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Old 02-04-2020, 07:10 PM
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Anyone use restrictors?

For those of you who dont run thermostats do you use flow restrictors? I just came across these washer looking things from Moroso that restrict flow to let the coolant capture heat better. Anyone use em? Do they take place of the thermostat?

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Old 02-04-2020, 07:28 PM
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Is there some compelling reason not to use a thermostat ?
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Old 02-04-2020, 08:15 PM
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I dont know thats why i ask. Ive seen circumstances where people cant seem to get one that doesnt stick, or deleting the heater or having high compression motors, dirt track cars getting radiators plugged from dirt. Ive had plenty of thermostats that didnt open.
But doesnt the thermostat restrict the flow of coolant so it has sufficient time to cool down? Just seeing what people thought about washers taking place of a tstat
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Old 02-04-2020, 09:02 PM
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The thermostat manages flow rate to establish a constant operating temperature. If it cannot do that then something in the function, design, and operation of the cooling system is not correct. This is assuming the thermostat does not incurr a failure which is pretty rare.

Flow restrictors are used in competition engines to sort of achieve the same end without the possibility of having a thermostat failure out on the track. 60 years of racing has shown me this fear is far more fantasy than reality, I think I've only seen 2 maybe 3 thermostat failures in all that time and two of the three stuck open and even at racing engine loading the damn things ran cold, but they kept running.

The problem with sustained high speed high RPM runnng usually is too much coolant flow, so the restrictor is used to reduce flow to maintain some averaged range of operating temperature which of course to discover you have to put some size resrictor in, then go out on the course for a bunch of hot laps to see what temp's you get. So you're going to be at this awhile.

Bogie
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Old 02-04-2020, 09:07 PM
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Isnt it true that the oils we use work best at optimum temps say around 190-200?
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Old 02-04-2020, 09:43 PM
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Ive been using them for years. I actually use a large 1" flatwasher...thin as can be found. Works excellent....temps right at 185-200 max...full tilt small block

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Old 02-04-2020, 10:00 PM
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I use restrictors. No problems.We used to drill holes in the perimeter of a thermostat for better flow rates. Like BogiesAnnex1 states thermostats are quite reliable now
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Old 02-04-2020, 10:50 PM
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How consistent are the temps? Outside temps a factor? Im just curious, i just saw them offered by moroso in a classic industries catalog and wanted some insight of these things
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Old 02-05-2020, 01:15 AM
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For what purpose?

A restrictor on the street in the southwest or deep south east weather isn't a big deal. If you live where it gets cold you'll have to do a hell of a lot of driving to get the engine up to temp if that can even be done. Drilling three 1/8 holes in my daily driver's thermostat to help with burping the system in various experiments required frequent drains and refills so to speed that up the holes were put into the thermostat. These changed the warm up on the coolat gauge from 1 to 6 miles in Puget Sound's pretty chilly but not bone freezing winter weather. That's just coolant, it delayed getting the engine oil up to 180-200 degrees for another 6 miles at interstate speeds but since I put at least 60 miles into each side the commute this wasn't a problem as the engine finally got the coolant and oil up to temp fora goog period of timee. So if this is a street mobile your just asking for troubles you don't need without a thermostat. Now that my machine and I have transitioned to retirement, I put a high flow thermostat in it with no bypass holes. In winter on long freeway runs the gauge reads 4 degrees under the thermostat opening temperature of 180. It gets there quickly in about a mile to mile and a half from a cold start which includes a minute of fast idle before dropping it in gear to warm up the unheated intake a little. Anote on a related subject, I had more intake icing issues with the 670 cfm GM TBI and aluminum manifold adapter than I've had this winter with an AVS with insulating adapter to the same manifold.

If you're have cooling problems you need to identify the root cause and fix them rather than install what appears to be a crutch.

If you're racing then you'll have to pick a size and try it out, generally 7/8 ths to 1 inch is a good starting point. The operating temperature will vary with load on the engine and weather as the cooling system except for engine RPM is operating in a static flow condition so operating temperature will vary with the conditions where a thermostat will vary its opening thus coolant flow to reflect these changing conditions, at least within its range of authority. Like I said earlier if it doesn't do that the system, which can include the thermostat, has problems that need to be identified and fixed.

Bogie

Last edited by BogiesAnnex1; 02-05-2020 at 01:27 AM.
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Old 02-05-2020, 08:17 AM
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restrictors are for race cars. on the street use a thermostat.
for oval racing I use a 1 inch hole restrictor for typical 5-600hp compression engine
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Old 02-05-2020, 08:29 AM
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I'm just gonna leave this here because it covers it all.
In fact, following all of these tip eliminates much misconception.

https://www.stewartcomponents.com/in...ormation_id=11
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Old 02-05-2020, 08:46 AM
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restrictors are for building pressure in the block, not controlling flow rate
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Old 02-08-2020, 08:35 AM
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Wrong...restrictor reduces flow. A 1" restrictor slows it ever so slightly to allow heat removal, and enough flow for high RPM runs. If you have a low HP daily driver that never or hardly ever sees above 5k RPM then use a thermostat. My RPM at highway speed is around 3300-3500 so I ensure enough flow available through the block especially with reduced ratio pulleys....no matter what Stewart says, it has been done with success for 50 years. And i use one of their no-bypass high flow pumps

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Old 02-08-2020, 01:01 PM
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Now im thinking, you say low HP daily driver what is low hp. Also, how about say a 350 bored .60 over where the cylinder walls are thin therefore more heat produced in the water jacket? Guess its more or less personal preference as to run thermostats or restrictors. I personally have never run a restrictor. I have an older monte carlo with a 350 i could do some "experimental testing" on......i dont really care if it over heats as its sits waiting for a facelift
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Old 02-09-2020, 07:05 AM
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I hate when this happens......Johnsongrass1 posted a VERY GOOD LINK about cooling systems......

YOU CANNOT FLOW TOO FAST IN A COOLING SYSTEM! The old adage about keeping it in the radiator longer is the biggest myth ever perpetrated on the automotive industry next to storing batteries on a concrete floor!!!

I wish people would stop saying you need to do that!!!! The best setup is with no t-stat at all and a high flow water pump! T-stats are used to maintain a certain temp and are the result of emissions controls!! An engineer for NASCAR frequents Speedtalk and goes by the nickname of Warp Speed. He works for Hendrick motorsports....Ask him if they use a t-stat or restrictor in their engines....

If you need a heater to work, you need a t-stat, but a t-stat will INHIBIT cooling. That's why the engine temp will climb with one. When it opens it will allow more cooling to take place, then close down when the temp drops....a restrictor does the same job for a short time until the water temps have stabilized, then they are useless...

Last edited by predator carb guru; 02-09-2020 at 07:13 AM.
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