Different 400 timing question
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Laughing Gas
Joined: Mar 2016
Posts: 757
Likes: 43
From: Cheyenne, Wy
Different 400 timing question
79 scab 4x4 400 c6
All summer the truck has started without a problem. The last 2-4 weeks, I'm sure the timing is messed up. When I go to start, cold or hot, it will crank but slow and sometimes like back pressure. All this week, definitely more back pressure and knock under load going up hill.
Until I can order a new timing chain and gears and install them, (working outdoors in Wyoming) can I turn the distributor back (counter clockwise) one/two degrees to stop the knock and relieve the back pressure at start up?
Is this the correct direction? Am I thinking this correctly or is my thoughts wrong and should do something else until I can install new set?
Next question, Is there a way to tell if a po has installed a straight up timing before dismantling or after dismantle while looking at the actual timing chain? I do know it has a double roller chain on it now.
Thanks for your help.
All summer the truck has started without a problem. The last 2-4 weeks, I'm sure the timing is messed up. When I go to start, cold or hot, it will crank but slow and sometimes like back pressure. All this week, definitely more back pressure and knock under load going up hill.
Until I can order a new timing chain and gears and install them, (working outdoors in Wyoming) can I turn the distributor back (counter clockwise) one/two degrees to stop the knock and relieve the back pressure at start up?
Is this the correct direction? Am I thinking this correctly or is my thoughts wrong and should do something else until I can install new set?
Next question, Is there a way to tell if a po has installed a straight up timing before dismantling or after dismantle while looking at the actual timing chain? I do know it has a double roller chain on it now.
Thanks for your help.
More Turbo
Joined: Sep 2016
Posts: 559
Likes: 4
From: Australian Outback
Hi mate, first thing I'd check is your batery - how old is it and what voltage under cranking? Stab some voltmeter prongs into the batter terminals and pop the hood. Place the meter where you can see it while cranking and check the voltage while doing so. You ideally want 12v or more, between 12v and 11v is poor but operational still, less than 11v needs replacement.
After that get a timing light. See what the initial and maximum timing readings are. Initial should be 6 degrees from memory, and max is about 30.
- boingk
After that get a timing light. See what the initial and maximum timing readings are. Initial should be 6 degrees from memory, and max is about 30.
- boingk
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
The initial timing setting, the ignition timing generally, will never change for many many thousands of miles, unless, somebody has changed it. One possibility (if the ignition timing really is suddenly "out of whack") is that the distributor innard mechanicals are broken or defective, stuck, etc. You'll have to do some checks with a timing light to be sure.
It is possible to check where a camshaft is installed using a straight edge along the tops of the #1 valves, when they are exactly at split overlap on the compression stroke, check and see where the timing pointer falls in relation to the "0" TDC mark on the balancer, this gives a rough indication if the camshaft is running advanced or retarded. Not as precise a degree wheel but is useful to check camshaft phasing, maybe a timing set is worn badly, when troubleshooting engine strangeness.
It is possible to check where a camshaft is installed using a straight edge along the tops of the #1 valves, when they are exactly at split overlap on the compression stroke, check and see where the timing pointer falls in relation to the "0" TDC mark on the balancer, this gives a rough indication if the camshaft is running advanced or retarded. Not as precise a degree wheel but is useful to check camshaft phasing, maybe a timing set is worn badly, when troubleshooting engine strangeness.
Logistics Pro
Joined: Jul 2005
Posts: 4,217
Likes: 154
Pop off the distributor cap and then crank the starter from under the hood, and observe which way the rotor turns. Probably counter clockwise.
If that is the case, then turning the dizzy counter clockwise will retard the ignition timing.
Check all of your battery cables and the cable to the starter too, because if they're corroded they will not allow enough current to pass to spin the starter at a proper speed.
If that is the case, then turning the dizzy counter clockwise will retard the ignition timing.
Check all of your battery cables and the cable to the starter too, because if they're corroded they will not allow enough current to pass to spin the starter at a proper speed.
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Laughing Gas
Joined: Mar 2016
Posts: 757
Likes: 43
From: Cheyenne, Wy
Thanks for the answers. Cable ends are good. My other concern is now it knocks pretty good under load like going up a hill. 30-40mph city driving. Not ALWAYS but most and it did not over the summer. At least not that I noticed.
Tuned
Joined: Mar 2010
Posts: 387
Likes: 25
I am with beartracks on this one. I had a similar thing on my 1979 F150 with a 400. An experienced (older) mechanic at the local Ford dealership suggested checking if the roll pin in the distributor gear was sheared off. He was bang on, the roll pin had partially sheared off. The truck still ran, but not well. His explanation is that a piece of debris can get caught in the oil pump gears and shear the distributor drive gear roll pin.
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