Hot Rods SBC overheating...yes I've tried almost everything!

Okay guys. I've been a fan of this forum for many years and finally got around to making an account. But, I'm having some troubles.

I have a 55 Dodge Town Panel with a 305 out of a 94 pickup that was TBI. I changed the intake, added a new gasket, and added a carb. The motor came out of a running truck with no issues other than frame damage from a wreck in the rear. I drove the truck to my garage before yanking out the motor.

I have looked at almost every thread here regarding overheating SBC's. I feel like I've tried most everything. The 305 will run 205-210 while driving, which isn't too bad, but when idling or sitting in traffic will get up to 230-235 and start puking.

It originally had a 195 thermostat in it and I thought it was bad. Replaced it with a new 195. No change. Went and got a new 160 thermostat, still no change. On to the next suggestion.

The 55 did not have a fan shroud. I added one that covers about half the fan area. It has a mechanical fan. Still no luck. I added an electric puller fan to try and run at idle to see if it would bring the temp down. No luck. So I've got two puller fans and still can't lower my temp, even with a shroud.

I read that maybe the vacuum advance not being hooked up could cause timing issues. Hooked it up, adjusted the timing, no help.

I changed both radiator hoses to ensure that there was no vapor locking, collapsing, etc.

I am running a griffin aluminum radiator. I will admit, I bought it at a swap meet but it doesn't leak. I ran water from a water hose through it and cleaned it out. It seems to be doing okay as both sides are heating up so I suppose it's circulating? (I am definitely not a radiator expert.) It had a cheap Chinese 16-pound radiator cap on it, so I switched to a Stant 7-lb from the local parts store. The overflow outlet is not hooked up so I don't have an overflow tank. Just the nipple from the neck of the radiator. (Is it possible air is in the system? If so, how would I know and how would I fix it? Would it cause overheating?)

At this point I'm getting very frustrated. I feel like it's something simple I'm missing but I can't for the life of me point out what it could be. I've done my research on here and have tried everything I've read. I wanted to make sure I did before starting my own thread. I even added a whole bottle of water wetter to see if that would help.

Does anyone here have any advice to offer? Doesn't seem to matter what temp it is outside. The only effect that has is how quick it heats up, not the max temp it reaches.

Please help me out here guys!

 

So you wrecked the truck or bought it wrecked? It idled fine temp wise prior to the motor swap?

Is the EGR valve open or closed @ idle? What about the pump? could it be that the pump is just stirring the water and not circulating it?

Just trying to stir your juices here.

 

Thank you for the reply! I bought the truck wrecked from my neighbor. It had no EGR valve on it now. Nothing on the intake except carb and temp sending unit. I wouldn't assume the water pump would be bad as it was doing fine in the other truck. I could be wrong though?


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Motor have reverse flow water pump?

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What is the timing and is the vacuum advance connected to ported vacuum on the carb or manifold vacuum? Mechanical advance on the dist? Total advance?

 

I honestly have no idea. I didn't change anything from stock other than the intake and added an A/C delete bracket and pulley. By leaving it alone I shouldn't have messed up the flow though, right?


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Did you change the distributer?

 

Did you change any pulleys or belt routing?

 

Other than the AC delete, all the original pulleys and belt are still on. I left the P/S pump on as well. No change to the belt routing. Only took the belt loose to add the AC delete.


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Air in the system could be a problem. Run the engine with the heater on/control valve open, this will push water through the heater core. After it cools, check the coolant level.

Other thing, how do you know it is running hot? Are you using a reliable gauge? Do you have one of those "touchless thermometers"?

 

It does not have heat. So no heater core or any of that. How else can I do this?


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I am using a Bosch gauge from one of the common chain retail parts stores. That is the only reference I have. I don't have a thermometer of any kind.


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Yes, I did change the dizzy.


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I couldn't tell you the numbers on it. I have always set timing by sound. It is connected to vacuum on the carb, on what I've read is a constant vacuum on the driver side bib of an edelbrock.


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I vote air in the system. Park it uphill, leave rad cap off and idle it for 20 or so minutes.

 

Did you change the water pump? are you using a serpentine belt or did you change the pulleys?

 

No I did not change the water pump. Serpentine belt still with original pulleys.


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If it's air, how do I prevent it from happening again? Or is it just where the radiator was out and put in? Would the overflow be sucking air in?


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Once the air is out it won't happen again. When you filled it after swapping it in your wagon, that's when the air gets in the system.

 

put a vacuum rubber cap on the overflow nipple and rule out the sucking in of air.

 

check the timing chain for strech , those EFI motors are retarded for emissions and when the chain starts to stretch it retards more and causes them to run hotter as the combustion heat is thrown into the cylinder walls verse in the head .I have seen factory chains start to go out at 75K and then temp of the motors start to creep slowly up the more the chain stretches out . one sign of a stretching chain is a hard or takes a couple of spins to fire start when cold .

 

Take out the left and right aft freeze plugs and clean out the sludge . A coat hanger works good .

 

get a timing light, set the timing, you want about 34 degrees advance "all in" (above 3000 rpm). Check the timing with the vacuum advance disconnected.

he mentioned sludge behind the freeze plugs...what does the cooling system look like inside, is it clean, or full of brown crap?

Pictures of the engine, including the radiator and fan, would help us help you see if something doesn't look right. It may look fine to you, but have some obvious problem that we can't see, and you don't know about.

Those little hand held infrared temperature guns are very handy, you can buy them pretty cheap on the internets.

If the radiator came with a 16 psi cap, it probably ought to have a 16 lb cap on it, instead of 7 psi. That will raise the boiling point, and it won't puke at 235.

 

I can only speak from experience but I had a griffin radiator and it was a piece of junk,my car ran hotter than a four balled tom cat,if it is a older one it is possible that half the cooling tubes could be blocked with the sealer they put them together with and not doing the job.

Photo's would help,how many blades are on the fan and is it a cheesy aluminum flex fan? HRP

 

If both of the tanks of the radiator are the same temperature, then the radiator is not doing it's job. Why it's not doing it's job...hard to say...could be not enough coolant flow, or not enough air flow. There are many different possible causes for each of these conditions.

 

Motor starts very easy upon cold start, surprising well actually. If all else fails I will look into the timing chain.


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I have my suspicions about the radiator but from what I understand about radiators it seems to be circulating. It is a flex fan, 6-blade.


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I figured putting a lower cap on would help with pressure in the radiator. If it's running 235 that's too hot though, wouldn't you say? I will try to time it with a timing light and see. The antifreeze/water is still green/clear so it doesn't appear to have much sludge or grime in it.


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Can overheating be a cause of air in the system?


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Or air in the system a cause of overheating. You know what I mean lol.


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