OEM dual fan setups often just turn on the one fan at a certain temp, and when under hi load, AC on, hot weather, towing etc will turn on the other to rapidly pull heat from the rad/system.

For our cars, its the idle temps that usually are the issue, this is where the right elec fans shine.

If elec fans were crap - OEMs would not use them. They have already spent a fortune doing the R&D, the secret is to adapt the right ones, wire them correctly and make sure the Alt has enough beans to keep the system topped up.

In other words match your parts so that they work as a system

my alt is a 100A from Toyota 4runner. works good, but dual fans may be taxing.

Oh yeah, forgot, I use a 440Source wp pulley and a Moroso underdrive pulley on the crank was worried about it with the underdrive pully but no problem on even the hottest days!

Those #'s are "SLIGHTLY" high - IMO. I won't quote any numbers, but most electric fans actually run slower at idle and how much slower will depend on just how much your alternator is up to the task at idle, where it supplies much less current. A flex fan actually works just the opposite from your explanation. There is much less HP loss at speed ( higher rpm's ) where the blades flatten out -( reads "FLEX" fan). No one on this site really cares what the HP loss is at idle. They're just concerned with cooling. And as I said, todays cars are designed from the ground up for electric fans. They have well over 100 amp alternators with a very fast current rise curve ( very small pulleys, serpentine belt driven ) and they are cooling sewing machine motors that seldom see 5K rpm. - Apples and oranges. Flex fans don't use ( or need ) a fan clutch. Stick with your Doctor's hat.

I've run flex-fans on a few cars, all with good success. I've read the horror stories, but never had an issue nor ever met anyone who had one come apart. My current setup is a summit 7-blade flex fan and a homemade aluminum shroud on a summit radiator. Water pump and housing are 440-source units, and I run a 160 stat. My car stays nice & cool on the street, and is generally plenty cooled down by the time I get back to the pits after a run.

Just last year my buddies chevelle started getting real hot between runs at the track one day. We thrashed between rounds to find that electric water pump relay had crapped out. We had to bypass it. Turned out okay , but he almost missed a call. I know the OP is about fans, not pumps, but my point is I like simple & reliable.

I agree with you. I'm gonna need a upper hose just like the one in the pic. original # part?

which makes sense in theory, BUT, that fan speed, and type, make all the difference. my fan, at idle, pulls MUCH more air than all the electrics i tried. my combination didn't work until i bumped the fan/water pump speed up. it only took a little. i ran before/after at the track, and it ran EXACTLY the same e.t., regardless of which fan i ran. i did try a 7 blade, and it did slow about a half a tenth. it didn't run any cooler. as far as my definition of "hot lap", it was a 100 degree plus day at my home track in central oregon. i had gon out in the first round, so i bought into the "gamblers" bracket, which i won, because the last two opponents were unable to make it to the line. i made three passes in 10 minutes. THAT IS HOT LAPPING, methinks. flame on... i can take it...

Making use of the vacuum advance could also help in keeping it cool on the street.

Most guys try and save a bit of HP by slowing the WP down. I'd rather run it a bit faster. I run my at 6% faster than OE.

vac dist. wont fit with victor heads. I bought a vac pertronix which I now have to resale.

Yes, if you have a properly designed electrical system, it won't slow down. That only happens when your alt can't keep up with the demand and maintain 14 volts.

And once again, a flex fan takes less but not "much less". The flex fan, especially without a clutch, consumes a lot more hp at high rpm than you think. Look at the tables.



You can stuff that attitude. I may not be as much of an old-timer as you (built my first big-block A-body around '83) but I know what works and what doesn't.

Picture is current as it sits (on jackstands with all sorts of things unhooked). New HP carb doesn't have provisions for vacuum advance. I'll have to plug it, just haven't plugged it yet.

I've had it for years, don't have the part number handy. All I did was go to the local Napa, and start rifling through all of their hoses until I found one that I though would work. Had to get a sleeve to step down the size of the radiator side.