The Stovebolt Site Forums The Shop Area Engine Shop 261 Question ??

** Just installed adapter plate and a 53 water pump on newly O/H 261 {to center the fan to the radiator} The 261 engine still has the bypass thermostat housing installed with the two hose fittings, the 53 water pump only has one hose fitting. My question is how should the hose's be routed or will I need to use a 53 thermostat housing??

I would use a 235 housing. Thermostats are easier to get and it will work fine.

What year is the 261? Just for info (you may already know this...) but the early 261's don't need the adapter plate and all the peripherals (water pump, thermostat housing, etc) switch over from the 216 without any mods needed.

Just sayin 'cause I just put a '54 261 in my truck ('49) and didn't need to do any mods to it at all. The water pump and the thermo housing from the 216 fit perfectly and in the lower position.

Regards,
John

John is describing 1954 and 1955st-series USA 261 engines/blocks.

Also, I have used a 1960 261 water pump with the by-pass ports on the pump & head-outlet plugged.

** My 261 is a 1962 with orig. head. ** I'm not sure if a 235 thermostat will work as the 261 thermostat housing measures 2&7/16" I don't think a 235 thermostat is that large??? I gather I will not be able to use the 261 bypass thermostat with a 53 water pump. Am I correct?

What is the brand and model number for the thermostat you are using?

I simply used the 261 thermostat that was being used in the 2-ton 1960 truck (school bus).

** Do not have a thermostat at all right now am trying to determine if I can use a 261 bypass thermostat with the 1953 water pump that only has one hose fitting nipple. It is my understanding that a 261 water pump would have two hose fittings on the t/stat housing and two on the water pump. Just trying to find out if I will be able to use a 261 bypass stat with the 53 pump and if so how would the hose's be connected as there are only three hose fittings not four as orig. 261 would have had.

I'm not sure if this would work, but I don't see why not. Put a tee in the water pump opening for the heater hose and run the bypass hose from the thermostat housing to the tee and from the other open end of the tee continue on to the heater core.

Maybe someone else can tell us if this would work or not.

** That is kind of what I was thinking but did not want to try it before hearing from the experts. Any comments from others greatly appreciated. **

Put a plug in the bypass port in the thermostat housing.

Use whatever thermostat fits in your housing.

I'd make sure there is an approximately 1/8" hole in the thermostat to allow a little flow (of air/coolant) at all temperatures.

I eventually did what John suggested - used a 235's thermostat housing and 235 thermostat. This avoids mismatched radiator hose ends between the small truck radiator hose end and the big truck thermostat housing's radiator hose end.

I have a bypass thermostat on my 235 and have it installed as Roy suggests above with a tee in the heater return line. Works fine.

Both of the hose fittings on a dual fitting water pump share a single chamber inside the pump just like a single fitting pump.

Your heater return line is probably 5/8" heater hose. 3/4" brass PEX fittings available at any Home Depot or Lowes fit that size heater hose perfectly to make the tee.

Matt