My big block always seems to run warm. I bought an infrared thermometer and confirmed the gauge is accurate. It settles around
210 when driving. When idling with the hood open it goes up another 10 degrees.

I'm pretty sure the radiator is copper. Certain it's not aluminum.

There were a few gaps between the fan shroud and radiator at the bottom. I used duct tape to cover the gap, just to test. Didn't seem to make any difference. I'm missing the lower shroud extension. Doubt it will make that much difference.

First thought is to replace the thermostat. Fan clutch is a question.
Has anybody experienced anything similar and found the problem to be the fan clutch? I'm very reluctant to buy an aluminum radiator unless I have no other choice. Seems the system should work if it shipped with a copper radiator.

Don't see how it could be the water pump. No leaks. Two belts driving the pulley.

What temps do others with big blocks see with a copper radiator?

It wasn't a hot day today, upper 70's or low 80's I think.

Any other ideas?

 

BBs will cool just fine with copper radiators. They came that way. But, with age the cooling fins break loose from the tubes, and there could also be deposits in the radiator tubes etc.

There are three things needed for cooling. A working radiator, water flow, and air flow. If it heats more at idle than at cruise, I would suspect an air flow problem. If it is not capable of cooling at speed, I would suspect the radiator. You can have the copper radiator re cored.

 

Thanks for the suggestions.

I think the radiator is in pretty good shape. It's a replacement. I'll take a closer look later this week. I don't recall seeing any debris stuck in it. I had painted it and reinstalled several years ago. Car hasn't really gone anywhere since.

While surfing the net for possible answers I found an article on Corvettes which stated the fan clutch should show considerable resistance to turning when the car is fully warmed. It stated the fan should stop almost immediately with the engine. I haven't looked immediately upon stopping the engine but did note the fan seemed to turn fairly easily even after warm up. I didn't notice a big difference in resistance to turning.

Other possibility mentioned was a combustion leak into the cooling system. Wondering how this would present itself? I don't see clouds of steam nor does the system overpressure and puke. If it has a leak, would it appear as running warm but not necessarily overheating? I can look at the oil. Don't remember ever seeing any evidence of water.

 

BB,

Continue to search the Forum for a complete list of cooling ideas for the BBC. Meanwhile,

1. With BB's you need every bit of air going through the radiator for cooling. Stop all gaps to keep air from going around or under. It makes a significant difference.

2. Dr. Rebuild sells a kit specifically for this purpose. It works! Lose the duct tape! Read his list of 12 ways to keep cool.

3. The list includes checking the radiator, rad seals, rad cap, fan shroud seals, the shroud and extensions to seal the bottom of the shroud, fan clutch, fan blade, thermostat.

4. Also, does your C3 have a properly installed front spoiler? This forces air through the rad.

5. Dr. Rebuild's #12 More Tips: "Clean the area in front of the rad & AC condensor. Remove the front license plate and bracket (if legal in your state). Check the engine timing. Use a higher octane fuel. Change to synthetic engine oil to reduce friction. Test the anti-freeze and increase the volume to raise the boiling point. Ensure an AT is not slipping excessively and that the cooler is functioning properly. Have the engine passageways boiled out. Check tires for proper inflation and alignment to reduce rolling resistance."

6. You can see that there a number of things that can be done to control temp. From my 1972 Corvette Owner's Manual, p. 22: "During normal operation, gauge will indicate around the 230 degree mark. If the gauge indicates 250 degrees, the engine is overheated."

Yeah, I'll say! With a combination of these techniques, you should be able to keep your temp at 210 degrees no matter how hot the weather. This assumes, of course, that your cooling system is working properly.

If all this fails, call Tom DeWitt for a DirectFit(R) Alum. Rad. I know for my 72 the price has fallen from $495 to $450. Put that baby in and forget about it!! Hope this helps,

Rickman

 

Hi Rickman

Thanks for the suggestions. I'll consider almost anything.
The duct tape was just an experiment. Certainly not a solution.
For now, I'm looking for ways to get this to run cooler while idling, standing still.
This is the condition which concerns me most right now.

I appreciate assistance from all on this forum. Offer some myself when I can.

 

I have a '70 BB with AC. Driving around, it always stays around 180. If I stop for gas, when I start back up, it will be at around 200, and drop back to 180 within a few minutes. If I idle in the driveway with the AC on, it will climb to 210-230 on a hot day, but I haven't had it overheat yet. It ran hotter when I got it, but I was missing the front spoiler. I have had some pains over the last 2 years of whether my fan clutch is working correctly or not, I'm still not sure if it is. But given that the car has not yet overheated, I figure it can't be all that bad.

 

Hi PK,

I think we talked before. I thought I remembered someone telling me their BB ran at 180. This is what bugs me. I verified the gauge is accurate, used an infrared thermometer to read the temp at the thermostat housing. I don't have AC so I'd expect to run on the cooler side.

Radiator was new when I bought the car years ago. I've keep the system clean so I tend to doubt the radiator is plugged. I'd guess maybe the thermostat opens late and/or the fan clutch is slipping?

I can see gaps between the fan shroud and radiator here and there. The duct tape was a simple experiment to see what effect blocking off the leak at the bottom of the shroud would have. Not much.

Seems to me either I'm not getting enough air flow, the thermostat opens late, or something is generating excess heat which the system can't handle. Explanations I've seen for excess heat have been late ignition timing or combustion leak into the cooling system. There's a test for a combustion leak. If I get stuck I may have this done, either rule it out look deeper into this.

I may try taking a temp reading on the lower hose, see what temp the water is coming back at. May offer a clue?

This car has run on the warm side for a long time. It has been apart for many years, now getting it back on the road. Trying to solve some old problems.

So far as the spoiler goes, I don't have anything extra bolted underneath. I did find a photo copy of a service bulletin from Chevrolet dated 1973 which discussed overheating issues with Vettes equiped with a 454 and A/C. The solution was to add a spoiler to the 73 only.
70 - 72 had another solution, forget what it was. I can probably find the bulletin again. Thought it interesting.

Your comments along with others suggest this car should be running cooler than what I'm seeing.

Thanks for the input, appreciated.

 

One thing that no one has mentioned is ignition timing. From the factory, with the TCS installed, the engine at idle has no vacuum advance in the ignition. Once the engine temperature reached a certain point, the temperature switch in the passenger side head, would activate the TCS system and advance the spark. This in turn, would lower the the idling temperature, not allowing it to get too hot. Sometimes, depending on the conditions, the TCS system my cycle as it aids in controlling engine temperature.

If you are not using the factory TCS system, and you are using a ported vacuum source for vacuum advance, then the engine will run warmer at idle.

 

My 72 BB has the original radiator, the only thing I changed is I went o an electric fan. It stays right at the 1/4 mark on the gauge.

 

The factory TCS is missing. I'm running with the vacuum advance tied to the carb. If I understand you correctly the configuration I currently have is much like the TCS when it's OFF? No vacuum to the distributor?
The TCS would kick in to advance the distributor when the engine started to warm?

Anyone else out there with a BB which runs under 210 have the TCS connected?

Thanks for the tip.

Maybe I should look into restoring the TCS?

 

If your car was running warm before the fan was installed, sounds like an air flow issue as others have mentioned. It may be worthwhile to look into sealing up leaks around the shroud? Possibly replace the fan clutch as well?

 

Set it up with full vacuum at idle from the carb. You will see a lot of difference.

 

Never said it ran warm. just what it runs. The only reason I went to the electric fan is for the spreader bar option.

 

What's a spreader bar option?

 

Sounds a bit like TCS when it switches on?
I'm a bit confused though. If I attach to a port which gets full vacuum at idle, wouldn't I expect the vacuum to drop when accelerating?
Seems the vacuum advance would work backwards?

I gather your telling me the engine may run warm because the timing is retarded?

Maybe I missed something?

 

I have heard of Big Blocks from the factory getting hot in traffic......you may need to go with Electric Fan.

 

The vacuum is supposed to fall on acceleration. Do it, you will be pleasantly surprised.

You will need to lower the idle and readjust the mixture screws.

 

I finally had a chance to start it up today and do some checking.
My vacuum advance is connected to the port on the driver side, front, lower portion of the QJet. There are only two ports available. The other is in the rear near the top. I think this is the fresh air port which the TCS would vent to. So it appears I do have my advance tied to manifold vacuum.

The temp seems to want to level at about 210. I checked with an infrared thermometer. The gauge is pretty accurate. Let it idle for about 15 minutes, checking the temp once in a while. I noted it took a while for the fan clutch temperature to get to 180+, far longer than it took the water temp. I stopped the engine when the fan clutch temp reached about 190. The fan did not stop right away, spun for a turn or two. The clutch still hadn't really locked up. Is this to be expected? Possibly a late opening thermostat?

Another bit of info. I checked the temperature of the radiator at the inlet, pretty much what I saw at the thermostat housing. Somewhere around 210. When I checked the temp on the outlet side of the radiator I read something around 180.

The car was idling with the hood open. Maybe the hood obstructed some of the air flow?

I'm missing the lower fan shroud extension. My next steps may be to replace missing extension and close off gaps between the radiator and shroud? Not sure about the fan clutch. I don't have another to compare to. Radiator would be my last resort...

I don't have an owners manual. What temp are the 70 big blocks supposed to run at?

 

You can also try a Hayden 2799 Severe duty fan clutch. You will get less then one turn on the fan when shutting the engine off when hot. This alone will knock 5* off of your highway temps. When I was having heating issues with my BB this definetly helped.....although my problem ultimately was my stock radiator was just too deteriorated......I had it cleaned/rodded so I thought it was fine but I still couldnt get the car under 205-210* on the hwy. It would cool down some in town....down to about 195-205*..... This was with new EVERYTHING in the cooling system...except the radiator.

I slapped in a Dewitts radiator and my hwy temps dropped to 170-175* and in town temp is around 180-190* idling with the AC on. The hottest it has gotten in town is 195* with the AC on and ambient temps of 95*+.

I will tell you that running the Hayden clutch kills some HP....I dynoed my car with the clutch fan on (w/Hayden clutch) and off and I lost 16rwhp with the fan on.

This Fall I am switching to a Lincoln MK8 fan, hopefully I will get better cooling at idle and less HP loss.

 

[QUOTE=BBCorv70;1575079579]I finally had a chance to start it up today and do some checking.
My vacuum advance is connected to the port on the driver side, front, lower portion of the QJet. There are only two ports available. The other is in the rear near the top. I think this is the fresh air port which the TCS would vent to. So it appears I do have my advance tied to manifold vacuum.

If the carburetor is the correct 70 carb., then where you have the vacuum hose connected is the factory connection, but it is not full manifold vacuum, it is ported. Put a vacuum gauge there and you will see.