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.>
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