The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: tilly on 05.01. 2019 09:21

Title: Do I need to retension head studs?
Post by: tilly on 05.01. 2019 09:21
I after some advice on the need to retension the head studs on my A10 following a rebuild. I’ve fitted a copper head gasket and used copper head gasket spray.  I was told to get the engine up to temperature and then to retension it once it has cooled down. Is this necessary?  It is a pain in the proverbial to remove the rocker box again, and don’t want to do so if I don’t need to.
While I’m asking questions, is the rockerbox meant to be so difficult to fit?  Mine is a very hard interference fit with the top of the valves when trying to lower it on. What’s the trick for fitting? It seems that I have to clear the exhaust valves first, but the use of studs rather than bolts to retain the rockerbox makes this difficult.
Any and all advice gratefully received!
Title: Re: Do I need to retension head studs?
Post by: Swarfcut on 05.01. 2019 09:42
G'Day Tilly

        Far easier to remove the rear rocker box studs, lower the box on from the inlet side, down past the springs and push it forward to clear the exhaust springs. If it still fouls  the front studs may have to come out. Fit the pushrods, settle the box and then use your gynaecologist skills to re-insert the studs. Some ruffians use Whitworth hex head cap bolts, or even cut a screwdriver  slot in the stud.  I have seen boxes with indents cut to clear the springs, but this narrows the  seal area for the rocker cover gasket.

    I would be inclined to leave the head alone, get some miles in, see if it leaks.  If you gave it a good bit of tighten, sleep easy.

  Well done for getting it back together.

  Swarfy.



 
Title: Re: Do I need to retension head studs?
Post by: muskrat on 05.01. 2019 10:18
G'day tilly.
If the copper gasket was annealed (read sot enough to mark with your thumb nail) and the copper spray it should be good to go. I only re-tension if the rockerbox leaks  *whistle*.
The alloy head rockerbox's are even harder but I've never had to take the studs out bar the top rear tappet cover stud. It has flats on it to help removal. Sometimes it takes 15 minutes, sometimes hours!
Cheers
Title: Re: Do I need to retension head studs?
Post by: Duncan R on 05.01. 2019 15:23
I have removed the head 3 times during ownership - never bothered re torqueing and have had no leaks. Never done it on my other bikes either. Maybe if the rocker box wasn't such a pain I would.


Good luck
Title: Re: Do I need to retension head studs?
Post by: Greybeard on 07.01. 2019 09:51
For me; annealed copper gasket. 20ft/lbs first then back off and retorque to 35ft/lbs. I've never gone back in to retighten.
Title: Re: Do I need to retension head studs?
Post by: cyclobutch on 07.01. 2019 16:08
Well I learnt something there. I thought re-tightening after a few heat  cycles was a given.
Title: Re: Do I need to retension head studs?
Post by: Greybeard on 07.01. 2019 17:18
The reliability of a once-only tightened head gasket probably has an inverse relationship to how hard the engine is worked. Mind you, if Musky doesn't retighten, that theory goes out of the window!
Title: Re: Do I need to retension head studs?
Post by: A10 JWO on 07.01. 2019 17:52
I don't re tighten, if it was a two stroke I would cause it's easy.
Title: Re: Do I need to retension head studs?
Post by: JulianS on 07.01. 2019 18:04
I always retighten after about 250 miles from replacing the head. Read it in the instruction book many many years ago and it has always worked for me. Usually find one or two bolts need just a little more torque.
Title: Re: Do I need to retension head studs?
Post by: KiwiGF on 07.01. 2019 19:22
A compromise approach is to check the head bolts you can get at after a heat/cool cycles, if any of those have loosened off significantly *problem* take the rocker box off and check the rest.....I DID’NT have to the rocker box off mine  *beer* and it’s been fine.

Title: Re: Do I need to retension head studs?
Post by: cyclobutch on 08.01. 2019 13:27
I think ... When Roger did mine for me he used a heat gun to cycle it a couple of times and then re-tightened as required before putting the rocker box on at all.
Title: Re: Do I need to retension head studs?
Post by: mugwump on 08.01. 2019 14:36
I believe a common place for these ( and Ariel ) heads to blow is btn cylinders and  down the p/rod tunnel, is probably caused by only the outer head bolts being re-tightened. I know its a pain having to remove the rocker box but worth it for peace of mind. 
Title: Re: Do I need to retension head studs?
Post by: Klaus on 08.01. 2019 15:32
The reliability of a once-only tightened head gasket probably has an inverse relationship to how hard the engine is worked. Mind you, if Musky doesn't retighten, that theory goes out of the window!

I make my own coppergaskets, special for every barrel from 0,8mm copperplate.
A light grease with HTL Silicone, and I never retight any bolts over 4 yaers hard work with a racebike.

cheers Klaus
Title: Re: Do I need to retension head studs?
Post by: Rgs-Bill on 08.01. 2019 22:27
For me; annealed copper gasket. 20ft/lbs first then back off and retorque to 35ft/lbs. I've never gone back in to retighten.

    Graybeard says to torque to 35 ft lbs, as does Haynes manual.  On alloy heads only torque to 26 max of 27 ft. lbs. so as not to distort the head, and cause leaks.  My 62 RGS I torque to 10-then 20-then 25-then 26-27 for final.  One heat cycle, with 2 foot box fan blowing across fins, then let it sit overnight, then remove R. Box  and you will find at least 2 that are too low in torque.  Usually in the middle where the push rods go down to the followers
    Could someone explain here how a heat gun could qualify as a heat  motor running heat cycle, do not see how it could heat evenly enough at same time, over the whole motor.
   When I was torqueing my alloy head to 35 ft. lbs. as per Haynes manual I kept getting leaks between cylinders, and push rod tube, since using 26 ft. lbs. have never had a problem, and the last time I  did it was 11 years ago.
Title: Re: Do I need to retension head studs?
Post by: scotty on 08.01. 2019 22:52
Very interesting

I have to replace my A10 head gasket when I return from little Norway (still on board Norwegian ship)

What is and how do you do a heat cycle ?.....

Enquiring minds and all

S
Title: Re: Do I need to retension head studs?
Post by: hdawson on 09.01. 2019 07:12
After my rebuild last year and half a dozen short rides I blew my head gasket.
Lucky that I had a spare on hand so I would be more cautious in the future.
Rocker box fitting is an art that improves with repetition (like with most tasks) and after making every mistake I now find it a satisfying challenge.
Cheers,
Hadrian.
Title: Re: Do I need to retension head studs?
Post by: muskrat on 09.01. 2019 08:32
G'day Scotty.
A heat cycle is getting it up to operating temp and letting it cool. 15-20 minute ride would do. Idling isn't good for the rings and bore.
Cheers
Title: Re: Do I need to retension head studs?
Post by: KiwiGF on 09.01. 2019 09:33
I reckon This is one of those topics that is unlikely to result in a clear consensus  *dunno*

The first time I built my “basket” engine it blew a head gasket when it done more than 500 miles, and over 10 rides. I fixed it (using the same solid gasket, re annealed) and worked out that the root cause was that my (nearly new) torque wrench was not accurate. It was over reading by over 40% so the bolts were WAY under tightened, but interestingly it held together for quite a while, and probably only blew because being the bolts loosened off even further, I guess because they were so loose to start with, with some ending up little more than finger tight, so I guess In my experience the applied torque is not super critical, provided they stay done up!

After fixing that and a few more miles it dawned on me that I’d used the same wrench on the big ends  *problem* *problem* *problem* *problem* *help* *pull hair out* so (after a trip to the pub) I stripped the engine to re torque those.

Anyway, the point is that people’s experiences will differ depending on the accuracy of torque wrenches, flatness of surfaces, type of gasket, how many heat cycles or miles before being re torqued, oiled or non oiled bolts, whether the head is iron or ally, washer hardness, etc etc

Regardless of that, like prior posts I agree the “gold standard” would be to re-torque (with calibrated wrench) all the head bolts after (insert your own number, maybe 10?) heat cycles or (insert your number, maybe 500?) miles which ever comes first. Unless I experience an unexpected blown gasket I’ll not be doing it though!


Title: Re: Do I need to retension head studs?
Post by: cyclobutch on 09.01. 2019 13:03
I always retorq on Guzzis, but then despite having to remove the rocker assembly you don't get all of the rocker box foolishness.

Talking of which, the replacement for my lost comb has turned up so all being well I'll be popping the (very) top to fix an oil leak some time over this coming weekend.
Title: Re: Do I need to retension head studs?
Post by: scotty on 09.01. 2019 17:30
Ahhh I see

Thanks Musky

S
Title: Re: Do I need to retension head studs?
Post by: Rex on 09.01. 2019 17:42
This is a standard procedure on Triumphs, but sensibly you can get to all the bolts without a major strip-down.
I'm worried now, but I think I'll wait until the Spring and see how it goes on the A7, which has a Drags composite gasket installed. I'll fit a solid copper item next time though.