I dont think timing is the problem but...
Base timing 12°...vac advance disconnected and plugged at carb... no vacuum leaking!
Set idle so park to drive engagement is not harsh yet high enough rpm to deal with AC on.
Plug in the vac can. It should add another 8-10°...at curb idle. If its adding more install a stop to limit it to 8-10.
When does the centrifugal start opening and where is the total all in...both rpm and degrees?

You need to adjust the AF mix at the same time you are doing the timing to seek the highest possible reading between the carb screws & timing.
I will not use a timing light at first. I will use just the vac gauge, Then put the timing light on it to see what the results are.
Road test it.

The specs in a book are a starting point. Find what the engine likes with the sea level, driving style, and octane considerations.

Back to the un-cooling issue:

Install a 192-195° HD T Stat.
Those temps look a bit off...the 220+ temps.
Does the clutch fan have resistance when its hot? Can you hear it?
Can you see good flow in the radiator after the stat opens?
Rev the engine you should see it moving. Keep the cap off and let it come up to temp.

I have had one case where an impeller was the problem. It was spinning on the shaft and not pumping water.

Is this a gap?

 

Thanks for the tips to check clutch performance. I'm running a new Napa clutch P/N 2713 (crosses to Hayden HD 2747). It does not free wheel at all, but it spins a bit more than I'd expect when hot, definitely more than "one blade width". This is the 2nd clutch I've tried, replacing a Hayden 2747 under warranty from 3 years ago. I'm considering trying Hayden 2947 - the low profile severe duty unit.

 

I remember Joe P saying that the Diesel fan clutches were NOT thermally activated but were rather always fully engaged at idle and always free wheeling at speed. Isn't this the best way to go?

 

This site did something weird. I had this post typed up last night, went advanced, uploaded a snipped pic then hit send and I dont see it this morning.
Didn't confirm it last night. It looked as if it was going into a 2nd thread page as it was all by itself. It's gone poof. I'll try again:

I mentioned the fan clutch thing Koda is speaking to. Can you hear it spool when it's hot? Does it behave like Koda mentioned?
Install a new HD 192-195° stat.
Once, and only once, I saw an impeller slip on its shaft.
With the radiator cap off, let the engine come up to temp, then rev the engine ~500rpm, see if you can see coolant circulating in the rad..

Timing, though probably not a root cause, is (suggested):
-Base 12-14° (at warm curb idle with the A/F properly adjusted).
-Vac advance 8-10° (at curb idle, nipple on carb plugged. If it's giving you more than 10, install a stop to limit it to 8-10°).
Soooo.... together at curb idle, timing should be ~ 20-22-24°. This is dependent on ambient temperature, elevation above sea level, fuel octane, and driving style.
Where does the centrifugal advance begin opening, and where is it fully advanced (RPM/degrees)?

I adjust timing AND A/F with a vacuum gauge to obtain the highest vac reading, adjusting both of these circuits simultaneously. Only then do I grab a light to see what the time is.
Road test.

The book specifications are a starting point, tune from there.
Curb idle is: when you put the car in drive it should not be an aggressive hit on the trans, yet be high enough to prevent stall with the A/C on.

Is that a gap I see??

 

I can confirm that, before I added the elec. fan the pressure would get so high the belt would start squealing due to the compressor dragging. The additional cooling fan solved the problem. The a/c also cools better at idle.

 

The OP said the lower radiator saddles were for a 2/3 row radiator and were hammered so the 4 row would fit. That likely messed up the lower shroud mounting point, which alters the alignment. I ran into that issue back in the 80s.

 

I feel for you. My 88 Cutlass ran hot with a 403, mostly at highway speeds. A Grand National rad surround dropped my temps 30 degrees. Other things that also helped, getting rid of fancy aluminum underdrive pulleys, which also caused a charging issue. Get that flap replaced. I used a Mr Gasket high flow thermostat. It would work fine around town but close at high speeds! I used the Robert Shaw versions without issue, try a 160 temp from them. A closed impeller water pump should be on your car, it might make a small difference. I run my at 1000 rpm in park, which drops to around 700 to 750 rpm in drive. Increase the idle rpm and advance the timing as much as possible.

 

I have a built 455 engine in my cutlass and have an aluminum radiator with 2 electric fans on a fan controller.
it’s been hot this summer here in Ontario Canada but fans come on at 190 and car doesn’t get over 205

consider going with electric fan set up is my bet

 

Great thread with lots of good thought and experience. Fun to watch, though we’ve all read a great many Summer-Overheat thread in the past. This is one of the best I can recall in a while.

I live in temperate and occasionally Summer-hot SF Bay Area. A couple of weeks each year we get over 95°F, but otherwise 40-80’s most of the year.

Just to offer up a couple of things I’ve not seen here.
1) If there’s air gap between the fan shroud leading edge and the back side of the radiator, you can close it with rubber gaskets from Trimlok corp. More or less this is a rubber bulb seal mounted on a U channel which slips over the leading edge of the shroud with the bulb sealing the air gap to the radiator back side

2) Echo the 75/25 H20 to antifreeze. I did that and on my cars it works. I also use 2 bottles of water wetter since that seems to help. Yeah, it’s secret sauce but a decade or so of use tells me it works for me.

3) I just ran Thermocure through my 66 98 with 455 big block, put in a fresh 160° Mr Gasket high flow T-stat and now I’m finding it hard to get the car _above_ 160 in around town driving. I probably won’t put in a 180°F, but it’s weird driving a car that too cool…

4) The rubber curtains act as a “front” or forward shroud. If any of your original 3 or 4 are missing, that’s worth replacing. Their job is to prevent incoming air from going around the radiator core instead of being forced through it. They help.

5) It will eventually be said that some of this is mental/emotional. We’d all like these cars to idle/run from 180-195 all day in all temps, altitudes & locations. But they won’t. Part of the game is figuring out what you can live with happily and work toward that point.

Good luck on solving the issue. Lots of us experience around town heating issues. Sharing solutions helps.

Chris

 

The fan tips should be within a half-inch or so of the ID of the shroud opening. Yours look 2 or 3 inches away! You may have the wrong shroud.

 

Good catch.

If both the fan and the shroud can be identified by part # it would help to figure this out.

 

Strongly agree - Water wetter and similar products like the one from VP Racing are effective and not snake oil like many additives. O Riley's carries several brands on the shelf.

 

Chris, here's an explanation of how Water Wetter works...

Recall looking into a pan of water being heated. Just before boiling starts, small bubbles appear and disappear on the bottom. Those bubbles are the product of nucleate boiling.

The bubbles cover part of the surface of the pan bottom. The bubble-covered parts won't transfer much heat from the pan into the water because the vapor in the bubbles is a poor conductor of heat energy.

The same bubbles can show up inside your block and heads under some conditons.

Using Water Wetter prevents nucleate boiling, so it increases heat transfer whenever you have those conditions in your block and heads.

It's not just a secret sauce!

Gary

 

Very interesting Gary.

I am one that believes many of those so called "snake oils" actually do work to some degree. But I had no luck with water wetter in my 67 Cutlass... Now I know it was because my hot running condition was beyond its capability.

 

Gary
Many thanks for the practical explanation about Water Wetter. Very helpful. Empirically I know it works from a decade or more experience. I had not dug into nucleate boiling and/or related effects, but then that’s the cool thing about physics (+science more generally) - it works whether you understand or not. In this case I didn’t understand it, but found it worked.

That was good enough for me. My Dad was a scientist of sorts. One of his lessons to me was that what you should care about 1st is whether your solution works. It’s all the better if know & understand why, but 1st make sure the success pattern holds up. In this case, I stopped at “hey my radiator temps are 10° lower”. That was good enough.

Again my thanks for filling me in as to why.

Chris

PS: I recall Water Wetter being just 1 of such products. The other one I recall, probably chemically similar was “Photoflow”. The latter was developed for darkroom photography but found its way into the automotive world from some intrepid experimenter long before me.

 

I'm finding this discussion particularly interesting because we are hitting on optimizing all the details to ensure the system is operating well.

1. So far raising the idle to 850 rpm has not had a noticable impact on engine temp while idling. It has also been getting progressively hotter here in AZ, hitting above 110F all week. After a drive midweek, where the gauge indicated temps of about 220-230, I had "dieseling" or "engine run on" one time. Not sure if that is just related to it getting too warm, or perhaps running the lower octane gas recently (87).

2. As noticed in the photos, there are some gaps, about 1/4" wide, between the shroud and radiator along the sides (about halfway) and bottom. Thanks for the tip about Trimlock, in the meanwhile I used some weatherstripping to plug the gaps were I could. Hasn't made a noticable difference.

3. The fan blades are inset about 1/2-1" in the shroud. It's not a completely buried as it appears, but still not an optimal configuration.

I suspect that the reason the shroud doesn't sit flush and the fan is not centered correctly is due to the lower radiator saddles. This was originally a 3-row radiator car, the previous owner installed a 4-row radiator and just beat the saddles to make everything fit. I think the massaged saddles do not center the radiator perfectly, causing the fan to sit deeper than intended. Not by a much, it all bolts together fine, but it's costing some cooling efficiency.

Next steps to try:
1. Switching to 70/30 or 75/25 water: antifreeze
2. Maybe a severe duty fan clutch. Though I think my current HD clutch is locking up fine at temperature. Once hot, if you try to spin it, it stops within a fan blade width.
3. Trim the fan shroud to expose more of the fan blades.

 

My vote is to go with the severe duty clutch and 7 blade fan. Fact is, your cooling system is fine when its getting enough airflow. At idle, its not getting enough airflow. The severe duty clutch has greater lockup in both the free state and in the locked up state. The 7 blade fan moves more air than a 6 blade.

My car had no issues cooling with the 6-blade and heavy duty clutch, except with the AC on, and long, slow, climbs uphill in the heat. Changing to the 7-blade fan with the severe duty clutch fixed it.

That said, your fan shroud does look off. The saddles should not impact anything, as the shroud mounts to the top plate and the radiator support on the bottom. Neither of those moved. You can't really change the position of the fan shroud without moving the mounting points. But the opening does look way bigger than the fan, and it shouldn't be.

 

1. 75/25 water/antifreeze versus 50/50 will increase heat transfer by 8%. That's in the right direction, but minor.
2. That description indicates your clutch is operating correctly.
3. Trim the shroud to expose half the fan blade (the fan blade tip should be centered at the trimmed edge of the shroud; half-in, half-out).

Comment on posts 50 and 51. That may be an important problem.

 

Just rescanned the thread and am remembering my experiments from 10 years ago.

I did a fairly thorough search of Hayden fan clutches at the time and bought both SD (standard duty) and HD (heavy duty) fan clutches just to have options to test. A long time ago, you could download a PDF of all the fan clutches Hayden made and start picking the one that might work best for your application.

As I recall they had (and maybe have…) LD (light duty), SD (standard duty), and HD (heavy duty) models. The fan blade interface is 4 slots and the center hole which may or may not need a bushing to adapt the Olds fan to the nose of the fan clutch. There were a ton of fan clutches that had the 4 bolt/centerhole interface.

If the fan clutch you’re looking at has that fan blade interface, the next question is what length fan clutch snout should you get to locate the fan blades just far into the shroud for max airflow? That’s when you have to measure or get a few clutches and fit the ones that look promising and drive the car.

I ran the heavy duty clutch on my ‘66 Starfire with 455 (A/C equipped) for 3-6 months. It kicked in at lower temperature and spun more RPMs, per engine RPM than the standard duty clutch. In short, it worked to keep the engine cooler than the standard duty clutch did - as advertised. But in my temperate environment, I went back to the standard duty (SD) clutch fan because the heavy duty (HD) clutch was very loud on startup and when it kicked in. I’ve settled on the SD clutch over time, but am happy to have the HD backup under the house in case I need it. I’d love to run my A/C car cooler, but live with the temperature variance since I hate noise. Like, _really_ hate it to the point of extreme hours quieting the cabin with all manner of noise reduction solutions.

Point is, the HD clutches _do_ have lower temperature cut in points and spin your fan blades faster, but you’ll hear it.

I may have posted some results under my username from 8-10 years ago, if you’re bored and/or curious, have a look and you might find something helpful.

Upshot: Hayden HD is cooler & louder.

Final recent experience: I had a bad Hayden fan clutch out of the box in 2024. Really p*ssed me off since they’d been good ‘til then.

Cheers
Chris

 

You have a HEI distributor, correct? What is it out of? On nearly any stock GM HEI, 8 degrees is retarded to severly retarded. Most of the HEI I have seen have around 18 mechincal. But I have seen a few degrees less, 5 to 10 less and some similar to a points curve, 20+ mechanical. That is what the Chinese HEI I have is but also had an old Autolite reman with the same. All but one, the curve would not come in before 3000 rpm, no matter what springs. Little things add up, I think your fan placement and timing with improper sealing around the rad might be enough. Less antifreeze with an additive, higher idle, high flow Robert Shaw high flow thermostat and closed impeller water pump all add up. I fought years of over heating with my Olds 403. It got to like 250+! A proper high flow thermostat, not a Mr Gasket thermostat which actually closed at high speeds and the overdriven A/C pullies vs fancy underdrive pullies all made a difference. I cured the low speed problems with no thermostat then a Robert Shaw. I found no difference with a new clutch, a 7 vs a 5 blade fan helped as did a better radiator. But the GN surrounding ultimately fixed this car. The under rad deflector had a chunk missing, fixing, then replacing it made no noticeable difference. I tried everything possible, it sucked.

 

1. Just changed the coolant composition to 75% water/25% antifreeze. Probably helping a bit, but not a noticable improvement. Still climbs into 220+F when left to idle with the AC on for a while, say 10 mins for so.

Clutch, fan, and shroud are the next troubleshooting items.



2. I contacted Hayden to get details about their low profile HD clutch and their severe duty clutch. Low profile may center the fan better, but I want to get their details about temp engagement and lockup for the severe duty. From the specs I found, it seems like it's 70-90% lockup for HD and 80-90% for SD.

3. I can't find a part number on the shroud or fan. If someone has markings I should look for to ID the shroud that would be great. Additionally, I see a few types of 7 blade fans out there. Which do people recommend? Here's is a picture of the current fan and radiator shroud

 

When I had my 2004 Land Rover discovery with the old Buick engine design they all ran hot 220-240
until you changed thermostat to a 180

verify what thermostat you have. Sometimes they are mislabeled out off the box

 

75% water only gives 8% improvement in heat transfer versus 50/50.

So far the fan position in the shroud is one of the most obvious problems.

The more you advance the timing at idle, the cooler your engine will run. You could investigate the total timing and see if you have leeway:

• mark the timing tab at 35° advance
• disconnect the vacuum advance and plug the hose
• rev the engine until the timing stops advancing. Stay out of line with the fan blades and belts in case something gives way. If you need to go over 4000 rpm, something is wrong.
• if the timing is less than 35°, adjust timing to 35° at that engine speed (two people doing this is easier and safer)
• check your temperature at idle

 

If it was a thermostat, it would run that temperature all the time. Idle, freeway, stop & go, everywhere. It runs lower on the freeway. So its not a thermostat issue.

 

Yes and the temp spec of at thermostat is just when it opens to flow the coolant, i.e. a 160, 180, 195 thermostat will keep the engine at that minimum temp NOT MAXIUMUM.

However, differerent designs of thermostats can influence running temp like the amount of coolant they can flow..etc..

 

[QUOTE
2. I contacted Hayden to get details about their low profile HD clutch and their severe duty clutch. Low profile may center the fan better, but I want to get their details about temp engagement and lockup for the severe duty. From the specs I found, it seems like it's 70-90% lockup for HD and 80-90% for SD.[/QUOTE]

I don't suppose you asked about the DIESEL clutch. Supposedly, it is NOT a thermal type unit and is always fully engaged at idle and fully released at higher rpms. My first post about this was ignored.

 

Well there are lots of opinions on what should work or what's working for others.....I'll share what works great here for me here in CO on a 95* day....

I have a large upgraded tube aluminum radiator with two electric fans and built-in shrouds. I also run a 165* thermostat in all my old muscle cars to keep them as close to 165* as I can for max engine performance. I run a high-flow thermostat and a high-flow aluminum water pump along with the right sized OEM water pump and crankshaft pullies. My goal is to move as much coolant as I can through the system utilizing the high-end radiator and fans to dissipate the heat. IT works extremely well on my 442 and BBC Chevelle. My antifreeze/water mix is 50/50. This combo will let me idle all day with the hood closed on a 95* day no hotter than 180*. If I am driving....I can keep it closer to 170* as long as the fans run. I will note though that I do not have AC or a condenser in front of the radiator.

 

I don't suppose you asked about the DIESEL clutch. Supposedly, it is NOT a thermal type unit and is always fully engaged at idle and fully released at higher rpms. My first post about this was ignored.[/QUOTE]


I will ask about it. I've contacted their customer service tech line and I am still waiting to hear back.

 

What is your fan dia.? IIRC it should be 19.5”.

 

My 70 455 with AC runs the stock 4 core, stock shroud, I have the "Thorton" 70 factory water pump, 180 Thermostat and now have "the Parts Place" 18" 7 blade fan clutch fan. Works great as combo. Biggest thing I see is your fan depth and maybe blades/diameter.
With the shroud sticking so far out from the radiator and thus your blades are in further, Try using the inner mount holes on the top plate for the shroud, I was able to do this. It pulls the shroud snug to the radiator and will by default also move your blades aft in the shroud. You may need to redrill the lower shroud screw holes too. But if you can get the shroud back, flush you eliminate bypass from radiator and your blades. This 1/2" may help until you get a clutch that moves the blades to the correct position.

 

Additionally, its a little snugger to the sides, but a great 19" fan is the GM 14006712 7 blade. Its also a little lighter than the 18" 7 blade. This was on my car when I got it,, but got wrecked when my crank pulley came loose. The 18" replacement has been working fine but I would not hesitate to go to the 19" if it was running warm.

 

I'll double check but I believe I have the 19" 6-blade fan. The blade pitch is ~2".

Thanks for the suggestion of the truck fan. I've been looking at this fan: it's a 19.5" 7 blade, pitch is ~ 2.25". I'm hoping the extra blade and deeper pitch will move more air and get the blades exposed a bit better.
https://www.classicindustries.com/product/3991431.html

I haven't heard back from Hayden yet, but I'm considering their heavy duty low profile clutch. It's about 0.5" shorter than the 2747 HD clutch. That would also move my fan back a smidge.

I'm not sure why the fan is so buried in the shroud. I'm almost positive it's a stock shroud. I'll check it I can use the inner most mounting points, but I don't think that will work due to radiator clearance. The shroud is flush against the radiator at the top, but there is a gap towards the bottom.

I'm considering trimming the shroud to be less deep, though as a stock setup that shouldn't be needed. If I trim it, I may have enough room for a 20" fan.

 

I know the Olds 400 and 455 share the same external dimensions but Im wondering if when the engine swap was done maybe the entire powertrain was unintentionally shifted forward... ever so slightly...

Shame you have to butcher a nice shroud. In any case here is a detailed suggestion with pic from Camaros.net.

Thanks to TomcatSTL of the Camaros.net forum. Post #4 here https://www.camaros.net/threads/new-...roblem.487423/

By the way the OP of that thread has/had a similar issue as you do. With pic of how deep the fan was sitting.

 

What distributor do you have and what is your total timing at idle? If you have 8 degrees, that isn't helping, only hurting. If you have the vacuum advance on the factory ported spot, you are way retarded. I have used water wetter and minimal antifreeze, only dropped a couple of degrees and most of that could be less antifreeze. Make sure your idle isn't too lean as well. Little things add up and might be enough to get from hot to good enough.

 

Assuming you have auto trans. It will contribute heat to the radiator also. Is trans in good condition? maybe throw a trans cooler on it, take some load off the radiator.
I have a small Hayden stacked plate cooler in line on the TH 400 on my D88 with a 455,140k miles, stays around 185-195 on the road 220-230 at idle, planning to add a small pusher fan in my massive grill for low speed/idle situations, but feel this is pretty close to N.O.T. for the car, factory light comes on at 240-250 I believe.

 

My convertible (no A/C) has a separate heat exchanger for the transmission too. It connects back to the TH400 with braided hose installed maybe 30 years ago. This certainly takes some of the load off the radiator, but with A/C, you’re putting yet another set of fins for incoming air to pass through which maybe just moves the heat load, not reducing it.

On timing, I’m using Progression Ignitions HEI. The key tweak is they allow you to build your own timing maps using your phone. This is off topic but they’ve worked well for a couple of years now. As I recall my advance at idle is set to 16°, or perhaps 14°, but certainly not 8. One of the tricks in that HEI is that there is no advance applied at all until 900 RPM, which is great for easy starting. I’m not recommending a high $ distributor to solve the problem, just reporting that my advance at idle is substantially higher than what you reported.

I believe the Hayden fan I’m using in one car is the 2747 and if I recall I’m using the 2765 in the other. I can’t remember which was which, but you’re on the right path looking at the HD,SD status and physical dimensions of the Haydn fan clutches to find a solution since the interface for most of their clutches is the familiar 4 bolt & center for the fan.

Chris

 

WearnWrals:
Have you solved your overheating issue? Many great suggestions here to dial that system in. I also battled overheating issues under various operating conditions in a 455 powered Vista Cruiser. One cheap and relatively easy test is to completely remove the thermostat and run without it for a while. Your summer warm up time in Arizona heat will hardly be extended but you can eliminate the thermostat as a cause if your problems persist.

If it turns out the thermostat was the problem, I suggest replacing it with the conventional OEM style thermostat shown in the top sketch below. The so called "high flow" design below it was just the opposite in my engine. The bottom balanced sleeve design turned out to be incompatible with the thick casting below the thermostat mounting flange on my aluminum intake, which made it actually flow less coolant than the OEM style design.

 

I had issues with the Mr Gasket high flow thermostat like the bottom picture closing at speed. The Robert Shaw, same design, modified by Stewart Warner with 3 balance holes worked fine. I only had one fail in the open position. Whether they actually flow more seems ro be in question. I still say his timing is way retarded and definitely not helping.

 

I am partial to the Stant Superstats myself.

 

also a ton of good info in this thread from years ago.. FYI


https://classicoldsmobile.com/forums...e-heat-105434/