[Jim7231]

Originally Posted by T-bucket23

I will be surprised if the hood make a difference at highway speed if you are not having issues in the city. A water cooled engine does not rely very much if at all on block surface cooling from ambient air.
I have seen several vehicles that don't have the heater connected and the block plugged that the internal pressure keeps the thermostat from opening.

What I was wondering about is at highway speed, if there was not adequate "venting" of the engine compartment, could a pressure front build up such that the flow through the radiator could be reduced?

[1BAD80]

You need a fan shroud also to cool the whole rad not just the area the fan covers, that leaves hot spots and very little air flow.
maybe a 16 lb rad cap to help the boiling point.

[T-bucket23]

Originally Posted by Jim7231

What I was wondering about is at highway speed, if there was not adequate "venting" of the engine compartment, could a pressure front build up such that the flow through the radiator could be reduced?

It is possible I suppose. I would think the air rushing under the car would suck the engine compartment air out as it would create sort of a vacuum. The is usually plenty of room around and under the engine for air to escape.
The bottom line is air has to move through the radiator to cool the fluid. Anything restricting this or causing the air to go around the radiator would hinder cooling. Some fans will actually reduce the forced flow of air at highway speeds. I have seen some very subtle changes to mounting or grill design solve cooling issues.

Over heating issues are hard to diagnose without having the car. A remote sensor on the radiator can also tell if the radiator is the issue of if the cooled water is not reaching the engine for some reason like a collapsed hose

[Jim7231]

Originally Posted by T-bucket23

It is possible I suppose. I would think the air rushing under the car would suck the engine compartment air out as it would create sort of a vacuum. The is usually plenty of room around and under the engine for air to escape.
The bottom line is air has to move through the radiator to cool the fluid. Anything restricting this or causing the air to go around the radiator would hinder cooling. Some fans will actually reduce the forced flow of air at highway speeds. I have seen some very subtle changes to mounting or grill design solve cooling issues.

Over heating issues are hard to diagnose without having the car. A remote sensor on the radiator can also tell if the radiator is the issue of if the cooled water is not reaching the engine for some reason like a collapsed hose

I assume by remote sensor you mean a temp sensor connected to a display or ? in the car. I may be able to do that and that's a terrific idea. I really want to know the cause and not purchase a radiator or something that may not be the problem. Ok, I'm adding a remote temp sensor to my list of things to do.
Thanks.

[454headache]

To set the timing for max vacuum-

Unhook the vacuum advance. Plug in a vacuum gauge to a manifold source. Turn the engine on. Now turn the distributor counterclockwise to advance it until you reach peak vacuum, and you are done.

You might have to re-curve the distributor's mechanical advance for less total advance if detonation occurs. I had to do that with my BBC, though they like more initial advance. Had 22 initial plus 38 mechanical advance, not good.

[Jim7231]

Well, I had the radiator (Walker 4-row) rebuilt at a radiator shop. Lots of stuff plugging the tubes he said. Now it really is nice at slow speeds, the electric fan even cycles off idling showing much better cooling (93 degrees outside temp). Still need to test on a long highway run, but expecting that this fixed the weird problem.
Thanks for all the help you guys provided, I learned a whole bunch!

Jim

[lg1969]

Glad to see it's working. Good luck

[oldbogie]

Originally Posted by Jim7231

I have a 350 in a '32 Chevy sedan with a th-350 tran. behind it. 3:55 rearend. Runs 180-185 in town, stop and go w/o air on, runs 190 with air in same situation. Go out on the highway and after 15 or so miles at 60-65 mph, the engine temp starts to go up and seems to run about 225 or so. Gets hotter if a semi gets in front of me. I have a hayden elec. fan on it. Don't know what the cam is but the engine is a 1969 vintage with Edelbrock manifold and 500cfm carb on it. Stock distributor with pertronix flame thrower II conversion in it and high voltage coil. How can I tell if it's timing (too retarded), to lean, air flow, or radiator? This is a real stumper for me. Where to go from here as I've done all the basic testing. I did back the timing off a bit after it was running hot and causing ping when accelerating.

Thanks

This is symptomatic of not enough coolant flow getting thru the core as a result of corrosion or crud plugging the passages. At lower speeds and RPMs where the BTU transfer is less, the engine operates at proper temps as sufficient coolant is passing thru the core. When the heat transfer demand increases and the RPMs come up, the returning coolant can't pass thru the core in quantities sufficient to feed the pump's demand. Pump head pressure increases with-in the engine and in the return tank of the radiator but falls within the core, lower tank, and ahead of the pump where the restiction of the core simply can't feed the pump's demand curve.

The core will have to be cleaned or replaced depending on how clogged up it is and how coolant tight it is. Many old cores sprout leaks everywhere when the corrosion and crud is cleaned out.

Chrome looks nice but greatly inhibits heat transfer. I'd limit it's use to places where it doesn't matter in engineering terms like license plate bezels.

Bogie

[302 Z28]

When you have time or money allows think about purchasing and installing a FlowKooler water pump impeller modification kit. It makes a high flow water pump out of any OEM or after market pump. Also use a water wetter solution.

As mentioned earlier about the quality of T-stats, I concur totally. Recently when I was doing a cooling system service on my 04 Tahoe I had a real problem finding a T-stat that was not made in China. Not at NAPA, not at Autozone, not at Car Quest, but found one at Oreilly. He listed two, one made in China and one made in Israel of all places. I took the one made in Israel and it is working fine.

Vince

[Jim7231]

Well, I still am getting a heat up on the highway at speed. So I decided to pull the thermostat and test it. It is a fail open unit and was open when I removed it. It released and I tested it in a pan of water on the stove with a digital thermometer. Seemed to work correctly and appeared to open all the way. Well I decided to try another thermostat and purchased a Mr. Gasket "racing" thermostat that has built in bypass. The one I got was a 160 degree, the other was a 180. Well I installed the new 160 and tested after making sure no air was in the system. The car actually ran hotter than before, and still started the temp climb on the highway.

So, I decided to do one more test. I removed the thermostat and put the system back together, made sure no air was in the system and went out for a test run. Outside temp was some cooler than yesterday, but ran on the highway for more time. Ran at about 185, warmed slightly when I came off the expressway, then started cooling. Got back on the highway, immediately cooled to about 185 and stayed there. It idles cool, runs at speed cool and acts like it should.

Now, then next hypothesis is that when the thermostat is in place, the water pump impeller is not creating enough pressure to overcome the head pressure created by the restriction of a thermostat. I'm thinking I should now replace the water pump. Opinions of this hypothesis?
Thanks.

[406 bug]

You may be asking too much from the rad. To relieve some of the load, you could install a remote trans cooler.