400 Timing Adjustment
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New User
Joined: Dec 2004
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From: Glasgow montana
400 Timing Adjustment
Just trying to get some info on timing and how it affects performance. I have a 77. It has a 400/c6 3:50 running gears. It is running a 600 cfm holly on top of an edlebrock manifold. Have dual 21/4 in exhausts from a set of headers. I have read that advancing the timing will get you better milage and performance. Does anyone know of how much to advance the timing and if you do what to look for if you have gone to far. I don't want to screw up a good thing but then again I would like to see if advancing the timing would give me a bit better performance and maybe a wee bit better milage. Any thoughts here would be appreciated.
Postmaster
Joined: Jul 2003
Posts: 2,544
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From: okc
i have a 460 so the numbers may not be the same, but in the years ive been wrenching on it i have found this, 12* BTDC gets me decent power and decent mpg, 14* BTDC gets me more power and torque but less gas mileage, i was told my 460 only needed a 650cfm carb to run like stock, i put a 780cfm on it and it has a ton more torque AND gets better mileage than the stock motorcraft 4bbl, with a bigger carb you dont have to hold the throttle open as far to acheive the same rpms as a smaller carb, its when you have your foot too deep in it that the economy goes out the window.....people have argued this with me over and over again, but i know what my truck did before and after the carb swap........ as for your timing, i would start at 12*, test drive it awhile, then bump it up 2* at a time and see what is better for your driving habits.............
Cargo Master
Joined: Dec 2004
Posts: 2,232
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From: NE Texas
If you start advancing the timing and you start to get pinging, back it off until you no longer get the pinging. Pinging, or spark knock as it is often called, can DESTROY an engine. You might experiment with higher octane fuel along with your timing changes.
Take notes and be scientific about it so you can optimize it.
Also, it sounds like you are going to mess with initial timing only. You also can adjust the vacuum advance and change springs on the weights. To adjust vac advance, use a tiny screwdriver through the vac hose port.
Good luck,
Doc
Take notes and be scientific about it so you can optimize it.
Also, it sounds like you are going to mess with initial timing only. You also can adjust the vacuum advance and change springs on the weights. To adjust vac advance, use a tiny screwdriver through the vac hose port.
Good luck,
Doc
Elder User
Joined: Jan 2004
Posts: 867
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From: Eastern Pa
Do you know what timing chain set is in it? If it has never been changed it could have one that is 4dgrees retarded. It also depends what it came out of. A new timing chain set to zero makes a uge difference in performance, especially with a cam change.
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New User
Joined: Dec 2004
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From: Glasgow montana
I am sure it has the original timing chain. I am the 3rd owner of the truck. It has 71,000+ original miles and has never had anything done to it. Good info on the timing chain sets from the factory.
Thanks
Thanks
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Fleet Owner
Joined: Jan 2004
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From: Brentwood,CA
timing chains are cheap and when you replace them you notice a whole difference in performance
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Cargo Master
Joined: Dec 2004
Posts: 2,232
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From: NE Texas
It won't give you near that much, but get a good aftermarket double roller and put it in straight up. It will make a difference. Since the engine was only rated at 165HP or so when new, 75HP would be too much to hope for.
Have a great day,
Doc
Have a great day,
Doc
