400 Cam timing confusion on 1981 F250
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4wd Low
Joined: May 2026
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From: Vancouver
400 Cam timing confusion on 1981 F250
I sure hope someone can explain to me what is the best method of fixing the 5 degree retarded cam/ timing gear thing. Just buy a new gear set and set it at "0"? ... Why do some come with 5 deg advanced? I want to pull off all the emissions crap at the same time.
Cargo Master
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The timing of the camshaft can be changed in a few different ways. Back in the 70's Ford retarded the camshaft by using timing sets that were made with around 8 degrees(crankshaft) retard built in to reduce emissions. These timing sets are easy to identify by looking at the dot vs the keyway in the bottom gear. In line, not retarded. Offset, retarded. This was done on the 460 and I think some other engines.
There were also cams that were ground with valve events that are retarded. If you check your camshaft and you find that the intake centerline is a greater number of degrees after TDC than the lobe separation of the cam then it is retarded and if the intake centerline is less than the lobe separation angle then the cam is thought of as advanced.
The reason for multiple keyways is to give the engine builder an easy way to adjust the cam timing in the engine.
There were also cams that were ground with valve events that are retarded. If you check your camshaft and you find that the intake centerline is a greater number of degrees after TDC than the lobe separation of the cam then it is retarded and if the intake centerline is less than the lobe separation angle then the cam is thought of as advanced.
The reason for multiple keyways is to give the engine builder an easy way to adjust the cam timing in the engine.
Moderator
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From: Virginia
I read that 1977-up 400 camshafts in trucks were installed not retarded. I would do more research. I would look for the part numbers for a early 70's car and then a stock timing set for your 81. See if they are different part numbers.
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4wd Low
Joined: May 2026
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From: Vancouver
That's a good idea ... more research on the part numbers.
Nobody really knows what they did back then, so I guess I will have to set the new timing gear set to "0" and degree it.
I am assuming that when they say "0" that means TDC ..... but who knows.
Nobody really knows what they did back then, so I guess I will have to set the new timing gear set to "0" and degree it.
I am assuming that when they say "0" that means TDC ..... but who knows.
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4wd Low
Joined: May 2026
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From: Vancouver
Thanks for the advise, but you kinda lost me at intake centerline. I think if someone was to do an in depth utube video on the subject it would be widely viewed. There are very few videos on the 400. Lots on the 351's. Nothing at all on the cam timing.
Cargo Master
Joined: Oct 2020
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All cams work the same no matter what engine. The zero position is supposed to place the cam in the engine within reason on whatever lobe centerlines were used when it was ground. This could be anything, advanced or retarded just depending on how the camshaft was made. A degree wheel, an indicator and a pointer are the tools that you need to allow you to measure where the camshaft is timed in the engine and then make a decision to advance, retard, or leave it alone. This is not difficult and you'll learn a lot about not just your engine but all engines.
Cargo Master
Joined: Feb 2004
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From: Central Texas
I found this yesterday, might be of interest.
https://www.ford-trucks.com/forums/4...am-retard.html
And what he ^^^ said as well.
https://www.ford-trucks.com/forums/4...am-retard.html
And what he ^^^ said as well.
Last edited by PROSTOCK; May 10, 2026 at 09:13 AM.
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