I need some ideas on 350 S/B "Over Heating"

I have a 350 Chevy S/B bored to .060 over and it's over heating. Not so much as to be kicking out all of the coolant but you can really hear it boiling (a gurgling sound) when it idles and also just after its turned off. You can feel the "pulse pressure" build up in the radiator hoses at the same time as the sound. I know I have some mismatched parts for optimum performance but hey, I'm on a budget and this is what I need to work with right now.

The car is a 1932 Ford steel roadster project with the usual 350 S/B Chevy engine, 350 A/T, and 8" Ford rear end. Some of these parts are new and others are well used. HEI generic distributor is set as follows, 15 degrees BTDC at idle, 30 degrees BTDC at 3000RPM with initial plus total mechanical advance, and 50 degrees BTDC combined initial+mechanical+vaccum all measured on the crank. I confirmed the timing marks to be correct with TDC on number one cylinder. The distributor vaccum is currently connected to the right side (passenger) timed vaccum port on the Edelbrock/Weber (Carter AFB) carb. I have tried it with full manifold vaccum also, and the over heating problem is the same. The block is cast with #3970010 on the rear and stamped in the front with V1201TYZ. The intake manifold is a "single plane" Edelbrock Torquer II with a "very lean" stock jetted #1406 model carb. I know this is not a good combination with my (advertised) 292 degree duration hydralic cam, 2.73 R&P, and 30" tall tires. The car has 1 3/4" shorty headers and a 2 1/2" dual "X-Pipe" exhaust system. The car has a brand new Walker four pass radiator, a 16" electric puller fan, 180 degree thermostat, Coolant with Redline "water wetter", and I've tried both 7# and 16# pressure radiator caps. The engine has an aluminum water pump of the generic imported variety. The car has no heater hoses and the pump and manifold outlets are plugged off.

Last weekend I pulled the heads off to check for bad head gaskets or to inspect for a cracked head and everything apears to me to be OK. No signs of water getting into the combustion chambers. The engine was rusty at some point in it's life and I cleaned out the water cooling holes in the heads around the spark plug areas from rust and scale. Is it posible that I have some kind of a "air lock" and the engine is not full of coolant?

My other "related problem" is a VDO water temperature gauge that has worked erratically since it was new two years ago. It stays at 180/200 degrees then quickly shoots up to 250 degrees and falls back to 180/200 for awhile and then repeats its cycle. The VDO gauge and sender were checked by a well known gauge shop and both "tested" fine. I have rerouted my wiring to avoid electrical interferance but nothing has helped this problem.

Sorry for my long post. Do any of you have any ideas what I should check next on my engine over heating, or gauge problems. Thanks for you time, John Palmer

I don't really know the most around here but I am also running a .060 over block so you should expect high temps... mine runs about 215-220 on a warm day... 190 all winter. But I'd suspect the lean condition adding greatly to the temps. But definitely stick around for some other opinions..

first place i'd start is to check your thermostat. Sometimes, especially if you used a stop leak additive such as Bar's leak, the thermostant becomes plugged and the motor has to get really really hot for it to actually open. Then i'd check for radiator flow just in case. I know yours is new but you never know... You might also look at that water pump. sometimes the old saying "you get what you pay for" is learned the hard way. If you bought a generic, cheaplike water pump, you might be getting generic, sucky results.

To the question about air lock, as the water flows through the engine, the air would eventually work it's way to the top of the radiator.

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Originally Posted by John Palmer

My other "related problem" is a VDO water temperature gauge that has worked erratically since it was new two years ago. It stays at 180/200 degrees then quickly shoots up to 250 degrees and falls back to 180/200 for awhile and then repeats its cycle. The VDO gauge and sender were checked by a well known gauge shop and both "tested" fine. I have rerouted my wiring to avoid electrical interferance but nothing has helped this problem.

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I don't think you've got a guage problem and possibly not an overheating problem. It sounds like your T-stat is doing almost what it is supposed to do, but it might be sticking a little. With the guage movement, you're seeing the T-stat opening and closing. I'm thinking that you might just have too good a cooling system. Making the thermostat close and restrict water flow far more often than it should. Does it mostly stay at 180, or at the higher 200? Does it run cooler than 180, especially after spiking?

I don't know about the gurgling sound. Maybe you've got air somewhere in there that shouldn't be there.

Just a question. Is the top of your engine higher than the top of your radiator?? If so the engine will get air locked. I'd check the thermostate and maybe flush the engine. Your not realy getting to hot but it is a situation that should be checked. How hot dose it get after you turn it off? You could run the engine with a hose in the radiator and the drain open and see how hot it gets. Over heating problems can be a pain but can be solved. When you changed the water pump you didn't perchance get one for a serpintine belt set up did you??? Sounds like a nice ride you'll get it figured out in time.

I agree that a lean condition can be deadly and can cause overheating. I would correct that as a first order of business. Fatten it up a couple jet sizes at least. Another thing to check is your lower radiator hose. If it is old and worn, it can collapse under suction from the engine and block or reduce coolant flow. With the engine cool, reach down and squeeze the lower hose, if it can be compressed easily, replace it with a new one. Let us know what you figure out.

Pat

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Originally Posted by cffisher

Just a question. Is the top of your engine higher than the top of your radiator?? If so the engine will get air locked. I'd check the thermostate and maybe flush the engine. Your not realy getting to hot but it is a situation that should be checked. How hot dose it get after you turn it off? You could run the engine with a hose in the radiator and the drain open and see how hot it gets. Over heating problems can be a pain but can be solved. When you changed the water pump you didn't perchance get one for a serpintine belt set up did you??? Sounds like a nice ride you'll get it figured out in time.

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Thanks for your ideas. I think I will remove the thermostat as a test and might install one of the "hole" flow restricters in its place as a diagnostic test. On the 1932 Ford with a 350 engine the top of the radiator tank and inlet is much higher than the top of the engine. I will run the engine with the drain open and a hose into the radiator top to flush out the system and check on the amount of coolant flow. I will run a water hose into the top hose (with thermostat removed) to check flow through the block. It sucks getting water on a bare steel frame and steel body, not to mention all of the polished stainless and chrome suspension parts. But I have to get to the bottom of this problem.

Interesting question about the possibllity of having a serpintine water pump? Do they look the same? I thought they were used only on the very late model engines. The pump on there currently is you basic swap meet (imported I'm sure) polished aluminum S/B Chevy pump. I might also take the pump off the engine to inspect the water pump impeller for damage, or that it's turning in the correct direction. This pump was on the engine when I bought it so I don't have much background on it.

Thanks again
John Palmer

John, a couple of more tidbits based upon experience:

The water pumps (regular rotation and serpentine rotation) look the same from the outside. The impeller is twisted the opposite way to account for the reverse rotation.

You can also have a wrong way fan. Symptoms of such are great cooling at idle (air is going out the front of the radiator) and sucky cooling at speed (air coming thru the radiator conflicts with fan pushing air forward). This is a bear to figure out....speed up and it gets hotter, stop and it cools off)

Some temperature senders are smaller threads than the tapped hole in the head so people use a reducing bushing to compensate. Some reducing bushings are made so that the copper tip of the sensor is shielded by the bushing itself and allows a pocket of air to be trapped around the copper tip. The result is usually a significant gauge offset but who knows what else it does. If you use a bushing to adapt the sender, look at how the thing presents the copper tip to the water.

Using sealant or teflon tape on the sender threads can insulate the sender and either make it not work or make the resistance higher, again causing an offset.

As one of the other guys said, the gurgling can be caused by air pockets. One of the older troubleshooting methods to see if there was a head gasket leak was to look at the radiator water to see if bubbles were coming up thru the water.

The engine code TYZ is listed as a 75-77 350 truck motor.

I have never tried running a SBC with the heater inlet/outlet plugged....I have only run a bypass hose between them....someone else reading this may
have a comment on that one.

Lastly, are you running a good thermostat? There are two designs that have been discussed on CHR in the past. The el cheapo has specific problems that I forget what the details are......anyone?

mike in tucson

I has the same problem with a stroker I built- drove me crazy, until I was giving someone else some advise on the need to run a solid damper, and it occured to me that if the damper was spining too fast- then so was the water pump- causing cavitation. I changed my pulleys and it never overheated again.