Timing Marks Bouncing Around

[cwestra]

When I check my ignition timing at higher rpm's (3,000 +) using a timing light, the marks on the damper (using timing tape) bounce around a lot, making it difficult to get an accurate measurement.  Is this normal behavior when the rpm's get up this  high or is something wrong?

[dodj]

I always use a shaft collar on my BB's to make timing rock steady!

What's a shaft collar?

[Strawdawg]

It is a collar that you slip over the distributor shaft and is clamped to the shaft against the gear so that the distributor gear cannot move up and down...when it moves, it rotates back and forth which changes the timing

here..a pic is worth a couple of million of my words...last post at the bottom of the page  http://www.jalopyjournal.com/forum/showthread.php?t=118716&highlight=hemi+tech&page=3

[cwestra]

Does the variation in timing at these rpm levels have a noticeable affect on performance?

[Strawdawg]

In a high output engine, it has an obvious effect.   The stronger the engine, the more obvious it becomes.   If one is serious about obtaining all that is possible from the combo, then it is one of the the things that can be removed from the equation.  For a daily driver that is not a race piece, then it is probably relatively immaterial.   

It is an easy fix as far as the collars go.

[Moparal]

Corey, a stretched timing chain can cause that issue to, if you have a stock engine or cheap aftermarket chain set.

FYI    lots of bb mopars died an early spun bearing death by a nylon top gear. The teeth clogged the oil pick up

[moparmaniac59]

I found that I had a nylon gear on my stock 318 (1973 Barracuda) when I went to do an upgrade. Glad it hadn't come apart yet!!

                                                  Matt B.

[wally426ci]

Corey, a stretched timing chain can cause that issue to, if you have a stock engine or cheap aftermarket chain set.

FYI    lots of bb mopars died an early spun bearing death by a nylon top gear. The teeth clogged the oil pick up

same symptoms on my truck, new timing kit cleared it right up. 

[cwestra]

Corey, a stretched timing chain can cause that issue to, if you have a stock engine or cheap aftermarket chain set.

FYI    lots of bb mopars died an early spun bearing death by a nylon top gear. The teeth clogged the oil pick up

Thanks.  When I rebuilt the motor I went with dual sprocket gear (no nylon) so it's likely it is the distributor gear bouncing.  I do remember those nylon capped timing gears for big blocks though.  You could always count on shaking them out of the oil pick-up during every rebuild. 

[Moparal]

a cheap dbl roller will stretch in about 10 minutes of use as well. Did you use a name brand?  Mopar performance ones stretch extremely fast and never install one without degreeing. The mp's need the kit most of the time

[dodj]

To get the collar in the right place, would you tighten it just enough to hold onto the shaft then put the distributor in place and let the gear move the collar up the shaft. Then remove the distributor and snug up the collar?

[Strawdawg]

yes

[Aussie Challenger]

Just a question when using these collars, does it put more thrust on the distributor shaft and then up into the distributor itself.   
Has anybody had any problems in this area down the track? I have heard of these collars but only now seen one, somebody has posted a similar question on another forum.
Thanks for any and all replies, I have been able to fix most timing scatter by replacing the timing chain as Moparal mentioned.   

[cwestra]

a cheap dbl roller will stretch in about 10 minutes of use as well. Did you use a name brand?  Mopar performance ones stretch extremely fast and never install one without degreeing. The mp's need the kit most of the time

I bought it from Mancini but not sure which one I went with.  I'm sure I went with a cheaper one though.  I'll try the collar and see if that fixes it.  Otherwise I suppose it is probably the chain.  Thanks.

[Aussie Challenger]

It was also mentioned about cheap chains that stretch, does anybody have a list of what chains not to buy apart from the original. Has anybody fitted the chain MP tensioners.