Overheating 4.9L 300 inline 6
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New User
Joined: Nov 2018
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From: Vale NC
Overheating 4.9L 300 inline 6
I have an old (1979) F250 with a 4.9L. I think the block is from a 1985 truck and the cylinder head is from a 60's model engine. Not sure if the head if from a 240 engine or 300.
Anyway, I drove the old truck for years with no problem until one night I was towing a tractor and it blew a radiator hose. I pulled over to let the engine cool and diagnose. I was able to repair the hose enough to get me home, but somewhere along the line I had gotten a crack in the cylinder head.
I got an old head from a friend. He said it was from an old 60's model engine. I had it shaved and then I put it on the truck. Now it over heats.
I have flushed the system multiple times. I have replaced the water pump, thermostat, and radiator. Still overheats.
I have been told that the head may be from a 240 and therefore causing it to overheat. I have also been told that older model heads (60's through mid 80's) are not compatible with 85 and up.
Is there any way I can tell if the head is from a 240? If not from a 240 engine then how can I determine the year of manufacture and the compatibility?
Thanks
Anyway, I drove the old truck for years with no problem until one night I was towing a tractor and it blew a radiator hose. I pulled over to let the engine cool and diagnose. I was able to repair the hose enough to get me home, but somewhere along the line I had gotten a crack in the cylinder head.
I got an old head from a friend. He said it was from an old 60's model engine. I had it shaved and then I put it on the truck. Now it over heats.
I have flushed the system multiple times. I have replaced the water pump, thermostat, and radiator. Still overheats.
I have been told that the head may be from a 240 and therefore causing it to overheat. I have also been told that older model heads (60's through mid 80's) are not compatible with 85 and up.
Is there any way I can tell if the head is from a 240? If not from a 240 engine then how can I determine the year of manufacture and the compatibility?
Thanks
Logistics Pro
Joined: Jul 2005
Posts: 4,217
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Get a mirror or a smart phone with a camera, and get a view of the underside of the head, where it hangs over the front of the engine block. You might be able to see some info cast into the head. A 240 head is said to have an engineering number like C8AE, where as a 300 head will have a T where the A is on the 240 head - like as in E7TE.
Cross-Country
Joined: Apr 2018
Posts: 96
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From: Texas
Don't think the actual block changed between years. Ford changed the head design in the combustion chamber for faster burn characteristics and emissions when they went to fuel injection.
Lots of guys have swapped FI style head on earlier blocks to get higher compression or put older style carb head for better flow.
Lots of guys have swapped FI style head on earlier blocks to get higher compression or put older style carb head for better flow.
FTE Legend
Joined: Nov 2015
Posts: 30,912
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From: Angier, NC
No one asked so I will:
How do you know it is over heating?
Is it pushing water out the radiator or you hear it boiling and the gauge pegged hot?
You going by the stock gauge in the dash?
If so is it using the right sender for that gauge and how do you know it did not get hurt when it over heated and cracked the head?
What head gasket are you using and any way it could have been installed wrong?
Dave ----
How do you know it is over heating?
Is it pushing water out the radiator or you hear it boiling and the gauge pegged hot?
You going by the stock gauge in the dash?
If so is it using the right sender for that gauge and how do you know it did not get hurt when it over heated and cracked the head?
What head gasket are you using and any way it could have been installed wrong?
Dave ----
Cargo Master
Joined: Jul 2015
Posts: 2,066
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From: tucson
I always heard it the other way for swapping heads. The 240 heads have slightly smaller combustion chambers, so swapping a 240 head on a lower compression 300 will raise the compression a little.
Ask on the I-6 forum further down the page for more responses.
Ask on the I-6 forum further down the page for more responses.
New User
Joined: Sep 2017
Posts: 22
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Cracked head gasket. Pull all the spark plugs out and check the compression of each one. If you find that 2 cylinders are low or one is really low, you could possibly have a cracked headgasket .
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Lead Driver
Joined: Mar 2004
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Did you stick your hand in there and feel all over the radiator core for cool spots ? Next, get a radiator psi checker, pump it up and see what happens.
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New User
Joined: Nov 2018
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From: Vale NC
New radiator, New water pump. Water boiling out of the radiator. The Gasket is installed correctly. I made sure it was aligned correctly before installation. Double and triple checked. If it is set on the block incorrectly it is very noticeable.
As far as the head being cracked I cannot say for certain, but other than the boiling out of the radiator there is not water loss. Also, there is no bubbling from the radiator when the cap is removed so I do not think that the head is pushing any air into the radiator due to leaking.
The engine runs great, just over heats after about 10 miles on the road. It does seem to take its time getting hot, but it gets hot. I can see the temp gage hand slowly moving up while driving, but it does eventually make it to the red and at that time it is hot.
I have been told that if a head has been shaved too much that the chamber could be small and the compression too high. Not sure about that either, but I have been looking at a shim for the head to increase the compression chamber some. Any advice on that?
Thanks
As far as the head being cracked I cannot say for certain, but other than the boiling out of the radiator there is not water loss. Also, there is no bubbling from the radiator when the cap is removed so I do not think that the head is pushing any air into the radiator due to leaking.
The engine runs great, just over heats after about 10 miles on the road. It does seem to take its time getting hot, but it gets hot. I can see the temp gage hand slowly moving up while driving, but it does eventually make it to the red and at that time it is hot.
I have been told that if a head has been shaved too much that the chamber could be small and the compression too high. Not sure about that either, but I have been looking at a shim for the head to increase the compression chamber some. Any advice on that?
Thanks
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Katmandu2
Ford Inline Six, 200, 250, 4.9L / 300
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Aug 22, 2003 02:09 PM