BTW I did a search and well....

I have my 502 installed, dewitts alum rad, duel felx a lite 210-220. 160 thermostat.

Running down the hwy its great, 160-170.

Get in city trafFic and ZOOM. It went to 230 or so this afternoon and caused a vapor lock. BUMMER.

Should I go back to factory fan shroud with a 7 blade flex fan, buy a pusher fan, get different elect fans??

I need more air and in Texas I want to hook up my a/c before summer. HELP

 

I'm sure you've fell victim of reading those long Mark IV fan threads.
Maybe give them a shot, they seem to be the most powerful fan setup around and cheap if you have some salvage yards in your area.

 

the dual flexlite 210-220 has not worked very well on my 78 with a 383. i never had overheating issues with a flex fan.
check for high flow thermostat ( no, really! )
water pump/ belt tightness
vettes are notorious for air pockets in the rad/cooling system

 

I would contact Dewitts. There are plenty here running dual fans without any problems. You should be able to cool that BB with your setup. Something does not sound right. Are you sure both fans are coming on at high speed. What temp are the fans coming on. I have Dewitts rad and dual fans, few less cubic inches and mine will go to 200 then both fans are on high and it drops like a rock back to about 170 and stays there.

 

Both come in at 160, I am not aware of different fan speed setting??

I do see summit has a higher volum fan set up. At this point after spending in excess of $14,000 on this engine/tremec/hydro cluth etc. I am ready to do what ever is necessary to cover my investment.

 

Get the Spals,I seen posts where the flexalites weren't getting the job done on a sb.
I had 91 F-body electric fans that worked good ,and bought some Spals, they cool too much now.

 

Brand doesn't matter much, you just need min of 4000cfm to cool a large v8 chevy.
If you want to run it that cold then you may need more.

 

I purchased the Derale fans through Summit Racing for $199.88 part number 16928. Also bought the Howe 19x31 Radiator for 199.95.
Now the tricky part, go to Home Depot or where ever and buy some 90 degree angled aluminum. I cut both fans and removed approx. 1/2 from each side of the fan shroud not getting into the internal shroud. Then staggered the fans in the bracket that I made for them to fit. The fan shrouds have grooves in both the top and bottom. I bought long bolts, I believe 1/2 and ground each side of the head to slide into the grooves. Then drilled holes in both the top and bottom of my frame and tightend the bolts evenly. There are 4 bolts holding each fan in the frame just out of contact with the radiator. I also purchased the Painless kit 200 on 185 off. I run aluminum heads with a 180 stat. This does not even come on down the highway, will come on in traffic, but cools it right down. This set-up was less than $600 and works great. I have a 355 built up, soon going to a 406. Now wit the 406, I am hoping it works the same

 

Summit has a 4600CFM, # FLX 295. (Vs the 2500 CFM with the 210/220 and I can send them back to summit as well as they don't work) Says fits 28 X17, what size is mine, 74 BB. I measured 27 X17 but not sure measuring at the right place????

 

I have to disagree. We've done hundreds of BB's with the dual spal's which are 2800 cfm. Do I think they would solve this issue? No, I don't. The 210's provide 2500 cfm, which is plenty. The aluminum radiator has 30% more cooling than the original copper unit. This cooling system is very robust as is. When cooling problems arise we tend to focus on only one side of the equation, in this case the rad/fan combo. The other side is the heat being generated and the instruments measuring it. Since we have plenty of cooling, I would ask why this engine is generating so much heat? Are we reading it right? Many times an aftermarket engine means a new sending unit was installed in the process and those can read high.

BTW, my paint booth has a 4000 cfm rating and that uses a 24" exhaust!

 

When running down the interstate or open roads it cools fine. It only heats up in traffic. It was close to 90 or over everyday this past week.
I have a 502 with hooker headers and side pipes. I placed a big shop fan in front and it cooled down FAST.

I have the dewitts perfect fit and its great.

I think I just have an air volume problem. I will know by Friday as I next day aired the new 4600 cfm fans from Summit.

 

I have one of Toms radiators cooling my rebuilt 454 along with the Flex-210's n up till now all seems to be going ok.....Hanging around 180.......At 1st I was worried about the temps as they were climbing a little over 200 but I found that 2 be an air pocket n once that was rectified all was ok....Jerrylee///

 

Hmm... are you using the vacuum advance on your distributor?

 

Yes

 

Maybe something's wrong with the flexalites? Wrong rotation? Speed control? Air flow is typically loud, and you should be able to hear 2500 cfm, even with headers. Just wait til you hear what 4600 cfm sounds like.

 

Ported or manifold vacuum?

 

Ported

The fans I have ordered coupled with the controler, only puts as much fan speed in as needed to cool. I should know by tomorrow afternoon if UPS delivers as promised.

 

I don't disagree with anything you've said.
Let's look at this a little more closely.

Highway is 160°.
Seems like the Dewitts' fan is doing it's 30% better. A little cold for my taste though.

Seems like the gauge reads right on the highway.

Seems like it shouldn't be creating heat at idle due to timing retarded. Most people have it too advanced.

Seems like that's all that's left.

That's another good clue.

I'm sure most people have read the ratings on the Markiv fans posted here, anywhere from 4200 to5500 cfm. I guess a few people at Ford thought high cfm worked in some cases.

A quote from Derale's site.

Supposedly the stock fan specs, although I can't confirm it.

TEXASRANGER
Even though it's a long distance diagnosis, I think you are on the right track with the fans. I think they are curved blade so that will help the noise.

A couple of things for thought.
1 At idle you may be recirculating hot air from under the hood back thru the rad again.
2 At idle since you have a bb with hot headers crammed in there, you might not be getting air out from under the hood. Idle with the hood up and see if it cools down.
3 Repurge the system for any air pockets.
In commercial buildings, the a/c /vent system is often required to pass a "smoke test" Using smoke thru the front of the rad at idle may tell you something about where the air is going.

And to make things even worse, when you start using the a/c in the Texas heat, you are adding a bunch more btu's to the radiator, so it will have to cool even better.
On the plus side, if you can keep a constant 200° with a/c, that's ok too.

Interested in seeing the results of the new fans.

I know your pain with the heat. I took my scuba diving test in Canyon Lake back in the mid 70's

 

OK, the fans came in from Summit, would not fit!!!!!

Need to do something, have a parade scheduled for Saturday am.

The 69 I picked up last Saturday with bad engine has a brand new fan clutch that will not be needed for a few weeks. I put the fan shroud back on the 502 and put the 6 blade fan and the fan clutch from the 69 on.

Test drove.......Wounderful....until I have to stay stoped in traffic for 10 min....ZOOM hit 235, had to pull over and sit for a few min. Cooled down and traffic now smooth, ran like a dream. Let sit in driveway for 5 min and temp hits 210.

Noticed that the fan clutch from the 69 is only 1 inch from the water pump, looked at the one from the 454 (its bad), 2 inches away which would make it set deeper in the fan shroud and hopefully pull more air at idle. I have a new HD fan clutch ordered with correct spacing and will pick up this pm and install.

Crap, I hope this solves my over heating problem.

I have a friend that says a 7 blade flex fan with 2 in spacer would solve my problems as well....any thought on that?

 

Just go back to the stock 7 blade fan and a fan shroud. My BB 454 71 here in Austin August rush hr traffic, never goes above 210ish. Its just a brass/copper rad too.