Jim,
I struggled with an overheating issue for quite a long time. The
radiator was my first stop, I had it flushed out and the rad shop said
they got some slop out of it and that it should be fine. The car still
overheated, so I went through every other possible cause (new water
pump, electric fan, timing chain, even pulled the head) and still the
car overheated. I eventually went back to the rad shop, at which time
they informed me that even when they flush out a rad, there's still a
chance of blockage. Great, thanks for telling me that when I first
brought the rad to you. A new rad fixed everything. So don't assume
that your rad is fine just because the previous owner had something
done to it.
That said, if your car is only overheating at idle but is fine when
cruising, then your rad is probably fine. A faster turning water pump
is not necessary, and can actually be worse (the water might move
through the rad too fast, and wouldn't be able to shed its heat, plus
it can cause cavitation). The first thing I would check is to make
sure your electric fan is turning the right way, and is sucking air
from the front of the car through the rad into the engine bay, not
blowing air from the engine bay through the rad into the grill. It
sounds stupid, but I've seen it before, and it's a pretty easy mistake
to make. Also make sure your fan belt is nice and tight, and make sure
your idle speed is around 800-900rpm, if its too low the water pump may
be turning too slowly. Also check your timing to make sure it's not
too retarded. You can do this with a timing light to check the dynamic
timing, or simply by checking the static timing (a lot cheaper if you
don't have a timing gun) since dynamic is pretty much equal to static
at idle. In both cases, you won't need to mess with the timing
settings at all, unless you find that it is set wrong. I have my car
set at 10BTDC static, but my car is warmed up quite a bit. I forget
what the stock setting is, perhaps 12 or 14 BTDC?
Static timing check is quite simple - just turn the engine to around
20BTDC (make sure you are on compression stroke, not exhaust), pull #1
plug wire and tape it down near a good ground, then continue to slowly
(by hand) turn the crank until you hear/see the #1 plug wire fire.
Note the timing mark on the crank damper, and this is your current
static timing setting. If it's off spec, then get the crank to the
spec setting, and then loosen the distributor and turn it slowly until
#1 plug fires, then tighten the distributor and check the static timing
again per the original procedure.
Tim Holbrook
1971 TR6
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