I literally linked to one source in my post, but @MoparCarGuy found one you can probably get locally. Hang on to your receipt, though, because the Mr. Gasket (a.k.a. Holley) version had a staggeringly-high failure rate in the recent past. That's why I recommended the Stewart/EMP unit or NOS Mopar.
1970 26" BB radiator fit in a 1974 Barracuda?
- Thread starter 440_man
- Start date
Right now, there is no vacuum advance. In the past, the distributor was set up for manifold vacuum instead of ported vacuum by Don Gould.
It definitely is much more responsive down low and is less gassy when hooked to manifold vacuum, but I don't know that one way or the other has made any difference on the idle temperature.
Thanks for the info on the thermostat. I missed the link the first read, and was having no luck finding a NOS unit... I thought from earlier research I did that that type of thermostat was more typically found in recreational vehicles and industrial vehicles that had the bypass built into the water pump. But after digging deeper, I think its a no-brainer to give it a try it if will flow that much better.
Can you expand further as to why the flex fan is a no-go? I have a 7 blade fan hanging in the garage that is the same diameter as the flex fan, just not sure if it is the correct OE fan for this application. Any suggestions on identifying the correct OE fan for this? And I hear a lot of talk about using the thermostatic fan. Any advantage to that other than it doesn't rob HP when the engine is cool?
Ricks72Chlgr440
Well-Known Member
The Napa THM 191 you have is NOT the correct one. It is basically a slant 6 thermostat! You need the one designed for the big block, like the one Summit Racing sells, the EMP-301.
Also, why did you disconnect the vacuum advance? The VA (primarily with manifold vacuum) will help street engines considerably. Quick story: when I got my Challenger, it did not have much low end oomph and ran hot when at low speeds/idle in traffic. I found the VA hose was disconnected. I connected it to manifold vacuum and set the initial timing back a little. Was like a different engine. No more running hot and had much better low speed response.
Xcudame
Well-Known Member
From the 71 Plymouth factory shop manual. Any temperature about 225° the valve switches from the normal delayed vacuum advance to direct ported vacuum to allow the vacuum advance in the distributor to engage and increase rpms.
Ricks72Chlgr440
Well-Known Member
Flex fans are dangerous. They have a nasty habit of coming apart and doing damage and killing people. My son had an old car that he scrapped that had a fan. I then got the Hayden 2947 fan clutch from Summit Racing which gave me the maximum clearance between the radiator and fan. I had a Champion aluminum radiator and needed a shroud to go with it. Got the shroud from Mancini Racing and modified it to fit the radiator. That setup moved a ton of air even at idle.
Some folks don't like the clutch units, so they just run the OE style fan, a spacer, and shroud. I prefer the clutch units like the Hayden. There was a reason why Chrysler used those setups on their high performance cars!
Ricks72Chlgr440
Well-Known Member
Can you provide a picture of the fan you have hanging in your garage?
heminut
Well-Known Member
This is absolutely the truth! I have a nephew who is missing an eye because of a flex fan. They told him after it happened that if the blade had gone just a little deeper it would have gotten into his brain, possibly killing him! I have not used a flex fan since that happened and I wont get near the front of an engine that has a flex fan and is running!
Ricks72Chlgr440
Well-Known Member
Sorry to hear that. Those stinkin' things are EVIL!!!
Xcudame
Well-Known Member
Flex fans are more dangerous than the worthless bumper jacks these cars came with! I'm partial to the old mopar performance asymmetric 5 bladed clutch fan myself. Somebody went to a lot of trouble to engineer them and they work well. In fact I think all the magnum engines have a reverse rotation version of that fan. I know my 98 Dakota does.
Ricks72Chlgr440
Well-Known Member
Amen. Those were (are) good fans indeed!
Adam
Well-Known Member
Years ago I had a Cuda with a 408 stroker. It would get hot at idle and at highway speeds. My fan clutch lost its ability to engage, I think because I left it sitting flat on a shelf for months while I was building the engine. There was a patch of slime on the shelf that look like it leaked out of the unit. I noticed at idle the fan was turning slower than the pulley! So I put a flex fan in it and it didn’t help much with the high temps. Later, I stood in front of the engine while idling & revved it up and noticed my lower radiator hose was collapsing flat as the revs went up. My old hose had a spring inside it and the new one didn’t. Simple fix, and I later went back with a new clutch fan, due to noise and it was all good.
Xcudame
Well-Known Member
I'm pretty certain that the fan diameters varied from make to make, radiator width and engine size. I've seen 20", 19", 18.5" and 18". There are probably other sizes. Obviously the shroud opening would vary as well. So if the fan shroud fits the aluminum radiator well, and the 19" fan looks too close to the shroud opening, I'd look for a 18.5" fan first or 18" fan second. Another thing that helps are the new motor mounts with the internal metal tabs that don't flex as much or break. This would allow a closer fit than oem.
Ricks72Chlgr440
Well-Known Member
With the blade pitch, that fan is an excellent air mover. Like Xcudame said, the challenge now is to find a shroud to fit your rad, or a smaller diameter fan to fit a shroud with adequate clearance. A properly fitted shroud is key to air movement thru the radiator to provide idle/low speed cooling. He also made an excellent point about the engine mounts.
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