Geo Hahn wrote:
> CFisher@borgwarner.com wrote:
>
>> Since I've had wrong torque figures in Haynes manuals before
>> (resulting in a
>> sump bolt broke off in an A-series motor)can someone confirm a
>> cylinder head
>> torque of 100 to 105 ft/# for a TR3a head? That's a lot higher than my
>> bugeye head, though the studs are a lot beefier.
>
>
> On page 48 of my Haynes manual (step 59.7) it says to torque the head
> nuts to 45 lbs. Elsewhere it gives the correct higher number but
> because of that paragraph I torqued my head to 45# and drove it w/o a
> problem for 20+ years. Not recommending it, just noting the Haynes
> error and my results.
>
> Geo Hahn
>
>
>
Actually, the correct way to torque the head on the Triumph 4-bangers is
to run them all up to 45-50 ft-lb, then, following the prescribed torque
sequence, you go up in increments of 10 ft-lb, until about 85-90ft-lb,
then 5 ft-lb to the 100-105 range. It is a good idea after each
torqueing step to hold a piece of oak against the top of the head at
various points and give it a whack with a hammer. This helps to relieve
the stresses in the head and the seating of the head gasket, as well as
the stud-nut combo. Head gasket sealing is not much of a problem IF you
use an original copper-asbestos sandwich type of gasket. I don't know
how available these are these days.
I have never experienced a streched stud with a Triumph (these are
pretty heavy dooty studs), but you must be sure that the stud is fully
seated in the block! Make sure that when you dissassembled the
engine/removed the head, that you did not back out a stud a bit. Use a
stud puller to make sure they are properly seated, not the double-nut
technique.
I know that you can actually pull a stud out of the block if you do not
have sufficient thread. Also, if a head has been removed a number of
times, the threading where the nut fits can be deformed. It is well
described in engineering manuals as to the number of times that a
bolt/stud can be toruqued, based on material and dimensions. I have had
the threading in a head stud nut give way on the torqueing process.
Sounded like a shotgun going off!
Cheers.
|