>From my experience with TR & Morgan cooling systems, the 4# caps are
appropriate for use with the radiator construction of the time and with the
original "bellows" thermostats. I still have a stock of those thermostats
and I prefer them to the more modern "waxstat" type because they incorporate
the by-pass closing sleeve that is not present on any of the "waxstat" type
thermostats. The bellows thermostats will not tolerate more than 4# pressure
in the system for very long without rupturing. At least when they fail, they
always fail in the open position. The more modern type normally fail in the
closed position. The water pump seal also has a pressure threshold at which
it will begin to leak. I do not know what that is.
With a modern aluminum radiator and a disc or broken thermostat to
increase block pressure, I do not believe that there is any reason to use
less than a 12 or 14 # cap. For racing with a restrictor and a standard
copper/soldered radiator, I have been using a 7 # cap set up to be a coolant
recovery cap.
Over the last 15 years we have encountered at least 6 or 7 English and a
couple of American made radiators which were perfectly clean and in visually
perfect condition, but which would not cool the cars that they were in.
Measuring the temperature drop through the radiator at 65 mph, with a fully
open thermostat at an engine temperature of over 180 deg. F and on a day
with an air temp around 70 degrees, we found the "bad " radiators would only
drop the temperature about 3 degrees F, while a "good" rad would drop the
temp a minimum of 10 deg. F. Your typical Japanese car drops the temp 20
deg. F. We have even found some brand new fresh recores that would not drop
the temp more than 3 deg. So if everything else is in order, replacing the
radiator may be what is called for.
Regards,
Greg Solow
From: "elliottd" <elliottd@look.ca>
To: <BillDentin@aol.com>; <cartravel@pobox.com>
Cc: <fot@autox.team.net>
Sent: Wednesday, March 05, 2003 3:28 PM
Subject: Re: Head Cooling Problems
> All the sidescreen TR's left the factory with 4 psi radiator caps. I am
on
> my second or third one since 1958. The story is that at 4 psi, you won't
> (or can't) separate the tubes from the fins in a radiator, over the normal
> life of a rad that was made in the 1950's. But if you blow a head gasket
> between the combustion chamber and the water jacket, you can get very
high
> pressures in the rad. Sur the cap will blow at 4 psi (or 15 psi), but
there
> will be some damage to the tubes in the rad. I don't care to say how high
> but maybe a lot more than 4 psi or 15 psi. This will bulge the tubes in
the
> rad and the tubes which are normally kind of a flat oval will tend to want
> to become round. If they do, the cooling fins are no longer in full
intimate
> contact with the flat (now a round) tube and the heat can't be transferred
> from the tube to the fins, so the fins stay cool with the air rushing
> between them and the water in the tubes stay hot and keeps getting hotter
> and hotter.
>
> Don+ Elliott, 1958 TR3A, Montreal, Canada
>
>
>
>
> ----- Original Message -----
> From: <BillDentin@aol.com>
> To: <cartravel@pobox.com>
> Cc: <fot@autox.team.net>
> Sent: Wednesday, March 05, 2003 4:12 PM
> Subject: Re: Head Cooling Problems
>
>
> > In a message dated 03/05/2003 2:14:08 PM Central Standard Time,
> > cartravel@pobox.com writes:
> >
> >
> > > However, it seems to
> > > me you'd
> > > be better off using a higher pressure cap.
> > >
> >
> > My mechanic Kevin and I argue about this. Mike Belfer always wanted to
> use a
> > 7# radiator cap. None larger! Kevin (old big block chevy guy) wants to
> use
> > 25#. I think we've been running 15#.
> >
> > Thoughts?
> >
> > Bill Dentinger
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