Help! What thermostat should I use?

[Bolisk]

So, for the last couple of months. . .I was having trouble dignosing why my temp gague did not apper to be working. When I would turn the key to "run" the temp guague needle woudl move up slightly. . .indicating that there was power to the gague. Next, I checked the temp sending unit lead wire by connecting a volt meter to the lead wire, and ground. I got 12 volts. Next I noted that the previous owner had the wrong temp sending unit, and had wrapped the sending unit threads with plumbing tape. I have sence ordered a new "correct" sending unit and lead wire from Letric Limited, installed the new parts (without tape), and have retested the volts to the leadwire. The gague still never moved into the normal temp range. So, last time I let the engine run for 20 minutes or so. . .and noticed that I could still squeeze the radiator hoses. . .and they were never really all that warm. They were warm to the touch. . but not what I would expect. . .and there was little if any presure in the hose. . .I could easily squeeze them.

Now, it's been in the low 20's and teen's here in chicago. . .so I suppose that could be keeping the engine running cooler than normal. . .but not like this.

So now, I'm betting that my newly aquired car either does not have a thermostat. . .or it's stuck wide open.

So that brings me to the question at hand. . .

First some engine details: I have a 1970 350/350 11:1 compression engine. Currently the engine runs on 93 octane with no knocking. Now the fact that it's not knocking could be related to severl things. But I can tell you that the heatrisers on the intake manifod have been blocked via the gasket. I also suppose that it can run without knocking because the car never gets up to operating temperature.

So, taking into account. . .that i would still like the engine to run on 93 without knocking. . .(and I don't know if a working thermostat would make a differnence). . .what temperature thermostat should I buy for my car? ZIP has a 180 and a 160? What should I have? Also, any recomendations about thermostat brands (and hi performance. . .vs. low performance) would be great.

 

[Vette79]

I use a 180 Stewart High Performace Thermostat that I got from Sumitt.

 

[Bolisk]

what are the pros and cons of 180 vs. 160?

 

[Vettehead Mikey]

what are the pros and cons of 180 vs. 160?

Your car was designed to operate with a minimum operating temp. of 180, there are no benefits to running a 160. A regular Robertshaw unit from Autozone or anywhere is all you need.

 

[Bob Chadwick]

A lower thermostat may hurt the engine by not allowing the engine to heat up enough in the winter to blow condensate, etc, out of the oil.

 

[Bolisk]

Thank you! I'll pickup a robert shaw today.

By the way. ..I verified that the temp gague works by grounding out the lead wire to the block. ..and the gague spiked. So I'm hoping it's the thermostat.

 

[minifridge1138]

It sounds like a stuck/missing thermostat to me.
You definitely want the 180 thermostat. 160 degrees is not hot enough to boil the blow-by out of the oil.
Robert Shaw is a good brand, but most stores don't carry it BUT they carry Mr. Gasket Hi-Performance thermostats. They are actually the exact same part.

I don't think temperature would have an impact on spark knock. That would be caused by ignition timing, not temp.

Good Luck.

 

[JohnZ]

Thank you! I'll pickup a robert shaw today.

By the way. ..I verified that the temp gague works by grounding out the lead wire to the block. ..and the gague spiked. So I'm hoping it's the thermostat.

That check (disconnect from the sender, gauge pegs full cold, ground the sender wire, gauge pegs full hot) just says the gauge is working, not that it's accurate. The easiest way to verify its accuracy (or lack thereof) is to take an I.R. gun shot of the upper radiator hose just above the thermostat housing and compare it to the gauge reading at the same time so you know what the gauge is really telling you.

The Robertshaw 180* balanced-flow thermostat is #330-180, and the identical Mr. Gasket thermostat is #4364.

 

[Bolisk]

I see your point about whether or not the gague is accurate, and I agree. Unfortunaly. . .I won't be sure it's the gague until I've exhausted all the other options.

I know there are ways to tell if the gague is shot. . .but I figure that since many of the ware items on the car are 20+ years old, I might as well replace them on the way to a final solution. Besides it's more fun that way.

I guess I'm looking for some agreement in that my logic about the thermostat being a potenital culprit.

At any rate, I've ordered new upper and lower radiator hoses. . .and I will tackle the cooling system this comming weekend. Drain the antifreeze, replace the hoses, thermostat / gasket, and re-fill.

Speaking of which. . .anyone from the Northwest Chicago suburbs (Crystal Lake myself) know where I could recycle the old anti-freeze?

 

[minifridge1138]

Here is what I was told to do with old anti-freeze: mix it with cat litter and throw it in the trash. This is what the recycling people told me to do.

 

[Bolisk]

I've know people who have tried that with motor oil and paint. . .with very poor results. Did you actually do that? How'd it go? How much kitty litter did it take for the whole thing? Did you use the clumping kind!?

 

[minifridge1138]

I haven't done it yet, but I know some people that have.

I would use the cheapest litter they make.

 

[Mr. Chuck]

One additional check point regarding your temp gage problem is that the sending unit needs a good connection to ground (i.e. vie the housing threads). Make sure that there isn't any plumber's tape left over from the previous owner installation of the wrong thermostat. Checking with an ohm meter from the sending unit center contact to any bare metal ground should give you a resistance reading (will vary with the temp of the engine block).

 

[Norsky4360]

Personally I would not do the kitty litter thing with the old anti-freeze. That is just wrong IMO. The stuff would most likely end up in a landfill and the anti-freeze would eventually find its way into the ground water. Not good.

Check in your phone book (usually in one of the front sections) or contact your city hall for locations that will accept hazardous waste fluids. In Minnesota most places that sell motor oil (service stations/quick lube places/dealerships) accept used oil for recycling. I don't know about used anti-freeze but would expect that they would accept that also. I take all of my vehicle's used fluids and oil filters to a county recycling facility.

As far as the thermostat is concerned use the temperature range that is recommended for the engine. A common misconception is that a lower temperature thermostat will make an engine run cooler in hot weather. The thermostat just helps the engine reach its operating temperature more quickly by keeping the coolant in the water jacket. With a properly working thermostat an engine is going to find its own operating temperature regardless of what the temperature rating is. But as has been noted in previous replies too low a temperature rating, or if the thermostat is not working properly, your engine may not reach its correct operating temperature (especially on short drives in cold weather).

 

[Bolisk]

Thanks for all the help so far. Here is an update:

Last weekend, I drained all the old anti-freeze into old milk cartons (I will try to find some service station that will take it). I then took the new temp sending unit out. . .and cleaned the threads on the block. Next I replaced the lower radiator hose and the upper radiator hose. Then I replaced the old thermostat with a 180 Degree High Flow thermostat and gasket. Lastly I refilled the radiator and block with new "green" antifreeze mixed to 50/50. I ran the car for about 20 minutes. . .then toped off the anti-freeze. I know the thermostat opened because the return pipe on the radiator (where the upper hose connects too) was hot.

Alas. . .the temp gague still only reads 100 deg. So I've come to the conclusion that the gague is tost. . .or someone had a resistor on the back for the old "wrong" temp sending unit. I will tackel that issue in the spring.

Anyone have any other ideas?

 

[Tom Bryant]

I would suggest following Johns advice and getting a IR gun to measure the temperature. This won't fix the guage but you will be able to see exactly what is going on.

One question. Are you watching your guage while the engine is warming up? You should be able to see the exact moment the therm opens. The temp will rise steadily untilt he therm opens and then quickly fall back a little.

 

[Bolisk]

Yeah. The gauge moves slowly off the stopper pin until it almost gets into the normal temp range. . .then never moves again.