The Stovebolt Site Forums The Shop Area Engine Shop Cooling system pressure 261

I have free use of a cooling system pressure tester for 2 days. Cap is a 7lb cap. Does that mean I should limit the pressure to 7lbs when I test the system?

What vehicle are you testing, and is the radiator original to it? 1950's cars and trucks would run 7# pressure systems, while 1940's and very early 50's vehicles sometimes used a "zero-pound" system. The heater core is often the limiting factor on an older vehicle that has had the radiator swapped for a higher pressure item. Modern radiators and heaters can handle 15 PSI or more. Over pressuring an older system can spring leaks or even burst seams. Every pound of pressure on a cooling system raises the boiling point 3 degrees F. so a 7 PSI system boils at 233 degrees at sea level, lower at higher altitudes. A 15 pound cap raises the boiling point to 247 or so.
Jerry

Original radiator, recored a few years ago. Heater core was also done. 62 C10. Never ran 261 caddy stroker. The one I plan to start Saturday. What pressure will that reach at 190°?

Put a 15# cap on it and don't worry about the temp. With a good radiator and a fan that moves plenty of air, it shouldn't get much above the opening temp of the thermostat. I'd suggest a 180 stat and a 14-15# cap.
Jerry

The original 235 always ran cool. Like 170. Never overheated. It would only get to over 190 on 100°+ days if I were driving over a pass.
Tonight I pressure tested at 7lb and found a couple leaks in my intake. The heatplate is slightly weeping, and both holes I drilled and tapped for the filter mount are leaking. Wrong bolt head and washers with insufficient thread sealer, I believe. I'll address those tomorrow and try again. But question still is, where should I max out on this pressure tester? If it holds at 7lbs, am I good?

Pressure test at, or slightly above the rating of the cap you intend to run. It would be difficult to convince me to use water heat on an intake, since when the heat is needed most the coolant is cold. Of course, it would be even more difficult to get me to run a dual carb system that the cylinder head can't use efficiently. "It looks cool" isn't a good enough reason to go to all the effort and expense!
Jerry

Thanks Jerry. And duly noted. After so many years, if I had to do it over, I would have just kept using my 235. But here we are. I'll make the best of it.

Stroker engines build torque in RPM ranges where there's little, if any need for extra carburetion. Unless you're planning to do some sort of racing it's better to concentrate on a camshaft and compression ratio, and an ignition timing advance curve that can maximize that low-end grunt, and add a higher ratio top gear of some type if you are interested in having better highway speed. I'm working on an idea to adapt a single carb stovebolt intake to a small bore Rochester 2 barrel carb like the one for a 265 V8. It's going to involve machining and modifying the manifold so the longitudinal runner is exposed and the carb sits with the 2 barrels and the throttle shaft facing front to rear without any restriction between the carb and the runners.
Jerry

I already have a gear vendors overdrive mated with my sm420 and 3:90 posi. 85 miles an hour at 2800 RPM with the original 235. Not on hills though.. I'm not looking for more highway speed. It would be nice to pull an airstream or a boat with less effort at highway speeds. And of course, it must look cool😁 And yes, I have the brakes to stop it. Front performance disc brakes with a hidden booster mounted on the frame. If I had money and patience to do it again, I'd probably go with the Clifford intake and a single 4 barrel. And exhaust heat. My water heat set up looks nice, but has been cumbersome.