TheBMan

I'm afraid I'm going to have to bite the bullet for the 4-row radiator. I'm not sure I should have to do that since this is a stock small block without A/C but I may have no choice. You guys may have to peel me off the wall if it still gets hot after doing that. 😝

I've heard this philosophy before (heat exchange). What Milodon told me is that being in the radiator longer means it's also in the block longer (getting hotter). I don't want to go to an aluminum radiator because I want to keep it stock fitting and appearing.

I tried a 160° thermostat before the high flow water pump. It behaved the same.

I recently talked to the folks at Milodon and installed a Milodon 16210 high-volume water pump and Robert Shaw high flow 180° thermostat. I just got it back together and running today. It's about 88 humid degrees here today and the temp slowly climbed when sitting still. It got up to 215° before I drove it to cool it down to 190°. I believe this car should have more than enough cooling system capacity so I'm completely baffled why it's getting hot. The temperature should sit on 180 to 190 (variations in where the thermostat is located vs where the sensor is located) and not go any higher. That's exactly what the purpose of the thermostat is - vary its opening/flow-rate based on temperature in order to maintain a constant temperature. Man, I hate to bite the bullet for the 4-row radiator. That thing is $1100 and what if it still gets hot? ARGH! @LS65Speed Thanks for your input. I don't have A/C and my timing is set at 12° BTDC (initial). My radiator is a full size copper/brass 3-row, brand new. Frustrated.

1972 402 big block car on Facebook Marketplace. https://www.facebook.com/marketplace/item/2126126461077941/

I got excited because the ad is posted here in Columbus (Ohio) but then I dug a little and read that it's an auction car and actually located in Mossyrock, WA. 😒

Yes, faulty circuit board.

I should have updated this after the repairs were complete, but the diagnosis and repair was all correct and the fuel gauge works properly now. I also replaced all of the bulbs. I had to fiddle with some of the connectors to get them all to work. Thankfully I had the foresight to check them before putting everything back together.

Right?! I had that exact same thought! Why go all that way and not spend $50 for the circuit board?

Good idea. I think one of the moderators has to do that.

@John S I do appreciate the analogy for sure. I'm using a stock AC Delco water pump and stock pulleys. Man, I hate to think I would have to fiddle with flow rate to get things right if I'm using "stock" parts.

@John S Thanks for the input. Like you, I have used a laser temp gauge to check at various points. Also like yours, mine is hotter at the cylinder head where the sending unit is than it is at the thermostat housing. I would expect this because the sending unit is much closer to the combustion chamber and exhaust exit of the cylinder head. There is generally 10° to 15° difference. My engine has never gone over 220° because I've been able to move to get the temperature down. It seems that it should get to a certain max temperature and not get any hotter if the cooling system is working the way it's supposed to. I'm afraid that if I get stuck in traffic on a truly hot day like we get here in Central Ohio during the summer, it will overheat. I guess it bothers me the most because I can't explain it and I've gone to great lengths to put the best parts on my car while not straying from the stock setup. If I was doing all sorts of crazy hotrod stuff and deviating from the stock setup, I might be more understanding about why it's not behaving. Thanks again for your input!

Update on this... I've tried both types of clutches for the fan (centrifugal and thermostatic) with similar results: temperature creeps up slowly at idle when warm outside (doesn't have to be hot). I sent a tech question to Hayden via their website and surprisingly one of their support people called me the same day (wasn't expecting that!). He explained that these clutches fully engage when the *air* temp across the coil spring sensor on the clutch reaches 170° to 180° not when the engine temperature gets to any certain number. I knew this and it makes sense but thought I would reiterate in case anyone didn't know. Anyhow, he suggested trying the severe duty clutch, which I did, but it performed the same. Turns out that the difference between severe duty and heavy duty is the depth and number of cooling fins on the clutch assembly. Technically they both engage the same amount (80-90% of engine speed) move the same amount of air. I have a new three-row heavy duty copper/brass radiator and the engine is relatively fresh so I'm sure I have no obstructions. I've tried multiple thermostats. I may go to a four-row copper/brass radiator but that's a $1050 proposition with no guarantee that it will make a difference (although technically it should). If I do that, I'll update here and let you know. I'm aware that there are aluminum options as well but I'm trying to keep the car as original as possible. copy: @John S

@DragCat For me, it was plug and play because I bought the gearbox and the rag joint (steering coupler). My car was already a power steering car so no issues with the pitman arm or fittings for the pump. It was one of the best upgrades I ever did to that car. 👍

Thanks John. I ordered one and will update here after I get it installed.

I've wondered if it was worth trying the centrifugal clutch. I've gone through everything else (twice). There really is no logical reason for this engine to get hot. I'm considering going to a 4-row radiator but that's a $1000 proposition with no promise that it will solve the problem. My only concern with the non-thermal fan is that it might be loud at idle. @John S, can you speak to that?

Yes, I did drill a small hole in the thermostat. 3/32". I'm very certain it has no air in the system. Thanks!!

Oh yes, mine is super stiff. I have a new Hayden HD unit. Appears to be working as it should. Thanks!!

Oh yes, the system definitely builds and holds pressure. The hoses get very firm. I have a 16lb cap, which should be correct for this car.

It got up to almost 220 while sitting in traffic. It didn't feel like it was pulling a lot of air through the shroud so I tried to stop the fan with some cardboard and it would not stop. Still not convinced it's fully engaged.

I just put 1/2 turn on it and reinstalled. Getting ready to go for a test drive now. It's about 80° here today. It does go back down to 190 when moving. It's a brass 3-row reproduction replacement. Picture of the setup attached.

This is the actual fan and clutch I've been running; I took it off to tighten the spring because the temp creeps up in traffic (has gotten up to 210°). I'm running a 180° t-stat, new 3-row radiator and 50/50 pre-mix coolant. If you're saying that it's supposed to be hard to turn the spring, I'll go for it. The clutch seems to be operating normally with good resistance (not freewheeling).

I have this type of fan clutch. I get to about 1/4 turn and it gets very stiff. I can't imagine trying to get one full turn out of it, I can't even get 1/2.

I was beginning to wonder if this was for an accessory that didn’t exist in my car. Closer inspection showed me that it doesn’t really reach anything. The part that threw me is that it was near a female plug that it could have mated with. The color change didn’t make sense though. I understand that the factory would make a harness that fits more than one car, that just seems like efficient manufacturing. I think I’m good to go. Thanks for confirming, Dennis!

Thanks Dennis, but no console. Column shift.