Coolant restrictor freeze plug

[Bill White]

    A couple of years ago, we had the radiator recored and the water pump rebuilt. Both were leaking. While we had it apart, we thought we would put the freeze plug with the 5/16” hole in the passage of the cylinder head water jacket. Before we drilled the hole, the freeze plug would barely fit into the hole. After we drilled the hole it would fit in very loosely. My first question is, how do you keep it in place, or did I have the wrong size plug?  Another question, do you just remove the valve, or do you have to cut the part out that holds the spring valve in place?  
    I found an old post dated 7/15/19, by Rodneybeaucha mp from Australia, who said he just put a brass tube over the center brass rod which would prevent the valve from closing. He stated that it worked fine for him. We are planning to drive it to Cleveland which is over 700 miles and are taking precautions. Sometimes in traffic the temp gauge starts to creep up. Any thoughts and answers to my questions are appreciated. Thanks, Bill. Forgot to say our car is a 1940 Buick Special mod. 46 with original 248 engine. 

Edited May 2 by Bill White
Year and make of car (see edit history)

[Ben Bruce aka First Born]

Bill, I WOULD REMOVE THE FREEZE PLUG!!    It does not belong there.   Install a proper thermostat.

 As to "creep" up!   From what temp to what temp? I run a 195 degree thermostat in mine.   

 

  Ben

[EmTee]

I think this is referring to locking the bypass valve in the thermostat housing.  I installed a piece of copper tubing inside the spring that holds the disk to lock it in the closed position (minimum bypass).  Even when 'closed' the space around the circumference allows some coolant to bypass the radiator by design.  My '38 shop manual says the space is equivalent to a 1/2" diameter hole.

[Bill White]

I was referring to the bypass valve in the thermostat housing. I just didn’t do a very good job of explaining myself.  I do have a thermostat installed, but for the life of me, I can’t remember what temperature one I installed. I was thinking of replacing the spring-loaded valve with the freeze plug with the 5/16 hole in it, or the brass tube over the shaft of the spring-loaded valve stem as an added level of insurance from over heating. I don’t remember how hot the motor got last summer, but it certainly didn’t peg the gauge while idling in traffic. Since the BCA National meet in Cleveland this year is in mid July, the thought of over heating is in the back of my mind.  I’m adding pics this time, two from Rodneybeaucha, and the other also from this forum. Hope they don’t mind my reposting their pics. I’m guessing we will have some 90 degree temps in June, so we will be driving it to see how well the cooling system is working. 

Edited May 2 by Bill White (see edit history)

[EmTee]

I locked the bypass valve closed on my '38 Century as described above.  I'm running a 160° thermostat with a re-cored original radiator (high efficiency copper).  My car runs right at 180° according to the gauge.  It will, however, creep up to ~195ish when stopped idling in traffic on a hot (>80° F) day.  The temperature drops quickly once moving again, which tells me that the original fan isn't very efficient by itself.  I will say the blade pitch looks pretty 'flat' and there's no shroud.  Coolant is a 50/50 mix of distilled water and Zerex G-05 antifreeze.

 

 

Edited May 3 by EmTee (see edit history)

[Bill White]

I found my receipt for my thermostat, and it also is a 160 degree.  We had our original radiator recored as well. Our gauge points straight down, 180 degrees too, and creeps up when stopped in traffic on hot days. We also are using a 50/50 coolant mix. Sounds like our cars are behaving about the same when it comes to cooling. I’m glad you mentioned the fan. I think I read somewhere that I could get a five bladed fan at Rock Auto possibly. We try to keep the car as original as possible, but we want it to be reliable too. We are not going to have the car judged so the fan might be an easy improvement. If all goes well, and there are no surprise issues with the car, we will be driving it to Cleveland in July. 

[1937-44]

 If you have installed new radiator hoses put a spring in the lower hose as they are using less rubber and it will collapse.

 I have a 1937 Special and I run a 160 thermostat (1/8 hole in the flange), original fan, unaltered bypass and original radiator and my car usually runs at about 170 in the summer. In Charlotte in 2012 it got up to 185 while idling for a train to pass with the ambient temperature around 100 but dropped as soon as I started moving.

 When I put the freeze plug in my bypass I had mine tack welded in place) the car rarely got above 160 so I went back t my original one.

 Have you flushed the engine? Has it been rebuilt? I've heard after rebuilding the engines tend to run hotter.

[EmTee]

Yes, I have a spring in my lower hose.  I also have both a Gano filter and an ankle-high stocking in my upper hose.  My water jacket was pressure washed by the PO, but I didn't want to risk any crud fouling my new radiator.  I did catch some rusty flakes in the Gano and rusty sediment in the stocking.  The Gano only had 1 or 2 flakes when I last checked, so I'm considering taking it out and just leaving the stocking, which had about a teaspoon of fine sediment in it after ~3K miles.

[1937-44]

15 hours ago, EmTee said:

My car runs right at 180° according to the gauge.  It will, however, creep up to ~195ish when stopped idling in traffic on a hot (>80° F) day.

I wouldn't worry to much if it hits 195 only when idling on a hot day and drops down once you start moving because your antifreeze also raises the boiling point. It's not ideal but doubt it would hurt anything. Does the temperature drop if you remain standing still but run the rpms up?

[EmTee]

9 hours ago, 1937-44 said:

Does the temperature drop if you remain standing still but run the rpms up?

I didn't really try that, since increasing the fan speed would also increase the heat output of the engine, which negates some of the benefit.  Temp was always under 200° F, so as you pointed out, the coolant didn't boil (despite the unpressurized system).  That was after idling in mid-80° heat for 20 ~ 30 minutes.  Once moving again the temperature recovered quickly.  Also, note the temperature sender sits at the furthest point from the water pump, so the coolant flow is undoubtedly minimum in that area, particularly at idle RPM.

 

Edited May 4 by EmTee (see edit history)

[1937-44]

52 minutes ago, EmTee said:

increasing the fan speed would also increase the heat output of the engine

 But it would also increase water movement by the water pump and air intake.

 Is timing correct?

[EmTee]

Yes, but I should check dwell and timing again before this year's driving season.