New to site, new to Mopar overheating issues

Small Block Mopar Engine

  1. D's Nuts and Bolts

    D's Nuts and Bolts Active Member

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    Hello,

    First post on the site, however I've already been using all the great information. I bought a 68 Barracuda convertible a couple of weeks ago and it needs some attention. One issue is that the car is overheating, when it's 90+ here in Kansas. Based on the vin the car was an original 6 cylinder car, but along the way someone put the 340 in it. The guy I bought it from owned the car for 2 months (small time deal in everything guy) and knew nothing about the car and any work done, just "drove it cause it was cool."
    So here is the cooling set up:
    - Fan with a broken shroud
    - Electric Fan, on the grill side, that's wired wrong, drawing power from the alternator resistor with no regulator or temp sensor. It wasn't working, I had it running but now there's no power coming from the resistor FLN side now (separate issue) where it was wired into.
    - First noticed the issue when I drove it home after buy it, was running about 3/4 of the way up the temp gauge then got one mark from the H so I pulled over. I tried running the heater but that doesn't seem to help.

    I was going to get the stuff to fix the electric fan, but am wondering if I just get the shroud and original setup running right it might be best. Any help would be great, thank you.

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    • 512Stroker

      512Stroker We are all here because we are not all there.

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      That dog wont hunt
      Ditch the electric fan all together and get rid of the mechanical flex fan.
      Find 18 inch 7 blade ridge fan and a good fan shroud.
      Swap out what ever thermostat for a high flow type stat, I use 160* in my 340
      Make sure that your water pump is not being under driven, the crank pulley and the water pump pulley need to be at least the same size diameter. It would be best to even over drive the water pump for more flow thru the system.
      This should help a bunch your next step is a 2 row aluminum radiator.
      PS welcome to the forum, there's always room for one more.

      Barracuda new 340 002.JPG
       
      Last edited: Jul 23, 2020
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      • toolmanmike

        toolmanmike Moderator Staff Member FABO Gold Member

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        Better check your motor mounts. Load the engine against the brake while someone carefully watches the engine for movement from the side of the car. Do it outside pointing away from the garage. A bad drivers motor mount will cause the engine to jump and break fan shrouds.
         
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        • Murray

          Murray FABO Gold Member FABO Gold Member

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          All good suggestions but I would start by confirming what size radiator you have (number of rows, condition, part number) since this is not an original set-up. Welcome to FABO.
           
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          • toolmanmike

            toolmanmike Moderator Staff Member FABO Gold Member

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            It looks like a 22" but best to measure to be sure. My 318 Swinger had the original 19" 2 core with dealer installed a/c. A bigger radiator wasn't part of the kit apparently. I kept having overheating issues with the a/c on. I changed to a 22" and all is good.
             
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            • 340doc

              340doc Well-Known Member

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              Don't know if its the angle of the pic, but that water pump pulley looks big!
               
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              • toolmanmike

                toolmanmike Moderator Staff Member FABO Gold Member

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                Everything in the system has to work correctly for it to not overheat. It sounds like the temp is rising but not overheating. Is it boiling coolant out? No overheating problem then. Who knows what temperature the "1 notch from hot on the gauge" really is. You could have something as simple as a bad radiator cap causing the issue. A thermostat controlled fan clutch is the best. It will draw air when needed regardless of engine or vehicle speed. The flex fan only draws air at idle and low engine speeds.
                 
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                • yellow rose

                  yellow rose Overnight Sensation

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                  As mentioned, you don’t need the electric fan. It’s just in the way.

                  If you were shifting at 8500 RPM that water pump pulley MIGHT be ok. For what you are doing it’s way too big. The pump and fan are turning too slow.

                  That’s the first 2 fixes I’d start with. They are cheap and easy. After that, if you still have issues you can go from there.

                  Also a new thermostat is a good idea. Just buy a good high flow thermostat.

                  That mechanical fan is close enough to the radiator it doesn’t need a shroud. The only benefit to one would be safety.
                   
                • 318willrun

                  318willrun Utube channel 318willrun

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                  I've been running Champion Radiators in both my Dusters without a shroud and one of them has a underdrive crank pulley and both have a 160 thermostat and both have clutch fans. Neither one overheat on any day that i chose to cruise. Now, I don't sit in a bank drive through for 30 minutes idling so i don't know what they would do in that situation, but I'm sure if i did that I'd install a shroud and not have a issue. Champion radiators fit nice and were about 200 or less shipped to my door.
                  • And welcome to the site!!!!
                   
                • Wyrmrider

                  Wyrmrider Well-Known Member

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                  yes on pulley and HIGH FLOW STAT
                  measure core
                  pusher fan does not hurt- not the problem
                  seal the core support and around radiator
                  put a valance under the core
                  fan shroud always helps to prevent flow sneaking around the ends and pull through all of core
                  do a search on fabo
                   
                • Nat

                  Nat Well-Known Member

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                  i use the stock 340 rad with a big clutch fan with shroud and it never overheated even at 90 degrees sitting in traffic and the 340 was not stock . Since changing to a 426 stroker now using champion 3 core rad with shroud an clutch fan never gets hot ever . those flex fans are garbage , get a decent fan make sure the rad is in good condition and at least a 340 rad if original and you should be good to go .and an alu rad is not any better in y experience , just a lot cheaper could buy 3 alu rads for the price of a new old style rad
                  good luck , nice car !
                   
                  Last edited: Jul 23, 2020
                • Mattax

                  Mattax Just the facts, ma'am FABO Gold Member

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                  It would not hurt to verify the temperature gage is ballpark correct. Even if not, it should have stopped moving up at some point. So it seems safe to say there is a cooling issue.
                  Since it continued to climb while driving, its not a shroud issue. The electric fan could be blocking some of the airflow at speed. So that's a possible contributor.
                  Another possibility is the thermostat didn't open. You can remove it and test in a pot of boiling water. Or you can run the engine with the cap off and watch for the surge in flow to the top tank when the t-state opens.
                  One more possibility to eliminate is a bad cap - ie not keeping the system pressurized.


                  Electric fan is not a great idea with the factory wiring and wiring strategy.

                  As far as going to 'original' there are a couple things to be aware of before trying to buy parts:
                  The 340 in your car has a water pump with a left side inlet. Before 1970, small block water pumps had a driver's side inlet. The pre-70 water pumps are also shorter.
                  It looks like a previous owner installed a '70 up style radiator to match the later water pump. That can be OK, but it uses a different shroud than 68-69.

                  All the suggestions about pulley ratios have merit. if you look in the last pages of the heating/cooling chapter of the service manual there is a table of the various combinatons of fans/shrouds/ water pumps.
                   
                • Mattax

                  Mattax Just the facts, ma'am FABO Gold Member

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                  Alternator doesn't have a resistor. It's a little confusing at first look because the 'ignition' circuit powers both the ignition and the alternator's rotor.
                  The ignition 1 circuit is also called the run circuit. The wires are only 16 and 18 ga. Not really big enough to be carrying more load.
                  FYI The grommet above the regulator has the hoses for the foot operated windshield washer.
                  upload_2020-7-23_15-25-3.png

                  The ballast resistor reduces the voltage to the points and coil when the car is running. So instead of drawing power at 14 Volts, they see something closer to 9 volts - the exact reduction depending on the current and the temperature.
                  upload_2020-7-23_15-38-1.png
                   
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                  • 340doc

                    340doc Well-Known Member

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                    The factory senders can be wonky sometimes too. I swapped intakes one time and the used intake had a sender already in it. All of a sudden the gauge would climb real fast to the hot side when idling then drop to real cool as soon as I got moving. It had a crazy swing on it. I put the original sender from the old intake back in and it was fine.
                     
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                    • D's Nuts and Bolts

                      D's Nuts and Bolts Active Member

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                      I wondered that,
                      Thank you for the advice! I'm searching for a pulley and fan, going to go ahead and do the thermostat as well and see how she runs then. Love your engine bay, very clean. I see the electronic ignition box, do you recommend that conversion? I think the alternator resistor is bad, because of the electric fan hook up, so I was thinking of converting to the electronic system, something like this Summit Racing® Billet Electronic Mopar Distributors SUM-851003-1
                       
                    • D's Nuts and Bolts

                      D's Nuts and Bolts Active Member

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                      Yeah I think I'll measure the temp with a gun and see what it reads, maybe just replace the sender.
                       
                    • cudamark

                      cudamark FABO Gold Member FABO Gold Member

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                      Lot's of good info here. IMO, first would be to verify that it's truly running hot. If not, change sender and retest. If it is running hot, I'd start by installing a new 180 degree thermostat and flushing out the block and radiator. If the cooling tube openings in the radiator have any crust on them, pull the radiator and have it cleaned (rod and repair) and flow checked. If the radiator shop says it looks sketchy, have a 3 row core installed. Ditch the flex fan regardless, and get a 7 blade rigid. I've seen those flex fan blade fatigue and grenade, sending shrapnel in all directions, including up through the hood. You don't have A/C so it shouldn't need a shroud. Doesn't hurt to have one though. Helps cooling in traffic. I've also seen mismatches on water pumps and it's pulley. They made 6 vane and 8 vane pumps. A/C and non-A/C. They spin at different rates. Having the proper flow is most important. There's always the possibility that the engine was bored beyond safe specs, or, there was a bad core shift. Too thin cylinder walls can result. In that case, it will never cool properly. Naturally, finish up with a good 50/50 antifreeze.
                       
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                      • D's Nuts and Bolts

                        D's Nuts and Bolts Active Member

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                        Thank you for the advice, I've been searching any suggestions on where to get the smaller pulley?
                         
                      • D's Nuts and Bolts

                        D's Nuts and Bolts Active Member

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                        Ugh I hope that's not the case. To me it looks like they installed a fan that's bigger than the shroud, it flexed and broke the shroud, but I'll check the mount.
                         
                      • cudamark

                        cudamark FABO Gold Member FABO Gold Member

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                        To me, it looks correct for a non-A/C setup. Is there a number stamped on it somewhere?
                         
                      • moparmat2000

                        moparmat2000 FABO Gold Member FABO Gold Member

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                        They are the correct pulleys for a non A/C setup. If you go with a clutch fan and 18" fan which I recommend, use an aluminum radiator which is thicker than stock, the fan will be too close with a stock mopar fan clutch. Use a Hayden fan clutch #2765 for a 1990 Jaguar XJ6. It comes with a centering bushing and is shorter in length to fit with a thicker aluminum radiator. I agree though, first need to see if the gage is screwy or if it's really getting hot.
                         
                      • yellow rose

                        yellow rose Overnight Sensation

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                        You have to search and see what you can find. The aftermarket is expensive and hung up on slowing the pump down so it’s hard to find overdrive pulleys.

                        Check here in the for sale forum and put something in the wanted section.
                         
                      • moparmat2000

                        moparmat2000 FABO Gold Member FABO Gold Member

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                        The stock pulleys are on it are for the NON A/C setup. They are fine if everything else is working properly. They were designed to work at that speed and coolant flow rate without overheating the engine from the factory. If the car is overheating now 50 some odd years later then it ain't the water pump pulley ratio. It's something else. Jus sayin. If you want more flow, then just install the 8 bladed style water pump on it if it doesnt already have one.

                        Your problems are multiple, but it ain't pulley sizing or trying to speed up the water pump. Especially on what appears to be a mild street 340. Contrary to what others are saying, overspeeding the water pump for flow is a bandaid on the problem if the radiator is partially plugged, not a fix. From pix and inlet/outlet it appears to be a V8 22" radiator. Verify the engine temperature with a digital point n shoot thermometer on the radiator, and on the engine at the thermostat. Once you know if it's running cool and the gage and or sending unit are off, or if its overheating, then take it from there.

                        A electric fan and mechanical fan fighting one another for airflow
                        B a possible partially plugged/ or undersized radiator. Get it unplugged, or recored, back flush out the engine, and heater core while at it
                        C ditch that flexi fan for a good clutch fan with an 18" diameter fan blade setup.
                        D put a good new 180° thermostat in it
                        E put a good radiator cap on it.

                        I'd place my bets on that radiator possibly being partially plugged, and there being possibly a too high of a temp rated thermostat in it.

                        Good luck.
                        Subscribed.
                         
                        Last edited: Jul 23, 2020
                      • 512Stroker

                        512Stroker We are all here because we are not all there.

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                        Electronic vs points is always a great ignition upgrade.
                        I dont believe there is a resistor in the charge system, you sure its not a fusible link?
                         
                      • yellow rose

                        yellow rose Overnight Sensation

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                        Really? The FSM shows OD pulleys for performance. It’s about FLOW. Air FLOW and coolant FLOW. You have to have both, and the OP is missing one or both of them.


                        Unless you are running down Warren Johnson for the money, the tiny bit of HP you save underdriving the pump is meaningless.


                        I’m sitting 15 feet from an all stock 1973 duster, factory air, factory cruise, two owner car.

                        It HAS an overdriven water pump.

                        It’s not complicated. The OP is down on flow somewhere. Speeding up the coolant is never bad.

                        Edit: I can take a picture of the FSM showing OF ratios. Your assumption that everything on the OP’s car is just that. He needs to figure out if it’s air flow, coolant flow or both.

                        BTW, the OP says his car is a 68 and the water pump is for 70 and later. So we have no idea of what else has been changed.
                         
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