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Overheated...

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10K views 324 replies 29 participants last post by  angs1957  
#1 ·
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Well it's been a little while since I've made a long post here, but I'm back from vacay and driving the car again. Today I was supposed to take it about a 26 mile trip, 35 minutes away to an alignment shop.

It's an uphill grade most of the way there and I watched the temps climb from 180 to 190 and then 200 and when it hit 210 going up a hill I called it quits. With my TH350 and stock '55 rear end (not sure the gears) I'm between 3100-3500 rpm at 60-65 mph.

I let it cool off and turned around for home, thinking it would be okay going downhill but at a red light at the base of a hill it hit 200 again and when I stepped on the gas to go, it bogged and died. After an hour a guy pulled over and helped tow me home, big shoutout to him, but I haven't been able to get the car started since this happened this afternoon. Did it vapor lock? I checked and it was getting fuel to the carb, but we cranked it until the battery died and no go.

details:
ECP aluminum radiator in V8 position
Derale 17" six blade mechanical fan
Unknown thermostat (a buddy told me to try driving without one, would that work?)
No fan shroud
Fan is only about an inch or so away from radiator


Side note, my dad is always a bit of a safety freak haha and is saying I shouldn't drive the car on an upcoming 9 hour trip to Kansas, but obviously the car needs some work and shouldn't be overheating at all, it should be ready to go anywhere, anytime. Right?? If the car overheats on a 26 mile trip, that doesn't mean it's a horribly unreliable 70 year old junker lol (i'm still proud of my car and want to prove it can go anywhere anytime even though it looks like crap 💀)
 
#44 ·
OK on the drivers side is a long part number and a casting date please post that.
 
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#46 ·
I disagree with that. if I take my car out of overdrive and put it in 3rd its 3200 at 70 mph after a while the temp comes up 15 degrees.
 
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#50 · (Edited)
that's a January 18, 1962 differential and codes out to a 3.36 ratio. below is the rpm vs mph chart for 3.36
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here is the link I used to determine ratio based on the casting date. 1958-1970 Full size rear Differential Identification
this makes more sense if you were keeping up with traffic probably going faster than you thought. If you speed isn't right or not working I would suggest a gps app on your phone.
 
#52 ·
#56 ·
Depends. What you said in the first post was 3100-3500 rpm at 60-65 mph. 3500 at 65 is in my view too high. 3000 at 65 would be a different story. So what you might need to do is double check the rpms vs speed. As for speed, you will not be able to rely on the speedo. It is not accurate with the change in gears and tire size so you will probably want to use a gps app or something to nail it down. If the rpms fall within a normal range vs mph, then the problem lies elsewhere.
 
#61 ·
Well, just another thought. The actual engine RPM isn't that important for the overheating issue and from your measurements the engine itself is not overheating, the fuel system is.
  • Did you install an aftermarket aluminium intake with the crossover blocked?
  • Do you use some sort of thermal spacer under the carb?
  • How is the fuel line routed? Far away from hot surfaces? Think radiator and exhaust manifold.
 
#66 ·
So as I was driving into town today to get a new thermostat I was watching the gauge and when the car is started cold and driven the gauge quickly climbs to 180, and when it hits 180 it drops really fast to 165ish. I assume that’s when the thermostat opens. So far I’ve driven it some more and I haven’t gotten it to go to 200 again although I haven’t tried to drive to the alignment shop again.

Still going to flush the coolant, check timing and replace the thermostat, but so far this is all sorta odd.
 
#71 ·
this is the issue with a old car who knows what gears are really in there. someone could have put whatever they had in the carrier, does sound like 4.11 though. not a good option with those small od tires. a 3.08 or 3.36 diff would be a much better option and lower your rpm a lot.
 
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#79 ·
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#80 ·
I’ve given it a lot of thought and I guess in the long run changing the gears will be worth it, although it may possibly mean I won’t make it to the Nationals. I guess while I’m at it, are there any other gear sets that would provide even more optimal rpms, or is a 3.08 the best one?
 
#81 ·
3:08 is the best ones. IIRC though I've heard ya have to do a hammer knock or two on the axle housing for 3:08s to fit. 3:36 is the next set up from the 3:08s but with either one your 25" tires are gonna still be a factor in the final ratio.
 
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