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My 57 runs hot if I get stuck in traffic or the dreaded construction zone. It is a J2 with a 270 degree cam and big valves. I have added Vintage Air but have not been able to enjoy it. I replaced the 4 blade 19 1/2 inch fan with a 76 Olds 6 blade same diameter with a Hayden 2947 clutch.I drove from Missouri to Texas And it ran very cool on the hiway (160) but when trapped in traffic it climbed over 200 . So we did not run the AC and worried about it. I've been told to tape up the temp gauge , but non alcohol gas is not always available and the carbs loaded up. I had already ditched the electric fuel pump for a stock AC pump and now have set its pressure down to about 3 1/2 pounds. Olds offered a 6 blade and shroud on AC cars but I have sought one on this forum and elsewhere since 2019. The Hayden clutch engages at 175 but that is air temp not water temp. My steady handed Dr brother is going to try to Dremel me a new groove so I can re-clock the clutch to engage at a lower temp. There is little metal and this is a one time try. If that does not improve low speed circulation I will try a 6 blade rigid fan. I have searched the Pick and Pull for shrouds. The online adds are almost all by application. I will have to make it a 2 piece, The fan [fixed or clutch] sits 1 inch from the radiator. A shroud to fan center would need to be shallow about 2 1/2 inces
Has anyone adapted a shroud for the 57 or 58?
An electric 16 inch SPAL is intriguing but there is only 3 1/2 inches to the water pump. Would it pull enough air?. A pulse width controller?
Thank you for your council.
Last edited by Pat McClelland; May 30, 2022 at 05:36 PM.
Reason: adding photos
I’m not sure what to tell you other than normal temps at highway speed and hot at idle sounds like an air flow issue.
I live in 115+ summer temps with 10% ethanol fuel and have not experienced your issues. My car has the factory clutch fan, shroud, and a 4 core radiator. GM HEI with 18 degrees initial, 35 degrees total, and advance canister connected to manifold vacuum.
Thankyou both. My 68 Cutlass does not overheat but it has a shroud. I think a fixed 6 blade is where I'm headed. I still want to adapt a shroud but a need clues before I start mail ordering hundred dollar mistakes.
I have a fixed 6 blade hanging on the wall; you're welcome to it. I'm in central MD.
As much as I am not a "fan", this actually sounds like a good application for a front mounted electric pusher. Running cool at speed says that the system is good on the fluid side, but getting hot while sitting still points squarely at the fan not moving enough air.
For what its worth,
Here are some pics of my 56 - Super 88 fan and shroud ( I have a knee freezer add on unit 134 that works great) per the previous owner he had the shroud fabricated, look closely and you can see the rivets used for assembly, Its a 6 blade fixed fan she runs about 190 even in AZ, heat ( she usually stays in the garage if its above 100 ) no overheat even at idle . I have
no idea what it would cost to have a shroud fabricated
but here is proof it can be done.
That is a generous offer of a 6 blade. And that is a nice fan shroud!
My bro is going to grind a new groove in my clutch which may render it engaged more or even all the time
And I ordered a fan shroud for a 68 Mustang today. I hate that it is plastic but if I don't get it aligned perfectly I may like the decision. I'm worried about it being ugly too.
May not be relevant, but the big changes in my '66's were redoing the front rubber curtains that force air through (not around) the radiator, a rear shroud and clutch fan. In my later engine bay, the original curtains got stiff, wore out, got lost and so on - generally letting air coming in through the grille go where ever it wanted. Not optimal.
You can (or at least could) get a roll of masticated rubber sheeting from Fusick to make the front curtains (top, both sides, and bottom) and cut it to fit. Curtains really is a bad description, they really act like a front shroud forcing incoming air from the grille through the core and not letting it go around. You could also fabricate a "front shroud" if you're interested.
I cobbled together a rear shroud from md-60's parts but the photo above looks like it might be a better solution for your car. The only advice I'd have there is make sure the shroud covers the whole radiator core and consdier some rubber seals to force the air through the center of the shroud where there should be a fan, -- fixed or clutch driven.
For the fan, I've found more blades pull more air, for a given diameter. But within the group available that are the correct outside diameter GM had many different blade designs. If you can find more than 1 that spin the right direction, test a few to optimize cooling against noise. I found coolest was noisiest and have backed off to quieter, but hotter.
The key is I no longer dread nor fear construction zones, nor traffic. Can confirm this is a great feeling.
May not be relevant, but the big changes in my '66's were redoing the front rubber curtains that force air through (not around) the radiator, a rear shroud and clutch fan. In my later engine bay, the original curtains got stiff, wore out, got lost and so on - generally letting air coming in through the grille go where ever it wanted. Not optimal.
You can (or at least could) get a roll of masticated rubber sheeting from Fusick to make the front curtains (top, both sides, and bottom) and cut it to fit. Curtains really is a bad description, they really act like a front shroud forcing incoming air from the grille through the core and not letting it go around. You could also fabricate a "front shroud" if you're interested.
I cobbled together a rear shroud from md-60's parts but the photo above looks like it might be a better solution for your car. The only advice I'd have there is make sure the shroud covers the whole radiator core and consdier some rubber seals to force the air through the center of the shroud where there should be a fan, -- fixed or clutch driven.
For the fan, I've found more blades pull more air, for a given diameter. But within the group available that are the correct outside diameter GM had many different blade designs. If you can find more than 1 that spin the right direction, test a few to optimize cooling against noise. I found coolest was noisiest and have backed off to quieter, but hotter.
The key is I no longer dread nor fear construction zones, nor traffic. Can confirm this is a great feeling.
Chris
this!!^^^^
The best fan in the world is useless if air won’t go thru the radiator. All the tar paper shrouds that GM put on these cars are there for a reason. Seal up all the gaps around the radiator, make sure whatever air enters the grill has to exit thru the radiator, a good thermal fan clutch with a good fan, chances are it will fix the overheating issue.
Thank you. I have not received pictures of the 58 shroud yet. I am anxious to see what it covers. I'm considering a 70 Mopar BB shroud as they had a 26 inch radiator. But so often factory is best.
Ron,
On the recommendation for the odd number of blades & feathered tips, could you tell us what runs best for air (CFM) throughout & quietness?
I found a 7 blade fan and Hayden HD clutch very loud for a ‘66 big Olds. It could be the design of my car though. Or the noise could have come from the HD clutch
Your tip sounds totally solid & I’m inclined to believe it, but when I went to 6 blade vs. 7 blade on my ‘66 Starfire, the fan noise got quieter. It’s got a short clutch fan (Hayden 4765), but I have no idea what a “feathered blade” tip is.
If you have time, please help me understand so I can figure out what to look for in the boneyard…
What I’m trying to figure out is optimizing clutch fan CFM draw vs. noise & number of blades. My goal is to keep things cool at idle, but quietly enough so it doesn’t annoy me sitting in traffic. In my view ‘66 Big Oldsmobiles were not meant to be loud.
Many thanks in advance for enlightenment you have to offer
Fan laws govern fans and noise and cfm.
Any fan over about 1100 rpm becomes increasingly noisy and wastes power in the form of noise.
The idea of fan clutches is to lower fan rpms as temperature permits. A cold clutch fan as in first start of the engine in the morning should be noisy as clutch is engaged due to settling and cold silicone fluid. After a few minutes the silicone fluid warms up and the clutch disengages with a very noticeable decrease in fan noise and fan rpm. As the engine heats up the fan clutch will engage and disengage gradually to cool the engine. At hi-way (about 40 mph and greater) speeds the clutch should remain mostly disengaged as ram air does the cooling and the fan is not needed. An engaged fan clutch at hy-way speeds (noisy) indicates an overheating engine or defective clutch.
Clutch hub lengths should have half the blade in a shroud or within 3/4 inch of the radiator without a shroud for proper cooling. Clutches should not be used without a shroud as the clutch blocks off roughly a 6 inch circle of radiator cooling area.
Heavy duty clutch has a 15 to 20 degree difference in clutch engagement - generally has an exposed thermostatic spring for faster temperature measurement.
A feathered tip is where the end of the fan blade is rolled backwards. This allows the air to gently roll off the end of the fan blade tip more quietly. A straight blade shears the air making noise.
Engine fans and alternator fans were altered in the late sixties to make for quieter cars as evenly spaced fan blades make for throbbing fan noise (harmonic noises).
The amount of air moved per blade is around 60 cfm (not exact value,) thus a 7 blade fan moves about 60 cfm more than 6 blade at the same rpm and blade pitch. Look up fan laws and use a 20 inch blade as a model which is close to a car fan blade. They generally show cfm ratings for 2, 3, 4, 5, 6, and 7 bladed fans. Some even show noise levels and horse power required to drive the fan. Same fan blade takes 3 times more hp to drive the fan as the rpms and noise increases - check out cube fan laws
I am not an expert but have done too much reading mostly related to early car air conditioning for my 55 98 and 49 98.
a 66 big olds ( I have a 69 98) should be quiet but sometimes you really notice the fan noise on acceleration like at a long red light with the windows down then the noise should slowly decrease as ram air takes over cooling.
Many thanks for the lesson. Always helps to go deeper.
I may try the 7 blade feathered unit in my hoard again, but this time without the HD fan clutch. When I used it in 2014 with the HD clutch, it was too loud.
If your 66 big olds is a starfire, the axle ratio is likely 3.42 which makes everything turn faster than my 69 98 which has a 2.56 - makes for a lot quieter car as all the noise makers turn slower.
Also a factory a/c car has more insulation to keep the car cooler but also makes the car quieter.
If your car is missing the hood blanket - then there is more noise transmitted thru the sheet metal.
Look for holes in the firewall that lets in sound.
Extra carpet underlay helps.
If your inner fenders are metal - undercoating helps.
I have located a 58 shroud which is of the ring type as opposed to the funnel type. While the funnel type is calling me toward adapting a plastic Mopar #326 shroud I also figure that some really good engineers with plenty of time and money designed the stock AC shroud. In 1957 the Hydromatic was a $230 option while AC cost $430!
On the over heating issue, your red light is coming on? Radiator boiling over? You have real gauges? The radiator is in good shape? The water jackets are clean? Using a coolant recovery system? Timing set for today's gas?
Just as fyi, I used the water pump pulley and clutch fan from a 1962 olds 88 on my 1956. The 62 pulley is smaller than the 56 and the clutch fan kept the noise down. I did use the 56 shroud.
From your 58 shroud picture the 62 setup would likely work for you with that shroud.
A good sheet metal shop should be able to make a funnel shroud like the one in an earlier post.
I personally would prefer metal over plastic. My 69 98 uses a plastic shroud that is getting brittle.
I just made one for my 56, with 455. I got an aluminum radiator for a 70 something vista Cruiser, with a 455, so it should cool it. But with the limitations of having an Impala subframe in the car, to clear the steering box, I had to raise it up a couple inches higher than the bottom of the fan. AND it is pretty close to the fan. So a custom shroud was the only way.
I cut out a piece of plywood, one inch larger diameter than the fan (1/2" clearance all around), and drilled holes in the center to bolt it to the water pump. Cut a strip of aluminum, 1" wide, to go all the way around the circumference, and attached it with a few wood screws. Then built the rest of the shroud around it, to perfectly match the dimensions of the radiator. While I did it out of alum. and welded it, you could pop rivet it, or do it out of steel, as well.
Your use of a plywood buck is cool. And that 56 shroud is what I hoped the 58 would look like. My radiator is 26 wide by 20 high {core} and the tank is different so I doubt the 56 would fit even if I might find one. The 58 shroud has 3 stampings and welds. Was it cheaper or better in the minds of the engineers?
As is true of manufacters, they do the most cost effective method iat the time n order to maximize profits. A penny saved is a penny earned.
Simply make your own custom shroud. Olds answer starting in 1957 was a ring shroud. Cadillac did not offer a shroud (it was a ring type) until 1957. Many manufacturers did not even offer a shroud or heavy duty fan or radiator or generator until the customers complained about over heating repairs and dead batteries.
We use our new a/c cars to go to the store now days. In the fifties and sixties you only used a/c on trips. The first dead battery or over heated engine rumors spread like a wild fire and likely the sales person updated the customer after the sale to only use the a/c on trips.
A/c capacity was limited in the fifties to like 8,500 btu in 1953/1954 to 12,400 btu in 1955 thru 1957 (about 1 ton of a/c) to about 18,000 btu 1.5 tons of a/c) starting in 1958 to over 30,000 btu (over 2.5 tons of a/c) in the sixties you could cool a hot car more quickly. Powerful alternators and heavy duty radiators became part of an a/c package.
I know I want my 55 98 to cool like a new caddy. I have retro fitted several items to make my 55 a cool reliable daily ride. Fan 110 amp alternator from a 30 amp generator enhanced condensor and lots of insulation are few of my enhancements. Some recore to a larger radiator or use a custom aluminium radiator.
