TR2 overheating

[Fred Winterburn]

Hello Rod, I have a TR3 engined car that is bone stock and also suffers from overheating after a brisk run or at stoplights. I believe that the problem with these engines is twofold but can be traced to the same cause. Poor flow distribution as the poor flow from the pump 'wafts' through the hole in the block effectively cooling only #1,2 cylinders to the thermostat setting as the flow bypasses most of #3 and #4 cylinders. That and the fact that I discovered this last week by experiment, that the standard pump with 85 thousands of an inch end clearance does not pump at all at 500 RPM pump shaft speed. In fact, just to get it pumping takes 900 RPM pump shaft speed and then if the speed is slowly reduced to 600RPM, the flow stops completely. I made a washer 77 thousands of an inch and used JB weld and 3 rivets countersunk, to affix it to the base of the water pump housing. This makes clearance on my pump about 8 thousands of an inch. I performed the test again, and flow starts at 500 RPM and is at least 4 times the flow it had just above 600RPM before the modification, and at least double the flow at 900RPM shaft speed. It is now works like a pump should, and this was done with the standard 4 vane impeller. With extra pressure and flow, the back of the engine should see more coolant and have fewer hot spots and boiling. Boiling produces vapour, and just like air, this robs 'pressure energy' from the system which reduces flow even further. I'm going one step further, and have made a backing plate for the pump housing that contains a nozzle and some smaller holes. It's function is to provide some back pressure to force coolant through a penetration (1/4 inch pipe thread elbow, and a hose barb) I've made in the discharge side of the housing to distribute some flow to the rear petcock hole. I have diverted by this method, about 1/6 the flow to the rear of the engine without reducing overall flow by much at all. With the pump clearances corrected, it will still have at least double the flow it had before anyway. The nozzle should force more flow by #1,2 liners and still have adequate flow to the front of #3 liner. The small holes drilled in the 1/8 aluminium backing plate were used to fine tune the flow ratio, and ensure that the front of #1 cylinder gets adequate cooling too. I'll be installing this next spring and testing its effectiveness at that time. Hope this information helps, Fred Winterburn (owner of TR3 powered Morgan, serial #3504) Ripley, Ontario Canada

 

Just an added note. I will be replacing the original water pump with the aluminium gold anodised impeller (it was the kind with a roll pin rather than a woodruff key) with a County brand pump with a cast iron impeller. The County brand pump has the same end clearance as the original, but is 50 thousands of an inch larger diameter, so it should be slightly better than the original, or at least no worse. Fred

[Mychael]

No issues at all for me using a 7p.s.i cap , being doing it for yrs, admittedly with a reco'd radiator core. Next time I have the water pump off I'll check those tolerances. We made a 'better' pump from an original one but all the work centered around shafts, seals and bearings, used an original impeller.

No overheating issues sitting at lights but I also have an electric fan. I have had the engine get hot after extended high speed driving but as soon as I dropped back to legal speeds the temp would stabilise again.

 

Mychael