atkinsom

I have a rebuilt 1969 455 60 over with Keith Black pistons, mild lunati cam, ported J heads and stock manifolds with 4 core radiator. Also have a shroud with a clutch fan. Nothing too radical. The car runs consistently between 190sh and 200 with a stant 180 thermostat in normal traffic and up to 65 miles an hour. Once I get over 65 it climbs up to 200sh and as high as 210 but never over. I'm trying to get the temps down and thought a Robert Shaw high flow thermostat might help. I had the rad tested before putting it in and the guy said it flows well but I have my doubts but before pulling a rad thought I would start with a better thermostat. Which one would be better from the link below...160 for all GM's or 180 for a Cadillac(probably works on olds?) thanks for all opinions if this isn't the way to go.

http://www.summitracing.com/int/sear...s?autoview=SKU

CutlassDad

With 190-200 coolant temps and a 180 degree 'stat, that's as good as you'll get. To get lower temps will require a bigger radiator, more water flow, or an increase in fan speed. The 180 degree 'stat will be fully open (or very nearly so) with 200-210 degree coolant.
Do you have the A/C fan drive setup for more fan RPM and the resulting increased water flow?

atkinsom

Thanks for the reply but no sure how to increase fan speed with the clutch. I've tried 2 different clutch fans off 2 different 1969 cars with AC and same result. Clutch appears to be working as it sounds very loud when it gets hot outside after running for awhile. Heater core in the car is bad right now so using a bypass cap on one side of the water pump. Is this bad as opinions vary. Should I run a hose from the one side of the water pump to the back of my edelbrock rpm air gap intake rear water outlets? thanks

oldcutlass

Since a thermostat only controls the minimum operating temp of the engine a change will not result in lower temps. If your temps are creeping up at hwy speeds, then its not your fan, clutch, or shroud. Your radiator my not be correct for the application or may have issues. Timing and carb issues can cause temp rises.

Intragration

If your temperatures are usually below 210, and 210 is the max you ever see no matter how you drive it, I don't see how this is a problem. I have a 2-row radiator, a shroud and clutch fan, a 195 degree thermostat, and my 455 quickly warms up to 205 and stays there unless I go on the expressway, in which case it goes up to 210, but never above. Again, to me these seem like fine temperatures. If your motor was recently rebuilt, it might be running hotter than it will when it's broken in a little more. IMO, you have nothing to worry about.

atkinsom

The reason I'm concerned is that everywhere I read it says it's running too hot and should be closer to 180-185 and stay at that temp on the highway when driving. Granted the motor has about 3000 miles on it after the rebuild so I figured that it's enough to break in. It's actually running a touch rich so shouldn't be a heat issue there and timing isn't overly aggressive as per my mechanic and builder. Maybe I'm overreacting but reading all the posts here and in other forums has me worried. Just want to make sure I'm not killing this new build and have to fork over more cash for not being careful. I'm probably going to take off that bypass cap off the rebuilt water pump and put a hose from there to the back of the intake to eliminate potential hot spots and see what happens.
Other suggestions are certainly most welcome. thanks again

oldcutlass

Your temps are normal with the exception of it getting to 210 at hwy speed. 210 is not hot but it should still stay around 190-200 at 70, which is why I suggested checking your timing or perhaps your radiator may have some minor issues.

jaunty75

I agree completely. None of the temperatures described by the OP are indicative of an overheating engine. It can run at 210 F all day long. The warmer the engine is, the more efficiently it runs. Too cool an engine leads to all sorts of problems, so this constant quest you see on this site of people trying to get their engines to run ever cooler is misguided.

Drive this car, enjoy it, and quit worrying.

atkinsom

Ok I'm sold on not worrying..I'll just reroute the bypass hose from the water pump to the back of the intake instead of using a cap off and be happy. Thanks guys for setting me straight and I'll keep an eye on the rad since it is an original 4 core rad from a 69 Cutlass.

lemoldsnut

What kind of fan are you using and does it have a fan shroud and the rubber along side the radiator to keep the air flowing through and not around the radiator? These are important things. If you are running a flex fan that is a huge mistake. A 7 blade clutch fan would be much better with a shroud.

Just some of the things that has helped me.

Octania

Retarded timing can lead to overheating

I put a high compression 403 in place of a 307 in the 85 442.

Initially overheated and had poor performance

I read up on altering the HEI to suit the HC engine, limited the VA travel, Set max timing to 35-36, used alternate weights on the MA system, then finally switched to manifold vacuum, which made all the difference.

Perfect well behaved motor now, and still using the original radiator. From the 307 setup. Clutch, car's original fan and shroud.

johnnyjaws

cant u put in a 165 degree thermostat in it

atkinsom

Using the factory original 6 blade clutch fan out of a 69. Tried 2 different ones and they both behaved exactly the same with a loud sound when the engine got hot. Have the rubber side mounts on the rad as well from fusick as the ones I had we're all torn up. Have the factory shroud as well. Also the air dam covers are all in place as well and are in decent condition. Thanks for the suggestions

Intragration

All this would do is increase the time it takes to get up to 210 degrees. It would also prevent the engine from warming up fully on shorter trips.

Fun71

Yes he can, but as already stated that won't do anything for his situation:

FYI, during the 110+ summers with the AC on if I drive at 70-75 (~3400 RPM) the temps creep up to 210-220, but if I slow down to 3000 RPM or less the temps drops right back to 190. I figure my engine is making more heat at 3400 RPM than the cooling system can dissipate.

oldcutlass

Understand and agree with you Kenneth, but he's not in 110 degrees right now.

jaunty75

If your engine was making more heat than the cooling system can dissipate, it would eventually melt. It's simply making more heat. Your cooling system is dissipating it just fine. But because it's making more heat, the system comes to equilibrium at a higher temperature. But the cooling system IS handling it. There's a limit to how high a temperature you can go, but even at 3400 rpm, you're not there yet.

Koda

Let me toss a couple things here.

1. Your radiator is more efficient at a greater delta T (that's change in temp) than at less of one. You get that two ways, either drive on cold days, or have the engine make more heat. As the radiator gets hotter, the amount of heat it can dump into ambient is more, because the difference of the temp between ambient and a hot radiator is more, just like driving on a cold day.

2. A thermostat is a flow restrictor. Depending on where the most restriction is, putting in a high flow thermostat, like a super-stat from Stant, may help, especially if it's a stock t-stat.

3. Getting hot on the road is a sign of the cooling capacity of the radiator not functioning as well as it should. Getting hot at idle is a fan thing.

I have a car from another GM division that the stock temp gauge was pegging 250 on the road. I hooked up an aftermarket gauge in the other head, and the gauge is accurate. I put in a Stant 160 Superstat, and the car now only gets to 220 ever, and usually is 180-190. The one I replaced was a low flow factory thermostat for emissions. My radiator is gunky, and will get redone when I restore the car. Runs great now other than an upper end tick which needs diagnosing. One data point, I know, but a hi flow stat did help a SBC.

Intragration

Good points, but it would be interesting to see what temperature you run with a new 195 thermostat. You may have gone from a failing 195 at 250 to a functioning 160 at 220. If this is the case, you'd also likely be running 220 with a 195, or a 180, or a gutted thermostat housing.

Koda

That's a valid comment. It could have been failing, not just poor. I may try another thermostat in a few years when I take it down for a while.

Fun71

Good catch. Thanks for correcting my mis-statement of the issue.

Professur

Just a note ... the boiling point of water in an open container is 212F. In a sealed system controlled to 16psi (your rad cap) water alone boils at ... 228F. Add in 50% prestone and it climbs higher still. But this is the average temp of the cooling system. It doesn't take into account hot spots in the engine such as siamesed cylinders or exhaust valves. Those points can still boil off water if it doesn't move past quick enough. If your water pump is working as it should, that shouldn't be an issue. The worry is that if those hot spots can get hot enough to boil the water, their temperature will shoot up to where it can boil the motor oil, leaving that hot point unprotected against wear. This is why the Min line on your kettle is where it is ... making sure there's enough water to move in to fill the gap when bubbles form as the water boils.

I'll just toss in that adding something like Water Wetter improves the heat transfer between the coolant and contact surfaces by reducing the coolant's surface tension without letting it foam. We use it extensively in water cooling computers. But before using it, I'd suggest a chemical flush to make sure there's no blockages or restrictions because of calcium. All it takes is one previous owner to have done a prestone change using well or tap water. Of course, a chemical flush can open pin holes in old rads and heater cores ... but if it does, you were already running on borrowed time. Better to discover it in your driveway than on the highway 100 miles from your tools.

Oldsragger

Im going with 160 termostate, if it will be to "cold" inside the car cause of heat problem i will instead place a plate in front of radiator with some few holes in to Keep thw radiator warmer. Cars use to do have it when its cold weather outside to get more heat inside the car if its not help with a higher termostat temp.

However i will install 2 x 14" or smaller fans as Well to have things cool down in hot cruisin summerdays. Just tought its ok to have the extra cooling aviable. Without the big heavy propel fan. (the propelfan is blowing nice actually)

Professur

If you have an automatic transmission, this is not a good idea.

jaunty75

It's actually more like 251 F. Scroll down to the first table on this page. The pressures listed are absolute (psia). Atmospheric pressure is the 14.69 shown in bold.

http://www.engineeringtoolbox.com/bo...ter-d_926.html

The 16 "psi" that the radiator cap works to is 16 psig, or 16 psi above atmospheric pressure. So that's 16 + 14.7 or approximately 31 psia. Looking at the table, 31 psi is at about 251 F for the boiling point of water.

Fun71

Adding to the above, ethylene glycol doesn't help increase the boiling point nearly as much as it decreases the freezing point. A 50/50 mix increases the boiling point by 15º over plain water and a 15 psi cap (which has a boiling point of 250º in the previous chart), but it decreases the freezing point by 64º.

freeze_boilchart-1.jpg

rustyroger

I don't think you will have any major problems with your cooling system if it's not at its best in Norway. Arizona heat is another matter. I don't mean blown gaskets or completely plugged radators, just not quite so good as when it was new.
I don't understand your reasoning, why have your engine so overcooled you need to obstruct the radiator to bring the temperature back up?.
Apart from anything else you might have trouble getting the carburettor properly tuned as well as the heater not working so well. Surely a good heater might be desirable in your climate?.
A clutch fan in a properly fitting shroud should be ample for cruising, the fan isn't needed then anyway, the ram affect of moving through air is all you should need. If the car runs hotter as it goes faster then you have a problem that more fans won't cure.

Roger.

Oldsragger

Well will try anyway this summer with 160 termostate, its easy to swap to another one anyway think its 180 terno i have used before, actually no problem with that.

Oldsragger

Yeah, the climate is much difrent here, lol, yeah you have a point about this...

toymobile

Most over heating comes from the liquid passing through the radiator so fast it doesn't have time to COOL.
A fan clutch made for the DIESEL Olds will help as it draws more AIR in a shorter time, Ford trucks use a good fan clutch as well (BOLTS RIGHT ON)Ones made for the V belt engine . Good luck.

jaunty75

This is one of the greatest misconceptions in all of automotive engine cooling. Heat transfer increases with increasing fluid velocity through the Reynolds number, so slowly-moving fluid would be a cause of overheating, not a mitigator of it.

Engine overheating can be caused by many things (coolant leaks, wrong coolant concentration, bad thermostat, blocked or restricted fluid passageways, corrosion build-up, faulty radiator, worn hoses, bad fan, bad fan belt, or a faulty water pump and even wrong engine timing), but coolant moving too quickly is not one of them.

MDchanic

Absolutely false.

This was discussed on CO, starting about here, as well as in several other places.

- Eric

Koda

People get confused about delta Q / delta T, vs delta Q / delta in^3.

In non engineering, what I mean is that you want change (delta) in heat (Q) in regards to time (t) not in regards to the volume of water (cubic inches). So, while a slower water flow may be able to pull MORE heat out of the water that is going through the radiation, the LESS amount of water going through the radiator will cancel it out.

Example. You have an expressway toll booth. It has 2 toll booths. Tolls are 1 dollar. It takes ten seconds to get a toll. The max money per minute is 2 times 1 dollar times 6 10 second periods in a minute, so 12 bucks a minute.

Now you have another setup, 10 toll booths. Tolls are fifty cents. It still takes ten seconds. Max amount per minute is 10 booths, times .5 dollars times 6 ten second periods in a minute, so 30 bucks a minute.

You can see that, even though the tolls are less (heat lost per each chunk of water) the overall money (heat lost per minute) is much higher since the water is moving faster.

66-3X2 442

This fan clutch is the absolute best unit for an Olds car. I have been using it for years without any problems with overheating. I have one on my 66 right now and it works great. Every Olds guy I have turned this clutch on to love it. Buy one for your car and you will not regret it.I had one Olds friend that was having problems with high engine temps and I got him one. He put it on before making a RT66 tour and he called me from the tour saying it was 95* and the engine temp was 190* with the A/C on.
http://www.ebay.com/itm/Engine-Cooli...c11097&vxp=mtr

Another note. There use to be a guy who wrote an article in JWO about technical issues with Oldsmobiles. He had an article about thermostats and he said Olds used a different unit than some of the other GM brands. He said that the Robertshaw unit was a very good equal to the OEM Olds unit. I can't really remember the reason(s) for this but he seemed to know a lot about Olds. I think he was an Olds engineer or some other title that allowed him to write an article.

Fun71

I see that you already have a realization that what the guys posted above is correct; you just don't realize it yet.

Let's examine this:
See Koda's explanation above as to why this is inaccurate.
Aha! You DO understand the concept that more flow = increased heat transfer. You just need to think about the water flow inside the radiator the same way you are thinking about the air flow across the outside of the radiator. It's the same principle.

MDchanic

Another way of explaining it is by pointing out that the rate of transfer (of anything) increases as the gradient increases (chemical concentration, pressure, heat, etc.).
As the difference between two levels increases, the pressure for them to equalize increases disproportionately.

That is why, if the temperature outside is 20° cooler, it costs a certain amount of fuel to heat your house. That amount increases if it is 40° cooler, and it increases A LOT if it is 60° cooler.
As the difference in temperature between the inside and outside increases, the flow of heat from one to the other increases, and increases MUCH more as the difference increases.

In the case of a car radiator, the radiator will shed more heat faster if it is hotter than it will if it is cooler.
Therefore, the hotter you keep the radiator, the more heat it will throw off.
So, if you have coolant moving through the radiator very slowly, some of it will cool noticeably as it passes through, and the cooler areas of the radiator will release less heat, but if you have coolant moving through the radiator quickly, it may be less cool by the time it is nearing the radiator outlet, but it will have transferred more heat to the air as it flowed through.

Also, note that if the coolant is moving slowly enough to cool off substantially inside the radiator, that means that the coolant that is still inside the engine is moving slowly enough to heat up substantially, possibly enough to begin to boil in the areas adjacent to the hottest parts of the combustion chambers (thus creating a layer of steam, which transfers heat poorly, or, in other words, which insulates the coolant from the combustion chamber).
If the coolant moves faster, the temperature of all the coolant will be more equal, which will reduce the chance of hot spots.

- Eric

seansolds

On a side note..another way is your exhaust gases and how fast it is leaving the engine! I found out I had too much back pressure when I had run dynomax mufflers dump just before the differential. My gauge which I replaced would climb 196, 198 with a 180 thermostat in it. With a 4 row and a shroud and no clutch. I had to redesign my exhaust which dropped it below 180 driving summertime! No fan clutch. Prior I was running hot enough I installed a back up electric fan, which I never have had to use. Just a thought!

jeffsims

I might be high jacking this post, so if it does come across that way, then my apologies. I am having what I think is a cooling prob. Stock gauge, so I do not know the temps. When I am up to operating temp, it stays at the mid range of the temp gauge. After I shut it off for a few minutes (like to pick up some food) it is almost maxed out immediately after restart. It does drop fairly quick once I start moving. Normal?

MDchanic

Yes.

- Eric

atkinsom

The clutch vendor indicates that it's not compatible with a 1969 Oldsmobile of any trim level. Is this a universal unit that you didn't have to modify? will the holes line up proper with the water pump pulley as I noticed the clutch has 8 holes. Just a quick question making sure before laying the money down if I decide to go this route in the future. Thanks