The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Terryb on 17.12. 2016 11:55

Title: Cylinder Head Bolt Torque Settings
Post by: Terryb on 17.12. 2016 11:55
Hi All,

Treating the Shooter to a Top End Refurb. Can any body recommend Torque Settings for tightening the Ali Head please? I've got the tightening sequence, but no torque figures. *conf*
Title: Re: Cylinder Head Bolt Torque Settings
Post by: terryg on 17.12. 2016 12:36
It may be less than you expect.  If I remember right it's around 27-32 lbf ft.  That's enough to tighten down a well annealed copper gasket - and that is the important bit.

Try the 'search' function.  I'm sure it's been raised a number of times in the past few years.

edit - the correct thick washers are also important, to spread the load effectively.

edit - searching on 'torque' and 'head' throws up one reply that says 32 lbf ft is already too much!

Now the experts can chime in!
Title: Re: Cylinder Head Bolt Torque Settings
Post by: Billybream on 17.12. 2016 14:46
Hi Terry
You will struggle to find official data, I used BSA A65 information and it quoted for 5/16" head bolt 25 ft lbs and for 3/8"  26 ft lbs.
Title: Re: Cylinder Head Bolt Torque Settings
Post by: muskrat on 17.12. 2016 20:38
G'day Terry.
I find 25 is enough for my low comp A7 (alloy head) but need 30 to seal up the 10.5:1 cafe.
As terryg said a well annealed copper gasket is a must.
Cheers
Title: Re: Cylinder Head Bolt Torque Settings
Post by: Rgs-Bill on 17.12. 2016 21:59
  BILL, here, I was setting my alloy head 62 RGS at 34 pounds as per my Haynes manual.  I am running 9 to 1, and an old timer told me Haynes sucks, alloy heads can distort at that much torque, and head gasket can leak, which is exactly what happened to me, until I started torqueing at 26 to 27 lbs, never had a problem since.  Also exercise your torque wrench if it sits for 2 to 5 years in between uses, like mine does, it gets the lubricants around inside to where they should be.  I do about  20 click stops on my Ford van lug nuts before torqueing down my cylinder head, so torque wrench is accurately operating.  Now I do not know about Iron heads, I am guessing you could use 34 pounds, they would not distort as easily.  What say you Musky, you raced these, can the Iron heads be torqued to 34 pounds without leakage ?  I do not know  if  you need to do this, he also said get the bike up to operating temperature, and shut it off, let sit over night, and re-torque head, I had 3 that were light on second torqueing.  Not sure the second torqueing is a must, but that is the way I did it 10 years ago, no problems since.
Title: Re: Cylinder Head Bolt Torque Settings
Post by: RichardL on 17.12. 2016 22:11
Retorquing is a pretty big commitment, since the rocker box must come off. I check compression right after assembly, then again after riding for some time. So far this has led to one box-off for retorquing at 32 ft-lb. Can't say for sure head is perfectly flat, but I'll check it next time it's off.

Richard L.
Title: Re: Cylinder Head Bolt Torque Settings
Post by: Terryb on 18.12. 2016 12:35
Hi Guy's,

Many thanks for the advice. You right about the Haynes Manual, I've found conflicting info on other bikes when looking. I new about the Annealing process being a must and I think I'll go for the 26-27 lbf ft for mine. Thanks Guy's

Terryb *smiley4*