I was referring to YOUR conclusions.

I don't know most people so I don't know what they'd agree/disagree with. I do know I was running the streets with these cars in 1963 and their owners and overheating (over 180*) was NEVER raised as an issue except for one guy that pulled his 327/340 out and stuck in a 396/375. He kept the 327 radiator/support. He only had problems sitting on the return road at the drag strip, engine idling, waiting for the next run, after a wide open run on extremely hot days.

And yes, I disagree but I'm not going to argue about it.

 

You are so knowledgeable, yet you have blinders on for a problem that doesn't seem to exist (according to GM's conclusion). In addition, you degrade those that try to assist... very clever on your part. In your last reply (before your edit), you concluded by asking, "What were you doing in 1963?" As per your astute reference to correlations, unfortunately, I fail to see any relationship between your age and common courtesy... if you show respect, you get respect. People like YOU are the main reason why people like ME refrain from adding relevant info to posts.

BTW- Since you are such a vast resource of technical info, why aren't you well versed in all the knowledge regarding the adjustment of a fan clutch... especially the 1990 article that was referenced? I can't take credit for penning the contents (very informative), but believe I was first to post that trick online (back in the late 1990's). Subsequently, I rescanned and the reposted that article in 2003 on the Corvette Action Center (my initials are embedded in the PDF properties). Since then, the article has appeared in multiple threads spanning several different forums... perhaps it helped a few fellow enthusiasts.

For a person that doesn't like to argue, you sure are doing an exceptional job. Once again, I respectfully ask that you please allow the OP to gather the info and draw their own conclusions. And if you check back to my initial post, my ONLY conclusion was for the OP to consider my reference to GM data... nothing more.

PS- If you really want to know... in 1963, I was morning the loss of JFK. Have a nice day.

 

Because all my stuff still has the OEM fan clutch still on it and operating satisfactorily. I've never bought a replacement clutch.

All I said was, the OP's driving conditions do not duplicate what the GM service bulleting said. I just don't know how we used to make it around the block, cruising through the drive-in restaurants back then at a stop/go pace for and hour at a time without huge geysers of steam coming out of the hood.

That's what I was doing in 1963.

You haven't helped anyone fix this problem by telling him his condition is "normal".
And then you continued to ignore my other points as well. You come across as someone who is used to being in charge maybe?

 

I'm very sorry... you are korrect and the GM documentation is totally false. In addition, I forgot to realize that basic science laws have changed since 1963. Currently, a 50/50 glycol/water solution (under pressure) with a temp of 210* will cause "huge geysers of steam coming out of the hood". I guess I also missed when the OP listed boil-over as a symptom (perhaps you can note that post number for me). As punishment, I will remove two sparkplug wires from my car and weld the heat riser closed... will that be enough penance?

PS- What exactly am I in charge of... does it pay a salary... and do I need to declare it on my taxes?
HINT: Judge not, lest ye be judged (excluding NCRS, Bloomington Gold, etc).

 

Don't know. There's nothing in your profile except "jack" is your name, you're from Massachusetts and you have a 2X4 block bolted to your clutch pedal so you can release the clutch.

 

Thank you once again for disparaging the handicapped and disabled... you are extremely thoughtful. No problem, Dad... I still love you.

 

As a foot note, My original fan clutch died a few years back and I bought a factory correct replacement. I also did the spring re-clock trick. The car ran hotter after the clutch was replaced, compared to the temps with the original clutch during normal operations.

The only factor was the clutch. I have been meaning to send my original off to have it overhauled, this thread prompted me to do so.

I read somewhere in this thread that someone installed a clutch eliminator (solid spacer block) to the original fan. DON'T do that. The factory fan will explode. You need a flex flan for that application, or limit your RPM to about 3K.

Mark

 

Good advice.

Member Westlatorn here posted a very good tutorial on how the fan clutches work, how to check them. I was hoping he would see this thread and bring up his old post. I tried a search and couldn't find it.

Going from memory on what he wrote, the original clutch, when fully engaged never spun the fan over about half engine speed.

 

[QUOTE=MikeM;1589635533
The carb might have even been leaned a little which would also increase temperatures, some/most of it going into the cooling system. [/QUOTE]

Yes, Mike, they did lean out the carb a bit for '66 and '67 with A.I.R. systems. Main jet size was 0.065" for 49-state cars but 0.062 in sunny California.



Steve

 

Thanks, I didn't remember. I do remember hearing reports of pretty miserable running cars in the "as delivered" condition in Calf. in '66.

 

Don't want to drift too far away from the OP's original question but you guys made me curious so I looked up the specs in the 66 Service Manual and indeed it does show two carbs for the 300/350 horse 327's, the #3367 which I thought was the one and only carb for those two engines and then it showed a #3416. Strangely, the primary jetting is listed as #65 for both. My 66 Coupe was a California A.I.R. equipped but someone must have swapped the carb somewhere along the line because it's a 4-digit date code #3367. I couldn't find that #3416 anywhere else but did see an old thread where JohnZ said it didn't exist
https://www.corvetteforum.com/forums...ing-66-sb.html.
So, was there a second List number carb used for A.I.R. equipped Corvettes and did they come with #62 main jets instead of #65's?
Mike T - Prescott AZ

 

According the 1966 AMA specs published by GM the carburetor used for K 19 327 engines was model 3605A, GM part # 3890499. This was used on both the 300 and 350 hp California engines.

 

Yes, Mike. The small-block A.I.R. carb for 1966 was the the 3605. For 1967, it was the 3814. These A.I.R. carbs haven't been available new for many years, but the 49-state carbs (3367 and 3810) ARE available new.



Steve

 

I have been out on Vacation for a week, late to this post.
I see the warning about not using a fan blade designed for a fan clutch with a clutch eliminator. Great and accurate advice. They are not designed for full time use and will fail, failure usually involves a fan blade flying through your hood, some have killed people when they fly off. Don't go that route. If you wish to have a direct drive fan blade there are companies that make and sell direct drive fan blades. They are very good at cooling, they are designed to spin engine RPM and not come apart but they are a huge waste of horsepower year around and they are very noisy, they sound like an airplane propeller spinning when you rev your engine. They are good for a Pump Engine that operates in a non moving environment, like a pump house and have to cool the engine without any air speed from a moving vehicle.
A flex fan is best at idle and useless at all other RPM.
The fan clutch is the best system if set up properly, this is why they are still used today on all hard working vehicles.
A fan clutch should spin the fan blade about 10% of engine speed when not engaged and should be able to spin the blade close to 90% of engine speed when engaged.
The fluid that engages the clutch is silicone and when hot it is thinner than water so you need to keep the clutch cool to make it effective. For this reason the fan clutches are covered with cooling fins. The better ones have fins on both sides to pull heat away from the fan clutch and keep it working when needed.
If you need to look factory stock you are limited to the cooling that type can give you.
There are stock and heavy duty fan clutches available. A heavy duty can spin a larger blade with more pitch longer and more effectively. The heavy duty would be larger in diameter and have more cooling blades facing the radiator. The front will be aluminum and not stamped steel facing the radiator.
An AC fan blade would be a good upgrade. More blades pull more air.
The blade should be as large as possible inside your shroud.
When the fan clutch engages it should sound like a airplane propeller spinning up.
It will growl when fully engaged and pull enough air to blow your hat off, (Thanks MikeM for this accurate description) if near the running engine. Never rev an engine if anyone is in line with the spinning flan blade, you are risking their life. Drag racers have been killed revving the engine while tuning and leaning over the fan blade.
As your fan clutch cools the engine you should hear it dis engage and the growl will quiet down.
With noisy Corvette engines, maybe with side pipes you may not hear the fan clutch engage but you should feel the WIND it creates. WIND, not a breeze.
Reading your post it does sound like you created the overheat with your change leading me to think the Clutch is engaging at a higher temp than needed or is bad and does not engage ever.
Test it, have a friend sit in the car, engine running, that person will watch the gauge full time and raise the RPM above idle while parked to create more heat. As the temp goes up the fan clutch should engage fully to cool your engine. If it engages fully quickly shut the engine down. Now try and spin it with your hand. It should have a lot of drag. If you spin it one or two revolutions this drag will quickly go away until the fan clutch free spins. As you turn it with the engine off the fluid will pump back into the reservoir dis engaging the fan clutch and this is normal.
On Cold Start up a Thermal Fan Clutch will be engaged, it will stay fully engaged for less than one minute normally. This is because the fluid will settle to the bottom of the fan clutch body when parked, it takes a short amount of time to warm and pump this fluid back into the fluid reservoir. This is normal.
If you can't get your engine to heat up for this test put a newspaper over the front of the radiator ( Bumper Side ) to reduce the amount of airflow, keep the area in front of the fan clutch open so it can pull air through directly at the fan clutch. This will heat the clutch and make the clutch engage for your test. You can infra red the fan clutch face to see where it engages. Normally the fan clutch engagement temp is 20 degree's cooler than the Engine temp so if you wish to have it engage at 180 engine temp the clutch will most likely be at 160 when this happens.
Kool Klutch used to be popular because it sold clutches that engaged at 200 engine temp while many other companies sold clutches that engaged at 220 engine temp.
Hayden bought Kool Klutch a few years back and I have no idea what temp they are at now.
You can learn more by going to the HAYDEN web site and read about how they function.
We talked about Thermal Fan Clutches, direct drive fans and Flex Fans. The other option people use but is highly discouraged is the non thermal fan clutch. The Non Thermal design will spin the fan blade 50% of engine speed year round. Unfortunately it works far better in winter driving and far poorer in Summer Driving. Just the opposite of what you need. These non thermal designs are only used because they are cheap to buy and fit in the space needed. They waste fuel all winter by engaging the fan when not needed and don't work when needed in the summer. Not a good choice ever but again, they fit the space and they are cheap to buy. A Non-Thermal fan clutch looks just like most fan clutches but if you look at the face, the front facing the radiator there is not spring, just a stamped steel cover.
Some Thermal Fan Clutches use a flat spring steel part to engage and disengage the fan clutch, this flat steel spring works just like the round wound spring you see in most fan clutches. When the metal gets hot it opens the valve and engages the fan clutch. When it cools it closes the valve.
I hope this helps.

 

My '61 has an aftermarket fan and clutch eliminator spacer - works fine and any 'roar' is negligible on a revved-up, dual-quad, solid lifter car. I noticed no loss of HP with the setup and the car is cooler in the Orlando summers.

When I added A/C to the '63 I was trying hard to keep an original look so I went with a larger fan and a heavy duty Hayden fan clutch - they work great and I have no overheating problems down here in Florida when running the A/C. I really, REALLY didn't want to put one of those electric pusher fans on the car and I've now avoided that.

Both cars have original radiators...

 

Thanks for the post Mark. This should be in the tutorials and be required reading for EVERYONE who has overheating at idle problems with a clutch fan.

 

I've asked this question before and didn't get an answer. My overheating problem is resolved after fighting it for over a year. But from what i've been reading, optimal affect is having the fan blades half in, half out of the shroud. Because I have a long neck water pump, this is not possible. My fan blades are fully inside the shroud ( back of blades are even with the shroud opening).

In your opinion, is this providing more, less, or the same cooling affect as optimal?

 

Most say the fan blade should be 50% into the shroud.
Some say it should be 2/3 into the shroud. I have no idea or any facts about what is best.
Flex A Lite says the fan blade should be 1" from the radiator for best cooling.
I think the best position for the fan blade to radiator distance would be determined by the shape of the shroud and optimal would differ on every shroud design but this is my opinion and not backed by any facts. Most factory designs locate the fan 50% into the shroud and the distance to the radiator varies. The modern shrouds fit tight to maximize the amount of air pulled through. New cars don't overheat anymore so they must be on to something.

 

If you look at many older cars that don't have fan shrouds, the fan blade is very close to the radiator. 1" sounds about right.

 

I continue to be amazed that people spend $10,000's for a highly desired popular 1960's era Corvette. Then the first indication of a problem some go to a default condition of "the Corvette engineers and designers in the 1960s were idiots, and we need after market modern parts".

When adjusted and serviced per the GM specs, these machines perform nicely and have been popular driving machines for decades.

In our NW Houston Vette group we have about 250 Corvettes of all types 54s to C-7 delivered this week, many 1950-60's era. When one of the gang is having a "cooling problem", I tell them follow me home. I time the Corvette correctly in 15 minutes, usually adding advance; they call me on way home with a cool car and much more throttle response.

My 200,000+ mileage 1961 (270 hp/283) has ALL original stuff under the hood except a DART 400 cu. in. stealth that makes 496 hp 450 tq.

It has THE original fan, THE original radiator and 7/8 of the original shroud (cut out a lower piece in 1970 at a Winslow AZ gas station to replace lower radiator hose, in the dark). It runs at 180° in our Houston 97 ° temperatures...properly tune engine makes power NOT cooling system heat.

I think the 1960s GM engineers did a pretty good job

Joe