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Unfortunate that airflow data is not known - could be of use to many others; not just myself. With a closed hood, a smart phone and a relatively low cost velometer, air flow could be measured at the radiator. Thanks!
Not being mean here but nobody else cares Your obsession with this is your own. In 50 years of playing with these old cars I have never seen anyone look for or attempt to try and fix an overheating problem by such a method. Just pay attention to the suggestion of the people posting here that have real world experience with this problem.
I did a search on the DeWitts website for the radiator number you gave (66-124427) and couldn’t find it. So, I’m not sure what radiator you have in your car. As you probably know, original radiators installed in midyear small blocks were a stacked-plate aluminum design with a heat rejection rate of 4600 BTU/min.
The DeWitts Restoration Radiator (Model 941 for ’65-’67) is also rated at 4600 BTU/min. I know of no other aftermarket radiator for midyears with this high of a heat rejection rate. So, anything less is a step backwards in cooling capacity.
As Duke said, I’ve never seen radiator air flow data either. I have seen data on things like water pump capacity (57 gal/min @ 4400 RPM) and fan clutch specs (fan speed 3200-3500 @ 4000 RPM & 135-155*F), which are almost imposible for owners to measure. Data like this is available in the Corvette Spec Books available from gmheritagecenter.com.
Since heat transfer and air flow are the two things that matter most for cooling, after eliminating previous suggestions, you might consider a Spal fan to increase airflow.
Here's a pic of the rad. I believe that's the Dewitt's model number. Working on the other suggestions. Thanks,
EXACTLY! This is not rocket science and what the OP is asking for sounds like a typical engineer over analyzing the situation.
If you don't have the radiator sealed, at idle you are pretty much just "windmilling" the under hood heated air. With the radiator sealed, the original type fan with shroud and the fan sitting in the correct 1/2 in at the rear edge of the shroud it will suck air through the entire surface of the radiator. This is how the engineering team designed it at the FACTORY. No need to try and improve on it 50 years later. Unless you have increased the engine size or h.p. DRAMTICALLY there is no need for anything else. This assumes your radiator is not plugged, in good condition, no collapsed hoses and your engine is tuned and running properly. It is pretty hard to out engineer an auto company that had to satisfy customers in all climates all over the country. People just keep trying to reinvent the wheel though.
Below is a pic of the fan placement relative to the shroud. I believe it to be proper unless the pump to fan spool is of the wrong length. Can you provide more detail regarding:"the original type fan with shroud and the fan sitting in the correct 1/2 in at the rear edge of the shroud it will suck air through the entire surface of the radiator. "Specifically, what do you mean by 1/2 in at rear edge of the shroud? What's the rear edge and what part of the fan blade?Thanks again.
You may have other problems as questioned by other members as well but I would really begin with checking the TRUE temp. with a heat gun as suggested to see if you are really running hot or not.
It is hard to tell from your picture (s?) regarding the position of your fan in the shroud. It looks like you have two pictures there overlapping. Just look at your fan from the side of the car and see how far it sticks into the back edge of the shroud. You want no more than 1/2 way in from the leading edge of the blades. If it is too far in the shroud the fan will actually be pushing much of the air back in towards the radiator. You want the fan to be sucking the air from this "tunnel" the shrouds is forming around the rear of the radiator. To make it work efficiently you need to SEAL the radiator so it is not pulling air from AROUND THE RADIATOR RATHER THAN THROUGH IT. Go back to post #4 and #6 and follow those instructions to begin with.
68hemi if his cooling system is borderline functionally adding the rubber seals is fair from the answer. he needs to find the true reasons or even if he really has a problem. before he starts throwing parts at it
68hemi if his cooling system is borderline functionally adding the rubber seals is fair from the answer. he needs to find the true reasons or even if he really has a problem. before he starts throwing parts at it
yes but instead of focusing on the core problem you seem to wonder off to think non issue parts are a quick fix
You just don't get it.
Read the article YOU posted in post #2. take a look at page 6 "fan shroud and seals." It is called a cooling SYSTEM for a reason. The entire system needs to be right for it to work efficiently. You start with that and if you then have a problem you begin you investigation into other things that may be causing your problem.
Why is it that when there is a thread that I try to help someone out in that you have to challenge everything I say and have to have the last word? Again as with the last one, I am done and you can continue on so you can have the last word.
Here's a pic of the rad. I believe that's the Dewitt's model number. Working on the other suggestions. Thanks,
Yes, that is a DeWitts restoration radiator model 941. The part number 3155316 was the original GM part number with a 66E (May 1966) date code. Like I said, I know of no other aftermarket radiator for midyears with a higher heat rejection rate.
You just don't get it.
Read the article YOU posted in post #2. take a look at page 6 "fan shroud and seals." It is called a cooling SYSTEM for a reason. The entire system needs to be right for it to work efficiently. You start with that and if you then have a problem you begin you investigation into other things that may be causing your problem.
Why is it that when there is a thread that I try to help someone out in that you have to challenge everything I say and have to have the last word? Again as with the last one, I am done and you can continue on so you can have the last word.
all I am saying non AC cars do not need these seals to cool correctly. that is it.
You may have other problems as questioned by other members as well but I would really begin with checking the TRUE temp. with a heat gun as suggested to see if you are really running hot or not.
It is hard to tell from your picture (s?) regarding the position of your fan in the shroud. It looks like you have two pictures there overlapping. Just look at your fan from the side of the car and see how far it sticks into the back edge of the shroud. You want no more than 1/2 way in from the leading edge of the blades. If it is too far in the shroud the fan will actually be pushing much of the air back in towards the radiator. You want the fan to be sucking the air from this "tunnel" the shrouds is forming around the rear of the radiator. To make it work efficiently you need to SEAL the radiator so it is not pulling air from AROUND THE RADIATOR RATHER THAN THROUGH IT. Go back to post #4 and #6 and follow those instructions to begin with.
I have read through this thread and I can't help but wonder why GM changed the angle of the radiator on the 66-67 small block cars. i also wonder if the above poster has a engine that's been bored as that could contribute to heat rejection to the block.
I would seal the areas mentioned and see how that helps.
68hemi, I think it's your post showing 1963 windshield installation and clip position, very good post IMO and a great reference for anyone with those 63 questions.
I have read through this thread and I can't help but wonder why GM changed the angle of the radiator on the 66-67 small block cars. i also wonder if the above poster has a engine that's been bored as that could contribute to heat rejection to the block.
Bored 40 over. Fan just less than 1/2 back into rear edge.Thanks for your input.
I would seal the areas mentioned and see how that helps.
68hemi, I think it's your post showing 1963 windshield installation and clip position, very good post IMO and a great reference for anyone with those 63 questions.
My 67 327 300 hp always ran hot (230 degrees F) with the original aluminum radiator in city driving. I didn't do much city driving so it wasn't that much of a problem. On the highway it ran at 195-210F. After about 13,000 miles the radiator developed a leak, being aluminum the radiator shops said it couldn't be repaired. I complained about the high operating temp and a radiator shop sold me a brass radiator for an automatic, he said it had more core layers and would cool it better. Its thickness was 3 inches compared to the stock aluminum at about 3/4 inch.
I bought it and had him change the thermostat to a 165F, that was the end of the hot running for that car. I had already tried more fan blades and different clutches without the result I wanted. I even tried a fiberglass fan that moved a lot of air at low speeds and flattened out at high rpm, it made a lot of noise but was ineffective. My car had the seals around the radiator, I might have installed them or they might have been stock.
Later I installed a solid cam big block behind the same radiator, it ran cool with no problems. I had changed the stock ignition sytem for an electronic system from a wrecked 68 big block, had no problems with that either. The big block ate starters until I built a custom starter using Pontiac 421 parts with the Chevy nose case and installed a truck battery with heavier cables.
Over the years solids precipitate out of the coolant, especially the old "green" stuff that had a lot of inorganic salts, including lots of silicates. They were good at preventing corrosion, but over the years, the precipitates clogged up the tubes, vastly reducing heat transfer.
Modern HOAT blends like Zerex G-05 contain much lower concentrations of inorganic salts, which extends radiator life substantially before the tubes get clogged up.
I don't know how you measured core thickness of the OE aluminum radiator, but it's definitely more than 3/4". "Bolt-in" replacement copper/brass radiators can't match the heat transfer rate of the OE aluminum radiator.
Given the big engines and low frontal area, GM spent a lot of time/money developing the cooling system and ended up installing premium components. The furnace-brazed, stacked plate aluminum radiator was unique to Corvette in that era. It was expensive, but for a given core area substantially outperforms conventional copper/brass designs. The viscous clutch fan was also a relatively new development and not used on many cars.
Bottom line is that these cars, especially small blocks, didn't have overheating issues back in the day when everything was functioning to spec. So rather than "re-engineering" the cooling system 50+ years later, replace or restore OE cooling components as necessary - radiator, clutch fan, and spark advance map to OE performance.
I bought the car in September 68, with 11,000 miles on it. I didn't get to take it on a trip until Thanksgiving that year so only did a little driving around Ft Eustis, VA. On a weekend pass to Key West, Fl it began to run hotter at highway speeds (220 f) so I had to run the heater and keep the top down until I got back to Va. It seemed to cool better at 100 mph + and the new Interstate 95 was deserted so I covered long stretches of highway at 120 mph. I remember being amazed at the good gas mileage it got, double the 12 mpg that my 67 Camaro 350 had been guzzling with its 410 gears. I got orders to transfer to Savannah, Ga so before I could do anything about the cooling problem I had to take another trip with the top down at 120 mph.
In Savannah I checked into Hunter Army airfield (an old AF B47 base), then went into town and found a radiator shop. The owner had to order a large core for me to go with the tanks he had on hand. In the mean time I had repaired the small leaks that began to appear on the original aluminum core with JB weld epoxy glue by taping the backside and filling the air holes with the glue. By the time I got the new radiator installed I had pulled the aluminum radiator twice and made three repairs with glue.
I was apprehensive that the high operating temps had damaged the engine, but after the new radiator was in the temps dropped to 165 F city and highway and the engine gave me excellent service (including constant racing, street and strip). Just before the new radiator was put in the operating temps were up to 240F. At the shop, the mechanic had to wait for it to cool, he couldn't get close enough to work on it.
That 327 engine was hopped with larger Holley carbs, Edelbrock manifold, a Crane street grind cam with triple springs, solid lifters and high volume oil pump to get it into the low 13s at 105 mph. At some point it got Doug's headers. Then I stripped the engine down and had the bottom end parts balanced and the pistons fly-cut for valve clearance, matched the ports to the manifolds and had a five angle valve job. It still had the smaller 1.92 intake valves which allowed very high rpms without valve float. I installed Chevy bearings with increased oil clearance, a light weight aluminum flywheel and a Z-28 clutch.
With its 3.56 rear gears and wide ratio transmission It turned 12.9 at 112 mph at Savannah drag strip shifting to 3rd at 90 mph + just before the traps. Before the hop-ups I had raced it up to 140 mph on a deserted stretch of interstate west of Savannah that was under construction that went 15-20 miles into forest, where it dead-ended.
The engine was changed to a Z-28 302 with a crank that increased the displacement to 350. The early Z motor had small diameter main brgs, I think I remember having the bearings turned down when it was balanced. That engine ran low 12s, I forget its top speed in the 1/4. I acquired a stock Vette fuelie system to install on it but before I got to do any more on the Z motor, I traded it for a solid lifter big block 402. All of these engine were run with the thick core brass radiator with no cooling problems.
Although the car was almost new when I got it, the former owner was an Army pilot who was sent to Vietnam, then returned in a box. The man's family consigned it to a Newport News used car dealer to sell for his estate, that's where I found it, traded my 67 Camaro and $2,000 for it and had fun tearing around with my hair on fire.
The Vette had sat for a time at the car dealer, I think the radiator had begun to corrode by the time I bought it. It probably had scale build up in the core that was blocking coolant flow. I remember the clutch pilot bearing failed just before 12,000 miles. The local Chevy dealer replaced the bearings and then parked the car under the body shop's ventilation fan for the paint booth. When I arrived to pick it up (took them 3 weeks to replace the bearing), there was a fine dusting of yellow paint over the entire car. I was pissed and the dealer offered to repaint it, but I refused to leave it with them any longer. It took me 6 months of polishing to get the yellow off. The 67 parked next to it is a bone stock 427 tripower 435 hp with a rock crusher transmission and 410 gears. I rebuilt its engine for cracked rings and he traded the tripower manifold and carbs for a single carb aluminum manifold off of an L-88. The car ran much better with the big 4 barrel Holley, he could control the wheel spin, which had been un-manageable whenever the tri-power's two secondary carbs opened. Besides being much better to drive, his gas mileage doubled to 12 mpg on Sonoco 115 octane. The 427 came with a thick core radiator, he never had cooling issues.
01-13-2018, 02:35 PM
This is not rocket science and what the OP is asking for sounds like a typical engineer over analyzing the situation.
