So, If I read this thread correctly I should have no problems switching to a
7lb or even 10lb cap in my 1958 TR3 or the 1962 TR engined Morgan that I
maintain for a friend? Neither of us has heaters out here in West Texas.
That would sure ease up a bit on all the spewing from the overflow under
fairly normal conditions.
Thx,
Bill
-----Original Message-----
From: triumphs-bounces at autox.team.net
[mailto:triumphs-bounces at autox.team.net] On Behalf Of Keith Stewart
Sent: Friday, March 16, 2012 7:59 PM
To: Randall
Cc: triumphs at autox.team.net
Subject: Re: [TR] Radiator Caps
On 2012-03-16, at 8:35 PM, Randall wrote:
>> The TR2 through
>> TR3A engines use a 4lb cap and the TR4 through TR4A engines use a 7
>> lb cap.
>
>> What is the deciding factor that makes the difference?
>
> Personally, I suspect there was no real reason except they originally
> thought 4 psi was enough, and later decided that 7 psi was better.
>
> But others think it was due to the change in heater design. The
> TR2-3B
used
> a circular heater element that internally had wide, flat tubes that
> weren't very strong. With only a little bit of internal corrosion,
> they can fail from too much pressure and dump scalding coolant onto
> the occupants. The
> TR4 & 4A had a more modern, round tube heater core.
>
> AFAIK, early TR4s used the same radiator and thermostat as later TR3s.
They
> did eventually switch to a pellet type thermostat, but I think that
> wasn't until later, maybe 1965.
>
> Certainly there is nothing in the engine itself, as the original
> engine in TS13571L is running quite happily with a 10 psi cap (and no
heater).
And so, if the heater in a TR3 (57) was exchanged for that from a Spitfire -
I think Bob Schaller did it to this car when he worked on it in Arizona -
because supposedly that was an upgrade, would that mean a 7 lb cap would be
more appropriate than the 4 lb cap?
Keith R. Stewart
London, Ontario
E-Mail: keithstewartATexeculinkDOTcom
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