What is usually ingnored by many is that the two front and the two rear
head nuts/bolts should be torqued down slightly less than the rest.
These four bolts have less surface to press down so the downforce should
be less as well. This is especially important for alloy heads, but it is
sound enginering practice for cast iron or steel heads as well. Go for
about 10% less torque.
Kees Oudesluijs
Alan Seigrist schreef:
> Russ, et. al.,
>
> There has been some confusion on this list (and with myself) on what is the
> correct torque setting for head nuts for the 100. This confusion is not
> helped by the fact that neither the factory workshop manual for the 100 nor
> the A90 specifies this.
>
> That being said, I have two other publications, and they both clearly state
> that this head should be torqued to 65 ft-lbs. I have been told to torque
> to 75 ft - lbs by several people as this is what is used on the 6-cylinder
> motor, but for the 100 motor it is only 65 ft. lbs. These are the two
> publications I am talking about, which I have found VERY useful over the
> years:
>
> 1) Glenn's Austin and Austin Healey. It's this book that details many of
> the detailed dizzy, carb and engine settings & equipment for the Healey 100
> & 6 cyl, as well as Austins with A-series motors. Very useful if you can
> get an old used one
> 2) Austin cars by TBD Service - This book covers all post war Austins
> (except AH's) and has a wealth of info for any A90 owner. Great thing is
> this book is very small and can be put in the glove box for easy reference.
>
> 75 ft-lbs should be perfectly fine, but the only downside of over torquing
> on the 100 motor is over time the metal around the studs will start pulling
> up. This can usually be fixed by drilling little bevels in the stud holes
> on the block but if it can be avoided with proper torquing, all the better.
>
> One thing to note - compression on the A90 is 6.9:1 and for a stock BN1/BN2
> compression is 7.5:1 - both very low. Compression for an M spec 100,
> however, is 8.1:1 and some racing stuff you can get out there will put it as
> high as 9.5:1. If running with higher compression, torquing to 75 ft-lbs is
> probably more correct. Using a solid steel or copper head gasket is smart
> too in this case.
>
> Regards,
>
> Alan
>
> '52 A90
> '53 BN1
> '64 BJ8
>
>
> <Turns out the head was inadvertently torqued incorrectly (only 55 ft lbs),
> when it should have been 70 to 75 ft lbs. The workshop manual I had
> inherited from a previous owner had a handwritten note indicating the 55
> ft. lbs. for the head nuts, and the mechanic working on the car did as it
> said.>
> _______________________________________________
> Support Team.Net http://www.team.net/donate.html
>
> Healeys@autox.team.net
> http://autox.team.net/mailman/listinfo/healeys
>
> You are subscribed as coudesluijs@chello.nl
>
> http://www.team.net/archive
_______________________________________________
Support Team.Net http://www.team.net/donate.html
Healeys@autox.team.net
http://autox.team.net/mailman/listinfo/healeys
http://www.team.net/archive
|