Rajo OHV question

[Fisher400]

For the guys running a Rajo ohv… or any OHV, do you need to run a water pump? I know in original articles in model t in speed and sport it was a common addition, but it seems the consensus now is a water pump is not needed if the rad is in good working order.

I have a 26 with a bb, hot cam, model a crank and had to remove the water pump and exhaust to remove my starter for repair. The pump is in ok condition and would benefit from a clean up. It did get me wondering if I even need the thing at all. If it was a stock engine, I probably would try removing it, however does the thermo siphon work well enough on ohv and modified T engines?

My rad was cleaned professionally last year and it ran fine/cool with the pump on but without a thermostat.

I know this topic can get us going, not looking for that just haven’t read if ohvs need a pump or if stock siphon is sufficient. Thanks!

[Susanne]

If you have a stock T motor, then no way, the original thermo-syphon system is fine. Once you start adding heat to the top end (eg an OHV system) you MAY need more water flow... you won't know until you bui;d your mot r and atart taking temp readings... mzybe even a larger radiator.

My biggest thing was taking a 2 tube radiator (which Ford's engineers would be just fine, even tho in less than 2 years they said no way) and expanding it to match your motors thermal outut. They did this in the 1970's.... no reason they couldn't have done this in 1920 except to make HF mad... which NO ONE wanted to do.

You always match the thermal out put of your motor to your cooling system; it seems diffcult until you do it for an autoshop class, then it's a piece of cake.

[Jerry VanOoteghem]

Your period aftermarket radiator appears to be the style that does not necessarily flow well. Especially with age. Their indirect flow pattern makes them easy to clog and hard to flush. You may need the pump for that reason alone. As Susanne states, you won't really know till you try it.

[KMcoldcars]

I ran my Model Ts with overheads and no waterpump with no problems.

[RajoRacer]

I'm running a nearly identical OHV set-up - my radiator started life as a Whippet but I had a new top tank made with Model T inlet & outlets - it cools O.K. but I'm also running a 5/8" shaft water circulator - been on several 200+ mile NWVSC events and have never boiled over.

[Kevin Pharis]

The cooling system on a T is sized appropriately for a stock T engine with thermo syphon. There are many overheads out there running without pumps, but I suspect they are producing little more than stock performance. With the addition of a pump the cooling system is capable of handling a much higher heat load.

If you have built up a “hot” motor (say 40+ hp) I would plan on keeping the pump. There are too many pumps for T’s to count, and not all have equal performance. Most pumps are circulators, and few are actually pumps. You could always build up a test rig to measure the pump output. With a 5 gallon bucket, pistol drill, stop watch, and a lot of duct tape, you can see what yours will do. This one was on the dyno supporting 55 hp with no issues

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[DaveBarker]

For what it’s worth, I have a Rajo Model 30 head with a Stromberg RF. Have never had a water pump (or circulator) and have never overheated or boiled over. That said, I just replaced a 100 year old worn out honeycomb radiator core with a new V-cell core. But even with the old core, it never overheated.

[Fisher400]

Thank you everyone for your insight. I really appreciate it. It ran happy with the pump so based off the suggestions, I will clean up the pump and put it back on.

[Fisher400]

For what it’s worth, I have a Rajo Model 30 head with a Stromberg RF. Have never had a water pump (or circulator) and have never overheated or boiled over. That said, I just replaced a 100 year old worn out honeycomb radiator core with a new V-cell core. But even with the old core, it never overheated.

Thanks! I really like your T btw, dual ignition? What type?

[DaveBarker]

Thanks for the compliment! No, it’s a basic Texas T dizzy, standard four plugs.

[Rich Eagle]

My Roof 8-valve runs incredibly HOT! I have not resolved where the problem is and am thinking about adding a pump. I haven't heard much of problems with the other heads.

[walber]

No pump, circulator or thermostat - Modern core in a high radiator keeps my Fronty cool. Mine isn't the hottest Fronty out there but the T head, A crank, domed pistons, Stipe cam and Weber carb provide all the performance I want or need. If it makes you feel good run the pump.

[Kevin Pharis]

My dad ran a T model Fronty for years in his speedster. Great runner, no pump. That motor is basically unchanged and is now in his brass touring car… with a pump. Smaller radiator, more weight, and no hood louvers may have had something to do with needing the pump…?

[YellowTRacer]

For what it's worth I've run both ways in old number 4 and saw very little difference on the Motometer. Not even close to overheating. To clarify, the head is a Rajo B. Engine, stock crank and cam. water pump is the Stockton, in the neck between the head and the radiator (a water pump that's a little better than nothing, in my opinion, but with a cross drive magneto drive it's the only easy option). And I'm running an early, pre 17 style, aftermarket honeycomb radiator. several years ago I was having a problem with the water pump and while it was being fixed, ran the car for a year or so without it and saw very little difference in the water temp (according to the Motometer). Then while preparing for one of our trips which included a drive across
the state of Nevada in July and I thought, "Hot Hot Hot, I better get the water pump back on". So bottom line, I couldn't tell much difference.

Ed aka #4

[Fisher400]

Thanks for the insight Ed! How well does your heat tubing work keeping your intake warm? It’s a neat look. Whole engine bay is very nicely done. Feel free to post more pics of your T/engine if you like!

[baltrusch]

I have never needed a water pump on any T and always remove them. However, my brass speedster with an early RAJO head would heat and boil until I put one on. It seemed like the rear of the head was not getting water and it certainly could be the radiator but the pump immediately cured the issue. Go figger!

[YellowTRacer]

The wrap on the intake took care of the carb and manifold icing up (on a 104 degree day!) long story that I won't go into here but 20 or so years ago that happened. I installed the wrap and it hasn't happened since. As for the other side of the engine, I don't have a picture of it but no great loss, not much to see just the exhaust header and Bosch magneto. But here's a picture of the pad on top of the rockers. My morning lube routine on long trips is to lift the pad and a shot of oil directly on the assy. then a "streak" of oil on top of the pad. You can see the "streaks" in the picture taken as I was in the process of oiling. First on the front half of the pad working my way back to the rear. Good for the day's drive.

Ed aka #4