I am running a chevy 350 in my 50 merc. I have been plagued by overheating. I am running a large radiator with a 160 therm and have cleaned it out. Running a spall 16" fan. Checked timing. So what's my problem. My heat sensor is a SW placed in the head.I constantly get a reading of at least 220 sometimes 240. I bought a thermal heat gun and shoot the rad, hose, intake after running this high they allways read at 190 or lowere but my heads usually read the 220 or more. Is this normal or do I have something going on
Bad sender or gauge . And that area of the head may be a local hot spot. Shoot that area with the heat gun and see what you get. If the thermostat housing is 190 or less you don't have a problem.
Do a spark plug reading... You might be running that motor a bit too lean... If that's the case, you might want to fatten up the jetting on the carb..
What is the timing? at what rpm? Heads do get hotter than the rest of the engine, especially on the exhaust side. Sounds like it's sort of normal. How about putting the sender in the intake manifold, at least temporarily.
I run a 19 inch four blade on my stock car.... at the end of a twenty lapper i'm about 210-215.... right where I want it.... your car doesn't run that kind of RPM.... you have a problem.... doesn't mean it's going to melt down, but it does mean that you have room for improvement. Deuce is right, lean condition is number one, timing number two, water pump number three. Let us know how you do.
Have run into this before--sensor in head reads about 30 degrees hotter than in intake on a similar 350-put the sensor in the manifold and it read 185 on gauge--thermal gun on t stat housing read 180
There is more than one temp sender for those engines,.... Each calibrated differently. Be certain to get the one matched to your temp gage. Also do theheat gun check on the area by the sender, as stated above. 4TTRUK
It's not common for a sbc to run hot, they generally cool pretty easily. I could never get the one in my 23 over 170 even with a 192 thermostat. The top hose would be warm and the lower one was way cooler. Sender position is critical on these motors. When I had the sender at the back of the block, near the distributor, I was getting a reading of only 120 degrees. Moved same sender to the spot by the thermostat housing and it went up to 150 there. That is when I put in the hotter thermostat and got it up to 170. Shoot the entire engine with your gun. See what the temp is right on top of the water neck, and the crossover where water enters both heads. I shot mine all over and found nothing that was hotter than the 170 reading I was getting on the dash gauge. Also, Advance Auto sells a Mr. Gasket radiator cap with a thermometer in it. It is extremely accurate, considering it only costs about $20. The sbf in my 27 was reading 210 when running along and the cap only reads 180, which coincides with the temp gun when I shot the motor, so now I know my gauge is wrong and just live with it. I would suggest anyone having questions about if their car is running hot buy one of those Mr G radiator caps, it really put my mind at ease. Don
I am running a 7 lb cap that was the only one I can find as my neck depth is 1 1/2 inch most caps are 1"
What 350 engine? Does it have Vortec heads on it? Vortec heads require an external bypass from the front of the intake to the water pump (like a big block) or you will have this symptom.
Hey guys thanks for the hints so far. I am changing the rear gears in a few days. I will probably change the temp gauge to the intake mainifold and see where it goes from there. Also am planning to install rear seats out of a 66 thunderbird. I saw them in a 50 merc at the Syracuse Nationals this year and they looked awesome. Should have been that way from the factory.
As I mentioned in my earlier post, when you install the sender in the intake the most accurate reading will come from the spot right next to the thermostat housing. The one on the back of the block gave me a 30 degree lower reading. It seems to me that the one next to the thermostat is reading the highest temp before the coolant goes to the radiator for cooling. Don
Look at coolant flow in the engine....cool coolant comes from the radiator into the pump, then into the block, to the back of the block, and from there into the heads, then forward to the front of the intake, where it exits thru the thermostat, back to the radiator. So yeah, the thermostat is where the highest flowing coolant temperature is. But the heads will be hotter at the exhaust ports, since that is where most of the heat comes from, and it does not all transfer to the coolant. A little bit of coolant flows from the block to the heads all along the way, but most of it is at the back of the engine.
The reason I asked re; the radiator cap pressure is because each lb. of pressure, will raise the boil point of a 50 / 50 coolant mix by 3 degrees. Yours is 7 lb, so it's raised by 21 degrees. Added to 212 degrees, and you have a 233 degree boiling point. if you want to use a shorter cap, there are radiator filler necks available from radiator shops, and then you have a wide variety of caps and pressures to choose from . GM has ran cooling system pressures as high as 18 lbs, in some late 50's vehicles. You won't need that much,...a 15 lb system would put yours at 257 degrees,... Well above what your highest stated temp has shown. I agree with the above posts, re; locating the sender near the thermostat,..to read temp just before it exits the block, to the radiator. Happy Roddin' 4TTRUK
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