We're here partly to learn from mistakes, right? In that light, I offer the following:
I have been chasing an oveheating issue for over two years. It first became apparent on our trip from California to and from New Mexico for the (aborted) National Meet in 2024. Albuquerque was high (5300 feet), hot (90's most days) and there's lots of climbing around town. This was the first long trip I had taken in the relatively new-to-me '31 Town Sedan, and I was regularly heating to over 200, boiling and spewing, and generally miserable. It got to where I was leaving a half hour to an hour earlier than my companions to drive slowly to where we were going. And on climbs regularly spewing, stopping, refilling, rinse and repeat. (Not to mention vapor lock, but thats a different story.)
When I got back to California I realized that part of the issue was that my radiator had a bent neck from someone dropping it in the past. So the cap didn't seal. hence the spewing. I had a barely-used Berg's Heavy Duty radiator that I had purchased from Snyders on the shelf. In addition, in going over the engine, I realized that it wasn't really up to snuff either - 0.080" over, big ridge at the top of the cylinders, valve gaps over 0.020" on solid lifters, and a timing gear backlash of over 0.015". I had a spare engine that was 0.040" over, just barely out of spec on cylinder diameter, taper and ovality, and the bearings were in acceptable shape. So I elected to refurbish that engine - new cam, new adjustable lifters, valve job, new rings, new timing gear, reshim bearings, and 5.2 head. I figured with a reasonably sound engine and a new radiator my cooling problems would go away.
Nope. I was routinely running 175+ under moderate load, 190+ under heavy load, and over 200 with climbing. The spewing did go away, though.
I got to thinking what was in common between the two power/cooling setups. 5.2 head - boiled out, fluxed and decked. Check. Carburetor - it runs well, right? Don't fix what's not broken (although I did put in a set of flow tested jets from Renners Corners). Check. Coolant - hmm, I'm using 50/50 antifreeze. So I used some cooling system cleaner, followed by Rust 911, and then refilled with 17% antifreeze, Water Wetter, and water. That was good for about 5 degrees more cooling, right track but not solved yet.
Fast forward to today. My next step was going to be to remove the radiator and have it rodded, although it was fairly new. (I'd held off because here in the Bay Area you almost have to mortgage your house to get anyone to work on copper radiators). But we got talking before a club tour this morning and one of the guys said "you know, your license plate is blocking a large portion of your radiator". I looked and doggone if he wasn't right. So I removed the plate, used the same stock clamps to clamp it to the bumper, and my problems went away just like that. I think that was good for about 15 degrees, meaning under a freeway load that I would have expected to see 185, I saw 165-170. More importantly, I have a long stretch of freeway that climbs from San Jose to where I live, and in warm weather like we're having in the Bay Area now I'm used to slowing down to about 45 mph to keep the engine cool. Not so today, 50+ mph and never got above 185.
So maybe if I'd just stepped back and thought about it, I would have realized that the radiator needs unrestricted flow to function properly. Doh!
I don't regret all the changes I made getting to this point. It's made me feel more confident that I know the car and what it's weaknesses are. I may still rod out that radiator just so I can feel confident that I've done all I can about cooling.
The dark area behind the light bar in the picture attached shows the extent of flow blockage that the license plate caused.
I have been chasing an oveheating issue for over two years. It first became apparent on our trip from California to and from New Mexico for the (aborted) National Meet in 2024. Albuquerque was high (5300 feet), hot (90's most days) and there's lots of climbing around town. This was the first long trip I had taken in the relatively new-to-me '31 Town Sedan, and I was regularly heating to over 200, boiling and spewing, and generally miserable. It got to where I was leaving a half hour to an hour earlier than my companions to drive slowly to where we were going. And on climbs regularly spewing, stopping, refilling, rinse and repeat. (Not to mention vapor lock, but thats a different story.)
When I got back to California I realized that part of the issue was that my radiator had a bent neck from someone dropping it in the past. So the cap didn't seal. hence the spewing. I had a barely-used Berg's Heavy Duty radiator that I had purchased from Snyders on the shelf. In addition, in going over the engine, I realized that it wasn't really up to snuff either - 0.080" over, big ridge at the top of the cylinders, valve gaps over 0.020" on solid lifters, and a timing gear backlash of over 0.015". I had a spare engine that was 0.040" over, just barely out of spec on cylinder diameter, taper and ovality, and the bearings were in acceptable shape. So I elected to refurbish that engine - new cam, new adjustable lifters, valve job, new rings, new timing gear, reshim bearings, and 5.2 head. I figured with a reasonably sound engine and a new radiator my cooling problems would go away.
Nope. I was routinely running 175+ under moderate load, 190+ under heavy load, and over 200 with climbing. The spewing did go away, though.
I got to thinking what was in common between the two power/cooling setups. 5.2 head - boiled out, fluxed and decked. Check. Carburetor - it runs well, right? Don't fix what's not broken (although I did put in a set of flow tested jets from Renners Corners). Check. Coolant - hmm, I'm using 50/50 antifreeze. So I used some cooling system cleaner, followed by Rust 911, and then refilled with 17% antifreeze, Water Wetter, and water. That was good for about 5 degrees more cooling, right track but not solved yet.
Fast forward to today. My next step was going to be to remove the radiator and have it rodded, although it was fairly new. (I'd held off because here in the Bay Area you almost have to mortgage your house to get anyone to work on copper radiators). But we got talking before a club tour this morning and one of the guys said "you know, your license plate is blocking a large portion of your radiator". I looked and doggone if he wasn't right. So I removed the plate, used the same stock clamps to clamp it to the bumper, and my problems went away just like that. I think that was good for about 15 degrees, meaning under a freeway load that I would have expected to see 185, I saw 165-170. More importantly, I have a long stretch of freeway that climbs from San Jose to where I live, and in warm weather like we're having in the Bay Area now I'm used to slowing down to about 45 mph to keep the engine cool. Not so today, 50+ mph and never got above 185.
So maybe if I'd just stepped back and thought about it, I would have realized that the radiator needs unrestricted flow to function properly. Doh!
I don't regret all the changes I made getting to this point. It's made me feel more confident that I know the car and what it's weaknesses are. I may still rod out that radiator just so I can feel confident that I've done all I can about cooling.
The dark area behind the light bar in the picture attached shows the extent of flow blockage that the license plate caused.
