[Fot] Collective wisdom

[yellow04 at tr4racer.com]

This is what has always worked for me. Plug the bypass ports on the 
water pump and thermostat housing. Install a plug in the back of the 
water pump housing for the pipe that fed the heater. The only hose off 
the water pump goes to the bottom of the radiator. Plug the head where 
the fitting goes for the heater, as shown in your picture.

On the TR2-4 engine, it is critical to block a few the coolant passages 
at the front of the head, and restrict the rest. Think tiny freeze 
plugs. Otherwise, the coolant barely circulates around the back of the 
engine, #4 will run significantly hotter than 1 - 3, so hot that 
localized steam bubbles will form. There was a thread on this here many 
years ago.

I used an oversized Griffin aluminum radiator in the 'gone but not 
forgotten' TR4 and the TR250. Runs so cool I have put a 185 degree 
thermostat in the car. The TR3 uses a stock sized Wizard aluminum 
radiator, I run a 165 degree thermostat in that one.

That's it. No header tank, no attempting to get flow out the back of the 
head from the heater port. I do use the petcock on the top of the 
thermostat housing trick to help bleed the system, that proved to be a 
nice addition to effectively fill the system with no drama.

Henry Frye
2026 KCup chair - Return to Mosport

On 2026-01-20 15:26, Chuck Gee via Fot wrote:
> Hello all,
> 
> In an effort to constantly improve the car, I’ve been looking at the
> cooling system on my TR4.  It currently has a header tank mounted to
> the firewall that functions as the high spot in the system.  This tank
> feeds the top of the radiator but doesn’t really circulate during
> operation.  I’ve been thinking of plumbing the feed off of the back of
> the head into the top of the tank so that it circulates.
> 
> Normally this rear head feed is plumbed to the back of the water pump.
>  In an exercise of overthinking, I’m not sure if there will be
> sufficient circulation since the tank is plumbed to the radiator.
> Does it matter?  What is the collective wisdom?
> 
> Here are some pictures to help illustrate.
> 
> Thanks,
> 
> Chuck
> 
> 
> 
> 
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