55 Fargo Posted February 6, 2015 Report Share Posted February 6, 2015 (edited) The rad I illustrated predates 1949 or 50, the rad filler neck has no lower lip to allow any pressurized cap to seat. Hence the overflow tube is higher up on the rad, where the hot expanded coolant could exit. For any reason that tube got clogged then the system could not outflow , causing a lot of problems. the rad in your picture sure looks like the early versions of the pressurized rads to me. Of course it could be made into a non pressurized rad by employing a a non-pressure rad cap. Chrysler went to 4 lb pressurized cooling systems,as well as internal water pump by pass in 1950 or 51, why would the truck line be any different? I suppose if the rads were not designed to accommodate the pressurized caps, what else could not support the pressurizing of the system by 4 lbs. These engines, other than the internal water pump by pass feature, have not changed a whole lot, but Chrysler did introduce pressurized cooling systems in 50 or 51..... PS My 1955 251 engine is internal water pump by pass, but I am using an external type t/stat housing, and do have a 4 lb pressurized cooling systems, works just fine... Edited February 6, 2015 by Fargos-Go-Far Quote Link to comment Share on other sites More sharing options...
NiftyFifty Posted February 6, 2015 Report Share Posted February 6, 2015 Clearly states in the 48-53 truck literature that they are non pressurized systems, and even the rad from my 47 Fargo only has one overflow tube coming from the filler neck, although I can't get close to it right now to see if it has the lip inside that could seat a pressurized cap. It had a cheese whiz lid for a cap, so of course it was not running any kind of pressure either Biggest thing in my mind, is to make sure is that new owners know what style cap belongs on these trucks and to get the correct info out there, or at least what will work safely, and yes a 4 lb pressurized cap is safe, but a plain cap is the correct one 1 Quote Link to comment Share on other sites More sharing options...
ggdad1951 Posted February 6, 2015 Report Share Posted February 6, 2015 personally, since non pressure caps are available I would only use one of those. These ARE non pressure systems, I'd have to look into how things all fit up for a low pressure cap on these rads. My gut reaction is that using a pressure cap of any sort COULD pose problems. Quote Link to comment Share on other sites More sharing options...
NiftyFifty Posted February 6, 2015 Report Share Posted February 6, 2015 personally, since non pressure caps are available I would only use one of those. These ARE non pressure systems, I'd have to look into how things all fit up for a low pressure cap on these rads. My gut reaction is that using a pressure cap of any sort COULD pose problems. That was my concern too, but the rad shop (been around forever) assured me I would be fine, and also mentioned the 4 lb cap helps a bit when your parked on a down facing slope where the rad may sit a little higher then normal.....not that we have that many hills to park on here where I live Quote Link to comment Share on other sites More sharing options...
Jeff Balazs Posted February 6, 2015 Report Share Posted February 6, 2015 The design and construction of the original radiator is the limiting factor. There is nothing in the rest of the system that won't handle some pressure. The radiators simply were not made to hold pressure. When I had my radiator re cored with a modern type core it was tested to 15# and the shop gave me a warranty to 12#. When I installed it I put a 3 hour 10# test on it. That said I run it without any pressure as it does the job just fine and there is less chance of having a leak develop. 4mula-dlx I think you should consider that the failure of this thermostat was an isolated case. Pretty much one in many millions. These engines were clearly designed to be run within a regulated temperature range. With a thermostat in place it takes several minutes for the engine to come up to it's true operating temperature. Without a thermostat you have no way to control the process. In effect it may never get or stay within the designed temperature range. These old engines have quite a bit of mass to them. You can actually hear the difference between a cold engine and an engine that has come up to full operating temperature. They quiet down significantly when they reach operating clearances which is a direct result of the block getting to the correct temperature. Jeff. Quote Link to comment Share on other sites More sharing options...
Geekay Posted February 6, 2015 Author Report Share Posted February 6, 2015 Regarding sludge build up - there is a little stop-cock/tap on the left side of the block, i regularly open this and let out about 1/2 litre of brown coolant before the clean green coolant comes through. Just remember to top the radiator back up. yes to thermostat, and a non-spring cap. Thanks Ian...good to see another Aussie. "on the left" do you mean when sitting in the driver's seat looking forward? I see a "tap" on the block between the generator and the dissy...assume this is it? Garry (a mexican...in Victoria..but on the Murray river at Wodonga) Quote Link to comment Share on other sites More sharing options...
Geekay Posted February 6, 2015 Author Report Share Posted February 6, 2015 Thanks for the lively discussion and all the information/advice. I will stick with the non-pressurised cap. I still have a couple of water leaks after pulling the fan/thermosate/water pump assembly off the front of the block, in particular the welsh plug at the front just under the pump housing that was rusted through. Temporarily repaired it with some arildite (glue). A gasket or two needs replacing also. I will need to completely strip the block later when I am close to putting it on the road. Replace all the welsh plugs then and clean out/replace the tube thingy in the block. It's all good fun and I am learning a lot. Now, if I could just get those bloody rear brake drums off!!!! Quote Link to comment Share on other sites More sharing options...
NiftyFifty Posted February 6, 2015 Report Share Posted February 6, 2015 The design and construction of the original radiator is the limiting factor. There is nothing in the rest of the system that won't handle some pressure. The radiators simply were not made to hold pressure. When I had my radiator re cored with a modern type core it was tested to 15# and the shop gave me a warranty to 12#. When I installed it I put a 3 hour 10# test on it. That said I run it without any pressure as it does the job just fine and there is less chance of having a leak develop. 4mula-dlx I think you should consider that the failure of this thermostat was an isolated case. Pretty much one in many millions. These engines were clearly designed to be run within a regulated temperature range. With a thermostat in place it takes several minutes for the engine to come up to it's true operating temperature. Without a thermostat you have no way to control the process. In effect it may never get or stay within the designed temperature range. These old engines have quite a bit of mass to them. You can actually hear the difference between a cold engine and an engine that has come up to full operating temperature. They quiet down significantly when they reach operating clearances which is a direct result of the block getting to the correct temperature. Jeff. Actually the water pump seals were never meant to hold pressure either, according to a good friend with 40+ years experience in the biz, and he actually said that was one of the first failures usually in the system if pressure did build, but as age goes on, I'm sure the rads have become the wink link in the system. For my truck, it never operates in winter, and even in fall and spring it doesn't go anywhere unless it warm outside, so it takes imo the typical warm up time, and runs great. I would put my 265 against anyone's for smooth idle and zero lag in all the rpm ranges. I'm happy with my set up, and being from the shop, I've seen lots of failed t-stats, not in these engines as we never worked on much older stuff back then, but plenty of 80's thru 90's stuff...the stuck closed ones always caused the issues, open just means little heat in the winter. In fact a buddy with a Studebaker that's has a 4.3gm in it hasn't had heat since the day he dropped the motor in...car have literally tens of thousands of miles since the drop and the t-stat looks to been stuck since day one, and never an issue with how it ran... Quote Link to comment Share on other sites More sharing options...
Robert Thornton Posted February 7, 2015 Report Share Posted February 7, 2015 I ran a 4lbs cap on my b3b 52 for a long time thought I had rotten radiator with small leaks had fixed it happened again ruined radiator. could only find 49 good radiator after installing notice inlet cap was a lot larger than old one. could not fined one for fair price. thin I remembered my old Int farmall H tractor had a large none psi cap. it was a good fit and very good price. you old farmers remember some old tractors did not even use water pumps moved water with conviction . robert Quote Link to comment Share on other sites More sharing options...
55 Fargo Posted February 11, 2015 Report Share Posted February 11, 2015 Here is a picture of a 1947 Chrysler radiator, a honeycomb type, non pressure, and overflow tube on top of the rad, separate from the filler neck.... Quote Link to comment Share on other sites More sharing options...
jpwuertz Posted February 11, 2015 Report Share Posted February 11, 2015 (edited) I have a b3b with a radiator that was redone with a modern core and I have been using it wit a 4 lb cap. Should I be concerned that the 4 lbs of pressure will be a problem or not. I just assumed the truck came with a pressure system. I have had the truck for several years and drive it regularly during the summer without any problems. I could leave the pressure cap on but not tighten it all the way which would not allow the pressure to build up. Edited February 11, 2015 by jpwuertz Quote Link to comment Share on other sites More sharing options...
Jeff Balazs Posted February 11, 2015 Report Share Posted February 11, 2015 Typically a radiator shop pressure tests their work. I would imagine they put much higher test on the re-core than they ever expected it to actually see. If it has been holding 4# then there shouldn't be any need to change the cap you already have. The one exception I can think of is if you have the old style water pump with grease fittings. Those might be prone to leak under pressure. The newer style water pump with sealed bearings will handle the pressure as long as they are not worn out. If you had the old honeycomb core it probably would not have held 4# for long.....a modern core should have no problem at all. Jeff Quote Link to comment Share on other sites More sharing options...
Young Ed Posted February 11, 2015 Report Share Posted February 11, 2015 Starting in 51(for cars at least) the honeycomb radiators came with a 4# cap. I am kinda surprised the trucks don't seem to have gotten that upgrade as quickly. Quote Link to comment Share on other sites More sharing options...
Brent B3B Posted February 11, 2015 Report Share Posted February 11, 2015 Starting in 51(for cars at least) the honeycomb radiators came with a 4# cap. I am kinda surprised the trucks don't seem to have gotten that upgrade as quickly. and that might answer my question about the size of cap and fill "neck" on the two different radiators i have (top one from my 51, lower one from Keven 49 or 50) Quote Link to comment Share on other sites More sharing options...
NiftyFifty Posted February 12, 2015 Report Share Posted February 12, 2015 Here is a picture of a 1947 Chrysler radiator, a honeycomb type, non pressure, and overflow tube on top of the rad, separate from the filler neck.... What was that out of? I had a look at my 47 Fargo rad today and although the filler neck location is different from my 51, the overflow tube still just comes out of the neck. Maybe cars were different Quote Link to comment Share on other sites More sharing options...
55 Fargo Posted February 12, 2015 Report Share Posted February 12, 2015 What was that out of? I had a look at my 47 Fargo rad today and although the filler neck location is different from my 51, the overflow tube still just comes out of the neck. Maybe cars were different Here is a picture of a 47 Chrysler rad, ( 1947 Chrysler C38 cars), not from the truck line. The cars were low pressure systems from 1951 and on, and tube and fin construction, not honey comb) Is your truck rad honeycomb type? Quote Link to comment Share on other sites More sharing options...
NiftyFifty Posted February 12, 2015 Report Share Posted February 12, 2015 Yes, honeycomb. Looks to be a bit different then a 48 rad...taller and narrower, definitely for a truck Quote Link to comment Share on other sites More sharing options...
Merle Coggins Posted February 12, 2015 Report Share Posted February 12, 2015 I don't believe that the truck radiators used that top overflow like that cars had. At least not in the Pilot-House trucks. Quote Link to comment Share on other sites More sharing options...
55 Fargo Posted February 13, 2015 Report Share Posted February 13, 2015 The newer designed low pressure tube and fin radiators, were more cost effective for Chrysler and production costs. The newer rads, were smaller, and possibly less material to produce them, so cheaper and more profits in the end.... My 1955 rad is a low pressure type, and not sure if this started in 54 for the truck lines or earlier... Quote Link to comment Share on other sites More sharing options...
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