Ignition Timing is way off

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scott657

scott657

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68 Valiant,
360, circa 75,76 5 post Electronic ignition. I set it up at about 8 BTDC. No Vacuum advance Idles rough with about 18 inches of vacuum and wont hold consistent Idle. So today I tinkered with the timing. Low and behold At about 10 After TDC The Idle smooths out and is consistent. The Idle screws react to tuning (brand new AVS2 650) and vacuum is around 20.
I am going to do a points distributor with a pertronix 1 module and flame thrower coil soon.
But just for now what are your thoughts Timing chain skipped or was installed wrong?
As always Thank you for your knowledge(and patience).
Ive been trying to get this thing down for an alignment, but every time I leave the drive way I have a new "adventure"
 
I run about 12 degrees initial in my low comp teeners and they run really good! Just my two cents.
 
Start with the basics,piston stop to check for tdc. Chain jumped? Unlikely,but if you pull cap and rock crank back and forth you can check for slack in chain. Guess you could pull fuel pump and see if you can feel for slack in the chain,but it requires some work,where looking at rotor would be easier and definitive. If it jumped, its gonna jump again.
 
I don't think you have a chain problem with 20'' vacuum ,how are your plug wires and other tune up parts?
 
Which way did you rotate the distributor to make it "smoothen out". It's as if your reading the timing events backwards.
 
You likely don't have a problem at all!!!! What you want for a performance advance curve is lots of initial timing, a short mechanical curve, maybe 20-22* for a factory or factory performance cam. Before mine came apart for paint I ran about 15 initial +20 mechanical advance for 35 total not including vacuum

However checking timing mark accuracy is ALWAYS a good idea. Use a piston stop which you can buy or make. I've had this one since the mid 70's I made it

stop2-jpg.jpg


Remove no1 plug, wrench or bump engine so piston is "down a ways" and disconnect the battery ground

Install the device, and wrench the engine CW until the engine stops on the device. Make an accurate, temporary mark under 0 on the timing tab onto the balancer.

Repeat wrenching CCW. Now you will have 2 temporary marks some distance apart. If the original mark is accurate it will be 1/2 way in between
 
Just did a TDC check with a screw driver, not Precise but the tdc is WAY off. I also found a mark on the distributor that someone before me added. Its about a cylinder off
 
scott657 said:
Just did a TDC check with a screw driver, not Precise but the tdc is WAY off. I also found a mark on the distributor that someone before me added. Its about a cylinder off
Click to expand...

I guarantee you that if the tdc is that far off, 10BTC will not cause it to run barely if at all.

Also Google "rotor phasing." If you have a Mopar breakerless distributor, the pickup leads could be reversed, and replacement pickups are sometimes wrongly made that way. "It may be" that the magnet was manufactured reversed, don't know
 
scott657 said:
why would the timing mark on the Balancer not coincide with TDC on #1 Cylinder?
Click to expand...
Hub,rubber ring,steel ring.
Old age,hard driving and ring will slip. Hence the checking for tdc. Marking “0” will give you a mark to work with. Although you will need a new balancer.
 
scott657 said:
why would the timing mark on the Balancer not coincide with TDC on #1 Cylinder?
Click to expand...

They couild have mixed and matched 69 and earlier timing chain cover and/or vibration damper with 70 and later timing chain cover and vibration damper....

Or the outer ring of the vibration damper has rotated from original position... This happens sometimes when the rubber between the inner and outer ring gets too old and dry rotted....

Here are pictures of the two different timing covers and you can see how the marks are 90° different from the 69 and earlier which is stripped to bare metal vs the 70 and later which is blue...

They also change the TDC mark on the damper to coincide with the timing cover marks moving...

Here's 69 and earlier... This should be used with the cast iron water pump...

DSC04218 B.JPG



Here's the 70 and later... This should be used with the aluminum water pump...

DSC04225 B.JPG



Here they are side by side for comparison:

DSC04216 B.JPG
 
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A white paint line across the face of the balancer will reveal if the outer ring moves relative to the hub.
 
scott657 said:
Thanks for all the help guys tool is ordered Any suggestions on a damper
Stock 360
Click to expand...

Ask @Eddie348 which one he used on his 340...

It has a removable weight so it will work on all small blocks.... You remove the weight for a 273/318/340, and leave the weight on for a 360...
 
AJ/FormS said:
Rev it up a little to see if the timing starts jumping all over the place. I have seen this with a reversed-polarity pick-up coil.
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Have seen this with chain installed one tooth off position also
 
Oh sorry I mean radical,random,timing changes ,in both directions, but mostly retarded, and missing strobes, worsening with rpm increases.

I haven't seen it with off-one-tooth chain installs.And I have advanced a sprocket a couple of times, to take a "well-used" roller chain a few more miles in a DD. There I have seen it only bouncing around at idle, as the valve springs do their thing, but only a few degrees, not the 8 to 15, or more like reversed polarity does.
 
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Got the tool, found TDC and tuned accordingly, remarkable that it even ran as far off as it was!
Smoother idle, initial is at 10* BTDC 19 to 20 inches of vacuum, and ported vacuum advance re attached.
 
scott657 said:
Got the tool, found TDC and tuned accordingly, remarkable that it even ran as far off as it was!
Smoother idle, initial is at 10* BTDC 19 to 20 inches of vacuum, and ported vacuum advance re attached.
Click to expand...

So the factory mark was actually off or what?
 
Great!!. I first learned to check TDC in about 72 I had a part time job at the auto hobby shop at NAS Miramar. I used to find "a few" Fords especially 352 and 289s the balancer had slipped
 
I'm learning as I go :)
Thanks for all the help everybody!!!!
It wont be the last time I ask for it :D
 
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