TR2/3/3A Rad Caps?

[karls59tr]

It seems I've been running my TR3 with a 7lb rad cap instead of a 4lb. They are both 1" type.(4A is 3/4") I believe the motors are the same. Is there an issue with running the 7lb cap?

 

[Gerald_Gordon]

My 1961 TR4 with a recored radiator and no TR3-style filler neck (but with an overflow bottle) now uses a 7 P.S.I. cap, which raises the boiling temperature of the coolant and, thus, https://www.tuneruniversity.com/blo...at-advantage-of-a-high-pressure-radiator-cap/ its ability to transfer heat out of the engine.

 

[groupdeville]

7-LB should be fine, as long as your engine and hoses are in good shape. It's a small increase over the stock value, and will just give you a few extra degrees of cooling-system margin against overheating. I've intentionally run my '58 3A with a 7-LB cap (also 1") for the past three or four decades and many thousands of miles with no ill effects.

Pressure-wise, the only thing that I watch for is the thermostat housing casting where the bypass hose attaches. On some castings, I've seen the nipple for the bypass hose to have a bit of a taper to it, which makes it easier for the bypass hose to come off, especially if RTV is used to seal the hose. Found that out the hard way back during the Carter years.

The remedy for this is to file a shallow circular groove in the bypass hose nipple, so that the rubber hose material, when the clamp is tightened, can squish down into the shallow groove and lock the hose in place. Never had the problem at the other end of the hose - probably due to the roughness of the iron water pump housing casting.

 

[karls59tr]

My 1961 TR4 with a recored radiator and no TR3-style filler neck (but with an overflow bottle) now uses a 7 P.S.I. cap, which raises the boiling temperature of the coolant and, thus, https://www.tuneruniversity.com/blo...at-advantage-of-a-high-pressure-radiator-cap/ its ability to transfer heat out of the engine.

Great article.

 

[karls59tr]

7-LB should be fine, as long as your engine and hoses are in good shape. It's a small increase over the stock value, and will just give you a few extra degrees of cooling-system margin against overheating. I've intentionally run my '58 3A with a 7-LB cap (also 1") for the past three or four decades and many thousands of miles with no ill effects.

Pressure-wise, the only thing that I watch for is the thermostat housing casting where the bypass hose attaches. On some castings, I've seen the nipple for the bypass hose to have a bit of a taper to it, which makes it easier for the bypass hose to come off, especially if RTV is used to seal the hose. Found that out the hard way back during the Carter years.

The remedy for this is to file a shallow circular groove in the bypass hose nipple, so that the rubber hose material, when the clamp is tightened, can squish down into the shallow groove and lock the hose in place. Never had the problem at the other end of the hose - probably due to the roughness of the iron water pump housing casting.

Did you block the Bypass hose or are you running the "skirt type thermostat? ...also what thermostat are you running and what fan setup do you have...electric??

 

[CJD]

I've worked on enough heater cores that I personally wouldn't put higher pressure in the heater core than the stock 4psi. The core is the limiting factor for system pressure. They tend to blow out like an accordion.

If you delete the heater...then no problem raising the pressure

 

[karls59tr]

I've worked on enough heater cores that I personally wouldn't put higher pressure in the heater core than the stock 4psi. The core is the limiting factor for system pressure. They tend to blow out like an accordion.

If you delete the heater...then no problem raising the pressure

Well I'm OK on the heater issue as the problematic and expensive stock heater has been swapped out for a Spitfire unit. That fits under the dash braces and throws great heat.