Author Topic: A10 alloy head torque settngs  (Read 1654 times)

Offline sprint

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A10 alloy head torque settngs
« on: 04.05. 2014 13:32 »
What is the recommended torque settings for the alloy A10 head bolts?

SRM spec them at 32ft/lb ( which seems way over the top for an alloy head as Triumph only recommend 18ft/lb for the 3/8" bolts and 15ft/lb for the 5/16" bolt?

Online RichardL

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Re: A10 alloy head torque settngs
« Reply #1 on: 04.05. 2014 19:43 »
I assume you have waisted head bolts, as are standard.  It seems that A65's did not use waisted bolts and called for 25 ft-lb.  According to standard torque charts, a 3/8"-16 SAE Grade 5 bolt (which, I think, we easily meet) would be torqued at 31 ft-lb. To stay a bit on the careful side, mine are currently torqued at 30 ft.-lb. with no bolt caps popping off and going through the roof. As I understand it, the waisting allows the bolt to stretch better under torque, since it's bolt stretch that does the holding

Apologies if I'm stating the obvious or well-known, but it is important that you use thick washers under the bolt caps, being sure these are the right diameter to fit the counterbores around the holes. I double-up on Grade 5 (or better) from the local hardware store because 1/8"-thick are not available. Finally (on the maybe-obvious front), if the head gasket is solid copper it needs to be well annealed.

Circling back in logic, a bit, perhaps the low torque values stated for Triumph are for use with a composite head gasket, which would not require as much pressure to seat as a solid gasket.  What I know of Triumphs is: "starts with a "T".

All this said, it would be good to have some more opinions.

Richard L.
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Online Billybream

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Re: A10 alloy head torque settngs
« Reply #2 on: 04.05. 2014 20:05 »
I use 27 foot pounds, and check and check again when run for a few miles. Its important to follow the pattern from the centre bolt and work out diagonally.
Tighten each bolt alittle at a time.
1960 Super Rocket, owned since 1966, back on the road 2012 after being laid up for 29yrs.

Offline Rgs-Bill

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Re: A10 alloy head torque settngs
« Reply #3 on: 04.05. 2014 23:13 »
Hi, Billybream has the right Idea, alloy heads distort at Haynes Book and SRM's suggested torque of 32 foot pounds. Start at 20,22,24,27, and then let sit a couple hours while you do something else, and check again.  Then with the rocker box put back on, run motor to normal operating temp, with a large box fan blowing across fins and exhaust pipes.  Now shut it of and LET IT SIT OVERNIGHT , then re-torque to 27, guaranteed 1 or 2 or even 3 will take more. And by the way you fellas that have a torque wrench sitting around unused most of the year, put a socket on there and make sure and do 10 or 20 click stops on some other bolt to get the lubes in the head working properly, so as to get accurate stops on your clicks.   Chase the threads in the block with a tap, and clean the bolt threads with wire brush, light machine oil on threads optional.  I did mine that way 9 years ago and have had no trouble since. Used to have to re-do every season at 32 pounds torque, it distorts the alloy and you get, (although small)  compression leaks, mine quit altogether one year. Careful and thorough annealing is very Important, done wrong and you will do this every year, whether you want to or not.

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1962 RGS
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