erratic timing on 360

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1) Ok so I do have 1 plug wire that is a different brand then the others but same size. Problem existed before swapping plug wires sets, but I will go ahead and rule that out, and triple check plug wire seating.

2) I ordered a distributor shaft collar and am going to install to rule out the possibility of I-shaft bouncing. The xe262 cam is fairly mild but its a 10 minute job to rule out this possibility.

3) I measured chain slop, yes there is some but it seems minimal without a degree wheel on the crank to put an actual number to it. The distinct snapping back-and-forth between two timing settings, all the way through the rev range with no wandering between, makes me strongly suspect this has nothing to do with the timing chain. Replacing it will be my last resort, obviously because it’s the most expensive and labor-intensive.
 
The vacuum advance can cause instability even when disconnected.
I am thinking this also or something in the electronic side of the primary ignition. the Pertronix magneto or what ever type ignition they use. Is there an air gap ajustment? I would think the module if it was electronic. i would do the distributor cap off turn the crank and see how much slop in the chain before tearing it apart. start easy then tear the engine apart but dont go straight for engine internals. It could be electrical. How are the grounds for the ignition? any High resistance connections?
 
I installed the shaft collar on the distributor and it immediately fixed my timing issue - well, the bouncing back and forth between two settings. Now I have a good steady mark at idle. Now that my mark isn't bouncing around, I can see the wandering around at higher RPM that would seem to support the timing chain slop diagnosis.

Looks like I had both problems, a bouncing I-shaft AND a loose timing chain. It runs much better now, we will see after a few tanks what happens to the fuel economy. Thank you all for the troubleshooting tips; the prize goes to Ch1ll for identifying the issue and $15 fix.

The timing chain replacement will happen in the near future when I get some time off work.
Can anyone recommend a quality timing set available on Rockauto that will be compatible with a tensioner and not tear it up?
 
I believe that you have found the timing problem when you found slop in the chain. To me , that is def it. I would not be happy that a machine shop used a cheap gear set. Makes you ask yourself more questions.
Anyway, you are gonna have to change out the cam chain and gears .
 
The shaft for the oil pump was raising and lowering. A collar shaft locks the iISHAFT AGAINST THE SDIST SHAFT SO IT CANNOT GO UP AND DOWN ANY MORE. If it goes up and down it will definately affect the timong because it is a spiral gear mated to the cam so it will advance and retard as it does it. On a dist machine it locks the shaft and housing in no bouncing. I would look at cloys or a similar brand for the timing set. You will spend 100 on a quality set for sure.
 
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RA has cloyes, this one will be fine for what you are doing CLOYES C3028X. IK would seriously think about changing out the oil pump drive shaft also if it is used and a new cam. I would also check the tower bushing for excessive wear. I would hope the machine shop put a new one in.
 
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If the car has a chain tensioner there should be no slop in the chain
the tensioners work so please no tensioner bs
remove the plugs
rotate engine to tdc - line up the marks
cap off distributor
with breaker bar rotate the engine backwards [ccw]
Distributor should turn, see how far the breaker bar moves before it turns, it should turn right away...if it does not time to disassemble and do the work properly.
If a shop rebuilt this engine and did not have the rotating assy balanced it is time for a new shop. Stock 360's had poor engine balance esp in the late 70's
 
The shaft for the oil pump was raising and lowering. A collar shaft locks the iISHAFT AGAINST THE SDIST SHAFT SO IT CANNOT GO UP AND DOWN ANY MORE. If it goes up and down it will definately affect the timong because it is a spiral gear mated to the cam so it will advance and retard as it does it. On a dist machine it locks the shaft and housing in no bouncing. I would look at cloys or a similar brand for the timing set. You will spend 100 on a quality set for sure.
How many shafts are there? I thought the oil pump drive shaft has the gear on top to be driven by the cam. There is a slot in the top of the gear that the distributor shaft indexes into. I don't understand what the intermediate shaft is?
 
the Ford 5.0 has an intermediate shaft for the oil pump drive. easy to screw up too...:)
 
Yeah the interesting thing is I replaced the I-shaft/oil pump shaft (needlessly) long ago troubleshooting this issue, the old one had some peening to the slot but when comparing measurements the new one was the same slot dimensions. Also, this distributor has a pristine shaft so we are dealing with two parts interfacing that are well within spec and have no wear issues. The bushing it rides in was new as well. Maybe the character of the cam is what was making the shaft want to ride up. I don't know, either way the shaft collar on the distributor fixed it. There is still some slop in the interface between the I-shaft slot and distributor tang, but I don't think its worth peening/filing/welding up the tang to get that last bit of stability. This is a daily driver that will never see the track.

As to the numerous comments about the quality of the machine shop, I have no evidence they cheaped out on parts, again this was third party so I had no direct dealings with the shop, but I don't see why they would when a Cloyes set is so inexpensive ($40). I imagine they tossed the tensioner because they are old-school and don't believe in tensioners, as some on this forum would argue they are unnecessary. There is some slop in my chain and evidence of stretching, but this might just be due to the poor quality of even name brand parts these days. I don't have a degree wheel to determine the exact amount, but it seems relatively minor. It has also only been 2k miles since rebuild.

When I rebuilt the front end (prior to entire engine rebuild due to wiped cam lobe on a tired motor) I used a Cloyes double roller, tensioner, the oil slinger and the hole-thru bolt to drip oil via the tab on the tensioner onto the chain. Hopefully the machine shop didn't toss my slinger and special bolt along with the tensioner.
 
Well, keep in mind that the "new" parts are made overseas,and yes the quality isnt the same. Also there is a timing chain measurement procedure to verify if there is slop. I dont mean the "watch the rotor" method,it involves a straight edge and measuring deflection with the timing cover off.
Had this same issue on my Dart, it turned out to be operator error. One of my plug wires wasn't fully seated. Timing jumped around exactly as you said and once I went through all the nightmare scenarios I found one ignition wire that wasn't "clicked" tight
Yup..never rule out electrical. I only say that because I also worked avionics on A-10s in the service, as well as did my stint at a dealership working electrical issues in cars. i had my dart running recently, and the Auto meter tach was erratic, I thought "w t hell is the ignition system crapping out? as it is wired into the negative side of the coil. It cleared out and started running, but I am waiting for it to happen again.
 
I’ve been having the same issue of timing jumping up to 8 digrees at 3k rpm on my 340. @yellow rose has recurved my distributor twice while using my digital 6AL box and has not seen the timing jump on the machine. We’ve used a few different timing lights and shows the same jump on each of them. I’ve not been driving my car nor had time to check the chain or oil pump shaft as noted in prior posts. @lead69 and @yellow rose along with some other friends have been seeing a lot of crappy chains in the last year or so with very little time on the motor the chains are having serious stretch... now I know I’m not the only one having this issue...
 
I had erratic timing but mine was caused by having solid motor mounts which cause the vacuum advance to to bounce the plate that it is suppose to advance. The motor moving with the cam I have.. I had a electronic pickup from a lean burn with a plate that had no advance in it,so I switch the plate into my other dist and no more erratic timing. Now that was on my motor I cannot speak for anyone else but that solved my issue. PS i do not use my vacuum advance so it did not matter to me if i had it or not.

The picture should show the difference.

100_7518.JPG
 
3) I measured chain slop, yes there is some but it seems minimal without a degree wheel on the crank to put an actual number to it. .

You can get a pretty fair idea without a wheel. Simply wrench the engine around until you have the timing mark "within range" on the tab. Remove plugs. Carefully move / wrench engine while watching rotor until you have a good "feel" for when it is up against the chain slop. You can feel this easily. Now do that while watching timing mark, and just measure difference in timing marks, 5* 10* whatever
 
check for timing chain slop, anything more than a 1/4 inch is too much. try disconnecting the vacumn advance then see if it jumps around. it could be that its starting to pull the distributor at idle.

i assume that is jumps around at all rpms? or just at idle? Also check the reluctor on the distributor. I had a jumping around problem once turned out the reluctor on the distributor looked like a bunch of mice had been chewing it. Changed the reluctor and the jumping stopped.

how many miles on the motor?

Have you tried connecting the light to another spark plug wire and see if it still jumps? Possibly something wrong with #1 plug wire .
 
check for timing chain slop, anything more than a 1/4 inch is too much. try disconnecting the vacumn advance then see if it jumps around. it could be that its starting to pull the distributor at idle.

i assume that is jumps around at all rpms? or just at idle? Also check the reluctor on the distributor. I had a jumping around problem once turned out the reluctor on the distributor looked like a bunch of mice had been chewing it. Changed the reluctor and the jumping stopped.

how many miles on the motor?

Have you tried connecting the light to another spark plug wire and see if it still jumps? Possibly something wrong with #1 plug wire .

You know i would not think a reluctor could go bad but maybe, you do have current jumping at it alot. But that is a possibility. I would never have guessed. I would think the magnet part which i think is called a phaser correct me if im wrong.
 
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You know i would not think a reluctor could go bad but maybe, you do have current jumping at it alot. But that is a possibility. I would never have guessed. I would think the magnet part which i think is called a phaser correct me if im wrong.


Yeah i could not believe it either , it was a mopar distributor too, granted it was about 15 years old by the time I noticed it was bad. Have never seen one before or since
 
Coming a little late to this game but where did you get the shaft collar from? Did some searching and my results have been not.
 
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