. I don't believe one can get it as accurate without using it (oil that it's).. I reuse head bolts and studs. Unless there's an issue that's obvious..

 

All I'm saying is mark the bolts at the 14lb step, if they all don't end up with the same rotation, somethings wrong

 

I've always reused head bolts on Evo and Twin cam, unless they where obviously something wrong or rusted, then the M8 cam along and started breaking head bolts with reuse, they're now included in the M8 stage kits.

 

,,,and if I use the Harley torque, mark, then plus 90 degrees, I still set the torque wrench to 40, double checks everything