I'll try to keep this as short as possible. I recently bought a '29 roadster pickup with a 295 stroker flathead. After a few test runs, the overflow puked immediately after shutdown. Both drives (10 miles or so) were in about 80-85 degree days. I have a temp gauge for each head. One runs about 190 degrees and the other runs about 185. I suspected the radiator cap wasn't holding pressure, so I replaced it with a new one (13#). I know the older cars mostly ran with a 7# cap and I have one ordered. I haven't checked what type thermostats are installed, but I can't see why that would matter since they're obviously opening, etc. I figured that I may be overfilling it, so I decided to let it "find it's own level". Drove it again a couple of days ago (45 milews) and it didn't puke, but I could hear it "bubbling" after I shut down. I guess I shouldn't be that concerned as long as the engine is not really overheating, but I'm mystified about the "boiling noise". I'm probably opening a can of worms, but what say you?
Changing to a 7 lb cap will just let it puke earlier, at a lower temp. My guess is that your suspicion about it needing to seek it's own level is right. Either put an overflow bottle on it, or run it lower on water as it seeks it's own level. Personally i would run the bottle as a Hot Stroker motor will probably tend to run hotter in the first place, so why not give it all the help you can?
Definitly run a coolant recovery system like any modern car. Then after it seeks it's own level after cool down the overflow water will be drawn back into the radiator. Frank
Sounds normal to me. You are exactly right on the seeking it's level. It might still puke a little if you get it to a little higher temp. Check water level daily, or until you are happy that the level it's at is not going down exxesivly. Let idle a couple of minutes before shutting off to help even out the engine temp. especially the long water heating exhaust passages. A puke can that can return the extra water won't hurt. But isn't neccessary.
Actually, you and I are thinking alike on this. I figure it wouldn't be abnormal for a stroker to run a bit hotter than stock. Maybe I'm over thinking this, but it is my understanding that for every degree of pressure, the boiling point should be raised about 3 degrees, so even a 7# cap would change it from 212 to 233 and I am having trouble understanding how the engine temp is at 190-195 immediately after shutdown and the water (with Water Wetter) is above the boiling point. Thanks for the input.
I doubt it, but don't know for a fact. I do know that it has been completely rebuilt and again, the engine temp isn't going above 190.
This may not be news, but the temp will go up after you switch off. This is because the pump is no longer circulating the coolant (only circulating via convection) and also there is no airflow through the radiator. So you end up with a hotter engine for a while. Overflow tank will catch the coolant and let back in to the settled level as mentioned previously, but if it still bothers you, and you want to spend some cash you can switch to thermo controlled electric fan and waterpump.
Thanks...my thought too. It has a switched electric fan (to the ignition). Next time, I plan to let it run for a couple of minutes and see what happens.
i had a stock radiator in my 37 chevy truck with a small block in it. if i filled it up to the brim it would fill the overflow tank up eventhough it wasnt getting too hot. I left it a ltiiel "low" and everything was good until I thre a rod through the block trying to impress some fat girl. It didnt work.
7# might be too much for your radiator if it's stock. Early flatheads didn't use a pressure cap, middle ones used 4# and the later series went to 7#. Don't know what you're running so it's hard to say. Your system sounds normal though - about like my merc in the 48 pickup. I think it's part of being old ... I gurgle too some days when I shut down : )
It sounds normal but you have to leave a couple of inches of room at the top of the radiator for expansion. If it is running 185/195 on the highway and in traffic and not puking then I'd say you have it set up just right. Just leave enough room for the coolant to expand after you shut it off without puking and you should be good. We tend to forget that when we are used to driving these modern daily drivers that run the coolant right at the top of the fill neck and use the overflow tanks to catch anything that might get past the high pressure cap.
It's only boiling inside the block after it's shut down, because as stated the engine temp goes up with no water/air flow. The gauge in my '36 will go from 195 to almost 220 in a very short time after shut down, but it drops immediately on starting it back up. Catch can, proper pressure cap for the radiator (don't put a 13lb cap on a radiator designed for a 4 lb cap), and an elec. fan with a thermostatic control will keep it happy. Brian
My 8BA cooled with an original 32 radiator always gurgled when I shut it down. Same thing for my Studebaker engine cooled with a re-cored and pressurized original 34 radiator. Neither one ever over heated. They just sound like my belly after a Taco Bell lunch.
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