There are many posts about over heating, vapor lock etc. Some members install electric fans sometimes two, return fuel lines clothes pegs, non ethanol gas and a host of other issues relating to over heating. I feel that the most important thing is that the block is clean and free of all debris. I have three original 259 engines and the blocks are full of crud, one engine I had dismantled removed the plugs and while hanging on a chain block from a tripod I used a garden hose with a 1/4" pipe and a wire probe and it took the best part of two days to thoroughly clean the block. I did this in the hot sun and let the
block dry then finished the job off with compressed air, the cloud of rust dust was massive. Fortunately the radiator was clean: to note this 259 is installed in to a 1954 sedan with an original 6 cylinder also with the original radiator. With the hose off the bottom a garden hose can run full and not back up. When assembled a 160* thermostat was installed and it rarely goes over that maybe 170*-175* idling in 100* temperatures. The timing is set at 4* BTDC static, carburetor adjusted all parts cleaned and confirmed, heat riser functioning. Starts smartly on 6 volts and runs on high speed idle for 1-2 minutes then kicks down normally. It will idle up to 160* and hold there. If a block is clean, radiator clean, heat riser functioning, timing set to 4* static and mixture in the middle (not lean) and the vacuum advance is functioning correctly there will be no over heating nor "vapor lock". What is frequently labelled "vapor lock" is fuel boiling in the carburetor and over fueling the engine. Fuel will not boil in the fuel lines. When the engine is flooded under these conditions after 15-20 minutes the excess fuel will evaporate and all is well again, this may repeat and it may not. Pouring water on the fuel lines, placing clothes pegs, return fuel lines, electric fuel pumps, spacers under the carburetor will not cure anything if the block is dirty, heat riser is not functioning, timing is out, radiator clogged and the vacuum advance is not functioning.
block dry then finished the job off with compressed air, the cloud of rust dust was massive. Fortunately the radiator was clean: to note this 259 is installed in to a 1954 sedan with an original 6 cylinder also with the original radiator. With the hose off the bottom a garden hose can run full and not back up. When assembled a 160* thermostat was installed and it rarely goes over that maybe 170*-175* idling in 100* temperatures. The timing is set at 4* BTDC static, carburetor adjusted all parts cleaned and confirmed, heat riser functioning. Starts smartly on 6 volts and runs on high speed idle for 1-2 minutes then kicks down normally. It will idle up to 160* and hold there. If a block is clean, radiator clean, heat riser functioning, timing set to 4* static and mixture in the middle (not lean) and the vacuum advance is functioning correctly there will be no over heating nor "vapor lock". What is frequently labelled "vapor lock" is fuel boiling in the carburetor and over fueling the engine. Fuel will not boil in the fuel lines. When the engine is flooded under these conditions after 15-20 minutes the excess fuel will evaporate and all is well again, this may repeat and it may not. Pouring water on the fuel lines, placing clothes pegs, return fuel lines, electric fuel pumps, spacers under the carburetor will not cure anything if the block is dirty, heat riser is not functioning, timing is out, radiator clogged and the vacuum advance is not functioning.
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