zz502 timing chain slack
Thread Starter
Pro
Joined: May 2011
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From: Karlsruhe (Germany)
zz502 timing chain slack
Hi,
while checking several things at my zz502 I came about the timing chain slack.
I can rotate the crank 4° back and forth without rotating the cam.
This ist about 5mm or 1/5" on the balancer.
(measured with a dial gauge on a rocker arm, but the slack is also feelable at the crank)
Should I replace the chain? The engine has only 30k miles of street use.
In my opinion a bit early for chain wear, isn´t it?
I know new chains have nearly zero slack, but they stretch soon after the first miles.
while checking several things at my zz502 I came about the timing chain slack.
I can rotate the crank 4° back and forth without rotating the cam.
This ist about 5mm or 1/5" on the balancer.
(measured with a dial gauge on a rocker arm, but the slack is also feelable at the crank)
Should I replace the chain? The engine has only 30k miles of street use.
In my opinion a bit early for chain wear, isn´t it?
I know new chains have nearly zero slack, but they stretch soon after the first miles.
Last edited by zuendler; Sep 15, 2019 at 11:02 AM.
Race Director
Joined: Jul 2015
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From: SW Florida.
4 degree back and forth is 2 degrees retarded. the chains wear a little bit almost on first fire up. then settle in for a long time. i would leave it.
Last edited by derekderek; Sep 15, 2019 at 03:50 PM.
Le Mans Master
Joined: Aug 2017
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From: Cool Northern Michigan
I don't believe he has anything torn apart yet except the valve cover. He wants to know whether or not to proceed further.
A couple of degrees isn't too bad. Will lose a little low end grunt.
A couple of degrees isn't too bad. Will lose a little low end grunt.
Last edited by HeadsU.P.; Sep 15, 2019 at 06:36 PM.
Dr. Detroit
Joined: Mar 2012
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From: New Braunfels Texas
OP, are you taking degree measurements at the pushrod tip with the rocker removed?
Jebby
Dr. Detroit
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Dr. Detroit
Joined: Mar 2012
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From: New Braunfels Texas
Yes....but I think the 4 degrees he is seeing is the lifter plunge......
BUT.....if that is all you are seeing at the rocker arm measured that way......put it back together and run it.
Jebby
BUT.....if that is all you are seeing at the rocker arm measured that way......put it back together and run it.
Jebby
Thread Starter
Pro
Joined: May 2011
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From: Karlsruhe (Germany)
Well the best way would be to have the chain cover removed. But dont have to explain how much work it is with all the belts, waterpump and coolant etc.
Usually people measure the slack with the distributor rotor. But this has some play, 2° in my case, which can give your additional measurement failure. So I decided to measrue directly on the cam. All you need to know is if the cam moves back and forth. Nothing else. The dial gauge shows every little movement, of course I had the the rocker on half of its travel for best indication.
Btw I saw on the dial how the lifter went down very slowly. I had to wait 5 minutes until the lifter was empty and bottomed out.
Then I made a marking on the balancer. Turned the crank for the second marking. Result is 4° movement of the crank.
This is also what I can feel by hand.
Is 4° a usual value for a broke in chain, or should I replace the chain?
Usually people measure the slack with the distributor rotor. But this has some play, 2° in my case, which can give your additional measurement failure. So I decided to measrue directly on the cam. All you need to know is if the cam moves back and forth. Nothing else. The dial gauge shows every little movement, of course I had the the rocker on half of its travel for best indication.
Btw I saw on the dial how the lifter went down very slowly. I had to wait 5 minutes until the lifter was empty and bottomed out.
Then I made a marking on the balancer. Turned the crank for the second marking. Result is 4° movement of the crank.
This is also what I can feel by hand.
Is 4° a usual value for a broke in chain, or should I replace the chain?
Last edited by zuendler; Sep 15, 2019 at 08:16 PM.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Well the best way would be to have the chain cover removed. But dont have to explain how much work it is with all the belts, waterpump and coolant etc.
Usually people measure the slack with the distributor rotor. But this has some play, 2° in my case, which can give your additional measurement failure. So I decided to measrue directly on the cam. All you need to know is if the cam moves back and forth. Nothing else. The dial gauge shows every little movement, of course I had the the rocker on half of its travel for best indication.
Btw I saw on the dial how the lifter went down very slowly. I had to wait 5 minutes until the lifter was empty and bottomed out.
Then I made a marking on the balancer. Turned the crank for the second marking. Result is 4° movement of the crank.
This is also what I can feel by hand.
Is 4° a usual value for a broke in chain, or should I replace the chain?
Usually people measure the slack with the distributor rotor. But this has some play, 2° in my case, which can give your additional measurement failure. So I decided to measrue directly on the cam. All you need to know is if the cam moves back and forth. Nothing else. The dial gauge shows every little movement, of course I had the the rocker on half of its travel for best indication.
Btw I saw on the dial how the lifter went down very slowly. I had to wait 5 minutes until the lifter was empty and bottomed out.
Then I made a marking on the balancer. Turned the crank for the second marking. Result is 4° movement of the crank.
This is also what I can feel by hand.
Is 4° a usual value for a broke in chain, or should I replace the chain?
Jebby
Le Mans Master
Joined: Aug 2017
Posts: 8,336
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From: Cool Northern Michigan
If your real concern is play in the chain, there are other factors that may have come into play.
Such as align-bore. Any time the camshaft line and the crankshaft line come closer together, even a thousandths of an inch will affect your measurement.
If the crank journals were turned 0.010 and the main bearings were not oversized to compensate, then again you have . . . . .
There are special chains that can be ordered undersized to compensate additional slack also.
Unless this is an all-out Prostock engine, I would not worry about 4* unless you have too much time on your hands and are a perfectionist.
Such as align-bore. Any time the camshaft line and the crankshaft line come closer together, even a thousandths of an inch will affect your measurement.
If the crank journals were turned 0.010 and the main bearings were not oversized to compensate, then again you have . . . . .
There are special chains that can be ordered undersized to compensate additional slack also.
Unless this is an all-out Prostock engine, I would not worry about 4* unless you have too much time on your hands and are a perfectionist.
Team Owner
Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Guys, don't you remember that the majority of cams are ground with about 4 degrees of advance in the valve timing events to allow for new motor chain stretch. So that the cams become correct for the majority of their useful life. That is why 40 = 50 years ago when the aftermarket vendors came up with gear driven cams to correct the valve timing and then the advent of quality double true roller timing sets with multi keyways. Or us guys having custom grinds and having them ground with valve events 4 degrees retarded and then use the best billet timing sets not allowing for chain stretch.
So to the poster your stretch was thought into the equation.
So to the poster your stretch was thought into the equation.
Last edited by gkull; Sep 16, 2019 at 10:29 AM.
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From: Karlsruhe (Germany)
With the 0.001 increments you can see the slightliest movement.
Valve spring is stronger than lifter, once it´s fully compressed there´s no more measurement failure.
@gkull, my main issue was slightly jerking at low load, cruising at aroum 30mph, feels like litte missfire. I started a own thread for that issue,
and will continue there. Started this one to get the right attention for this special topic.
Engine runs perfect despite the tiny jerks. I want it perfect, and valve train was the last thing that was not checked. (everything ok there)
Bouncing timing could be a reason for my problem, that´s why I could be concerned about the slack in the chain.
Unfortunately I did not measure it when the engine was new. But who measures all that stuff at a new engine? You think you are fine for at least
100k miles.
I think I will check the slack later and see if it gets worse.
If other zz502 owners could post their values this would be a good comparision.
Last edited by zuendler; Sep 16, 2019 at 11:55 AM.
Dr. Detroit
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From: New Braunfels Texas
Jebby
Le Mans Master
Joined: Aug 2017
Posts: 8,336
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From: Cool Northern Michigan
gkull,
The O.P. is not comparing the manufacturers cam specs with the specs he is finding. No degree wheel is involved. He is comparing when the crank moves and when the cam moves, both in clockwise rotation & counter-clockwise rotation. This test has nothing to do with four degrees built into the cam or zero degrees into the cam.
Its strictly chain stretch comparison.
Also, the four degrees of advance built into the cam, from stories I have read was for customer satisfaction. When a customer spent his or her hard earned money on a cam kit, they wanted instant results. As soon as everything was bolted up, a test drive showed gobs more torque than before = one happy customer. How do you get extra torque? Advance the cam four degrees.
The O.P. is not comparing the manufacturers cam specs with the specs he is finding. No degree wheel is involved. He is comparing when the crank moves and when the cam moves, both in clockwise rotation & counter-clockwise rotation. This test has nothing to do with four degrees built into the cam or zero degrees into the cam.
Its strictly chain stretch comparison.
Also, the four degrees of advance built into the cam, from stories I have read was for customer satisfaction. When a customer spent his or her hard earned money on a cam kit, they wanted instant results. As soon as everything was bolted up, a test drive showed gobs more torque than before = one happy customer. How do you get extra torque? Advance the cam four degrees.
Last edited by HeadsU.P.; Sep 16, 2019 at 12:40 PM.
Team Owner
Joined: Apr 1999
Posts: 21,953
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Yes, look at all the comp cams h flat cams and pull up the valve events and they are ground 4 degrees in advance . They did this for all the cheapest parts motors
The OP was wondering about chain slop. It's okay
The OP was wondering about chain slop. It's okay