John,
I posted a similar throw out bearing question a while ago. Comments for the
Gunst were universally positive so thats what I went with along with a Sachs
clutch. They haven't been installed yet since everything is still in pieces so
it is a little premature for me to comment on how they work. As far as the
flywheel is concerned, since you're into it to that level, it wouldn't hurt to
have it resurfaced IMHO. Check the orientation of the ring gear as well since
some TR6s had them installed with the bevel towards the back of the car. This
was the case with mine and I had the shop doing the grinding flip the gear to
the correct orientation.
On the topic of the connectors used in these LBCs, this is subject near and
dear to my heart since I've spent the past 20 years developing connectors. I'll
try to give a quick Connector 101 here without getting too deep into the gory
details.
It is OK to solder the pin side of the connectors but NEVER solder the
receptacle side. These are typically made of a tempered cartridge brass and
putting any heat to them will anneal them so they no longer exert the correct
amount of normal force on the pin. You can carefully squeeze them together to
get a bit of additional normal force but they'll never be the same afterwards.
You're better off buying the appropriate crimp tool to terminate these things.
When properly terminated, the crimp is a gas-tight, permanent termination that
out-performs solder terminations.
The second item worth mentioning on these connectors is the fact that these are
plated with tin. Tin poses some problems since tin is subject to fretting
corrosion. In a nutshell, fretting corrosion occurs during thermal cycles
(current on - current off) that causes the connector to thermally grow ever so
slightly. When this happens, a thin film of oxide (resistive) immediately
builds up on the exposed tin. As the current is removed and the contact cools,
the contact interaface moves back on top of this oxide increasing the interface
resistance. As this cycle continues over years, interface resistance gradually
increases thereby increasing the internal heat generated by current flowing
through the contact. As the heat increases, the contact eventually begins to
self-anneal which drops the normal force at the interface thereby increasing
the resistance further. The heating of the contact continues to accelerate and
the annealing rate increases and so the cycle continues until the
Prince Of Darkness arrives and ends the whole cycle in a melted puddle of
brass and insulation.
You may ask what can be done to minimize this? Ideally, if all the contacts
were silver plated and lubricated, the Prince of Darkness would be out of
business. Unfortunately, this is not practical or cost effective. We're left
with a couple of items to keep him at bay. #1 is don't solder the receptacles.
#2 is use a contact lubricant to prevent the fretting corrosion. Your local
electronic shop (not Radio Shack but a "real" one) probably carries such a
product or a search on the internet will come up with companies that offer
products for this purpose.
Sorry for the long dissertation but I hope this helps.
Ron Weber
'71 TR6 (still in tiny pieces but getting closer)
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