302 overheating

First, do you know for sure that the guage is correct? Have you subbed in a mechanical guage or other known guage? Many shops have a temperature guage that can check it w/o touching it. This can be used to find hot areas or even a misfiring cylinder.

If you have confirmed that it is really hot, and you have done the regular checks like a new thermostat and a correct pressure cap, it is time to look at the basic setup.

Do you have a shroud for the fan with the fan properly positioned about 1/3 into the shroud. Is the fan clutch operating as it should? Do you have the correct fan clutch installed? There are 2 basic types. On is strictly tempreature limiting in which case it only operates when the air tempreature it sees is too hot. This may not be good enough. The other is more expensive and is torque limiting where it senses temperature for full engagement but, pulls air all the time. It locks on high temperature but pretty much unloads at higher speeds. Is the clutch even operating as it should? Do you have the correct fan installed for the direction it turns? The air should blow front to rear with the engine running. Wouldn't be the first time this happened on an engine swap.

Another area to look at is the water pump itself. There is both the early model normal rotation and the late model reverse rotation which is used with the serpentine belts. If you are using regular V belts, you must use the early type pump.

Is the radiator setup in a way that would create or allow air pockets in the engine? An air pocket in the water pump may prevent proper circulation. How many coats of paint are on the radiator? Some folks go a bit overboard when resto'in a car.

Is your ignition timing correct and, is the advance system working as it should. A frozen advance or incorrectly set timing can result in bigtime overheating along in poor performance and fuel economy.

How about your fuel system? Could it be running lean or rich? A rich fuel mix generally will not cause an overheat condition but, too lean could cause problems. The carb may be fine a certain speed ranges while being completely out of whack at others. Does the overheating occur only at certain speeds/loads? If this is setup as a performance engine, it will be more sensitive to this and may require recal of the carb.

Is the engine freshly built? If so, are all of the components like the heads, cam and intake compatible units? Another area to look at is gasket compatiblilty and installation. This is particularly true of head and intake gaskets. Common mistakes include wrong gaskets or wrong orientation of head and intake gaskets. Make sure the water passages line up properly before installing any gasket. Don't forget that many times, a gasket will cover a passage intentionally to make sure water flows the correct direction in the engine. If there is an open hole that should not be open, water may bypass a hot area of the engine.

Another problem area is the camshaft and it's installation/breakin. The cam timing can be a problem especially if it is late timed. Some cams are not properly marked by the manufacturer. I always check a new cam for proper lobe center and timing with a degree wheel and dial indicator when installed. Each lobe should be checked. I have seen a couple of cases where a single lobe was not correct - this is not likely with todays computer-ground cams. They are sometimes off a few degrees regardless of manufacturer. If it is off a degree or two, it can be corrected easily with a multi-keyed crank sprocket or offset cam key. Otherwise, get the cam replaced with a good cam.

One of the biggest problems with cams is lack of proper breakin to prevent the lobes "going flat". This must be done correctly the very first time the engine is fired after a rebuild with new cam and lifters. There must be proper breakin lube on the cam and lifters and, the engine must be fired and run between 1500-2000 rpm with the speed varying for at least the first 20 minutes or so of engine operation. This is the time period where most cam failures begin even though the failure may not become apparent for a few thousand miles afterward. You must start it with a proper viscosity oil that would normally be recommended for the engine/climate/operating conditions. The reason for the breakin procedure is that the cam lobes are lubed by throwoff from the crank bearings - you need this RPM to maximize oil throwoff to the cam area. Many camshafts fail or go flat very quickly if this is not done. If you are concerned about starting the engine above idle because of dry crank bearings, get a long 1/4" drive extension with a

5/16" socket. Tape them together and put it in your 3/8 or 1/2 drill turning the same way the distributor would and prelube/prime the sucker thru the distributor hole. You should do this on any dry rebuilt engine anyway. If you want to go first class on the tool, buy the priming adapter from Summitt or Jeg's. Years ago, I fought with my 351C for a long time before I gave in the the idea that the cam had gone flat like a new Volvo boat engine had done before that. Both engines came back to life after replacing the cam and lifters and breaking in properly with no more overheating problems.

Good luck

Lugnut