[pontiacphil]

I'm sorry to say that replacing the old flex fan with a new clutch fan Hayden #2797, and new Hayden fan blade #220618, didn't solve my running hot problem. Actually it worsened somewhat in that it now runs around 205 at 55mph where it had been in the 190 range. Idling it goes to the 220-230 range. As my previous posts indicate, I've performed most all the other suggestions for overheating and my problem still exists. I gues it's time to consider replacing my factory Harrison 4-core (which has been recored) with an aluminum radiator. I would like a direct drop-in (not a universal fit which has to be modified). I've read all the posts using the search function trying to find the best radiator that would solve my overheating. Rodney Red, Griffin, Be Kool, etc. all have their supporters. Some have one inch tubes while others have 1 & a quarter inch tubes. I know I'm going to have to spend between $500 to $600 to buy a GOOD radiator. I just don't want to spend that much money and get one that doesn't solve my problem. Can some of you who have had a similiar overheating problem tell me which radiator would most likely be the one I need to buy and where is the best palce to buy it? I have the non-a/c 15 & half inch radiator support. Any advice any of you can provide will be appreciated. Thanx.

[Repoman]

Originally Posted by pontiacphil

Idling it goes to the 220-230 range.

Your fan isn't doing anything but getting in the way at 55 miles per...

You have other problems beside your fan. Where's your timing at? Running lean? Running water, or anti-freeze?

Before you spend any more money, drain all the anti-freeze out, and fill it with water/rust inhibitor. See how it runs.

[pontiacphil]

Running a fresh mixture of 50% water, 50% antifreeze. Timing is at 10 degrees at 800 rpm, port vacuum, total of 37 degrees at 3,500 rpm. Quadrajet carb. that appears to be just about right, not too lean, not too rich. AC R43 spark plugs. This 400 ran hot before my total rebuild and runs just as hot after the rebuild. Running synthetic Rotella motor oil. New radiator core has less than 500 miles. Total rebuilt motor has less than 200 miles. I'm really getting frustrated in trying to find both the cause and the correction for this overheating. Thanks for the reply.

[kate`s67gto]

I had a severe overheating issue @idol to . This is what i did purchased Rodney Red rad, checked pump was stamped impellor found cast impellor , tweeked divider plater to impellor 1mm clearance (without gasket). Put a mid 80's cadillac fan on with hayden severe duty clutch. I use a 160 Mr. Gasket stat. Problem solved car did idol at 230 at 750 rpm's Now idels at 170 needle on Auto Guage does not move at idol now . I have done the towel test and yes it was drawn towards the rad at idol. Have checked plugs nice tan color. No pinging heard when shut off car. I run 15/50 mobil one oil, 50/50 mixture of water antifreeze deionise water(sp). I use sunco 94 gas. Run 10* timing and manifold vacum adance. Hope this helps .

[Doug Christie]

Was the fan in the same position before the engine was built and was the same shroud used? From what I've read about shrouds, the fan should be sitting so there's about a 1/2" of fan sticking out the back of it, towards the engine.

[Z Code 400]

Best fan ever made (in my opinion) is the old 7-blade solid fan found on Non- Air-Conditioned MoPar's. The ends of the blades are curved and it is very, very quiet.

It pulls a lot of air, even at low rpm and it costs less HP on the dyno than any of the flex fans we tested.

They were often found on the Slant-Six vehicles.

We have spun them as high as 8600+ rpm, seaon after season, in oval track cars with no problems whatsoever.

Best of luck...Robert

[pontiacphil]

Yep, the fan fits inside the shroud with about one-half inch not inside it. One other question I have for everyone regarding my overheating problem is: my automatic tranny lines are real close to the Ram Air Performance HO exhaust manifolds I installed. On the passenger side the factory lines are about one-quarter to three- eighths inch away from touching the manifold. Could this cause a major overheating problem? I don't think I can bend or move them enough to get them farther away. Guess I would have to fabricate and run new lines if this COULD be the reason for my heat problem. Do you think this is sufficient clearance for the lines or should I install new lines in an effort to get exhaust heat away from them?

[tonytitus]

Had identical overheat problem as your now expereincing--66 GTO 406 ci.
After chasing a tonne of "probable causes" it turned out by replacing the water pump divider plates corrected the problem as in my case the plates were corroded and should not have been re-installed.

[hisgto]

Phil,

Have you verified that your gage and sender are accurate? My stock gage reads 10-20* hot.

[Tom Vaught]

I would like to have the fan blade be 2/3 in the fan shroud and 1/3 out of the shroud to pull air properly.

Having the whole fan inside the shroud does nothing.

JMO

Tom V.

[pontiacphil]

I have tried 3 separate temp. gauges, 2 mechanical & 1 electric, and all 3 were pretty close--------HOT. I wish it would have been a faulty gauge. A whole lot cheaper and a whole lot easier!

[Brandi Kay]

]]]

[Ray Cox]

Do any of you have your intake crossover plugged wher it use too feed into the back of the water pump housing?

I have myn pluged and was developing a problem sometimes with an air pocket in the top of the water pump housing/timing chain cover I had to add a bleeder in the top of the cover right behind the water pump

[mzbk2l]

Originally Posted by pontiacphil

Yep, the fan fits inside the shroud with about one-half inch not inside it. One other question I have for everyone regarding my overheating problem is: my automatic tranny lines are real close to the Ram Air Performance HO exhaust manifolds I installed.

In my previous job, I got to do a LOT of cooling tests on a variety of different vehicles in the nice Arizona sunshine. I once spent a week testing a city bus cooling system, removing the radiator and spacing the fan in or out of the shroud about 1/8" at a time. We found that (as the engineer had predicted) having the fan just over 1/2 way out of the shroud worked the best in that setup. He explained that by having a good portion of the fan exposed, the air was thrown off the blades centrifigally and gained a lot more velocity than it would by traveling straight through the shroud. This creates an area of lower pressure and enables more air to be pulled through the shroud than would be possible if the fan is entirely in the shroud.

As for the transmission cooler lines, we also did extensive testing to see how much heat could be gained or shed by the transmission fluid as it traveled through the cooler lines. This testing was on Allison transmissions in GM pickup trucks, so the cooler lines were 5/8" ID, not 3/8" (That may make some difference because of the ratio of volume to surface area). We had thermocouples at several places in the lines, as well as at several places in the ambient air around the lines. We tested with exhaust heat shields in place, without exhaust heat shields in place, with the lines insulated by hi-temp insulation tape, without the lines insulated, and with flexible lines run along the outside of the frame far from the exhaust. Basically, we found that nothing we did changed the temperature of the fluid in the lines more than two or three degrees. It just goes through there too fast to have time to tranfer a significant amount of heat.

[70GS455]

If you've decided on a flex, the Derale HD Flex Fans from Summit have solved some coooling problems as they move a lot of air at idle, yet flex out at higher rpms.

http://www.derale.com/hdflexfans.shtml

[Region Warrior]

I have used the flx 19" with a 1" spacer for years. Will have to double check the #.
It is the largest they make rated to 10K. Has 7 blade's like the GM thermo's.
Found that having it 2/3 out of the shroud works best for me.
At idle, it will suck a paper shop towel to the front grills!
When it flattens out at high rpm's, it's just about 1/2 in/out of the shroud, and stills pulls the towel.
I'm in the process of installing one in the 68FB.

[pontiacphil]

I had two options when replacing my fan in an effort to cure my overheating problem.
1. Go with a clutch fan and the one recommended most here at PY was the Hayden #2797 and a 18 in. blade by Hayden #220618. My local Advance had both these in stock (clutch was $65, blade $28).
2. FlexFan #1818 for $45 through Summit. Also highly recommended at this site.
So, I take the quickest route and buy the clutch fan at Advance as I didn't want to wait a couple days for the FlexFan to be shipped. Took about a good hours time to take the shroud loose, the radiator fan guard off, buy a stud kit for the clutch fan, and a two inch spacer, and get everything back together. Result, no help whatsoever over my old, unbranded 18 in. flex fan. Maybe even runs a little hotter. So tonight, I'm ordering a FlexFan #1818 from Summit.
I see you run a one inch spacer with yours. What yr., model, and motor are you running? I want to order the correct size spacer from Summit when I order the fan. I've been running my fan about two-thirds inside the shroud and one-third outside. But if you've had good luck running it two-thirds out I'll try that approach. If this fails to help I guess a Rodney Red is my last option. Wish me luck.

[Doug Christie]

Have you tried the shop towel again to see if it's drawing any more air through? We just put a new fan on a "67 mustang with no shroud and sitting about 3" away from the new 2 core (3/4 " tube) rad. held a paper towel there no problem. Granted this was only a mild built 351, but even without a shroud it pulled air and cooled. I think your problem lies elsewhere. Have you checked the thermostat? The fellow who owns this 'stang was complaining about over heating. Not only was the old rad plugged, but the thermostat was in upside down. Just a thought.

[pontiacphil]

Even with the new Hayden clutch and fan blade I get no movement from a paper shop towel placed in front of grill at an idle of 800 rpm. When I bump the rpm up to about 1,200 then the towel blows like a flag in the wind towards the radiator. I've always been told that you wanted the fan blade to be inside the shroud with about a third of it not inside. Another poater here says he has had good luck with only about a third of the blade inside the shroud (with a flex fan). That's my next step, new flex fan with about a third of it inside the shroud. Can't hurt to try it. The thermostat is a new Mr. gasket, 180 degree, high flow type. It appears to be working properly as my gauge shows temp. going to 185, thermostat opens, and water temp. drops to about 175. This is while the motor is still somewhat cool. After driving a while, my temps. slowly start increasing and going up proportionately. I agree with you that there is something causing my overheating but I just can't find what it is. Frustrating as hell!

[Region Warrior]

Installed the 19" last night.
Flexalite 1319 with a 1" spacer which put it 1/3 into the shroud when not running.
Would liked to have tried it with a 1.5 spacer, but dont have one.
A 2" puts it in all the way into the shroud.
Forgot how much they flatten out at idle. Looked almost 50/50.
Holds a shop "paper" towel to the grills. Behind the grills, it pulls it to the radiator and trans cooler.
Had the engine running for 10-15 minutes in the garage(about 90* temp) to adjust dwell/fuel/timing.
The gauge never went passed 160.

Is yours a 18 or 19"?
Have a 17" from another car i bought. Held it in there, and it looked WAY to small for the shroud opening.
Just eyeing it, i think an 18" would be marginal.
Would use a factory thermo clutch instead.