jensenracing77

Let me explain what I have first.... My wifes Jetfire runs a little hotter than I like in stop and go traffic. It goes to 210 to 220 roughly in heavy stop and go but don't go over that. Everything is tuned well and not really my concern in this post. I run a 160 thermostat and it stays at 160 to 170 while on open road on a hot day. I chose 160 because it buys me time when I get to stop and go traffic before it gets to 220. Many times we are only in stop and go for 10 to 15 minutes and it does not get to 220 like that. Well, Last night we were cruising town with hundreds of people for two hours. I would get to open road at each end of town and the temp would get to 160 and then back to 210 again when back in town. It was back and forth between these two temps several times in 2 hours. My concern is with the large swing in temp. Should I just run a higher temp thermostat to prevent this wide swing in temp. Is this wide swing bad for head gaskets or the aluminum block and heads? Any thoughts on this?

oldcutlass

The wide swing is not an issue, however you might consider what the cause of the poor airflow through the radiator at idle and low speed driving.

jensenracing77

Short of fabricating a fan shroud I am not sure what the fix is for that. They never offered a shroud for these cars and not good at fabricating something like that. I do have a 6 blade fan instead of the original 4. The underhood temps on these cars is crazy already with the turbo sitting on top of the intake. Before I took my 4 speed car apart it never got above 180 no matter what I done and it had the original 4 blade fan and original radiator core.

oldcutlass

It wouldn't hurt to try the other fan.

matt69olds

Could you adapt a shroud from another big car? I’m not familiar with Starfires. If all else fails, big electric fans.

jaunty75

220 idling in traffic on a hot day is just fine. Your problem is that you have a temperature gauge. If you didn't have one, you would be driving your car without a care in the world. But because you DO have one, you're constantly worried. The solution is to get some duct tape and cover up the temperature gauge.

I'm not kidding.

jensenracing77

As I said in my first post, I was not really asking about the 220, I was more worried about the wide temperature swing between 160 and 220 several times in one night and if I should bump up the thermostat to 180 to lower the temp swing back and forth or if it even mattered. Didn't know if a 60 degree swing was bad on the head gaskets or something like that.

jaunty75

My advice still stands. If you had only an idiot light, you would be driving your car and enjoying it. But the temperature gauge has ruined that.

What thermostat did the engine come with originally? Probably a 180. So why did you put in a 160? Because you were trying to fix something that wasn't broken. An engine running at 160 to 170 on the open road is not necessarily a good thing. Engines can be damaged by running too cool as much as they can be damaged by running too hot.

Put the 180 back in, the temperature will stop swinging so widely, and then put some tape over the temperature gauge.

droldsmorland

Try a 190-195* HD T-Stat.
Does the system need a good flush?

jaunty75

The '62 Olds chassis service manual says that the F-85s should have a 170 thermostat.

Schurkey

Of course running 50 degrees above the thermostat rating is a problem. Where do folks come up with the nonsense that having a thermostat wide-open at idle or cruise ISN"T an indication of fault?

I wouldn't be thrilled with the temp swing, either. Yeah, the temperature swings more than that every time you warm-up the car from cold--but I'm not happy with the constant 50-degree swing in terms of engine expansion/contraction given the aluminum construction.

First Guess: Faulty radiator. Corroded/scale-filled tubes, or the air-fins have corroded away from the coolant tubes.

Of course, all the usual items are in question--fuel mix, spark advance, airflow/ducting of the engine compartment, radiator condition, coolant flow, pulley ratio, and the list goes on and on.

Does that turbo engine still have a functioning Turbo Rocket Fluid injection system?

Koda

If the car runs fine down the road, the radiator is ok. If the problem is at idle, airflow is the issue as said above. I don't think that temperature swing is going to be a problem. If you consider a higher thermostat, go do the slow roll idle thing for a long long time to make sure the car actually gets stable at a temp. If it does, the higher stat would just keep it higher on the low end. Perhaps consider a high flow, high temp stat. I had on the road high temp issues with my Chevy. I put in a 160 degree Stant superstat. The temperatures do change, but, it stays lower at the high end due to more flow. It needs a redone radiator.

Were there flaps of material sealing the radiator front to the grille opening? Maybe those are needed if so. Which fan did the turbo cars get? Is the radiator dirty?

I suppose you could run another pump system and spritz the radiator with rocket fluid when too hot. (That's about 1/3 serious.)

MI68442W30

Eric you should also add a bottle of water wetter to the cooling system as well as a high quality thermostat

69CSHC

I think shroud is precisely what oldcutlass is alluding too. I'm with Matt as far as looking for a possible donor match that only needs slight alteration. I've had non shroud and shrouded Olds V8s. World of difference, shrouds should be standard on all V8s period....


With that said I couldn't agree more with jaunty75 these cars were just not that precise nor do they need to be, they are not delicate by any means. Cant speak to the turbo Jetfire but this era of Olds V8 run hot. Both my first and my current Olds only had/have dummy lights. Eventually I will likely go with real gauges because I enjoy occasional track time, so far every single pass has been an educated guess as far as ideal temp goes. Other than that I would be fine with factory set up forever. Definitely don't want to drive myself batty with a gauges fluctuations.

My first, 1967 Cutlass Coupe 330 V8 was factory 4 blade, no shroud, 2 row rad. She overheated once in a blue moon.

My current, 1969 Cutlass Coupe 350 V8 is factory 7 blade. with shroud, 3 row rad. She has never overheated with me, knock on wood !

(Which includes going to the track on a 95 degree day, I overheated she didn't. A couple of hundred miles including several 1/4 mile passes, within a 6 hr period)

Shroud, shroud, shroud !


P.S. Once again jaunty75 absolutely nailed it in post 6 and 8. If there was a sticky for a dedicated temperature section. They should be it. At least as a initial heads up.

My442

Use a Robertshaw high flow thermostat.

I recommend 180 degrees.

69CSHC

I believe this is really more of an issue when the heads and block are of different metal like the notorious Cadillac HT4100. Although once again if this is a concern a shroud should help minimize the large fluctuations you are experiencing.

Good point, forgot about those.

jensenracing77

The cooling system is all good. I am not really worried about the 220 it gets to at times. It is really rare that it gets there because I don't usually have much stop and go driving and if I do it is not more than about 15 minutes. This past weekend was an exception to that. I was only wondering if I should go with a higher thermostat to get a more even temp range and less of a swing. I actually like the 160 T stat because when it is running that cool, it boosts much better and pulls harder. Not that it is a muscle car but I do like to boost with it now and then. I think I am just going to leave it alone. I do plan to build a new fluid injection and carburetor for it next year and may switch to the original style door t stat then.

jensenracing77

The fluid works fine. It is not any big deal for an engine to run hotter than the t stat. The t stat only controls the minimum temp. I could put a 100 degree in it and then it would be 120 over and still be the same as now. I could put a 200 in and only be 20 over.

matt69olds

The Starfires are turbocharged? Like I mentioned earlier, I’m not familiar with that vintage car or engine.

If it is in fact turbocharged, and knowing how touchy turbo engines are with air temp and engine temp, I would want to keep the engine on the cool side of the temp gauge.

Id seriously look at adapting a shroud from a different Olds big car. If a shroud isn’t a easy swap, I’d look for GOOD quality aftermarket fans, or OEM fans from a big car. Generally I’m not a fan of electric fans, but in this case if there is no factory option, then electrics are a good option.

If the good high octane gas like what was available when this car was new, I probably wouldn’t worry about the temps. Unfortunately, today’s premium fuel is about the same as regular gas back then. Detonation and turbos don’t play well together!

83hurstguy

The problem with a large temp swing and variance is that all the clearances change. Bore shape/diameter, ring conformance to the cylinder wall, etc. Old engine blocks are nowhere near as stiff/dimensionally stable as the new stuff so they'll move around more. That's being picky, I'm not sure that you'll see a real problem with it.

I agree that you want the cool water for power and boost when you're moving. I'd probably try to figure out how to get more air across the radiator, custom shroud or better fan.

62 Cutlass Convert

Hi Eric,

There are lots of shroud kits you can adapt. I agree sounds like an air flow issue at low speed, a shroud would make a difference in that flow. Northern Radiator has a bunch of aluminum generic shroud kits you could adapt with a little creativity. Summit and others sell them and Northern will talk to you directly about them.

You have any other heat exchangers in front of the rad-trans or A/C? You would see more effect of those at low speed vs. at speed.

Where you pulling your temp gauge from-replace the stock idiot light sender or?

You sure your gauge is correct? I had a bad SW sender that was good at 100 and off something like 35degrees up at 180!
Talked about the journey on the Jetfire forum.

Layne

69CSHC

Matt its a Jetfire, Jetfire's are turbo charged Cutlasses which were compact cars in early 60s. As you probably know Starfires are full size tanks. ( meant affectionately)

So polar opposites in one sense.

matt69olds

Got it!!! I knew about the Starfires,I knew those were the big cars. I also knew about the first Cutlass body style. I also knew a little about the turbocharged engines. I just didn’t know how all that random knowledge fit together, until now! Of course, by the time I need or can use that knowledge again, I will have forgotten it.


The say memory is one of the first things to go when you get older. I don’t remember any of the other things that go as you age, maybe it’s memory?

62 Cutlass Convert

If you're interested in checking out the Jetfires go to oldsjetfire.com for the Jetfire site.

Its also for the olds F85 platform 61-63. The F85 base, Cutlass, and Jetfires. Very unique cars for the time, a precursor of things to come which GM dropped.

droldsmorland

Jensen, If the system is good like you say above...nothing is missing etc... Im telling ya try the 190-195 HD Stant. What do you have to lose...a little time and coolant. Report back.
My BBO 68 stays at or below 200*F

Schurkey

Your thermostat has UTTERLY LOST CONTROL of your coolant temperature at low speed. That in itself is a problem.

The purpose of an automotive thermostat is to remove efficiency from the cooling system, so the engine will quickly warm up, and maintain a minimum temperature in cold climates. Your cooling system is inherently so inefficient at low speed that the temperature is way beyond the control zone of the thermostat. A small part of the problem is that your thermostat's temp rating is colder than GM specifies...but only by 10 degrees, as someone else noted. I'm not a fan of 160-degree thermostats, but for a high-compression antique with a turbo and known detonation problems...I'll make an exception.

If your cooling system were working properly, at idle or low speed--when the fuel flow and therefore horsepower are low, and therefore the heat generated is minimal, your engine's temperature would be at or just above the thermostat rating--well within the thermostat's control zone between "shut" and "wide open". The cooling system would have excess capacity, for the heat generated by greater load. The fact that this isn't happening is cause for concern.

Apparently you need vehicle speed to enhance the airflow through the radiator. Perhaps you've got fan/shroud issues, perhaps the air fins of the radiator are corroded, folded-over, or dirty. Perhaps, given the age of the vehicle, it's some combination of problems.

RyanAK

Does the fan on the Jetstar have a clutch? Also, if the fins on the radiator are bent, they can dramatically reduce the CFM of air passing through the radiator. A couple passes with a fin comb could make a difference.

I know shrouds on full size GM squarebody trucks make an enormous difference in low speed cooling capacity. These trucks get modded and beat on so much that the original shroud and fan are long gone and/or have been "upgraded" (questionable...). A properly sized and fit shroud along with an efficient, properly working fan - even stock! - is usually all that's needed to keep big GM iron cool.

$0.02

Ryan

oldcutlass

Did you try the 6 blade fan? It needs to be spaced so its about an inch from the radiator.

cfair

I’m no expert on 215 aluminum V8’s, but I’ll offer up a few general tips that helped my 455 iron big blocks:

1) Buy, build, or install a shroud behind the radiator. Big difference. Size the shroud to cover 100% of the core (heat exchanger). Less coverage means the car will run hotter. If you’re really into it, get a roll of flap seal from TrimLok and seal the gap between the core and the shroud to be sure 100% of the incoming air is being ducted through the core. For detail, the U channel pushes onto the leading edge of the shroud, the flap sits forced on the inside of the tanks (so it doesn’t blow out).

2) If you can get a 7 blade bolted up, that’s the move for max airflow through the radiator. 6 blade will work better than 4 blade too. Aim for maximum CFM (Cubic Feet/Minute). Clearance between the fan and shroud circle should be ~1/2”. Whatever shroud you get/make/use, go a 1/2” smaller diameter for the blade diameter for clearance. Motor mounts can deteriorate and cause fans to hit shrouds when the engine torques.

3) Get a heavy duty Hayden fan clutch that puts 1/2 of the fan blade depth inside the shroud, 1/2 out. Or close. Hayden heavy duty fans cut in at lower temperature and keep temps cooler, but they are noisier. I suggest getting standard duty & heavy duty of similar length (or close). See which you like best.

4) Olds in 65-66 used masticated rubber in _front_ of the radiator and A/C condenser to duct air through the heat exchanger. Effectively this is a front shroud. You can cut and make it for cheap. Just get a roll of masticated rubber from Fusick, cut it with scissors, and spring clip it into 1/4” holes in front of the radiator. I have no idea if your car has the 1/4” holes, but that’s what a drill is for. The point is to forcibly duct incoming air through the radiator fins from the front _and_ the back.

5) I second the recommendation for Water Wetter. In my experience it helps. Also known as Photoflow.

6) I’m a big fan of FlowKooler water pumps. They have an aluminum disc behind the impeller which helps move coolant. Their products are new, not rebuilt. I will be using their stuff from here, exclusively. I have no idea if their pumps are available for engine, but their stuff works great.

7) I’m a big fan of the Robertshaw high flow thermostats. I run 160 degree units for additional in-traffic heat up time, like you, but am wondering if the engines would run better at 180. These thermostats are available from FlowKooler, but I don’t want to sound like a shill.

8) Check timing, retarded timing causes more heat. But it’s a balance because too much advance causes knock.

9) Check your mixture at idle (like in traffic). Consider adding O-rings on the pointy end of your idle screws to seal up air leaks from the idle screws. I was surprised how much a good idle screw seal smoothed out my idle.

I know very little, but I believe that 215 lived for decades as a Buick, Rover, Leyland, and other makes. I’ll bet there are tips to be garnered from looking up that engine under other makes.

Finally, I just learned that most all Pontiac 400’s run hot. I was helping a friend revivify a Firebird 400. The accepted tweak seems to be run a Chevy big block radiator (with more surface area) in place of the factory radiator. This is probably especially true if you have A/C. When in doubt, you might want to cut the radiator support to drop in a bigger radiator and solve the problem (and stress) permanently. At the cost of having a non-factory solution. If painted, I doubt anyone would ever notice or care.

It’s no fun worrying about overheating when enjoying your old car. Today’s gas is cr*p, traffic is worse, and temperatures are up. All of those things contribute to over heating. Cool the h*ll out of it. When/as/if you gain confidence, I wish you stress free driving with a 180 degree thermostat.

Cheers
cf

Schurkey

They're noisier because they don't release properly when used with typical automotive fans. Hayden specifically does not recommend them for fans having less than 2 1/2" of pitch. I haven't seen anything on the Hayden web site saying they engage at lower temperature than the standard-duty clutches--they just have more drag that keeps the fan turning faster.

Mostly a marketing gimmick. I have a FlowKooler for Olds, turns out I got the wrong one for my application--I needed the extra-short one that FlowKooler doesn't make. I bought one for Father-In-Law's Pontiac, before I understood that the Pontiac engine has a stamped, sheet-steel baffle that does exactly the same thing as the FlowKooler disc. In SOME applications, they can be of benefit. Not all. And the pumps that FlowKooler modifies are imported. They don't "make' the pump. They take a pump someone else made, take it apart and modify it, and then repackage it in their own "FlowKooler" box.

How many do you want? I've got half-a-case of 160 degree Robertshaw thermostats. I think they're just about useless. 180 or 190-ish 'stats make sense. Some marine applications use a 160.

Yup. GM sold the tooling and rights to Rover. Rover eventually got bought by Ford. Ford continued to produce what was essentially a heavily-revised Buick design. One of their better engines. TVR, Morgan, and other independent makes bought the engines from Rover for use in their cars.

Only the ones with bum cooling systems or poor tune

jensenracing77

For the most part I have the answer to the question. I was not looking for advice on lowering the temp, just if the wide swing back and forth in a short time is bad