Road trip with an overheat

GB SISSON

GB SISSON

Well-known member
I took the woodie on it's first road trip to the mainland this past week. About 200 miles or so and drove most of it on the interstate. Slept in the back of the wagon for 4 nights and had a fun time. I was quite surprised to see my speedometer app on the cellphone synced with my speedometer exactly. I was even more surprised to see 66 mph. At that speed the temp gauge climbed to over 3/4 on the scale. Temp was about 85 outside. I backed off to about 50-55 and it cooled down and stayed there. Coming home yesterday afternoon, same outside temps I was pulling a long grade and held 60 for too long and temp climbed to the far right and before I could back off the truck started missing and sputtering and I took to the break down lane at about 20 mph. Fortunately there was an exit really close by so I limped to it and found a lone gas station. I determined that the steady power was coming back as things dried out. After about 20 minutes cool down at the station I added a full gallon of water and hit the road at 50 and it never went past 3/4 scale after that. It was getting dark and cooling off. Caught the 9:00 ferry and home in bed by 11. I detect no lasting effects in power or smoothness and the oil is bright and clear. I don't have a shroud on, but have two hanging on a nail. I also don't have the air defector underneath, but have one of those too. The radiator has been flushed, and I cleaned the block with long steel tools during my overhaul. Subaru 180 degree thermostats and Drake water pumps. It hasn't gotten hotter than 5/8 scale in the 500 miles on Orcas island where 40 mph is a top speed, so I though I was home free. Will the two missing pieces help at hiway speeds? Just going too fast for a pickup?
 

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A shroud will make a big difference. Several articles in various street rod magazines have run articles and tests and without a shroud, you can't get all the air you need thru the radiator. Tests have shown that without a shroud that the air is all over the place and like water will take the path of least resistance and not thru the radiator.
 
GB I would defiantly fit the shroud even consider a 6 blade ,the idea is to get the motor running as cool as or colder than what's needed then you will have reserves for the hills .You can keep the thermostats that will keep the temperature up to optimum operating temperature , .but on a down hill run they could be even closed ,but some do not flow enough in the middle of summer .The Drake pumps could work against you when water gets hot and expands they could pump out the over flow ,to keep this in check a pressure tank /valve can help ,its a matter of experimenting, Ted
 
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It would help to know the specific build level you have? Only 3(three) factors are involved. It could be one or more of these.

1. Insufficient water flow.
2. Insufficient air flow.
3. More heat is entering the system than design configuration can control.

If everything is basically stock there should be no speed limit.
 
woodiewagon46 said:
A shroud will make a big difference. Several articles in various street rod magazines have run articles and tests and without a shroud, you can't get all the air you need thru the radiator. Tests have shown that without a shroud that the air is all over the place and like water will take the path of least resistance and not thru the radiator.
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Used to install dealer AC and the amount of shrouds and flaps etc. they would include with the AC kits was amazing. Same parts as the factory would have installed if it came with it. They knew how important the parts were to make it work. One time we had to do a recall and it was a simple foam seal but it lowered the inside temp of the car 7 degrees. Recall was just a simple piece of foam that directed the air were it supposed to go. Later model or course but airflow was the key.
 
Thanks all! Build is a 3 1/16" 59 block with a .030 over bore. Stock other than adjustable tappets. Very slight ridge so I reamed it and ball honed it. New Hasting rings. Nos valves and seats triple ground with my VanDorn seat grinder. Plastigauged the mains, mic'd the rods and bearings, all good. Best gaskets from Olsen's gaskets. I have retorqued heads twice, but will do one more torque now. I picked out a nice shroud from a 47 1/2 ton and a lower air deflector. Not sure I can get them on today. Will I need to pull the rad to do the shroud?
 
2 other things to consider: are you getting proper spark advance and proper fuel flow? Could it be running a little lean at higher speeds?
 
flatjack9 said:
2 other things to consider: are you getting proper spark advance and proper fuel flow? Could it be running a little lean at higher speeds?
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For me the spark advance is a crap shoot. I have a new Bubba distributor with a crab cap, but the vacuum brake area was whistling a high pitched note so I adjusted the screw down til it stopped. The brake could be way outa whack at this point. Also there is a film of red-orange rust in the radiator neck that sticks to my finger. I thought I got things cleaner than that. Maybe run some vinegar through the system? And what is a good starting point if I re-set the vacuum brake? I want to point out I have had excellent service and results with Bubba. I probably shouldn't have messed with it.....
 
Gary. In addition to the fan shroud and the air deflector under the radiator there is an air deflector on either side of the radiator that attaches to the inner fender and prevents the airflow from bypassing the radiator. (photo attached) Regarding the install of the shroud there are 3 bolt holes on either side of the shroud that attached it to the radiator frame. You may be able to install the shroud by removing the radiator hoses, loosening the two radiator mounting bolts and tipping the radiator forward and sliding the shroud over the fan before attaching it to the radiator frame.

A thought that may have an effect on the the cooling while operating at high speeds. If you're running the OEM 4.86 differential gears and using the OEM water pumps your engine RPMs at 60 MPH may be so high that the water pumps are cavitating which will reduce the effectiveness of the coolant. The fact that the engine temperature stabilizes at 50-55 MPH would seem to indicate that this is the case. There are 4.11 gears available from Chuck's Trucks for our tonners. Its not an easy swap, but at 60 MPH you'll reduce engine speed by about 500 RPM. Les
 

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Better to run the dizzy spark advance all the way out for high end spark, if you dont know where it's at. It'll run "well-sh or better" with out any vacuum brake. Till you can sort it out anyway.

Add tension to retard high end spark.


The vacuum brake is there for fine tune. If the dizzy is setup well you can fine tune the vacuum advance. All the way in is not the way. All the way out, add as needed.
 
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This is just an observation on my part. Ever since I had the radiator in my '51 recored about 30 years ago, I have not had any problems with overheating. A couple of years ago, I added an additional mechanical temperature gauge to supplant the stock gauge. Ever since then, it has run at 180 on the mechanical gauge and a little over half scale on the stock gauge when fully warmed up. About a week ago, I was coming back to town on the new four lane bypass they opened last year. I found myself going about 80, just keeping up with traffic. This is probably the first time I've run it this fast for any period of time (about 8 miles). When I got to my exit, I checked the gauges and saw the mechanical was reading a little over 190 while the stock gauge was at 3/4 scale. I was kind of surprised, because I had never seen it read that high before. After I turned off and did the final two miles back to my shop (at about 50 mph), the temperature on both gauges had returned to their normal readings. I decided it was not something I had to worry about. I just think that if you push these cars to speeds they were never designed for, they will run a little hotter than normal as a matter of course. I am running a '51 Merc engine with Edmunds heads, a 2GC, a Mallory dual point, and 180 degree thermostats; the car has a standard 3 speed (no overdrive) and 3.55 rear end gears.
 
If you are getting a whistling, you have a leak by the vacuum brake. Sounds like the piston is too loose in the bore so the brake is not retracting properly. With it tightened down, it probably is not working. Generally the brake is backed off almost all the way with todays gas.
 
Once again, more good info to digest (and act upon). While my primary interest has been the tonner variants of the jailbar trucks, this is my first 1/2 ton. Not sure what the axle ratio is, but I would guess stock as this was an old farm country survivor. As I address this situation I would also like to flush the system. I don't run a heater yet so I was thinking about introducing water at the temp sender locations and having it exit at the radiator cap. I would pull the thermostats. After work today I will be painting the needed sheet metal pieces used for air flow. Thanks!
 
They (peak,prestone) make a reverse flush kit for little money. Check with your auto parts store or E gay even wally world. Makes flushing a bit easier.
 
Water flow is from the block into the top tank, this deposits crud onto the top of the core so its best to reverce this by flushing it backwards ,I like soaking in vinegar just the core then water blast it from the bottom out lets
 
Take a thermal gun ( the red dot laser gun that cats love and also gives temperature). Measure the temperature difference between the top and bottom of the radiator. On my 1941 3 1/2 ton I had 30 degree difference without shroud and 50 degrees with shroud. It overheated idling in 94 degree weather without the shroud, but was below "N" with shroud.
 
Upstate gearhead said:
Take a thermal gun ( the red dot laser gun that cats love and also gives temperature). Measure the temperature difference between the top and bottom of the radiator. On my 1941 3 1/2 ton I had 30 degree difference without shroud and 50 degrees with shroud. It overheated idling in 94 degree weather without the shroud, but was below "N" with shroud.
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I looked at a thermal gun on amazon and was surprised how affordable. It would be really great to know the results and not just guess or assume. I can easily see how the shroud helps at idle, but from these posts it seems it helps all through the spectrum. Also I drew a bit of coolant from the system tonight and it was as clear as the day I poured it in. I expected a rusty brew. Funny thing though.... I can't drive over 35 for any length of time on our twisty-turney up and down narrow roads so I can't test results until I get off island again. OK, I order the gun now.
 
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