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1970 26" BB radiator fit in a 1974 Barracuda?

NoCar340

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Ok I found it - its a Napa THM 191 180 deg thermostat. I would say it does NOT look like the picture above. Where does one find the actual correct thermostat for the 440?
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.
 

440_man

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Pictures of your current radiator/shroud/fan would help. If you still have the flex fan that is a no-go. The OE style fan moves a ton of air, and when mated to the proper shroud worked very well. The fact that it starts getting hot at idle means you likely have minimal airflow through your radiator. Another thing to consider is your timing. Retarded timing can also put a load on your cooling system. Are you running vacuum advance on your distributor?
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.
 

440_man

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Are you using the right thermostat? Your cooling system was engineered to work with a particular thermostat design. It was so important that in some instances Chrysler put a decal in the engine bay to make sure the correct 'stat was used. This style isn't available through regular channels anymore.

View attachment 109770


The "Robertshaw" design shown, now called a "high-flow" unit, is what came new in every single Chrysler V8 built during the musclecar era. It was a part of the system design. They're still available NOS (break out the parts books!) and through EMP/Stewart Water Pumps (although NOS are cheaper). The orifice area is at least twice as large as the junk we sell at auto parts stores. If it doesn't look the like one on the decal, it's not the right one no matter what the supersession or parts person says.

I have a 10.5:1 iron-head W2 340 in a '69 Valiant with a factory-style 22" radiator, a stock water pump, clutch fan (no shroud) and an NOS Mopar 2808631 (180°) thermostat. The engine bay is more cramped (less airflow) than an E-body. It stays right at 180° even on days in the high 90s. Traffic, idle, racing? It doesn't matter, the needle doesn't move.

Don't underestimate what the right thermostat can do. Always try the right thermostat before wasting money on anything else.
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.
 

440_man

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Pictures of your current radiator/shroud/fan would help. If you still have the flex fan that is a no-go. The OE style fan moves a ton of air, and when mated to the proper shroud worked very well. The fact that it starts getting hot at idle means you likely have minimal airflow through your radiator. Another thing to consider is your timing. Retarded timing can also put a load on your cooling system. Are you running vacuum advance on your distributor?
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

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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.
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

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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.

20230831_142006.jpg
 

Ricks72Chlgr440

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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?
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!
 

heminut

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Flex fans are dangerous. They have a nasty habit of coming apart and doing damage and killing people.
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

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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!
Sorry to hear that. Those stinkin' things are EVIL!!!
 

Xcudame

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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

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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.
Amen. Those were (are) good fans indeed!
 

Adam

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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

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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

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Approximately 19" diameter
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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