thermostat or restrictor?

grumpyvette

Administrator
Staff member
READ THIS THREAD FIRST
viewtopic.php?f=57&t=853
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FACTS
your T-stat potentially restricts coolant and in a few cases air flow and is designed to restrict water/coolant flow thru the engine ,below the temp rating where it opens, it has little effect on the upper engine temp,IF IT OPENS FULLY AS DESIGNED AT THE RATED TEMP. its designed to allow the engine to reach and maintain the MINIMUM rated temp.
FACT
restrictors were designed to replace T-stats in applications where there was little or no need to worry about minimum temps BUT there was a valid concern that the water pumps impellers might CAVITATE (IE spin fast enough to spin loose of the water/coolant) and fail too pump effectively,at high rpms without some restriction to the flow to the radiator or in applications where the t-stat might be slow to respond and the engine might overheat, if air got trapped under the T-stat,(READ STOCK CAR RACING) remember the water pump SUCKS (creates a NEGATIVE PRESSURE) the coolant flows from the heads into the intake and flows thru the upper radiator hose into the radiator, where it releases trapped heat to the air flowing over the radiators fins,and is routed out of the lower radiator hose to the water pump,where it moves toward that negative pressure the impellers create, and pours into the impellers where its spun with centrifugal force, and flung, under pressure into the the block, from the water pump impellers , it flows to the cylinders then the heads collecting heat and back to the top of the radiator ,that coolant circulates thru the engine on the GEN 1 CHEVY sbc. gen IV-VI BBC
(the LT1 reverses the direction, the water pump forces coolant into the heads, and sucks it from the radiator thats fed from the block, not the intake like the GEN I design SBC)

just some info too think thru

1) eliminate trapped air or steam at the thermostat
2) prevent debris in the cooling system from blocking coolant flow thru the thermostat bleed hole (blockage here can cause overheating if there is no recirculating bypass built in)
3) minimize thermal cycling and thermal shock that occurs when cold water from the radiator(s) hits a hot block or cylinder head

you could buy a factory drilled t-stat
http://www.stewartcomponents.net/Mercha ... Code=Therm

On the street, thermostat drilling may prevent the engine from ever warming completely, especially in cold weather.

the engines state of tune effects the heat generated, vacuum leaks tend to increase heat, octane used effects the heat, your ignition timing curve effects the heat

the type of coolant effects the rate heats transferred

the amount and type of oil effects the temp transfer rates

a larger oil filter, and larger capacity baffled oil pan, tends to reduce temps due to exposing a larger surface area to the air flow, keeping the average oil temp in the pan lower:thumbsup:

anything that reduces airflow thru the radiator reduces its efficiency

the water pump and T-stat both effect the rate heats transferred, high flow water pumps can help

the electric fans work off a sensor and the temp they turn on at can be modified, larger or additional electrical fans can be added

on an auto trans car,the transmission fluid adds a good deal of heat to the radiator, adding a separate ADDITIONAL trans cooler with a separate electric fan,removes a good deal of the load from the radiator

oil in the engine flowing over parts absorbs and transfers heat , having a larger baffled oil pan hanging down in the airflow under the engine helps cool the engine

headers remove heat faster than stock exhaust manifolds

aftermarket aluminum radiators can be far more efficient

the diam. of the pulleys your using does effect the coolant flow

running the correct T-stat can help cooling, generally the 180F-190F is the best compromise
most t-stats work by by having a thermo reactive wax that starts to expand at a set temperature , then over about 10F-20F it continues to expand,and allow heated coolant to flow to the radiator, thus the t-stat will remain closed until its rated temperature range is reached and it will open wider up to its fully open position over about a 2-5 minute time frame
http://www.digitalcorvettes.com/forums/ ... hp?t=81691

http://www.becool.com/

http://www.dewitts.com/pages/categoryre ... p?catID=19

http://www.kevko.net/images/1090_full.gif

http://www.kevko.net/wetsump_chevy.htm
http://www.stefs.com/products/oilpans/c ... etsump.htm

http://www.radiatorbarn.com/?source=overture

engine oil needs to reach and stay at about 215F-240f to lube and clean correctly and burn off moisture

trans fluid I try to keep under 160F,surely below 180F ,


Ideally I try to keep engine coolant in the engine in the 190F-200F range but don,t get overly worried below 230F. BTW I run a 190F t-stat, temp ranges should be kept within these ranges or the wear and emissions won,t give you the long engine and trans life and low emission levels you expect , drop the coolant temps lower and you may gain a few hp but the wear tends to get worse as the fluids can,t operative correctly, drop the oil temp below 211 F and acids can form in the oil (bad for bearings)

read thru this link
http://www.troubleshooters.com/tpromag/ ... 200005.htm
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in an ideal world the coolant temp would stay in the 190F-200F range, install a 180F-or-190F t-stat and have the fans reprogrammed to come on at about 185F-200F and you'll see a marked stabilization of the coolant temp IF everything's functioning CORRECTLY

her are the fan control kits

185F

http://store.summitracing.com/partdetai ... SUM-890015
200F

http://store.summitracing.com/partdetai ... toview=sku
this external trans cooler

http://store.summitracing.com/partdetai ... toview=sku

personally I selected the 190F T-stat 185F fan control , but IM seriously thinking of getting the 200F fan control simply because with my external trans cooler the engine oil temp seldom gets over 220F and it takes 215F to burn off all moisture in the oil.

on my corvette I felt the proper route was hot tranny fluid out to radiator then to the electric fan cooled trans cooler then back to the trans, simply because that maximized the temp drop to the trans AND I was not having ANY trouble cooling the engine, in fact the oil temp seldom exceeds 230F and takes a fairly long time to reach 215F.
I don,t know the trans fluid pressure but I did verify that my trans cooler was designed for transmission heat/pressure and was factory tested at 300PSI.

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BTW if you route the other direction, IE separate trans cooler first then to the radiator it makes for a significant reduction in coolant temp, and the fan on the separate tranny fluid cooler runs constantly, but the engine coolant has a difficult time getting up to temp,(at least on my corvette) of reaching or allowing the oil temp in the engine to reach 215F LETS NOT GET INTO HOW I KNOW THAT :laughing:

btw some common areas people SCREW-UP

(1)
theres TWO different types of water pumps, most serpentine belt water pumps are REVERSE ROTATION compared to the standard SBC water pumps and of course wont work correctly if they get installed in an application where they spin in the wrong direction
(2)
some head gaskets have significantly smaller than standard water flow passage holes that significantly restrict coolant flow rates to the heads, you'll need to verify your using the correct gaskets
(3)
your ignition timing has a huge effect on the engine temp, verify its close to correct, on both total timing and it advances smoothly as the rpms go up.

(4)never mix the older GREEN and newer ORANGE COOLANT (ANTI-FREEZE) they CAN in rare cases form a JELL over several months and clog a radiator

(5) air flow thru the radiator is critical, make darn sure theres no crud blocking the radiator fins, CLEAN IT FREQUENTLY with soapy water and a hose it takes surprisingly little mud or grass stuck in the fins to significantly raise temps and you won,t be the first guy to have a plastic bag or paper or leaves sucked up and blocking the air flow

(6) T-stats can go defective, Id advise using a known brand in a 180F-190f RANGE, and type , not the cheapest crap you can find

BTW I normally drill 8-10 equally spaced 1/8" holes in the flange of the corvettes t-stat all around the perimeter this allows coolant to flow even if the t-stat locks closed and prevents air trapped under the flange, the picture below is of a semi similar mod on a different cars T-stat, yes it takes longer to reach full temp, but Ive found no down side and it works better with this mod in my opinion

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heres a couple chevy t-stats
mil-16400.jpg

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Ive seen fewer of the t-stats that look like these two upper designs directly above fail to function correctly
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the steward high flow design tends to be more expensive but less prone to sticking but both designs in my opinion benefit from drilling 6-to-8 holes in the flange
now IM sure some guys will say that defeats the T-stats purpose but it still works and theres a noticeable increase in coolant flow at 190F when the t-stat opens so I feel its a no lost deal
6-9 evenly spaced 1/8" holes drilled in the flange of the t-stat, will work wonders at making the cars coolant temp remain at a more constant temp, but it also tends to slow the rate the car heats up the first time a little bit.
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It may help to realize most engines running fairly lean emission friendly f/a ratios in cramped engine compartments run fairly hot in the 190F-220F range unless you have done the necessary mods to keep them cooler
Id also point out that 220F is nothing to get crazy over with a car sitting still, the radiator could obviously use more air flow and a more effective fan and duct work will help, your generally not going to have any problems if that 220F-230F in coolant temps is rarely exceeded, especially if it drops rapidly once your moving the car, before I added a transmission cooler my corvette almost always ran at 195f-210f coolant temps and oil temps in the 210f-235f range under hard driving and easily jumped up a few degrees in traffic.
adding an oil cooler also keeps the engine temps top low for too long so I only run the trans cooler now
but ID point out that almost all the hotter components in an engine are cooled by OIL FLOW and the OIL after its absorbed most of the heat transfers some of that heat to the coolant as it flows back to the sump, so an OIL COOLER and a 7-8 quart BAFFLED OIL PAN will go a long way to LOWERING the ENGINES total temperatures, the radiator needs to deal with, its not at all unusual to drop engine temperatures by 20 degrees with a 7-8 qt baffled oil pan and an oil cooler added to the engines oil system
ID also suggest drilling 8 1/8" holes in the T-STAT flange so any trapped air will circulate and exit the system and you ALWAYS have at least minimal coolant flow

http://forum.grumpysperformance.com/viewtopic.php?f=54&t=296

http://forum.grumpysperformance.com/viewtopic.php?f=57&t=1540

http://forum.grumpysperformance.com/viewtopic.php?f=57&t=149&p=183#p183

http://www.mrgasket.com/Portals/0/downl ... t_1992.pdf

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OIL COOLER
Perma-Cool 12318 $195.95

http://store.summitracing.com/partdetail.asp?autofilter=1&part=PRM-12318&N=700+115&autoview=sku

Perma-Cool 13311 $169.95

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OIL AND TRANS FLUID COOLER

Ive used those swivel t-stat housings several times, the seal o-rings generally seal, well and are easily replaced if damaged, the only issue I had was the t-stat housing is so tall it won,t fit in a few applications (clearances on some intakes like TPI)

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