[geeteeohguy]

Originally Posted by Schurkey

Good, not great.

A shroud on the fan would make it far more efficient, which means you wouldn't need the "extreme-duty" fan clutch with a modified spring--or the horsepower to drive it.

The Heavy- and Severe-duty fan clutches are not suitable for use with typical automotive fans, (Less than 2 1/2" of pitch) because they'll never properly disengage. Hayden says as much on their web site.
http://www.haydenauto.com/Featured%2...s/Content.aspx

How much engine vacuum do you have at highway cruising speed?



That's all the evidence I need to know that either your cooling system doesn't have the heat-rejection capacity it should, or there's problems with excess heat generation.

210 is 40 degrees over the nominal 'stat temperature. The 'stat lost control of the temperature at 20 degrees over. The cooling system is running wide-open and has zero capacity for additional load.

Nonsense. These numbers apply to the 9 GTO's I've owned and others I've driven over the past several decades. I have put 100's of thousands of miles on these cars without issue at temps of 200-215 degrees. New cars RUN at 220-240 as a norm. Not one of my GTO's would run 180-190 degrees on a 110 degree day at 75-80mph for hours at a time. My experience, no matter what GTO I drive, is that they will run OVER thermostat temp on VERY HOT DAYS, period. And this experience is with MANY GTO's, not a single car with a suspect cooling system.

[AdamIsAdam]

Good info. Next summer I may back off the mod on the spring to have it lock up later since it runs well now. I do hear it moving air as I drive down my street!

I'll check vacuum too some day. Taping a gauge to glass is much easier than running along side the car at 65mph

[Formulajones]

Car Craft did some dyno testing of cooling fans probably 15 years ago??? Memory is fuzzy but here's an old article about it.

Interesting read. Fans can suck quite a bit of HP apparently.

http://www.network54.com/Forum/21565...+Fan+Dyno+Test

[HWYSTR455]

That's what I was trying to get at, vacuum at highway speed. You figure 65-70 mph, M-21, 3.42 gears, that's got to be in the 3000+ RPM range, but the kicker is, throttle position.

You're probably at 1/2 throttle, with the blades open that far, I bet you have less than 8, if not less than 6" of vacuum. So no vacuum advance. That's why it runs hot at highway speeds.

.

[AdamIsAdam]

Originally Posted by HWYSTR455

That's what I was trying to get at, vacuum at highway speed. You figure 65-70 mph, M-21, 3.42 gears, that's got to be in the 3000+ RPM range, but the kicker is, throttle position.

You're probably at 1/2 throttle, with the blades open that far, I bet you have less than 8, if not less than 6" of vacuum. So no vacuum advance. That's why it runs hot at highway speeds.

.

Very interesting. I'll hook up a gauge. I will say this, when I was using a different vacuum can that wasn't fully engaging at highway speed, that's when I was getting the "trailer hitch" surging, which went away when I changed to this can.

[Formulajones]

Originally Posted by AdamIsAdam

Very interesting. I'll hook up a gauge. I will say this, when I was using a different vacuum can that wasn't fully engaging at highway speed, that's when I was getting the "trailer hitch" surging, which went away when I changed to this can.

I tune power valves on occasion driving with a vacuum gauge. It's interesting how quickly it will move when throttle is moved quickly, and how easy it is to dip into the power valve circuit.

Also interesting how we loose 3-4 inches of vacuum up here at 5,000 ft vs sea level. Makes PV tuning fun. Sometimes you tune it up here and then end up with a part throttle stumble down at sea level because you aren't getting into the PV circuit soon enough anymore.

Haven't had too much issue with vacuum advance really. Only really noticeable on the cans that have a wide timing/vacuum range. When running manifold vacuum on those cans, adding 3-4 inches of vacuum when driving down to sea level kicks up the idle a couple hundred rpm. On cans I run with a shorter range where they are all done at say 8 inches of vacuum, it tends to not be a problem because it's already running max vacuum advance most all the time, even up here at 5,000 ft.

[Sprocket]

I've lived in Texas my whole driving life (Houston, Austin, and Fort Worth). I've driven my '70 GP in complete stock form (high compression 400, factory cam, TH400, 2.93 gears, factory timing, and A/C) and in hot-rod 455 form (455, electronic ignition, 3.42 gears, and still with A/C). Using it as an example (i've had numerous other pontiac from mild to wild with and without a/c), I have found that the cooling system works best and suppresses overheating better when I ran a 195-degree thermostat. The engine runs great at that temperature and certainly no worse than at 180 or so. If your engine is consistently running hotter than the thermostat rating (more than just a few degrees), then the thermostat is just always running wide open and doing nothing anyway other than acting like a restrictor plate. I've always heard that running an engine in the 190-210 range is best for cooling efficiency, engine efficiency, power, and minimizing engine wear. Except when it does not open or close at all, the thermostat really is the component that has the least to do with cooling.

[Sprocket]

Correction, my thermostat is a 190-degree. Just checked my records on that.

[Will]

This brings up a question -

Should a thermostat be fully open at its rated temp, or is the rated temp the temp it begins opening at?

[Formulajones]

Originally Posted by FrankieT/A

Not necessarily true. I have FI on my car and one of the breakpoints for engine temp is 170. My car had a 160 thermostat in it from the carb days. My temp would only get to about 156 or 157. Then I brought the car to North Carolina last week and warmest it would get was 152 (40 degrees outside). I was trying to tune the FI and figured I'm never going to get this right unless I get the temp where it needs to be. So, I changed the thermostat while up there to a 180 Stant superstat. Now my car only gets to about 172-174 which I'm good with because it brings me over the 170 breakpoint I was looking for. Point is my car still does not get to thermostat temp even back in S Florida. Both thermostats did the same exact thing and one was about 5 years old and one brand new. In theory it should bring the temp to thermostat temp. I do have a Flow Cooler wp with about a .010 gap, an aluminum radiator, fan clutch and aluminum heads. My temp guage is confirmed by the FI coolant temp sensor.

And let's not forget thermostats don't open and close...they modulate.

Originally Posted by Will

This brings up a question -

Should a thermostat be fully open at its rated temp, or is the rated temp the temp it begins opening at?

For this to be clear and everyone understand, these aren't set temps. Frankie, My statement above holds true and to the point, engines won't run cooler than the stat rating, that's what they are designed for, but if we want to get technical then some things have to be explained.

I'm sure I'm not the only one here that has watched a thermostat work in a pot of hot water and a temp probe.
We'll use Frankies example of a 160 stat. On the stove I've had a 160 in hot water. 160 is just a general temp rating. It actually starts to open around the 154 mark and isn't fully open until about the 165 mark.
So yes, it is possible to have it run only a few degrees cooler than the stat rating, my chevelle does this on cooler days, it will run 157-158 on the gauge, because the stat is already just cracked open at this point, and coolant is flowing coupled with very cool ambient temps. Usually this can be achieved on a car that has an excellent cooling system.
I explained it the way I did at the risk of generalization for the sake of making things more simplified here.

[70GS455]

Originally Posted by Will

This brings up a question -

Should a thermostat be fully open at its rated temp, or is the rated temp the temp it begins opening at?

Doesn't really matter - the relevant issue is that the temperature thats stamped on the tstat box is the desired operating temp of the cooling system. Every vehicle I have owned will register on the temp gauge the desired operating point of the tstat (within measurement accuracy) , as long as the cooling system capacity is adequate or it's cold enough outside (i.e., winter) regardless of where or how much it is open.

Sent from my SM-T817V using Tapatalk

[dataway]

For $6 for a top of the line Thermostat rated at say .. 180 ... yeah, if it opens at +/- 5 degrees ... you are lucky. They are NOT made by NASA.

Add thermostat error and gauge error ... within 10 degrees and you should be a happy camper.

But in general .. any engine running with say a 180 thermostat and it's running more than 10 degrees below 180 .... the thermostat is bad. Absolutely no two ways about it. You could have the entire Atlantic ocean running through your radiator and if it's running 10 degree below the thermostat rating ... then the thermostat is broken.

[68 Firebird]

Yes there are some serious misconceptions about how a great many things work.
When I ran the one eighty superstat it performed fine, no complaints.
Just noticed that the car felt smoother and more responsive after a highway run that
really heated things up. That's the only reason I tried the warmer thermostat.
I mostly do very short trips and can say she purrs right at one ninety.
Some very true points were made in this thread and I am happy to see others have had
similar results as mine.

Was at a car show and a younger guy with a 78 trans am approached my car to see my
cooling setup as his was overheating. I explained mine was a stock setup of an AC car even though mine has never had AC. Every part was important and worked as a system.
Consisting of factory shroud, upper and lower baffles, clearanced water pump, 8" CP, 6.5"
WP, Aluminim rad with 2 rows of one inch tubes. Hayden Severe Duty fan clutch and
a 7 blade AC fan from a 68GTO.
-He concluded he needed to take some of the shiny pieces of and get some factory parts back on. well I had given him my cell and we texted back and forth for a while and
he finally went thru it all and got it resolved with his old rusty parts.

No answer is wrong.

I just enjoy tinkering.

Gerry

[Formulajones]

I see that a lot in Phoenix, even on not so hot days. Mid 80's now this time of year with Goodguys next week. Every time I attend that show with 2,000+ cars, it's a log jamb when it comes time to leave. It never fails, I always see several high dollar cars that can't even idle in traffic when it's just 80 degrees outside. They pull out of line and puke coolant. Something seriously wrong with those cooling systems if a car can't simply idle in 80 degree weather for 10-15 minutes or so. But, it's common for people to spend 10's of thousands of dollars on cosmetics, paint, interior, but drop the ball on their tune up and/or cooling system making the car unreliable.

[HWYSTR455]

Yeah, no kidding, can't idle for 10 min without having to shoulder, there's something wrong there.

I like rowing gears just like the next guy, but these days, I lean more towards autos. Guess I'm just getting old!

.

[Stuckinda60s]

Time is an important factor. The longer the coolant stays in the engine, the hotter it gets. Conversely, the longer it stays in the radiator, the cooler it gets, with the ambient temp being the limiting factor. Slowing the flow can increase cooling because the engine coolant is what causes the thermostat to open and if the water entering the engine is cooler because it has stayed in the radiator longer, then it can cool the engine better. If the system was free-flowing, the engine would almost certainly run hotter if the ambient was high. But with the thermostat and its orifice being the limiting factor that it is, slowing the flow, the temp may well drop if the system is in good shape and the flow is slowed.

Not to hijack the thread, but I think it's been pretty well covered. Now, here's an interesting question. If you halved the number of vanes on the water pump and kept the speed the same, what happens to the cooling? I've got some ideas and input, but I'd like to see what you guys think and why.

[dataway]

I think you are correct. I think the cooling systems were designed for a particular flow rate, a particular T drop across the radiator, a particular T increase though the engine and a particular ambient temp range.

In other words ... they probably knew what they were doing. And if a "user" alters one of these parameters without making corresponding changes to the rest of the system, there is going to be a imbalance that causes problems.

[Stuckinda60s]

Looks like this thread has run its course, I guess I'll start another.

[STEELCITYFIREBIRD]

Originally Posted by Stuckinda60s

Looks like this thread has run its course, I guess I'll start another.

[dataway]

I always lean towards a starting point of a stone stock system in very good shape. After all, a brand new GTO in 1968 could drive through Arizona with the AC on, with hood insulation, sitting traffic and not over heat. And they could probably do the same when they were four years old. Otherwise there would have been a huge outcry.

I think a lot of us live in fear of overheating because 35 years ago we hopped up our cars, added headers, lower gears, pulled off OEM parts that "seemed" unnecessary and we ended up with an over heating car .... usually we thought it was because our car was now so bad-azzz that it needed modifications to make it run cool. It was actually because we just screwed up, or didn't maintain the absolutely adequate stock cooling system.

Those stock four row radiators are huge, and in good condition, with shrouds, air dams, sealing panels and the right fan can cool just about anything.

My 2011 GMC truck with HD cooling (5.3) has only two electric fans ... on 90+ degree days ... in 6 years, I've heard ONE fan come on maybe a dozen times. I've heard TWO fans running maybe twice (while towing). It's amazing how that truck can run right at 220 on hot days with no fan running at all, even with the AC on.

(with the caveat that I don't know if they are multi-speed fans ... they might have a low speed option, if it does, it's VERY quiet)