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I finally got the 62 back on the road after getting the front end aligned. As I started driving, the temp gauge rose gradually all the way to 200 and then fell back to 180 as (I assume) the thermostat opened. What happened next, I have never seen before on this or any other car. The temp would rise to 200-220 and then fall back to 180. Again and again. Almost constant up and back. Thermostat sticking? I cannot imagine what would cause this behavior unless it is a problem with the gauge itself.
Any ideas?
I would monitor it with secondary instrumentation (IR thermometer, thermocouple) to compare to the dashboard gauge, and take it from there. If the gauge is telling you the truth, I'd replace the thermostat.
That was my thought. And, yes, it is a name brand thermostat from Summit. NAPA here I come.
If it's a Mr. Gasket Chinese clone of the Robertshaw hi flow stat, that's the problem. I have never had one that worked right or was anywhere near the right calibration. I have 2 of them on my desk right now---A 160 that doesn't start opening until about 190 degrees and a 180 that opens at 160 degrees---They're JUNK. Get a real Robertshaw or a Stant thermostat.
No, they restrict the amount of flow to control how long the water stays in the block to absorb heat from the engine block. Larger hole, faster flow less heat absorbed from the block. Smaller hole, coolant held back to absorb more heat. The only downside of course, is that the cold start engine takes longer to warm up. Lots of race cars use them.
If it's a Mr. Gasket Chinese clone of the Robertshaw hi flow stat, that's the problem. I have never had one that worked right or was anywhere near the right calibration. I have 2 of them on my desk right now---A 160 that doesn't start opening until about 190 degrees and a 180 that opens at 160 degrees---They're JUNK. Get a real Robertshaw or a Stant thermostat.
RON
Are the Robertshaw ones worth the money? I've noticed that my NAPA one usually drifts up to 200* before opening and then takes quite a while to come back to 180*. Once at 180* it stays there - no problem, so not sure it is worth changing.
Are the Robert Shaw ones worth the money? I've noticed that my NAPA one usually drifts up to 200* before opening and then takes quite a while to come back to 180*. Once at 180* it stays there - no problem, so not sure it is worth changing.
They work for me, so for me, that makes them worth the money
I've had good luck 'in the past' with brands like Gates and Stant and Robert Shaw but just checked the Robert Shaw website and they don't show our old style thermostats.
I also checked NAPA and they do sell one that 'looks' like a Robert Shaw but in the fine print, it says it's manufactured by Mr Gasket.
I also took a pic of the Stant 180 thermo I bought a couple years ago and no big surprise, it's also made overseas...this time in Israel.
Mike T - Prescott AZ
I put a Robert Shaw thermostat in my 66 recently and it solved the problem of slow warmups and running too cold. For the first time in many years my engine and gage act normal. I would say they are worth the money.
Since it has been awhile, let me briefly recap: I have a 62 with what is essentially a 1970 LT-1 engine. It has always overheated. This year I decided to bite the bullet and installed a new DeWitt HP radiator, new hoses, new high flow water pump and new 'hi flow' thermostat (Mr. Gasket). I am not sure what makes it 'high flow', it looks like every other thermostat I've seen for SBC. That was when the hysteresis began. On advice from this thread, I swapped in a NAPA std thermostat. No hysteresis, but it was still overheating. I thought that maybe it really did need a high flow thermostat (The water pump said it needs it). I tried an Edlebrook high flow. Looked like all the others. Had the same hysteresis - 180*<>220*, Finally, I bit the bullet and bought a RobertShaw from Summit since there have been so many positive post about it. This thermostat does look different so I had great hopes. Nope, same hysteresis.
Is there ANYTHING other than the thermostat than can cause this? I am about ready to try no thermostat at all or maybe one of those restrictor rings. What are they called? Where do I get them?
Never mind. I found them on Amazon. Any recommendations for a size to start with for a street driven LT-1 engine?
No, they restrict the amount of flow to control how long the water stays in the block to absorb heat from the engine block. Larger hole, faster flow less heat absorbed from the block. Smaller hole, coolant held back to absorb more heat. The only downside of course, is that the cold start engine takes longer to warm up. Lots of race cars use them.
So I got a set like yours. Which size provides max cooling? From what you said, it seems smaller hole gave more heat extraction, but that is sort of counter-intuitive.
So I got a set like yours. Which size provides max cooling? From what you said, it seems smaller hole gave more heat extraction, but that is sort of counter-intuitive.
yes, it does seem backwards but think about it this way. Heat transfers from the cast iron to the fluid. In order for that to happen the fluid must remain in contact. If it rushs by and back to the radiator it doesn’t have a chance to absorb as much heat as it would if it stays in contact longer.
Easy theory to test. Take the stadt out and drive the car. Go back and put the restrictor in (smallest hole) and drive the car and compare the results.
I would start with the middle one and then go up or down as necessary.
Keep in mind it is going to take the car a lot longer to warm up than with a conventional stadt.
Good Luck.
06-06-2023, 10:57 AM
Temp hysterisis??
