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jgerardi
New User
Oct 25, 2015, 6:38 AM
Post #1 of 11
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Timing chain question
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I have a 1986 Ford F350 with a 460 4bbl. I bought this truck a while back knowing it needed some work. I had both heads rebuilt and the truck starts and seems to run ok however it has quite a hesitation (sort of like a bad accelerator pump) when pulling away from a start and it idles quite rough.
I have narrowed it down to the timing. My issue is that i can't get the truck to run when i set the timing correctly. If the timing is advanced by about 25 degrees, that is the only way it will run. Im thinking slipped timing chain or incorrectly installed timing chain? I haven't touched the timing chain but i don't know what was done before i owned the truck.
Any help or guidance is greatly appreciated.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 25, 2015, 7:51 AM
Post #2 of 11
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Re: Timing chain question
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Advancing timing CAN cover a jumped timing chain. It's really not that hard to install a new one on time when there with clear marks like this......
Pic was there^^^^?
So if that shows it would show how much defection you could measure but pointless as by the time you got to this view you'd be nuts if not new now to toss it anyway.
Other is to set timing (engine off) to TDC noting which way you turn the engine by crankshaft bolt and distributor cap off noting rotor. Now turn engine the other way and see how many degrees you turn by bolt before the rotor moves. IMO if more than 5 degrees easily it's enough and more it's in trouble or could have jumped and still run at all.
Setting it could be wrong? Are you following any remaining info on radiator cover/shield frequently you remove a tap such that it can't adjust itself to set. Found 8 degrees advance at normal idle was spec - check under hood if it differs.
Other not unheard of is you might have a slipped crank damper where marks should be and seem and looks fine! Kinda rare but you're kinda old with this too and have seen that happen.
A vacuum gauge could be VERY telling if it's right or close without knowing the timing by light. When set at correct timing if you can get it to run there manifold actual pressure (vacuum reading) if "teed" into it should be about 18 Hg at sea level, maybe higher. It would go higher if advanced or be way too low all around you have a problem.
Not sure on this nor sure if OE was a total metal cam gear or had a nylon ring which would be highly suspect now if OE. Being a carb still not sure if you can get a view of chain and maybe a finger on it for looseness thru a removed fuel pump? Plain not sure for a truck 460 on that or any 460.
Always - are you convinced carb is good and there aren't any serious vacuum leak - any - PCV + hose, brake booster* or any larger leak. It's such a large engine would be a substantial leak and since heads were off lots of brittle stuff no doubt got touched or removed and may not have been replaced if still original,
T
* Brake booster might be hydroboost not a vacuum booster and use PS fluid pressure to power brakes?
(This post was edited by Tom Greenleaf on Oct 25, 2015, 7:53 AM)
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kev2
Veteran
Oct 25, 2015, 8:21 AM
Post #3 of 11
(1678 views)
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Re: Timing chain question
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out by over 25 deg has me thinking... something is way off or?
what plug wire are you clipping on - what is location?
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jgerardi
New User
Oct 25, 2015, 10:17 AM
Post #4 of 11
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Re: Timing chain question
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I'm connected to #1 (pass side closest to front of truck). Im thinking it jumped time
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Tom Greenleaf
Ultimate Carjunky
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Oct 25, 2015, 10:42 AM
Post #5 of 11
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Re: Timing chain question
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Should be correct cyl. Now only uncertainty is if Ford made this a counter rotating engine and don't thing so........
If at all possible everything says the distributor while cranking/running this would look as if you are coming in thru the side of any vacuum advance,
T
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kev2
Veteran
Oct 25, 2015, 12:01 PM
Post #6 of 11
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Re: Timing chain question
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I was hoping for a simple easy explanation... yes #1 is front R/S.
maybe remove R/S valve cover, Turn engine to TDC compression by watching valve movement - then confirm dist is correct.
thinking of whys to dbl check before tearing into timing cover.
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heavylevy26
New User
Oct 26, 2015, 12:30 AM
Post #7 of 11
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Re: Timing chain question
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You said the heads were redone right? Did you adjust the valve lash? If so, maybe that would be worth redoing just to see if maybe you made a mistake somewhere. If you did do it. Maybe it wasn't really at top dead or perhaps you tightened one at the wrong time. Just thought its worth looking at since you don't want to open up the timing cover if you don't have to.
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jgerardi
New User
Oct 26, 2015, 12:55 AM
Post #8 of 11
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Re: Timing chain question
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When i did the heads, i had a bitch of a time resetting the distributor. When I set the engine on TDC and set the distributor on #1, i could not get the truck to start for anything. I ended up way advanced before i could get it to start.
Now I'm thinking a compression test should give me an idea. If it jumped time, wouldn't it likely have low compression throughout?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 26, 2015, 1:27 AM
Post #9 of 11
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Re: Timing chain question
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Did any trauma happen to this distributor in the course of things? The post before about valve lash adjustment shouldn't apply to a hydraulically adjusted valve train like this unless somehow heads were reworked so extensively they probably should have been discarded.
You can get idea of compression in seconds with a vacuum gauge without going thru a full compression test - either if valve timing is really off should show evenly low readings if lower end of this engine is all in spec. Speaking of which - this monster V8 is both well known as a wild fuel pig but tough as nails too.
You need to post or answer some results or this thread won't get anywhere.
What happened that made the distributor had to set?
T
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jgerardi
New User
Nov 9, 2015, 5:41 AM
Post #10 of 11
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Re: Timing chain question
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I decided to check the timing chain and it did not jump. The sprockets and chain are all in order. It does appear that the damper ring slipped.
That explains why the timing can't be set with a light. I did however set the cam and crank where they should be and set the distributor on number 1. I then marked the damper ring to get an idea of what is happening when i try to time it. The truck runs when i have it timed using my new mark but it idles very rough and hesitates terribly on acceleration. Almost as if the accelerator pump is bad.
My compression is good in all cylinders, timing is pretty close, carb has been rebuilt, plugs are new.
I am going to send the carb back and have them look at it. I think the accelerator pump may not be right because when i look directly into the carb and pull the throttle, the pump stream is not strong. It is there but somewhat weak. They sent me a new diaphragm but it didn't seem to help.
If i advance the timing quite a bit, the truck runs better but it is very hard to start when warm. (sounds like battery is dead)
Im not sure where to go from here with this.
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Tom Greenleaf
Ultimate Carjunky
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Nov 9, 2015, 7:07 AM
Post #11 of 11
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Re: Timing chain question
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NO. If you tried to make new timing marks on a bad damper you are still wildly guessing. It's only a inch area that it really will run at all and 1/4" area to be right.
You can fake it with a known good damper (some you just can't see marks anymore) by both knowing your altitude above sea level, compression of an OE engine in shape and "T" in to actual manifold vacuum. OK - set to where it will read 18Hg to 19Hg is close.
This is still not right. That damper if it moved has to go. Get the right pointer if missing.
Older stuff and assorted fuels and alterations people would set to where you could hear knock and back off to the exact point where it wouldn't under load. That just isn't very practical for much of anything in use today and for the last 30 years or more for that matter,
T
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