350 overheating...i think?

Just recently swapped my 283 for a 350 and my temp gauge says i'm runnin @ about 210 and it creeps up to about 250 according to the gauge...I have a new 4 core radiator... mech. fan w/ the stock shroud...an electric fan mounted in the front...new water pump...its never puked any coolant...50/50 mix...my exhaust is short im runnin 17" glasspacks w/ dump tubes...is that creating too much backpressure?..

 

is it boiling?
puking?
if not i wouldnt think its over heating..maybe its the sensor or gauge thats reading wrong.
or air traped near the sensor.

do you only notice it sitting or does it do it going down the road too?

 

If I were you I'd make a run down to the parts store and buy a diffrent guage hook it up and see what it says also make sure you have gotten as much air out of the system as you can if there is an air pocket the steam in it will read hot also did you replace the thermostat those little bitches can cause that.
oh yeah do the first sugg. last.

 

Not to be a smart ass but it the front fan going the right direction? It seems like you have all the other bases covered.
Did you burp the cooling system too?

 

nice camino by the way I had 60 hence the name. but I sold it. still kick myself for that one

 

You said several things that strike me as odd. It had a 283 and you swapped to a 350. That means you already had a V8 radiator. You didn't mention if you are using A/C. I'll guess not, given the nature of this forum.

Assuming you were getting double the horsepower, you might need a better radiator. The exhaust is not an issue. You can confirm your timing to make sure it isn't doing anything weird. Check the color of your plugs to see if any are just snow white. Otherwise we'll assume the engine is in tune.

Now why would you want a 4 row radiator? This is usually a mistake. It creates too much resistance to air flow versus a GOOD two or three row. To fit 4 rows into the tanks, they have to be small and close together with short fins. A nice two or three row will have slightly larger tubes, wider fin spacing and give better air flow.

Then you add an electric fan out front while having a good stock fan and shroud. The stock design was plenty for factory big blocks for decades. Now you put an object that impedes air flow and creates turbulence in front of everything.

Remember that the only time the fan matters is at low road speed. Once you pass about 35 or 40 mph, yo have enough pressure on the front of the radiator to overwhelm any flow it can achieve.

Start by pulling the electric fan off, then make sure any holes that would let air move through the core support without going through the radiator are closed. Confirm the fan is inside the shroud more than half the depth of the blades. Run at idle and check the temp of the core between the fins with a meat thermometer. It should be stable for 20 to 30 minutes without any issue at idle. You won't be making enough BTUs to overheat with any radiator. If it creeps out of control here, you have another issue. Mixture, timing or combustion leak into the coolant. Make sure the fan rotation is OK, if you changed it with the motor. If all is OK, hit the hiway, constant speed. With hiway airflow, you should be stable at cruise RPM. If none of the previous issues are found, and you still run-away, I would be concerned about the radiator or tune-up.

Let me know how it goes.

 

My original radiator had a hole in it thats why i switched...if i knew a 3 row would have been better i would have got it, and i would have saved at least $70....my mech. fan is a bit too far from the radiator...prob at least 3"...i picked up a bigger spacer...hopefully that helps....and im pullin the electric fan ....it doesn't seem 2 me like it makes much of a difference...the thermostat is new...its never puked coolant...gotta recheck the timing too...

 

Remember that with a shroud the fan blades should be about half in -half out of the shroud. With the shroud and fan posistioned corectly it don't matter how far the fan is from the radiator that's the purpose for the shroud.

 

Also do you have a late model block?they are known to run about 210.anything above 240 i would start worrying.

 

Agreed. Look at how far the fan is on a Monte Carlo.

 

i'm also questioning the gauge...it jumps around alot...its a 69' block...also the coolant level stays the same....never had to add any...

 

Different ohms on the temp. sending unit for your temp. gauge. Switch them and your troubles are over. If you have no symptoms but are reading hot, this is your solution.

 

i was thinkin about that 2 since i never changed the sending unit...thanx..

 

What size thermostat? You never said if the car was moving when the temp went up.If you are using a 195 degree thermostat you will probably se 210 with the stock gauge. Like already mentioned thats really not hot but advance the timing a few degrees and see if that helps.If you not running a thermostat you will more than likely see some over-heating at speeds since thremostat as a restrictor to slow the coolant and allow the radiator to disapate the heat.Also use a 14 psi or higher radaitor cap.

 

Does your car have the original fan blade or a flex fan or a real clutch fan? You mention a spacer. By the era when 350s were common fans were much larger and had clutches. Try a more aggressive mechanical fan. Good luck

PS forget everything you think you know about exhaust pressure. It's not doing you any favors.

 

kool...thanx

 

Is the sending unit in the head? That's the location for idiot light sensors, but if you put a gauge sensor there it'll read hot. Make sure your gauge sending unit is in the manifold near the thermostat housing. (It won't hurt anything to have it in the head, but it'll read hot and it'll move around more.)

 

Have a 1967 elcamino used for towing racecar,ran 240 replaced rad with a 3 core,then 4 core still ran 240 towing never lost coolant,replaced stock fan shroud with a newer chevelle shroud,installed a clutch fan,advance timing on hei,now runs 195 all the time.

 

Also try pulling the thermostat out and set it on the bench. Take a 3/16 drill bit and drill a hole in the flat surface next to where it lays in the manifold clean any burs from hole and reinstall. This will cure any air pockets in the cooling system..Simple fix and it works on any system.

 

Lots of good suggestions here so far, here's another quick thing to check: your ignition timing. Make sure it's not too retarded, it'll run hot if it is.

 

I dont think your over heating..

no puke? no boil?

gauge is wrong

 

I had the same problem only in a Plymouth. The 63 383 temp sender made the 58 Plymouth gauge read very hot. After spending a bunch on an Imperial radiator and all the assorted remedies listed above, I put the 58 sender in and everything was Jake.