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Posted: September 10th, 2020, 3:40 am
Hi guys been a while since I posted. Well i'm still having overheat problems . Yesterday temp got up to 230 f. in stop and go traffic. I have to the distributer pretty well dialed in. At least I think so. Today I took a look at the distributer, and found number one lead is in the number seven position.but timing order is correct of course.Pulled a couple of spark plugs the color is light tan. Sparks plugs are Autolite 26's. I haven't run across a spec for plugs .The engine is a Pontiac 350 1972, bored .030.The distributer is not stock all I know is its red. Exhaust is sooty by the way.
I've been thinking of seeing if I can find a lower baffle to help direct airflow over the engine. Wife wants a/c which will contribute more to the overheating problem.
First car I've ever owned with overheat problems, suggestions.
Posted: September 10th, 2020, 6:05 am
What pressure cap psi? Is it a good cap? Condition of radiator? Have you pressure tested it for leakage? Do you have a dedicated temperature gauge showing temperature in degrees? If so, where is it mounted on the engine, intake or head? Thermostat? Pull the thermostat and test it to see when it opens. How: Use Pyrex measuring bowl with a meat thermometer. Have water at 160, then 180, then 195 degrees and see where the thermostat actually opens and how much it opens. I have been using a 160 for many years and this seems to do fine in my modified 400 engine. Hawaii and South Florida are similar in temperature so 160 may be the right degree for your 350 too. BTW I have tested several different thermostats in the past and found them to not work, or not work at the prescribed temperature. The one in my engine was the best one of the lot.
Posted: September 10th, 2020, 7:19 am
What size pulley’s are on the front of the engine? Pontiacs that had A/C turned the water pump faster with a smaller pulley on the water pump.
Posted: September 12th, 2020, 1:03 am
I bought a 160 thermostat.It starts to open at 155 its open about 1/4 at 160,about half way at175, fully open at 180. Radiator is a new Champion bigger than the 6 cylinder radiator the previous owner installed.Fan pulley is 7 &1/2 inches in diameter . Should the lower radiator hose have a spring in it? Previous owner installed an after market water temp gauge. Temp.sender is in the rt head. Manifold is a Edelbrock Performer if that makes any difference.
Posted: September 12th, 2020, 9:12 am
The lower hose usually does have a spring in it to prevent it from collapse, especially when the engine is hot. I’ve noticed in the last decade or two that a replacement lower hose many times does not come with a spring, so I usually pull the spring out of the old hose to put in the new one.
Posted: September 12th, 2020, 11:12 am
I had the same problem after I rebuilt my motor to which we replaced everything, to include the water pump. Could never figure out why it would run a little hot. Replaced thermostat, hoses, radiator, and while that helped a little, it never solved the problem until I decided to replace this expensive high flow water pump with a stock water pump. All my over heating problems went away once I did that. I'm not saying that is your problem but sharing a story that might be helpful. I swore up and down for months that it could NOT be the water pump ... go figure. In my case it was the only component of the cooling system I had not replaced in attempting to figure out my issue. So, by process of elimination, the last piece I thought would not be the problem, ended up being the problem.
Posted: September 12th, 2020, 1:48 pm
Rich-haha, doesn’t that always happen?!
Another thing, in Jim Hands book he mentions “clearencing” between the water pump impeller and the divider plate. I did this to my divider plate when I rebuilt my engine. Did it help? I don’t know it wasn’t running hot to begin with. Figured I’d do it since I had the engine out.
Posted: September 12th, 2020, 2:12 pm
Regarding the water pump, I Think the previous owner may have reduced the clearance for the impeller . Ive been putting off removing the water pump, but I suppose that is next if the thermostat doesn't solve the problem,. The radiator cap is what ever Champion uses. What is the recommended cap?
I decided to check the water pump height dimension it appears to be 4 inches . As everyone knows Pontiac changed to a 4.5 inch pump mid year. Could this be the source of my problem ?
Posted: September 12th, 2020, 7:01 pm
The 69 and later 4.5” pump would be a good place to start. Then swap to the smaller pump pulley too.
I doubt the smaller water pump pulley by itself would help. That is something you could try, if you could find one. I am not sure if it is the same between the 4” and 4.5” pumps. Pretty sure they are different.
The A/C cars and cars that had a H.D. radiator option have a 6 5/8” diameter pulley instead of the std 7”. I think there are some that are smaller yet from the aftermarket. If the plan is to add A/C to the car a 4.5” with a larger capacity radiator and the smaller pump pulley would be improvements.
Adjusting the plate behind the impeller mostly help circulate water at low engine speeds. That is pretty important for an A/C car.
Posted: September 12th, 2020, 9:48 pm
Just me,I always go to timing first for over heating.When timing is somewhat retarded they run hot.I only found that by accident years ago.I had a car that was running perfect and all of a sudden started running hot.I found the dist hold down was a little loose and it had retarded itself a few degrees.Kicked it back where it should have been,locked it down and never ran hot again.FWIW,Tom
Posted: September 13th, 2020, 2:12 am
Checked the Champion cap it is a 16 lb cap. Radiator is one year old or so as is the cap. I noticed the over flow tank was empty.
Posted: September 13th, 2020, 5:15 pm
You said the overflow tank / reserve tank was empty. When the pressure in the cooling system exceeds the pressure specified on the cap (16psi) fluid in the radiator will be released by the cap into the tube that runs into the reserve tank. When the pressure drops below 16 psi and the coolant drops in temperature, the cap will allow the coolant in the reserve tank to be siphoned back into the radiator.
Rich, Is there a marking or level indicator on the side of the reserve or overflow tank showing the level of coolant that should be in in when the engine is cold? The cap should have a tube running into the bottle and it should be immersed deeply into the coolant.
Posted: September 14th, 2020, 10:39 pm
I think the 7 & 1/2 fan pulley may be part of the problem . Butler has a 69 1/2 pump for 40.00 bucks I just need to find a 6 and 5/8 pulley.
The over flow tank has no tube in the cap, it is fed from the bottom .
Posted: September 15th, 2020, 9:16 am
Rich, can you post a photo of the overflow tank?
Posted: September 16th, 2020, 2:21 am
Sorry Bill,I can't upload photos I only have a smart phone.