A friendly argument is unfolding around the plumbing on my 261. A close friend has "loaned me" a bypass thermostat housing. It is currently plumbed as you see in the photo - top of housing to one of the outlets in the dual-outlet water pump. A guy who claims to "know his way around engines" suggests that the hose should go to the plugged opening "A" instead of the top outlet. from the water pump. There may be merit to his argument - by doing so I will be getting water through the 848 head instead of back to the radiator until the thermostat opens. I know there is lively conversation surrounding these housings and the fact that you cant buy a thermostat for these.
Second photo shows housing, bottom casting, before powder coating. Thermostat seats in this casting and top casting has a large outlet to the radiator, and a small outlet assumed to go to the heater.
I just want to start with proper connections.
Thanks for your comments, and Sweet - its not leaking......yet.
From what I can see, and maybe I am looking at it wrong, That is the same type of lower housing that is used on the car 55-58 235s, probably the 59 -63 motors, very likely others. That upper hose outlet is not a rare part or anything but part of the heating system for some vehicles with 235s. For example, on a 57 car, the Hose goes from the thermostat housing to the heater control valve, when the valve is opened, water flows through the heater core and then exits, and goes to the water pump. On passenger car pumps for that year there is only one boss. But the two hole pumps were sold to be used in that application and applications that did not have an outlet on the therm housing. The pump on my 261 has two holes, heater return hose is plumbed into upper hole. Thermostats are the same as other gm products. I can probably get you the stant, tuff stuff or other part numbers.
Taking another look at the photo, is the boss for the hose in the upper or lower part of the housing? If it’s in the upper, disregard the above, lol. I don’t think I have ever seen an upper housing with a outlet boss in it!
Just asking here, but why are you bypassing or trying to run without the thermostat?
It's a bypass type housing. There is an outlet in both the top and bottom castings. i am just trying to make sure I get water through the head until the thermostat opens. I hear they can crack without it. I also hear it's witchcraft and you would do just fine without the bypass. I figure I got ti - I'll use it. Just want to use it right.
Drill a 1/8" hole in the thermostat and you will get a little coolant flow to/through the head until the thermostat opens.
I have been doing this a 1960 261 for 47 years, and with a 1959 261 thermostat for 20 years.
I cannot see your 261 "bypass" housing, but I doubt it is the same as any housing used on any 235. I'll see if I can post some photos that were posted here when Deve was drawing/reaching some interesting conclusions regarding the later 281s' by-pass thermostat and housing.
The thermostat designed for use with that housing is obsolete and no longer in production. Simply using the housing without the correct thermostat creates a constant leak of hot coolant back to the water pump inlet, possibly compromising cooling when the engine needs it most- - - -heavy load operation at full throttle. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Thanks for explanation amtrakjoe. It never ceases to amaze me how year after year, through out the year, I learn something new! All the years playing with these motors, I have never seen an upper thermostat with a threaded boss. I will have to go on the prowl to find one to add to my collection of parts, lol.
