bouncing timing mark

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Ironmike

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OK. You guys got me running REALLY good. Timing fine, re curved distrib. All seems to be well, except..... My TDC mark on my damper bounces around when timing the thing. It's a 509 cam....it really only bounces about 6 degrees back and forth. Can't figure it out. Can't tell EXACTLY what my initial is.
I've had some pretty radical cams in GM products and when setting timing at around 1000 RPM, that mark was steady as a rock. What gives?
 
Had the same problem with my MP dist. Switched to MSD dist problem gone.

The problem was the mechanical advance was kicking in to soon.
What dist and springs are you running?
 
There are a couple of things, loose timing chain, or loose bushings or advance mechanism of distributor. The distributor problems also create spark timing deviations on a cylinder to cylinder basis.
 
I'd guess that with that lumpy cam, it's bouncing around the sloppiness in the timing chain, dist. gear/cam gear etc. Is there any way to get the idle down lower and smoother?
 
Got the same issue. I have an MSD distributor and I replaced the oil pump/ distributor gear shaft in order to remove some of the slop. Still have some, alot of the slop comes from the piss poor design of how the distributor meshes with the cam gear.
 
Maybe if you put it in gear, that could help smooth it out.....unless you've got a high-stall converter or a stick.
 
cudavert said:
I'd guess that with that lumpy cam, it's bouncing around the sloppiness in the timing chain, dist. gear/cam gear etc. Is there any way to get the idle down lower and smoother?
Click to expand...

Yeah, change to a mild cam or install EFI...LOL

As was pointed out...the timing chain and gears can cause this. Install a 5.2/5.9 Magnum timing chain tensioner P5007709 (available at the dealer, production part) and, if it is the problem, it will smooth right out. It replaces your cam plate on the front of the block. I started using these on all small block mopar engines...it is an improvement.

The internals of the distributor, the oil pump/intermediate shaft and gear, and the bushing in the block can all cause this problem. The bushing is pressed into the block from the top and, if it has never been replaced and you've got a bunch of miles, it's probably worn out of spec.

Another culprit is the design of the distributor drive itself. By design it allows some play in the timing because of the oil pump, the valve springs and the general slop between all of the parts.
Dan Dvorak came up with a timing stabilzer that mounts on the distributor.
His website explains it pretty clearly.
http://www.dvorakmachine.com/timing_stab.shtml
TimingCorrector.jpg
 
Not the distrib...I don't think. Accel Street Billet. Mech advance is just about perfect. Guess maybe everything else mentioned could be the culprit.
Can't remember if it's more stable at higher RPM or not. All my advance is in by 2500 RPM. Maybe I'll throw the light on and check it at 2500.
It's a 4 speed. Won't idle much below 875 or so and REALLY lumpy that low.

Anyhow, it's running pretty strong so I shouldn't let it bother me but.....you know how it is.
 
Ironmike said:
OK. You guys got me running REALLY good. Timing fine, re curved distrib. All seems to be well, except..... My TDC mark on my damper bounces around when timing the thing. It's a 509 cam....it really only bounces about 6 degrees back and forth. Can't figure it out. Can't tell EXACTLY what my initial is.
I've had some pretty radical cams in GM products and when setting timing at around 1000 RPM, that mark was steady as a rock. What gives?
Click to expand...

Try this I bought 3 of them but engine is not fired off yet.......

http://www.hughesengines.com/Index/...aXZlIEh1Z2hlcyBFbmdpbmVzIEl0ZW1z&partid=25200
 
well looks like the idle quality was tossed out the window with the choice of the 509 cam there is a alot of RPM fluctuating going on at idle due to lope. the dist, oil pump drive and bushing and timing chain all get jerked around when at idle with a large cam. i believe that at idle as long as it is not stalling the real test is at or around 2500 to 3500 RPM if it smoother there. good, if not then there is something wrong.
Peace
 
Mad Dart, that device from Hughes will stop the slop where the distributor shaft meets the intermediate shaft/gear but it does nothing to keep the intermediate shaft/gear in place. The distributor bearing/bushing (inside the distributor housing) has to take all of that. The fix that Dvorak came up with eliminates that. It uses the distributor housing (with a bearing between the housing and the stabilizer) to secure everything. It's just a better way to go and it solves both problems. I still reccommend the timing chain tensioner regardless of what's going on at the other end of the cam.

From Dan's site:
Timing Stabilizer - A devise that installs between the body of the distributor and the intermediate shaft "Tightly." Eliminates timing fluctuation by keeping a constant pressure on the intermediate shaft which in turn keeps the cam from moving, which keeps the CAM from "sensing" cam in and out movement, I-shaft up and down movement and relief spring cycles from the oil pump. Final fitting required. $79.95
 
mopar340dave said:
Mad Dart, that device from Hughes will stop the slop where the distributor shaft meets the intermediate shaft/gear but it does nothing to keep the intermediate shaft/gear in place. The distributor bearing/bushing (inside the distributor housing) has to take all of that. The fix that Dvorak came up with eliminates that. It uses the distributor housing (with a bearing between the housing and the stabilizer) to secure everything. It's just a better way to go and it solves both problems. I still reccommend the timing chain tensioner regardless of what's going on at the other end of the cam.

From Dan's site:
Timing Stabilizer - A devise that installs between the body of the distributor and the intermediate shaft "Tightly." Eliminates timing fluctuation by keeping a constant pressure on the intermediate shaft which in turn keeps the cam from moving, which keeps the CAM from "sensing" cam in and out movement, I-shaft up and down movement and relief spring cycles from the oil pump. Final fitting required. $79.95
Click to expand...

Sorry about that I just posted without reading your reply in detail. Had to take off and go somewhere. Seems that between the two parts depending on where the issue is along with a timing tension er, which I always run would take care of the problem. If not than it would be something else. Could it be a SLOPPY oil pump drive gear?? Just a thought, I always run a new one with each rebuild.
 
Mad Dart, I bought that same thing at the hardware store for my 360 w/ MSD dist. and my timing still jumps so don't get your hopes too high.
My motor does this same thing and I'm leaning towards a bad or twisted balancer, the rubber O ring thing gets old and dry and who knows what it's doing. Also if you have an MSD box it can cause timing lights to get "confused" with the 3 sparks at low rpm so it may look like your timing is jumping but really the light is flashing too early or late. So if you've got an old stock balancer on it I'd lean that way
 
If you are running a MSD ignition box or any other type of multiple spark box your timing will fluctuate at idle because the pickup of the timing light might pick up any of the sparks at any givin time. The only way I know of to cure it is to figure out your total mechanical advance and when it is all in and set your timing light to the total degrees of timing you want then rev the engine up to past the all in point and then check your timing. It should be rock solid on zero at that point.

Jack
 
I run a .509 in a big block and my timing at 800 RPM only jumps 2 degrees so somethings sloppy. To check to see if the balancer outer ring is loose and bouncing around try this. With engine at idle, use the timing light to capture the balancer looking at it from underneath and figure out which part of the balancer face you can see the easiest. Shut the engine off and rotate by hand till the part that you'll be able to see is at the bottom. Then paint (I use my wifes white nail polish) a 1/8" wide line that starts at the outer ring and extends all along the face of the balancer, use a ruler it's got to be straight. Start the engine up and using the timing light on the face of the balancer to see if the line is breaking at the margin between outer ring and inner hub, right where the rubber is. If your timing is moving 6 degrees and the balancer is the culprit you should see something.

Terry
 
Here is what my 360 balancer looked like with the rubber ring having worked it,s way out.Hope this helps!re and re of 66 Dart 017.jpgAnd the new one

re and re of 66 Dart 017.jpg


re and re of 66 Dart 019.jpg
 
Most likely a timing chain being sloppy even a little slack will make it walk back and forth, a chain tensioner or a gear drive will fix it but a new chain and a tensioner would be a good choice, it will let the motor run a little better too with stable timing
 
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