Vortec Thermostat Experiment

[Jerrys1990]

Thank you. There's so much misinformation about cooling systems floating around automotive forums. Nice to see truth.


Technically true, but the "draw" (I'd have said "inlet" or "suction" side) SHOULD be the already-cooled fluid coming directly from the radiator.

Water pumps can cavitate, though. I think it has more to do with impeller speed and inlet restriction rather than inlet temperature.

Similarly, when there's a problem with the lower radiator hose collapsing, most folks say to shove a "spring" inside to "support" the lower hose. I say to check the radiator for restriction. If the lower hose collapses, it's because you're pumping water out of the hose at the water pump end, faster than it can re-fill from the radiator side.


Propylene glycol (PG) anti freeze is popular with the Eco-sensitive; I've used it too. Doesn't poison dogs or squirrels who might drink a little out of the coolant drainpan left unattended too long. I figure it's better to appropriately contain 'n' dispose of the waste anti-freeze in a timely manner. But like I said, I've used the stuff and it worked OK. Been a long time...

The PG antifreeze doesn't have to have anything special in the cooling system; it is just a little "thicker" than ethelyne glycol; and doesn't have quite the freeze protection. You'd need a different freeze-protection tester than Ethylene glycol.

https://www.amazon.com/old-world-sep003-antifreeze-coolant-propylene/dp/b000ccm5ja

"High flow" is very welcome...but only when the heat load demands it. The whole point of a thermostat is to choke-off coolant flow to make the cooling system much less efficient, so the engine warms-up quickly and stays at a reasonably-steady temperature. This is why engines operated at idle or cruise should run within a few degrees of the thermostat rated temperature; if the engine is more than 20-ish degrees above the thermostat rating, it's lost control of engine temp. Of course, some of that depends on when the fan(s) are activated--GM often doesn't turn on an electric fan until 220 degrees or so. The second electric fan may not come on until 230. If the cooling system is running way hot at idle or cruise, it's got no reserve capacity for when you're dragging a trailer up the mountain, or other heavy-throttle use. THAT is when the thermostat should be WFO, and the engine coolant temp may climb some.

The "big deal" with having a restrictor in the thermostat housing--either an actual thermostat, or a restrictor disc--comes from the older, top-to-bottom flow radiators. UNLIKE a typical cross-flow radiator, the pressure cap is on the inlet side, ahead of any restriction presented by the coolant tubes in the radiator. Having radiator-cap pressure, PLUS water pump pressure (especially at high water pump speed) that isn't moderated by the restriction, will overpressurize the radiator cap, causing it to release pressure and therefore loss of coolant. Then the system is low on coolant, so the engine overheats.

A cross-flow radiator has the pressure cap on the outlet side, so it maintains cap pressure despite water pump suction, leading to higher overall pressure within the engine. Cross-flow radiators are way better than vertical-flow radiators for this reason. And then GM starts building vertical-flow radiators after decades of cross-flows, for the GMT360/370 Trailblazer/Envoy series of vehicles.

With this information, it appears there would be no benefit to a high flow stat for my all stock TBI engine? I've been reading reviews, trying to make a selection for a quality 195 degree stat for my '90.

 

[Schurkey]

What worked as OEM will work for you now...provided the rest of the cooling system is in good condition.

Plenty of folks try to crutch a failing/corroded/damaged radiator, for example, by installing a "high flow" thermostat...or removing it completely.

 

[L31MaxExpress]

What worked as OEM will work for you now...provided the rest of the cooling system is in good condition.

Plenty of folks try to crutch a failing/corroded/damaged radiator, for example, by installing a "high flow" thermostat...or removing it completely.

Some of us needed the high flow because we doubled our HP. My radiator was brand new and the engine still wanted to run as hot as 220F in the Texas heat. I went from a 180F to the 195F high flow and it cooled my engine down nearly 20F. If I could find a quality 170F or 180F high flow with the Vortec blocker ring I would absolutely have it in my engine. My SBC engines have always run strongest around 170F at the hottest. Over that temp they start to lose power and by 205F it is very noticeable. By 210-220F they are slugs. My C3 Vette like all of them wanted to run 230-240F same as my 3rd gen F-car in the heat of summer. Those cars have major airflow issues to the radiators which is compounded by running ac and those engines did not even want to idle properly running that hot. Quick 15-20 second heavy throttle blast down the highway with the clutch fan roaring would cool them back down to 180-200F and make them happy again. Those cars never would cool with garbage electric fans either. Part of the sluggish performance is heat soak, every part of the engine bay heat soaks including the air intake, I saw the IATs on my Express van at 194F this past summer around town. I do not remember the IATs on my G-van, Vette or Camaro getting that hot even with an open element sitting on the TBI. I have seen most vehicles get to 150-160F IATs during the heat of summer here. It is not hard even on vehicles with well designed air intakes outside of the engine compartment considering the air over the pavement is over 120F.

 

[Schurkey]

it appears there would be no benefit to a high flow stat for my all stock TBI engine?

Some of us needed the high flow because we doubled our HP.

Yes, but clearly he didn't increase his horsepower since it's "all stock".

 

[Jerrys1990]

Yes, but clearly he didn't increase his horsepower since it's "all stock".

Yes. I ended up ordering a GM replacement right from the dealership I work at. My parts manager said don't waste time with the "junk" aftermarket ones. Now I just need time to install it! As long as it works and lasts a long time, I'll be happy. The rest of my cooling system looks good. The radiator is newer, water pump looks ok, hoses are newer, etc. The heater core is suspect...I got a junkyard core from a 94 that looks excellent and had no debris in it. I was originally interested in the high flow after reading this thread because it seemed dead solid reliable and consistent. However, the OP's setup is completely different than mine so it doesn't seem like there would be any benefit.

 

[yevgenievich]

I ended up with high flow tstat, high flow water pump, stock big block radiator, and modified clutch fan to keep operational region in 180 to 195 range. Running decently built big block motor. For stock applications, modification to the clutch fan for 190* range can be considered but otherwise everything stock works.

 

[L31MaxExpress]

Yes. I ended up ordering a GM replacement right from the dealership I work at. My parts manager said don't waste time with the "junk" aftermarket ones. Now I just need time to install it! As long as it works and lasts a long time, I'll be happy. The rest of my cooling system looks good. The radiator is newer, water pump looks ok, hoses are newer, etc. The heater core is suspect...I got a junkyard core from a 94 that looks excellent and had no debris in it. I was originally interested in the high flow after reading this thread because it seemed dead solid reliable and consistent. However, the OP's setup is completely different than mine so it doesn't seem like there would be any benefit.

GM does not make "OE" replacement for our trucks any longer. The AC Delco stuff for our trucks is largely the same "junk aftermarket" as everyone else. I have not good luck with AC Delco in a over a decade when it comes to vehicles that are age of ours.