Timing Jumping Around

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Ricks70Duster340

Ricks70Duster340

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New 440 build, new timing set, distributor/oil pump gear, distributor (Firecore), ECU (4 seconds flat). When I check the timing, the timing mark jumps all around from retarded to advanced and then will settle on the "0" mark for a second or two. I can hear the engine sound like it's surging a bit while its doing that, idle speed going up a little, then back down.

Not sure where to go with troubleshooting this.
 
How much slop was in the timing chain? I had a similar problem on the 340 of timing all over the place, used 4 different lights to check. Have a MSD mechanical distributor and no vacuum leeks. Turns out the “top of the line” chain was junk after about 20 hours of run time. New timing set from Hughes and a tensioner fixed the problem.
 
Scody21 said:
How much slop was in the timing chain? I had a similar problem on the 340 of timing all over the place, used 4 different lights to check. Have a MSD mechanical distributor and no vacuum leeks. Turns out the “top of the line” chain was junk after about 20 hours of run time. New timing set from Hughes and a tensioner fixed the problem.
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The chain & gears were new, about 500 miles ago.
 
Some times the collar will solve it. Other times it won’t. We ran my distro in the machine, 3 different times and it was perfect.
 
I've never seen one that didn't move around a little for what that's worth.
 
Distributor Shaft collars helps if it is not a timing chain issue.
Check Distributor shaft bushing/bearing for side play.
Is it just a degree back and forth or is it 3 or 4 Degrees.
Be sure weights in Distributor move freely and do not stick if
it is not locked out. You could try a bit more spring tension on
the weights (Bend tabs but not so far that it hit case).
Is it a Mopar or MSD unit?
 
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Newbomb Turk said:
You can go to any Ace Hardware or any other decent hardware store and buy the same thing for 3 bucks.
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Cool, but now he knows what one looks like and this one comes with instructions (I’m a dumbass and instructions would come in handy for me).
 
GTX JOHN said:
Distributor Shaft collars helps if it is not a timing chain issue.
Check Distributor shaft bushing/bearing for side play.
Is it just a degree back and forth or is it 3 or 4 Degrees.
Be sure weights in Distributor move freely and do not stick if
it is not locked out. You could try a bit more spring tension on
the weights (Bend tabs but not so far that it hit case).
Is it a Mopar or MSD unit?
Click to expand...
It is a new firecore distributor. The mark jumps 5 or 6 degrees back and forth.
 
ch1ll said:
Cool, but now he knows what one looks like and this one comes with instructions (I’m a dumbass and instructions would come in handy for me).
Click to expand...
my thought is for 15 bucks i know that it's gonna fit right, it's hardened and correct for the application, and i don't have to drive to two different hardware stores hoping that they might have it.
 
GTX JOHN said:
Distributor Shaft collars helps if it is not a timing chain issue.
Check Distributor shaft bushing/bearing for side play.
Is it just a degree back and forth or is it 3 or 4 Degrees.
Be sure weights in Distributor move freely and do not stick if
it is not locked out. You could try a bit more spring tension on
the weights (Bend tabs but not so far that it hit case).
Is it a Mopar or MSD unit?
Click to expand...
It's a new Firecore FC-1002.
 
I think the distributor drive has a bushing in the block that can wear. Seems like I ran into that back in my youth
 
Mike69cuda said:
I think the distributor drive has a bushing in the block that can wear. Seems like I ran into that back in my youth
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Pretty sure that was replaced when the engine was rebuilt. Guess the only way to know for sure is to pull the distributor and partially remove the drive gear to see how much side to side play it has?
 
Was the vac adv hooked up while you were checking timing? Should be disconnected & plugged.
 
Carnut68 said:
What advance springs are in the distributor?
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Ricks70Duster340 said:
The distributor has the medium blue springs that came with the unit. According to them 22-24 degrees of crank advance is all in by around 3300. I have not tested that.
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Try one heavy and one medium as a test. What cam? How much duration @50? Initial timing? That's a lot of crank degrees, So at 36-38 total for iron heads you would be at 12-16 initial. I would think 18-20 initial on a street engine.
 
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