Can use some Thermostat and Rad Cap advice

[Driver Ed]

Hello All:
Assessing my new '64 Daily Driver Dart cooling system. With the rad cap off, I see coolant flow at cold start. So either the thermostat is stuck or does not exist. The car has never overheated, even when running above 200F in traffic. Nothing even showing in the puke tank. I am not comfortable running without a working stat. Looking for help on what make, temp and what rad cap. Here are the particulars:
Engine: 1977 318. Engine built in 1990's with Comp Cams "Thumper" cam(don't have specs but is plenty lumpy at idle). Engine likes 12deg initial timing. Edelbrock Perfomer intake and 600cfm carb. Points dist. No headers. No A/C. Has PB and 904 trans.
Cooling System: Water pump stock. Rad is Mopar #38086. No soldered #tag visible. Both hoses on driver's side. Rad measures 18"H tank to tank, 21.5"W. Rad cap is 13lb. 6 blade steel fan, 17"(+-) dia. No shroud (searching-anybody know a source?). No fan clutch(should I install one?)

I realize these are basic questions, but I've never owned a Mopar or a non-stock engine before. I'm trying to learn, though!
Thanks

 

[MidnightSwinger]

Drain the radiator on pop the top hose off the thermostat housing and see what you have. If there is no thermostat I’d recommend putting one in. Stock temp is usually around ~195. I like to run 180* on my stock/drivers. 160* on anything built to beat on. 13lb cap is good.

 

[RustyRatRod]

Yeah 13 pound cap is perfect. Guys sometimes think more is better. It's the other way around. The lowest PSI you can make the cooling system run and not puke is best. Pressure is bad on the cooling system. I think the 180 thermostat would work well here. But get a high flow one. I actually like the Edelbrock thermostats. They're made outta stainless steel and most parts stores have them or can get them in a day.

 

[melcardona]

Drain the radiator on pop the top hose off the thermostat housing and see what you have. If there is no thermostat I’d recommend putting one in. Stock temp is usually around ~195. I like to run 180* on my stock/drivers. 160* on anything built to beat on. 13lb cap is good.

if you dont see a stat...most likely theres an issue with summer temps that the cooling system cant handle....ie...parts of rad pluged....fan bleeding...or collapsing lower hose.....all easy to deal with..good luck..

 

[Bewy]

Production engines have a safety bypass in the cooling system in case the stat jams shut. A portion of the returning coolant is bypassed to the feed side of the pump. The bypass is pretty big on the SB, so you might see some flow at idle when cold. If no stat, I would use a 180.

If you think the engine likes 12* initial timing with that cam, it will LOOOOOOOOOOOOOVE 20-25*. Move your dist with the engine running & see....

 

[Dana67Dart]

If you find that your engine doesn't have a t-stat yet it idles at 200 f that's proof right there that the cooling system is working as it should. (Unless you have another issue as mentioned earlier and is minimally capable

The t-stat ONLY sets the MINIMUM temp and has nothing to do with the running and idling temp unless the outside air temp is really low.

If the state is 160 deg it is fully open at 200 and has been for 40 deg.

If it's a 180 same thing and has been for 20 deg.

If it's 195 it is still fully open BUT when you start to drive the air cools the fluid and the thermostat will start to close and regulate the engine temp to be no less than 195.

 

[RustyRatRod]

If the state is 160 deg it is fully open at 200 and has been for 40 deg.

Naw. That ain't how it works. The thermostat doesn't magically pop open at the specified temp. It BEGINS to open. It MIGHT be completely open in ten degrees. Might not. But the specified temp of the thermostat is where it begins to open.

 

[Dana67Dart]

Naw. That ain't how it works

We will have to agree to disagree.

I do agree that it does not pop open and i never said or suggested that it does it is a thermostat and it regulates (buy increasing or reducing the flow of coolant THROUGH the radiator) but once the engine it above the temp the thermostat is fully open it plays no role on the cooling / heating of the engine.

 

[RustyRatRod]

We will have to agree to disagree.

I do agree that it does not pop open and i never said or suggested that it does it is a thermostat and it regulates (buy increasing or reducing the flow of coolant THROUGH the radiator) but once the engine it above the temp the thermostat is fully open it plays no role on the cooling / heating of the engine.

Throw one in a pot of boiling water and you'll see.

 

[str12-340]

some suggestions to the OP:
use a high flow thermostat if you can find one. I am assuming that you have an intake with the larger thermostat. Given your cam and stuff I'd go with a 160 degree unit. Mr. Gasket #4366 (they also have 180 units). This is the same type of thermostat that Mopar Performance used to sell (Robertshaw style?).

I agree with Rusty regarding pressure caps. If you have no info on the history of your radiator, like when and who it might have been recored by, then too much pressure is pushing your luck. I've been using 7 lb. caps since the early 1980s on my 70 Darts with no issues. Since you have a recovery tank, you'll know if this is too low.

 

[abodyjoe]

i run a 180* stat in our dart. i need some heat on those cool days.. .
i run a 16psi cap. i believe thats what it had from the factory.

 

[Darter6]

No shroud (searching-anybody know a source?). No fan clutch(should I install one?)

This is just a idea. When I did my early A I got a 1980 Dodge Aspen radiator, fan shroud and clutch fan, the last 2 were from wrecking yard find.
The radiator I bought new. They have thin long tanks that give extra room.
You will have to relocate the mounts. I just extended from existing holes with 4 brackets.
Worked very well in the Nevada summer 100+ heat.

 

[Driver Ed]

Thanks everyone! I'll try a high flow 160 stat if only because the system currently seems to do fine with flow sooner than later. I'll keep the 13lb cap.
Any suggestions on how to order the correct shroud when you don't know where the Rad came from and have no P/N tag? What year did the hoses both end up on the driver's side? Originally my car came with a Slant 6, but had a donor '66 Dart GT V8 installed. But, I don't think the bottom hose switched sides that early.
Thanks!

 

[72bluNblu]

If you're not drag racing there's no reason to have a 160° thermostat. A 180° or even the stock 195° will work just fine for your application. You say it idles at 200°, so guess what? It will still idle at 200° with a 160° thermostat.

Your engine tune will be different at 160° than 200°, if you're street driving the car you're better off tuning the engine for what the temperature will be most of the time. If it's not tuned to run at 160°, on cold days when the cooling system can keep it at 160° it'll always act like it's running cold. Because it is.

 

[toolmanmike]

Throw one in a pot of boiling water and you'll see.

I test every one that way.

 

[RustyRatRod]

I test every one that way.

So do I and they always just barely crack open when the get to temp. Some don't start until later or before. They never start right on the money. Better to test because they might be stuck closed brand new!

 

[Darter6]

Some don't start until later or before.

I was taught that the stated degrees, say 180* is when the thermostat STARTS to open. Fully open may be 8 to 12 degrees more.

 

[RustyRatRod]

I was taught that the stated degrees, say 180* is when the thermostat STARTS to open. Fully open may be 8 to 12 degrees more.

Yup and possibly sometimes even more.