312 thermostat bypass hose plug question

Abchoppers

Abchoppers

Member
1956 Mercury 312, I’ve read about the thermostat 312 bypass hose mod. I have a new 5/8” heater hose and a 3/8” plug with a 3/16” hole drilled into it. How do I screw the plug far enough into the hose to be able to get both ends of the hose on? It screws into the hose easy enough but once it’s inside the hose I can’t keep a wrench or socket on to continue screwing it in. I’m sure there is a simple answer but I’m scratching my head
Thanks all
 
If it's the square extended-head type plug, hacksaw a screwdriver slot in the head. Install with dish soap for lube.



Terry
 
Bob from Northport said:
Maybe a foolish question, but what is the purposes of plugging the bypass hose??
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I believe the bypass hose allows the car to heat up faster, but once at running temp it continues to allow too much coolant to bypass the radiator. By plugging the hose, but leaving a small hole in the plug, the coolant will all mostly pass through the radiator leading to cooler temps. Most people who have done this mod are happy with the results from what I’ve read. I should also add that most will drill small holes into the thermostat along with this hose mod
 
Anchoppers said that pretty well. I’ve done it. Some will tell you it increases cavitation of the water pump and shouldn’t be done. Others will tell you to try a smaller water pump pulley to get the pump speed up at idle.

A lot of this comes from the T bird side. The water pump spacer does reduce the efficiency of the pump, and the airflow thru the bird radiator seems to give a lot of us cooling problems. Especially stopped in traffic. But I know several guys who drive cross country and hot weather over 85 or so can cause cooling issues at 70. At least according to them.

Drilling the thermostat, and using a high flow one (I think it’s a Chrysler part) helps to some degree. The drilled hole does more to help purge air from the system when you fill it.

Talking about bird and Yblock overheating is like talking about “which oil”. Enough said.
 
I would advise against doing this unless you do one more modification. And that is drilling some holes in the thermostat for additional water flow.

Why do I advise against it - I did the modification in my 56 Bird. What happened to me is the decrease in water flow made the temperature go way up at the begining until the thermostat opens. Scared the devil out of me. Maybe a bigger hole in the plug will suffice.

I found out later that the person who did this successfully also made the holes around the perimeter of the thermostat.
 
Is there a fan schroud? The typical problem is in traffic, not on the highway. This goes for most any car.
 
“Talking about bird and Yblock overheating is like talking about “which oil”. Enough said.”

Haha very true!
 
Gene F said:
Is there a fan schroud? The typical problem is in traffic, not on the highway. This goes for most any car.
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No fan shroud and as far as I can tell nobody makes one for a 56 Mercury. I would love to have one, as I think a shroud with a puller fan is ideal for cooling. I’m not actually overheating at all, but I do notice a slight temp increase when sitting at a light or traffic, and it will go down once moving. I think this mod is an inexpensive thing to try first before maybe doing a smaller pulley or different blade.
 
paul2748 said:
I would advise against doing this unless you do one more modification. And that is drilling some holes in the thermostat for additional water flow.

Why do I advise against it - I did the modification in my 56 Bird. What happened to me is the decrease in water flow made the temperature go way up at the begining until the thermostat opens. Scared the devil out of me. Maybe a bigger hole in the plug will suffice.

I found out later that the person who did this successfully also made the holes around the perimeter of the thermostat.[/QUOTE

I definitely agree, I think if doing the bypass plug, doing the holes in thermostat is a good idea as well
Thanks
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What is happening at a light is normal. It seems you have no problem. Let sleeping dogs lie. An easier fix would be a smaller fan pulley.



There are aftermarket shrouds around that most likely can be made to fit. Try Jegs , Summit or Speedway.




Abchoppers said:
No fan shroud and as far as I can tell nobody makes one for a 56 Mercury. I would love to have one, as I think a shroud with a puller fan is ideal for cooling. I’m not actually overheating at all, but I do notice a slight temp increase when sitting at a light or traffic, and it will go down once moving. I think this mod is an inexpensive thing to try first before maybe doing a smaller pulley or different blade.
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Paul’s right about the heat reading on start up. I had an OT engine with no bypass hose do that. Changed the tstat twice before the light bulb came on. I finally figured out it didn’t happen if the heater was on. That provides enough water flow (at least in that one) to get hot water to the stat location. I added a bypass, small #4 AN hose and fitting. Solved it, I didn’t know about drilling the stat.
 
paul2748 said:
What is happening at a light is normal. It seems you have no problem. Let sleeping dogs lie. An easier fix would be a smaller fan pulley.



There are aftermarket shrouds around that most likely can be made to fit. Try Jegs , Summit or Speedway.
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True, but where I live it can be very heavy traffic at times. I’m thinking of worst case scenario. I looked up those universal shrouds and I think I can get one to work, thanks for the tip
 
miker98038 said:
Paul’s right about the heat reading on start up. I had an OT engine with no bypass hose do that. Changed the tstat twice before the light bulb came on. I finally figured out it didn’t happen if the heater was on. That provides enough water flow (at least in that one) to get hot water to the stat location. I added a bypass, small #4 AN hose and fitting. Solved it, I didn’t know about drilling the stat.
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I’m hoping the holes in the thermostat prevents that from happening
 
If it's a hot day, what i do at a light is shift into neutral so the rev's go up which increases the flow. This doesn't work if you have a stick car.


QUOTE=Abchoppers;2239361]True, but where I live it can be very heavy traffic at times. I’m thinking of worst case scenario. I looked up those universal shrouds and I think I can get one to work, thanks for the tip[/QUOTE]
 
paul2748 said:
If it's a hot day, what i do at a light is shift into neutral so the rev's go up which increases the flow. This doesn't work if you have a stick car.


QUOTE=Abchoppers;2239361]True, but where I live it can be very heavy traffic at times. I’m thinking of worst case scenario. I looked up those universal shrouds and I think I can get one to work, thanks for the tip
Click to expand...
[/QUOTE]

I’ve done that trick as well, works good!
 
I got my shroud from Concourse parts, but I have a 57. I also have a 6 blade fan. I put a spacer on it, so that approx 1/2 the depth of the blades were int he housing. I had some of those that I likely bought over the years from SpeedwayMotors
 
Gene F said:
I got my shroud from Concourse parts, but I have a 57. I also have a 6 blade fan. I put a spacer on it, so that approx 1/2 the depth of the blades were int he housing. I had some of those that I likely bought over the years from SpeedwayMotors
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I think the problem is the power steering. I looked on concourse parts and that doesn’t fit with the power steering, I’ll probably have to do a custom universal one. They did have some 6 blade fans though that I think would work.
Thank you
 
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