I asked the list on Wednesday about TR6 main bearing cap bolts.
As I understand it you can get new main bearing cap bolts from TRF and Moss.
However these appear to be simply grade 8 bolts****. I did receive some
valued opinions that the Grade 8 bolts would work both from the list and
from the guys at BPNW. However, there was a mention of a grade 8 bolt used
on a bearing cap breaking and taking a crank with it. Since this is an area
of the car that I would rather not have to worry about I looked for
something a little stronger.
I called APT (www.aptfast.com) and they had just built a TR6 motor and used
a set of ARP studs for this. I ordered a set and they arrived today while I
was at work.
The studs I received are for a 1500 spitfire motor. Since the Spit has 3
main bearings and the TR6 has 4 they break up the sets there at APT and sell
them as a set for the TR6. You get 8 studs, 8 hardened flat washers and 8 12
point nuts. The suggested torque is 90 pounds, a lot more than the stock
bolts. I assume that it is necessary to torque them to 90 pounds in order to
get the correct clamping force on the bearing caps.
There are two things that I see as possible problems with using these, but I
am far from an expert.
1. The threaded portion of the stud that fits into the block is about .25"
shorter on the stud then on the TR6 main bearing cap bolts. It appears that
these studs are cut down at ARP from longer versions. If the studs are
chopped down from longer ones ARP might be able to provide studs with a
longer threaded length on the half of the stud that engages the block.
2. The other problem will be at the front of the block where the aluminum
sealing piece is. The studs appear to be a little long and it might be
necessary to cut them down and fit the cap without the flat washer. If ARP
is cutting down the studs then it might be possible that they could make a
set special for the front main bearing.
Thanks again everyone. It's a great feeling to drive the TR, and I can't
wait to do it again really soon.
Don Clark
Seattle, WA
72 TR6
****DISCLAIMER**** It may or may not be the case at this time that grade 8
bolts are sold by Moss and TRF. I didn't call to try to confirm this with
either TRF or Moss. However given that the bolts list for something less
than $2.00 each I find it impossible to believe that they were purpose
built.
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