Are they known for running hot? Its a 49 with the original block bored to 324. It has 56 code 10 heads and matching 56 inlet manifold. Heads were pressure tested and rebuilt. Runs dual exhausts with Smitties and an Edelbrock 4barrel carb, still on points with timing set at 3000rpm by a competent rolling road. Rad has been recored and water pump and thermostat are new. OK, enough waffle. It gets very hot in normal driving and if sitting in traffic it boils up. The paint has burnt off the inlet manifold where the centre hotspot is. There appears to be some sort of adjuster under it? There isnt much room under the bonnet (sorry, hood) for airflow. All the air enters through the grille and flows through a hot radiator to get to the carb. With a batwing air filter on it runs badly though it was fine on a rolling road without one and a huge fan blowing cold air over it. So. Is there a mismatch between the later heads and my earlier block? Are 303 gaskets the same as 324? (as far as I can find out they are) Is there a way of ducting cold air under the hood to the carb that looks period? And any other advice. Many thanks, Jim
What is it IN? Almost always, "overheating" on the road is not enough radiator. At slow speed, not enough air. Ben
Don’t where you are or your gasoline blend but the only difference I see from the mid 50’s what most of drive is the gas. These cars for the most part didn’t heat up then and didn’t need 6 blade fans and over sized radiators. Most of us just keep throwing bandaid fixes at them until we can sit at a light and not get to 220. Most engines then had 160-170 thermostats and now everyone says 190-200 is ok but the car itself was not built for whether it’s better for the engine or not…
Im in UK. Agree that the fuel is a problem. Its worse on E10. And also that the ambient temperatures from the 50s were not that different. What is different is traffic density-cars sit in traffic more now. At least they do with our (almost) third world road network over here!
no, they are not known for running hot. with radiator cap off and engine running can you see coolant flow? are there bubbles? did you verify no vacuum leaks with the carburetor swap?
I do suspect slight head gasket leaks. Compression test shows all cylinders about 200 psi but there is a dribble of water from the drivers side tailpipe. Hoses dont bulge up and it runs ok though. Before I pull the heads and wait for gaskets to arrive from the USA I thought id sound out some ideas here first. The gaskets used were Felpro which are OK usually. Seen some advertised called BEST Gaskets, are they good?
Water will condense from the exhaust gas under some conditions when cooled, unless you are burning something with no H in it. What does the engine temperature gage say? Pontiac heads and others with lengthy or exposed exhaust port passages will cook off most any paint. I'd pressure test the cooling system before changing parts.
either brand gasket should seal fine. I would use Felpro copper if available and spray with aluminum paint and install wet, torque per book.
On the passenger side bottom of the exhaust manifold is a heat riser valve. When the engine is cold it shuts of that side of the exhaust and forces it to go under the intake manifold to heat the carb to prevent icing. That is where the paint on your intake manifold is burning off. I bet the heat riser is stuck shut causing the engine to overheat. It has a weight on it and a thermostatic spring, the weight closes it when cold and the spring opens it when hot. If the heat riser isn't on the passenger side look on the drivers side.
Get yourself a BLOCK TESTER. It is used to check for exhaust gases in the cooling system. A good radiator shop should have one. Have them test for exhaust gases in the cooling system.
Just another thought, have you tested the radiator cap. I once got a screaming deal on a car because it boiled over all the time. I changed the radiator cap and problem solved. You could also try a high flow thermostat.
Do you flush the cooling system and have the block baked? I have picked up several 261s (the big truck version) of the 235. Every one of them the coolant passages were full of sludge, congealed antifreeze and rust! I knocked the core plugs out of one of them, the sludge was from the floor of the passages to the bottom of the core plugs. I put a garden hose in the block in several places to flush it out it took almost an hour for the water coming out of the block to run clear, and more came out after I had them baked at the machine shop.
Had a quick look , both exh. manifolds are just normal cast iron log type. No flaps on them. They are the original 303 ones. The inlet manifold has a centre port which is exhaust heated. Through this is some sort of narrow tube . It looks pretty siezed in place. What does that do?
I'm not seeing it turning. At bottom dead center the valves are closed and the cylinder would be full of compressed air. The engine couldn't turn at that point. It's not clear how hot this is really getting as its not been mentioned. And 'boiling up' could be mistaken for a puking of excess coolant? Chris
If you have the cylinder very close to TDC, the engine will not turn. Sun Electric had a piece you put in place of the rotor (with the distributor cap off) with 6 and 8 cylinder marks. You lined number 1 up at TDC, did your leak down test, then bumped the starter until the next number lined up where number 1 had been and you had the next cylinder in the firing order right at TDC.
The heat riser valve may be below the exhaust manifold, between the manifold and the exhaust pipe. That narrow tube should go to the choke, it heats the bimetallic spring in the choke and opens it as the engine heats up.
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