400 Compression numbers and options
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Laughing Gas
Joined: Nov 2002
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400 Compression numbers and options
1978 F-150 400, 4-speed, 4x4. Starts and runs decent, but produces a small amount of grey/black smoke. Previous owner stated engine was from a '76 LTD. I've had this truck for 8 years, and never got around to fixing it up. It is run a few times a year just to move it around the yard. All spark plugs looked about the same: good gap, but black with fuel smell.
Compression test numbers:
1: 138
2: 138
3: 119
4: 124
5: 40
6: 100
7: 124
8: 120
I did squirt oil into 3 and 5 with no change in compression. I'd like to fix up this 4x4 truck at some point since it is the kind of truck I grew up with. I also have a 1979 F-150 4x2 C6 with a 400 that is bored .030. No info on who did the work, or when that motor was built. I've installed a Comp Cams kit and a lot of new stuff on that engine. However, I'm trying to sell the 4x2 since I completely lost interest in it (Honestly, I never should have bought it). Neither truck is road worthy at this time. I could steal a lot of new parts off of the 4x2 and use them on the 4x4, including the engine (after switching over the necessary 4x4 parts).
Curious what you guys think of those numbers. Were the heads on truck and car 400's the same?
Compression test numbers:
1: 138
2: 138
3: 119
4: 124
5: 40
6: 100
7: 124
8: 120
I did squirt oil into 3 and 5 with no change in compression. I'd like to fix up this 4x4 truck at some point since it is the kind of truck I grew up with. I also have a 1979 F-150 4x2 C6 with a 400 that is bored .030. No info on who did the work, or when that motor was built. I've installed a Comp Cams kit and a lot of new stuff on that engine. However, I'm trying to sell the 4x2 since I completely lost interest in it (Honestly, I never should have bought it). Neither truck is road worthy at this time. I could steal a lot of new parts off of the 4x2 and use them on the 4x4, including the engine (after switching over the necessary 4x4 parts).
Curious what you guys think of those numbers. Were the heads on truck and car 400's the same?
Last edited by 88grandmarquis; Oct 18, 2025 at 08:25 PM.
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