[Fot] Head Studs

[Kenneth Knight]

The lengths and positions for the head studs on the TR-3/4 motors is in the
manual.  

 

By this time ALL original head studs, rod bolts, main cap bolts and assorted
nuts/washers are scrap metal only for a race motor.  Main cap bolts should
be thrown away and replaced by ARP studs.

 

If you use the ARP head stud kit (Moss carries it) refer to the tech section
in the ARP manual on these fasteners as it is very interesting.  The ARP
manual is on-line.  In general I do the following;

 

1.       I mark the bottom of all head studs with a # using an electric
scribe.  I lightly sand flat. 

2.       Using a 12" caliper I measure and record the length of all of the
studs on my build sheet, 1 through 10.  Try to do this at about 70 degrees
F.

3.       When rebuilding the motor I recheck the lengths of each stud and
when it has stretched .001 beyond new I replace it as it is in failure.
This will happen after several rebuilds, possible 5 or 6.  The ARP spec is
to replace after .0005, I just looked it up, but that is damn hard to
measure with a caliper and I do not have a 12" micrometer.  This is not F1
where they just get replaced after one race.

4.       When installing I always use ARP lube and a good torque wrench.
Quality fasteners are like a springs, they need to be stretched to work
properly but there is a limit as to how many times this will happen with the
fastener going back to it's original length.  They will not hold proper
toque when they start to fail.  On a lightly stressed street motor this may
not be so important, on a race motor the bang can cost thousands.

 

All of the fasteners in an engine (the critical ones like head studs, rod
bolts, main studs) are consumable items in a race motor.  I also only
install rod bolts with a stretch gauge.  I find that the torque to proper
stretch, say .005, will vary as much as 5 pounds per bolt.   Each brand of
rod bolt has a stretch spec for that specific bolt.  

 

That's my 2 cents on the subject.

 

Good Racing All, Ken

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