Ever done this? Yeah I'm a REAL genius. (NOT)

[akghound]

Yup, been there done that. I didn't have your luck. Both of the heads cracked when the cold water hit them. Mine is a 20/2, anybody have heads they would sell after the first of the year?

[dieselgman]

We stock all the parts and pieces in Kansas.

dieselgman

[mauicole]

I don't have a thermostat or a valve but use an adjustable thermostatic switch like this one:

http://www.summitracing.com/parts/hda-3653

I noticed the return hose (from the radiator) feels significantly cooler than the top hose.
Isn't the difference between the two supposed to be fairly close? Like 10 degrees? Originally
I had the sensor right below the intake of the radiator. Then I moved it about 1/4 way down.
It seemed to make a difference, but not enough. Has anyone with one of these adjustable
switches found a sweet spot on the radiator? I am going to continue lowering the sensor in
the hopes of getting a higher temperature in the return hose. If that doesn't work, I am leaning
towards installing a valve on the return hose instead of a thermostat.

[BruceM]

There are Murphy brand sensors and actuators (rack closer), plus controllers for doing auto shutdowns.

My system is all homebrew and ebay bargain (vibration sensing switch).  I have air, and needed remote start, so use homebrew pneumatic actuators for rack closing and decompression, they are always applied together, as the original Lister Startomatic did.

Plenty of guys here have very fancy monitor/shutdown systems.

The simplest thing I tried that worked well for emergency shutoff was a brass wire on a terminal strip to hold the end of the governor spring.  With 12V applied, the brass wire goes poof, the spring is released, and the rack is closed by the governor forces.  This would not stop the engine in case of some governor failures or IP jam, but would be fine for other failures.  The Murphy fuel shutoff has been reported to work, the one I tried did not; the IP was able to create so much suction that it leaked.

For over temperature switch, I used an adjustable snap disk type thermostat weld bonded to the cylinder head.
For oil level, I use a sight tube with magnet in a plastic float, and reed switches to sense high and low oil.  RPM is sensed by a gear tooth sensor next to the flywheel spokes and my homebrew PICaxe controller. 

[selmawp]

I would like to recommend to retorq the head bolts and check the valve clearens, any time a engine runs hotter than normal these specs will change and 10 minutes of work could save a blown head gaskit about a week from NOW Just my 2 cents worth.

[ronmar]

I don't have a thermostat or a valve but use an adjustable thermostatic switch like this one:

http://www.summitracing.com/parts/hda-3653

I noticed the return hose (from the radiator) feels significantly cooler than the top hose.
Isn't the difference between the two supposed to be fairly close? Like 10 degrees? Originally
I had the sensor right below the intake of the radiator. Then I moved it about 1/4 way down.
It seemed to make a difference, but not enough. Has anyone with one of these adjustable
switches found a sweet spot on the radiator? I am going to continue lowering the sensor in
the hopes of getting a higher temperature in the return hose. If that doesn't work, I am leaning
towards installing a valve on the return hose instead of a thermostat.

If you are thermosiphon, there should be a significant temp difference between upper and lower radiator hose, like 195 on the upper and 90 or so on the lower.  If you have a higher volume pumped system, then you will have less difference.  Low volume high temp difference or high volume low temp difference = same BTU transfer..  With the temp range on that switch, I would bond it to the top tank of the rad near the upper rad hose with some heat sync compound in there to insure good transfer to the sensor.  Then I would set it's turn on point to near the desired operating temp.  The temp you maintain at the head will depend on the flow and the hysteresis of the switch, so you may have to tweek it a bit to get the desired head temp...

[mike90045]

Just a side question, I'm about to pull the head, and replace gaskets.  When pulling the lower coolant fitting off, does that drain the entire head, or is there water retained, ready to slosh down into the crankcase ?

[BruceM]

There will be some  coolant left in the the head, but you shouldn't have an oil contamination problem.

[overbore]

Shouldn't the thermostat bypass hole be 3/32" in diameter?

overbore

[ronmar]

Shouldn't the thermostat bypass hole be 3/32" in diameter?

overbore

WIth a very large volume cooling system and good thermosiphon flow, IMO, yes, the bypass hole/holes should be larger than the traditional air bleed hole that sometimes has a cotter pin in it to keep it from getting clogged with debris.  You either need to limit the peak flow thru the system, which a valve does.  Or you need to slow down the rate of change in temperature(which the bypass holes do) to match the reaction speed of the thermostat.  Or you need to taylor the heat dissipation capacity of your cooling system to match the heat output of your engine, which is basically what a valve in the system does.  Ever see a big rig in the wintertime?  Tooling down the highway in 30F air provides a cooling capacity far greater than the engine outputs.  SO the drivers taylor the cooling system to the engine by adding a zip/snap up cover that limits the airflow thru the radiator.  Both this and the valve however can limit the maximum cooling capacity.

If you have a radiator sized to match the engine, the bypass hole isn't as important, particulary if you have an automated fan or use convection.  The radiator is low mass and can have lower thermosiphon flow which better matches the thermostat cycle times...

[fabricator]

Why would you shut a valve in the cooling the thermosiphon cooling system?