Spitfire Water Pump rebuild/upgrade questions.

[triumphlux]

When I look at your radiator setup I see the alloy plates beside the electric fan which certainly reduce airflow throught the radiator.

And it seems that you don‘t have any guides (cardboardboard or alloy) in front of the radiator to guide the air trought the radiator.

I‘m sure that decent airflow throught the raditor is as important as all the other aspects dicussed about cooling.

Regards

JC

[PeteStupps]

On 4/3/2025 at 6:51 PM, aoie said:

@triumphlux makes a great point, the setup in this pic looks distinctly sub-optimal. You'll get practically no natural airflow through the rad, and the surface area available is constricted to the size of your fan. Have you ever had those shroud boards in front of the standard rad to funnel air through it? Might be worth trying that before flushing the block and getting the radiator re-cored

[aoie]

2 hours ago, PeteStupps said:

@triumphlux makes a great point, the setup in this pic looks distinctly sub-optimal. You'll get practically no natural airflow through the rad, and the surface area available is constricted to the size of your fan. Have you ever had those shroud boards in front of the standard rad to funnel air through it? Might be worth trying that before flushing the block and getting the radiator re-cored

Quote

 

Shroud boards deleted since switching to the GT6 radiator which is brand new, I did have them previously (no-help). 

Overheating has been a long standing problem, not as bad/critical as when I first started.

Good point on the fan mounts possibly restricting outer air flow! I could address that by rounding some of the upper and lower extra aluminum on the mounts, and drilling peg-board type pattern of holes for breathing.  I did not want electric fan mounted using those through the radiator-fins thingies.

Adding shrouding back is a future project to mount remote air cleaner/intake for plenum upgrade.

[Nick Jones]

On 4/5/2025 at 6:06 PM, triumphlux said:

When I look at your radiator setup I see the alloy plates beside the electric fan which certainly reduce airflow throught the radiator.

And it seems that you don‘t have any guides (cardboardboard or alloy) in front of the radiator to guide the air trought the radiator.

I‘m sure that decent airflow throught the raditor is as important as all the other aspects dicussed about cooling.

Regards

JC

JC is alive  

Long time, no hear! Hope all is good in your world?

Returning to the original problem; many changes have been made without much impact.

Suggests the underlying issue has not been touched yet - so flow obstruction within the block/ head themselves seem like a possibility.

I’m still not clear whether this is “runs scary hot while creeping in traffic” and cools down on the open road, or whether it heats up when going at speed or whether it just runs hot all the time?  Please clarify!

As regards pump speed, these pumps can only be described as crude, with very basic impeller design. This means their efficient speed range might not be all that wide. However, so long as it runs fast enough at idle to give adequate flow (see overheats when creeping in traffic), realistically you are probably not going to be over speeding it enough to cause cavitation and flow-loss in normal road use, not for long enough periods to matter anyway.  This can certainly be an issue on the race track where high rpms and loads are maintained and some racers do run larger pump pulleys to help this.  
 

ISTR a discussion on this years ago started by @GT6Steve, one of the rpm kings,  which also explored the possibility of using a more sophisticated (looking) impeller from a tractor in the quest to improve usable rev range. Not sure that went anywhere in the end.

Edit:

Found it. Some pics missing 

Possibly not entirely relevant but a great read anyway!

[triumphlux]

Thanks Nick, I'm still alive and doing well 😎

And I still have all my Triumph cars 😀  hope to pull at least one out of hibernation later in the year ...

Back to original thread :

The original GT6 radiator cowl exists in cardboard (£ 45) and as an alloy reproduction.

[flatter4]

+1 for using shrouds and cowling.

When driving: the forced air flow will take the path of least resistance = around the radiator core, not through it

When stationary: the fan will do the work and the air will recirculate.  Hot air off the back of the rad will be pulled round the sides and back to the front of the radiator to go round again and get even hotter 

 

Both easily validated with a couple of thermocouples positioned on radiator core

 

[aoie]

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On 4/6/2025 at 2:07 PM, Nick Jones said:

I’m still not clear whether this is “runs scary hot while creeping in traffic” and cools down on the open road, or whether it heats up when going at speed or whether it just runs hot all the time?  Please clarify!

 

Nick

When the outside temperature is above 80 Fahrenheit the temperature creeps up to the  200-210 range while driving for extended times slow (or fast). This is after upgrading to the 3-row GT6 radiator and additional oil cooler, was much worse before.

Unfortunately fellow Spitfire owners in my local car club have all moved on, so I no-longer have anyone to compare with on long planned drives with the club. 

In the states we have a water pump re-build Guru called the Flying Dutchman that is still active, he can rebuild the pump and upgrade my impeller to a 5-blade version if I want to pay the price. I just recently watched a Jay leno's Garage you-tube post on his own personal 57 Cadillac were he gave the Flying Dutchman a shout out for the good work he did on that cars water pump.

I just revisited my existing water pump installed before the GT6 radiator upgrade and found that it's impeller is smaller than the original pump I still have on the shelf. I don't recall if anything was wrong with the original pump, I believe I just swapped it out as another attempt at the resolving the problem.  So looks like I will be re-installing the original to see what happens.

I also see a couple more responses to my problem on adding back the radiator shrouds! I do plan to do that in the future but still ruling that out as not the root problem since I did have them originally before upgrading radiators.  I did some googling to find images of folks that have added custom shrouds on a GT6, and found a post for a TR6 that closely matches what I would like to-do. Small world appears he is a member of Sideways, so would like to give him a shoutout on all the documentation he did on the build.

https://bullfire.net/TR6/TR6-87/TR6-87.html

[Gt64fun]

The TRs are probably easier to shroud effectively than the GT6 due to the shape of the bonnet and the way it closes. I have built an aluminium version of the original cardboard radiator shroud and also extended the side cheeks to the limit that the bonnet allows. Used in conjunction with a 12'' Spal fan at fan switch in the top of the rad and a manual override, cooling is pretty much ok in normal UK conditions. Ian

[aoie]

Quote

On 4/2/2025 at 6:01 AM, JumpingFrog said:

A random thought, I've read about but not exactly sure how much of a difference it would make. Have you fitted a replacement heater pipe (under the manifold)? There is some talk of these being remanufactured without a restrictor in the bypass connector (from the T on the inlet manifold), this allows coolant to short circuit the radiator as it feeds back into the water pump.
 

First of several member suggested improvements!

Added a 5/32" restriction hole on the manifold coolant/heater bypass pipe connector (SEE PICTURE). The aftermarket stainless heater pipe return to the water pump was unrestricted, so I added a 5/32 restriction hole on my DIY copper heater pipe under the manifold at the bypass T on the manifold side. 

 

[Nick Jones]

Son’s Spitfire uses a Golf (Rabbit) mk 2 radiator, fan and shroud with his own fabricated ductwork in front of the rad.  I know it’s got a wacky engine fitted in these pics but it had exactly the same rad arrangement in original 1300 Triumph form.

Very similar arrangement in my GT6 except I made the fan shroud as the VW arrangement is too big to fit with the 6 cyl.

[Escadrille Ecosse]

On 4/2/2025 at 12:01 PM, JumpingFrog said:

A random thought, I've read about but not exactly sure how much of a difference it would make. Have you fitted a replacement heater pipe (under the manifold)? There is some talk of these being remanufactured without a restrictor in the bypass connector (from the T on the inlet manifold), this allows coolant to short circuit the radiator as it feeds back into the water pump.

The bypass/restrictor is only there to provide a minimum flow for the heated manifold when the heater is off. Introduced on the Mk2 Spitfire which got the heated manifold and the additional pipe from the thermostat housing.  Mk1s didn't have the heated manifold or the bypass.

If you are running Webers or injection without a heated manifold then the bypass is superfluous and simply complicates the plumbing. Just fit the heater pipe for the Mk1 Spit and block off the extra connection from the thermostat housing (or fit an additional ECU temp sensor) instead. Neat and simple.

Edited April 14 by Escadrille Ecosse