Bits and Pieces

Tests on Water Pump Impellers

James Neel kindly sent me the following which was written by Geoffrey M Baker, Arizona, USA following some flow tests he did on three different types of water pump impeller.

“Here finally are the results of the flow tests I did on the 3 impellers, the standard 4 vane impeller that came with all TDs and TFs, the 6 vane impeller currently being used by most rebuild services when they offer an upgrade, and the newly designed 6 vane impeller that I had 3D printed on, using a design with a narrower rake and a curved blade.

I built a testbed on an outside table, using my drill press motor and a jig which held the water pump. I mounted a 100 gallon stock tank on the table and filled it. The reason for this was to avoid any vagaries of water pressure that might occur if I simply connected a water hose to the pump.

Tucson water pressure varies from about 30psi to 80 psi. With 100 gallons in the stock tank, I had a reasonable “head” of pressure that would not vary significantly over the course of the test (as we will only be removing 7 gallons from the tank each time). Before each test I added water to bring it back up to the same level in the big tank.
I then took a small galvanized tub and using a gallon bottle, measured how many gallons it took to fill to a known point on the tub. It took exactly seven gallons to bring the water up to the top of the first “lip” of the tub. Hence this is now a 7 gallon test…

I connected up the pump and the tank, opened the tank, and held the output hose from the water pump out and down, until water began flowing without the pump running (water can move easily around the impeller and out). I then raised the output hose until the water stopped flowing by gravity, then held it at that point for the rest of the test.

Then I started the pump and the timer simultaneously, and waited until the pump had filled the lower galvanized tub to the 7 gallon level. I stopped the timer and turned off the pump.

Here are the times it took for each impeller to transfer 7 gallons of water:

Original 4 vane water pump: 8 minutes, 16.21 seconds.

Standard 6 vane water pump: 5 minutes, 48.81 seconds (nearly a 1/3 improvement, not surprising with 6 versus 4 vanes this seems pretty appropriate!)

Modern 6 vane impeller pump: 5 minutes 18.7 seconds.

The curved modern impeller with a narrower section definitely moves more water, approximately ten percent more.

Beyond this, I make no claims for the impeller, and clearly a standard six vane, if you can buy it, is a good bang for the buck. But the modern impeller offers a 40 percent improvement over the traditional 4 vane, vs about 30% for the standard 6 vane currently on the market.

For pictures and links, look for the original threads on the improved 6 vane impeller. 

Here is the shapeways link:
I hope this data proves useful to people when they are looking at working on their cooling systems.”

Repair of Clocks in TDs and TFs

Further to Russell Dade’s endorsement of David Ward’s service the following has been received from Pete Dyke:

“Just wanted to comment on David’s excellent service.

Sent him an email asking if he could look at the clock on my TD, which has not worked since I have had the car (and probably long before that!) He responded very promptly indicating he would look at it, but could not guarantee success, as he has very few spares.

Sent the clock to him via ‘before 1pm’ registered post and even by the next day, he emailed indicating that the clock had a damaged component and was not sure of success, but he would try.

After a couple more days, an email indicated that he had indeed met with success!

Clock returned, fitted back into the car and working, all within just over a week and at a cost of just £20 from David, including special delivery!

Brilliant service and communication – can’t recommend high enough.”

Ed’s note: David Ward’s e-mail address is warddavidc(at) Please substitute @ for (at).

Colour matching (Paint) (from Nick Fitzhugh)

“It is my belief that no two red coloured MGs are the same shade of red. TC4222 is red and was in need of a little attention to the edges of the wings. Obviously none of the standard reds matched and you suggested Brighton Autopaints who do custom colour matching.

My problem was to find a sample to send them for matching. None of the painted parts of the TC fit into a small envelope! It has taken over a year of searching to find an object that matched the car – there are so many red objects around any house and garden from supermarket carrier bags to mouse mats, but none were suitable. Eventually I found the perfect match – the red plastic sides of my Swiss army knife. I sent this off to Brighton and I am pleased to report that they sent back aerosols and a tin which were an exact match to both the knife and car. The car is now touched up and the join is invisible.

Brighton provided a prompt service and the result was excellent (they do cellulose paint).

Clearly the shade of Swiss army knife red which matched my MG would not match any other red MG on the planet!

Thanks for the suggestion.”