Spridget cooling system question??

[Curtis]

Dear Spridget Gurus,

I am, but should I be running the little tiny hose from water pump to head at front of a 1275 engine?? Doesn't seem likely, but is it possible that I get enough bypass flow under light loads to cool the engine with closed thermostat?? Something else I should look for??

Thanks in advance for any assistance.

Background....pretty stout 1275 in an old Turner street car. Went way overboard on the cooling system with VW alloy radiator and monster oil cooler. System bleeds fine, and engine heats up when parked, or when driven hard on a hot track day can get to 160-180. However for easy street use in mild weather the temp quickly decreases to 130-140 or so degrees once in motion.

 

[Gary Wittman]

I block it off on my 1098. It came that way when I bought the car so I have always left it that way. Other than just another thing to break, I have no other reason to not use it. I do drill a couple 1/4" holes in my thermostat to get some flow just in case it sticks closed.

 

[Curtis]

Thanks Gary. That helps knowing the head doesn't count on that flow.

 

[fprod64]

From the characteristics that you describe, I say that you are running a thermostat that opens at 160 degrees and maintains a maximum 180 degrees under medium to high speed driving. The other condition of low temperature from idle to low speed driving answers your second question. The bypass between head and water pump is too large so that the engine never reaches a "normal" operating temperature with the oversize cooling system. I personally run a 180-190 thermostat with the bypass blocked and never had an over heating problem with the same radiator and oil cooler you have. Most, if not all, spridget racers block that bypass but do not run a thermostat. They put a restriction plate in place of the thermostat with a hole of about i/2 inch diameter to allow circulation. They control the temperature by blocking air flow through the radiator to maintain a temperature between 180-200 degrees under race conditions.

If you want some theory behind that system, send me an email to fprod64 at yahoo dot com

 

[Curtis]

Thanks to all including the individual providing similarly helpful advice via pm. Will confirm this fixes it Sat morning.

 

[Joel McGinley]

I think you've got it but just to make sure: That troublesome little hose just lets some coolant circulate through the block/head when the thermostat is closed (cold). On every street and race Sprite 948 I have seen in 30 years, it was blocked off- probably too much trouble to install, especialy with milled-down blocks and heads for racing compression. I always drill about two 1/8 inch holes in the surrounding disc of a thermostat so that there is some flow during warmup. This took the place of the little hose to allow some flow during warmup. If your car is not getting warm enough, you could try a higher thermostat or just block off some airflow and consider yourself a lucky guy to have this problem!