I will soon be installing a new thermostat in my 292. Recent posts on this subject ha given rise to confusion on my part. Should I install a 170 degree NAPA #6, a 180 degree one or perhaps even a 160 degree unit. The NAPA units are supposed to have a larger orifice. Some say use a Robertshaw while others say they are junk and go with Stant (others claim that the Mr Gasket thermostat is junk as well). I have a C2AZ-8575-A from Mac's that lists as a 180 degree unit. Another supplier lists it as a 160 degree unit. The C2AZ-8575-A cross references as a Stant 13478. Does this mean that the C2AZ is in fact a Stant 13478 or that it is simply a suitable replacement.
I read where Ted and others recommend a ristrictor with a 3/16 orifice in the bypass tube. Can this modification be made in isolation or do I understand that a hole (s) must be drilled in the thermostat? Does this (these) modifications require a specific thermostat?

In the past if I needed a thermostat I took the one the Parts guy gave me and if the rad didn't boil over I was good to go. Now I'm paralyzed by all this information.

Mark

1956 Mercury M100
1955 Ford Fairlane Club Sedan
Delta, British Columbia

Hi Mark, for the restrictor in the bybass hose use a 3/8" pipe plug with a 3/16" hole drilled into it. (sorry for the blur, turned off my flash).

As for the thermostat I'm sure you will get a lot of different opinions. I use a 170°F Thermostat in addition to a 190° thermal switch to turn on my electric fan (if needed). I live in Southern California.



"The Master Cylinder"

Enjoying life at the beach in SOCAL

I for one have never had a problem with the Mr Gasket "Robertshaw" style of thermostat - not to say it couldn't happen - just wasn't a problem for me. They all use the same tyoe of "pill" - a small brass cylinder full of expanding wax to operate - its just a matter of how much water the housing will pass when wide open. The Mr Gasket 160° I tested on my bench opened at the right temperature and the full opening was a cylindrical space 1.5 inches diameter and .44 wide. A little over 2 square inches of area. Heating it up with a heat gun - then watching it with infrared as it cooled and closed in open air - I never saw anything that concerned me.

The opening temperatures - basically sets the minimum temp before circulation to the radiator begins to occur - and the 160° - 170° - 180° - all (3) numbers are within a range of 20° top to bottom. For what its worth, the Ford spec for my T-bird says opening temp is 157°. I chose the 180° so that the "warmed up" temperature of the engine was in a narrower range min to max. Makes the idle tune more stable (in my opinion). If there is such a thing as a high flow 190° - I might even try that.

The plug for the bypass works like a charm - I wouldn't have believed it except for making a deliberate test. The bypass is a 5/8 (garden hose sized) pipe that connects the hottest water in the engine directly to the greatest suction of the water pump. Maximizes reheating the already hot water. There are those that recommend drilling some auxillary passage holes in the thermostat to prevent "dead heading" the pump when the bypass is closed up. My T-bird pump impeller is so inefficient, its hard to imagine how little pressure it can provide - so I don't think that is a problem for me. I have drilled three 3/16 holes in my thermostat which I believe encourages the warming water to flow right over the "pill" and get with the program of opening the t-stat.

 
 Steve Metzger       Tucson, Arizona

Ditto with Greenbirds56 comments. I too prefer the 180 for the same reasons. My experience and observations have been exactly the same for about 20 years. Some flow tests were run years ago by the CTCI (Gil I think) that showed the same. Also, I believe the new Airtex impeller may be a lot more efficient. Many 'Stant" style thermostats appear to have substantially less area when fully open hence will be more restrictive. I too use the plug in the bypass and it really seems to help, especially noted a measurable difference on Sherwin Grade , US 395. The pusher fans on my Bird are set up similar to his, plus I run a thermostatic 5 blade clutch fan (originally from a Mopar) that fits the original shroud perfectly. Back to the shop....
WLJ

Mark: Yes the info available can be confusing. Info from someone that has a T.Bird & lives in Texas may not be what you need, cause you live in the Northwest, and don't have a Bird. In your case you should likely use at least a 180 deg stat. Robert Shaws are likely fine & some other too. But, I know one shop that won't use Stant at all, due to come backs..

Paul

Thanks everybody. I will add the brass ristrictor with the 3/16" orifice, however it I am still unclear on whether I need to add the bypass holes in the thermostat. Is there a picture of where these holes should be drilled? Also does anybody have a part number for a 180 degree Robertshaw thermostat (is this the NAPA item)? Thanks again.

Mark

1956 Mercury M100
1955 Ford Fairlane Club Sedan
Delta, British Columbia

I think it is a mopar application that you need so,

http://www.summitracing.com/parts/mrg-4367/overview/make/plymouth

I can check my receipts to verify.

I don't know what is junk about them, but I've had it for over 10000 miles now without a problem.


Lawrenceville, GA

Thanks Charlie, that helps a lot. Its not my opinion that any junk is involved, just something I read. It was something about Robertshaw selling the automotive thermostat division to someone else who now manufactures overseas. The opinion here seems to be that they are good so I will go with that.
Anything can be junk if you abuse it and many times I think that is the case.
Thanks again.

Mark

1956 Mercury M100
1955 Ford Fairlane Club Sedan
Delta, British Columbia

The Mr Gasket high flow thermostat is made in the style of the older Robertshaw unit - and probably comes from an overseas vendor. I've used several on different cars and projects - they work. The big block Mopars use a 2 inch nominal diameter sealing surface - same as the Y-block - so same part as for a 413/426/440 in whatever opening temp.



The three 3/16 bleed holes are drilled as shown on that style of t-stat - if you want to see the original source of the modified part, look for Stewart Water Pumps on the web.



They really open up as seen in the photo - 1.5 diameter poppet and 7/16 at full opening.

 
 Steve Metzger       Tucson, Arizona

Thanks Steve, now I see.

I plugged Dodge 440 Thermostat into goggle and got a Mr. Gasket 4367. The same one Charlie recommended so I will be good to go. Thanks.

Mark

1956 Mercury M100
1955 Ford Fairlane Club Sedan
Delta, British Columbia