VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 IS the 207 engine Radiator Pressurized..??

Buying a 4 core aluminum radiator ( with proper 1934-36 Chevrolet mounts) that has a pressure cap.... it is a down flow type with proper
1 1/4" inlet & outlet..... I don't think the stock 1934 Chevy with the 207 engine had any pressure in the radiator. QUESTION.... Can I use the 4 core aluminum radiator WITHOUT a pressure cap (perhaps drilling a small hole in the pressure cap, to release pressure) and have it simply gravity feed into the engine like the original radiator...???? PLEASE educate me on this... Thanks, Sunny

Yes, you can run that radiator with a non pressurized cap.

The reason that cooling systems are pressurized is to increase the boiling point temperature of the liquid coolant.

The water pump creates a pressure differential that causes the coolant to flow. The flow is not caused by gravity. The bottom tank of the radiator is lower than the lowest part of the water jacket in the engine block

I do not know if the inlet and outlet connections were the same size on that year radiator. Often the outlet from the radiator is larger. This provides less resistance to flow on the suction side of the water pump.

Is the hole for a MODERN sized cap? Or some huge 1930s 4 pound pressure cap?

If it is for a modern sized cap, caps exist that are just flat caps, nothing sticking down. They are used in systems that have the pressure cap elsewhere, like on a surge tank. I can't remember offhand what I have seen that on, but it exists. If you have a good parts man at your local parts store (and maybe a stant catalog) you could probably figure it out.

A big difference between radiators for pressurized systems and radiators for open systems is the location of the overflow tube. On a pressurized system the overflow tube is between the upper and lower seals of the cap, it is separate from the system.

On an open system, the overflow tube, which is vented to the atmosphere, is inside the system with the coolant. On factory systems it is located up as high as possible.

If you put on one of these thin caps I am taking about, it will seal around the upper rim of the neck, leaving the overflow tube inside the system where the coolant lives. That is where it belongs. The only way to do it any better than that would be to weld a tube in up even higher.

Don't overfill the system. There needs to be airspace for water/coolant expansion at the top of the radiator. If it is too full some is going to squirt out.

Thank you two... I understand what you are telling me.... both the inlet and outlet holes on my "34 207 engine are the same size 1 1/4" it is the same on this new radiator ...... I think I can find a cap that only seals on the top rim of the filler neck.... if not.... i could cut off the bottom seal that sticks down on a pressure cap...leaving only the upper seal on the cap. this would allow the over-flow tube to be down in the coolant tank breathing freely with the outside air ... I know to not fully fill the radiator... but to just cover the core with about an inch in the upper tank... leaving an air space for hot water expansion.... I am hoping that this 4 core aluminum radiator will cool better than the stock one... dissipating heat more efficiently.... and be free of accumulated rust & debris.... I called around a bunch of radiator shops within 150 miles of where I live... and NONE of them take apart a radiator and rod it out and clean the cores and tanks... all of them only replace more modern radiators.... The old fashion radiator shops are disappearing, just like good old fashion body shops that used to pound out dents or lead fill them... no longer work the metal.... just buy replacement parts.... this is becoming a throw away & replacement society.... not a fix & repair.... so I decided to buy a new one ... getting it cheaper than having my old one boiled out, taken apart, rodded, and put back together.... IF I could actually find someone to do that around here..... The new one cost $177 free shipping... Here is the link: https://www.ebay.com/itm/265801837364 Thank you for your Help, Sunny

Here are 2 different neck sizes:

https://www.rockauto.com/en/moreinfo.php?pk=48497

https://www.rockauto.com/en/moreinfo.php?pk=5937219&jsn=3

Make sure you do everything you can to clean the cooling passages in the head and block. Flush the system to remove as many loose particales as possible before you install your new radiator. Otherwise your new radiator will get plugged fairly quickly.

My experience and observations are that overheating problems start in the block and head. That is where the corrosion occurs first. The copper radiator is not nears a susceptible to corrosion. The corrosion in the engine interferes with heat transfer to the coolant. As the corrosion grows it restricts flow. The particles break loose and eventually plug the tubes in the radiator.

Good advice!^^

If you want you can also put a filter in there to catch all the trash that is coming out of the engine:

https://forums.aaca.org/topic/381501-grimys-sock-cooling-system-filter/#comment-2396383

Bloo.... I read that whole post about using a panty hose or nylon stocking to filter the water coming out of the block into the radiator... but that posting DOES NOT tell me HOW TO INSTALL The SOCK FILTER & WHERE....?? Do you know...? could you Tell me..?? or better yet post a Photo.... Thanks, for the idea... I want to try it with my new radiator.. Sunny

What they are doing is putting the stocking (or some of it) in the radiator through the top hole then folding the cut end over on the outside of the radiator nipple where it is held in place by the hose and clamp. You don't want it getting loose. You probably need some sealer to keep coolant from seeping at the hose connection.

My car, a 36 Pontiac, has a cross-flow radiator, so it is a real pain to get it in there. It hangs down in the driver's side tank, which is the one fed by the thermostat. I suspect mine in the pictures are longer pieces of sock than most people use, thanks to my weird radiator. On a normal car it would be laying out flat in the top tank. I have on at least one occasion used garden hose pressure to make the sock lay out, but I don't think that would normally be necessary. Don't lose the end.

I'll try to get a picture up later.

Upper hose connects here.

Thank you.. that shows & explains it very well.. Sunny

Bloo,
How much Evaporust do I need for my 35 Chevy? Do I run straight 100% Eveaporust (3 or 4 gallons) or do I use a smaller amount diluted with distilled water until the radiator/block is filled? I like the sock/filter trick. I will also do that along with cycling it by running the car until hot then shut it off and letting it cool and running it again 3 or 4 times a day.
Thanks for the cool tricks. Love this kind of stuff.

Pete V

You might want to check the Evaporust website and read about Thermocure.

Edinmass over on that other site is responsible tor the Evaporust trick. For various reasons it did not work for me when I tried it, but I will be trying it again soon. Ed advises regular Evaporust and using it only full strength. When it is spent it turns black, and you can tell if it is shot if you have doubts by testing it with a specific gravity gauge (a cheap glass floaty thing and a beaker sold on Amazon and elsewhere to home wine and beer makers to check sugar concentration). I did buy the floaty thing on Amazon and it does tell you when Evaporust is bad. The Evaporust website tells you what the specific gravity should be in their FAQ. I've been using it for a lot of non-cooling-system things, and there are times I wonder if it is spent. Some cars may need to be treated more than once. I have no personal experience with this, other than my one failed try. That said, Ed is typically not wrong, and I am going to try again just to clean up in there even though I don't think my engine is that terribly rusty inside.

Thermocure might be fine, but I have zero experience with that one, and have not even heard stories. I'm a believer in Grimy's sock though!