Cam Chain Issues... HELP! NOW WITH VIDEO!

[SHOracer14]

In all my years of taking SHO's apart I have been fortunate enough to never have to deal with a bad cam chain tensioner or chain issue until now. My 95' MTX had a rattling type noise in the valve train since the day I bought it. The car never had any running issues of any kind and pulled very strong. After driving the car intermittently for a couple of months I finally decided to pull the upper half apart and check the valve lash and investigate the rattling noise.

I pulled everything apart and found all shims in spec but did find an issue with the rear chain having a ton of slack. I let it sit for a week before re-tackling the issues today. I pulled the rear exhaust cam gear and tensioner. I then pulled apart the tensioner (thinking this may be the problem) stretched the spring cleaned everything and re-assembled the tensioner. Before dis-assembly I marked a spot on the chain and spot on the cam gears on both cams just to make sure everything lined back up. I just turned the engine over with a breaker bar until there was clearance to remove the bolts. During reassembly I lined the chain marks back up with the gear mark and bolted the exahust cam back in place. Before I bolted the tensioner back down with the guide cover I decided to turn the engine over a few times by hand to make sure all marks line back up. I noticed a very strange thing when doing this.

Without the tensioner being bolted in place there are points in the rotation when the chain is nice and tight (even without the tensioner being bolted down), this seems to happen when the exhaust valves are depressed on cylinder 3 in the cam rotation. Other times there is a ton of slack in the chain (even if I depress the chain tensioner). Also, the marks I made do not line up after rotating the engine. WTF!

Is it possible I have an extremely stretched chain or did I just totally screw up during re-installation? The cams should still be timed properly as I never removed the timing belt (or even the timing cover for that matter) and the shouldn't have moved too much just rotating the engine by hand, correct?

This is the first time I have felt stupid when working on a car in a long time... please help.

 

[boat]

The intake cams can still be timed correctly, but the exhaust cam can be off. Bubba and I had that problem with his wife's SHO. We changed the rear cam chain tensioner, but didn't realize we had the exhaust cam out of time, sounded like the car was choking every time you tried to start it.

The cam gears have dots, the cam chains have lighter links where the they go on the cam gears lined up with those dots. Then these dots line up at the top edge of the head, facing to the outer edges of the head. I am sure you know this, but make sure you have the raised up lettering "KOA" marks on the cams all facing straight up. I think there was a little slack in the chains when we put that back together. I'd say as long as you have all those marks set the engine should be timed correctly.

I have a SHO Engine book in PDF document form. If you want it, it has all of that information in it. I can email it to you if you want it. Let me know...

Anyone else want to chime in?

 

[Mr Anonymous]

Turning the engine over by hand there will be times that the cam chains will be slack because a. there's no oil pressure, and b. at manual turning speeds spring tension from the valve springs is going to push the cams forward and backward.

Just like the timing belt, the timing chains and sprockets have different numbers of links and teeth, so the marks will only line up every X number of rotations.

 

[SHOracer14]

Turning the engine over by hand there will be times that the cam chains will be slack because a. there's no oil pressure, and b. at manual turning speeds spring tension from the valve springs is going to push the cams forward and backward.

Just like the timing belt, the timing chains and sprockets have different numbers of links and teeth, so the marks will only line up every X number of rotations.

After thinking about it I wasn't so much worried about the marks not lining up for the reasoning you mentioned (I over reacted). I know the cams didn't move and I know I installed the gear in the same orientation I removed it. May main concern is the ridculous amount of slack in the chain at certain points. I understand what you are saying the valve springs pushing the cams forward and backwards but the front chain has some normal slack and again a little more at some times then others but that rear chain is just flopping in the wind to the point I can probably lift it a good 1/2 inch up even with the tensioner installed at some points in the rotation. If this seems normal to you I will reassemble everything and call it a day. I just hate having to take apart everything twice if the issue isn;t cured. At some points my chain is this loose(not my video) http://s184.photobucket.com/albums/x6/wablackwell/?action=view&current=100_0585.mp4...... and maybe even a bit more loose. At other points it is very taught. Thanks again for the responses

 

[SHOracer14]

Just another note as I have totally re-inspected and everything seems to be correct, I can easily depress the tensioner, compared to some I have seen before it seems normal. It does not need a large amount of force to depress correct? The tensioner moves freely and I can depress it with my hand (like a pulling the handle of a 409 bottle). I will look at it again some more after work. I;m hoping everything is ok I just want to get this thing back together... but I am paranoid to have to take it all apart again. I am going through withdrawal as I haven't driven the car in a couple of weeks.

 

[rubydist]

as I recall, depressing the tensioner took a lot more force than pulling the trigger on the 409 bottle, I'm wondering if it has enough tension in the spring.

 

[SHOracer14]

as I recall, depressing the tensioner took a lot more force than pulling the trigger on the 409 bottle, I'm wondering if it has enough tension in the spring.

I have another running driving parts car in the driveway. I think I am going to pull that one apart and compare. It's the only thing I can think of to do. I know the parts car has no engine rattle and worse case scenerio at least I can yank the good parts off of that engine.

 

[HotRodKid]

Just like the timing belt, the timing chains and sprockets have different numbers of links and teeth, so the marks will only line up every X number of rotations.

all 4 cam sprockets actually have exactly the same number of teeth, and all cams rotate at exactly the same speed. If your marks are lined up and you rotate the engine 2 full turns on the crank ( which is 1 full turn of the cams) the same set of cam timing marks will line up again

 

[jimtash]

The factory tool set has a specific tool in it that allows you to line up the cams to each other plus keep them in place when working on the valvetrain. I highly recommend you buy one as it has come in very handy.

 

[Mr Anonymous]

all 4 cam sprockets actually have exactly the same number of teeth, and all cams rotate at exactly the same speed. If your marks are lined up and you rotate the engine 2 full turns on the crank ( which is 1 full turn of the cams) the same set of cam timing marks will line up again

I know this.

The cam CHAINS however have a different number of links than the SPROCKETS have teeth, so when rotated the marked links on the chain will only line up with the index dimples once every x number of revolutions of the cams.

The same applies to the number of cogs on the timing belt. Haven't you ever rotated an engine after installing a new timing belt and noticed that those pretty little white lines you so carefully aligned with the index dimples no longer match up with those dimples on each rotation?

It's the index dimples that matter, not the marks on the timing chains or belt.

As to the issue with the chain tensioner, what was the condition of the "shoe"? A perfectly functioning tensioner even at full extension can't adapt to a shoe that is too worn.

 

[SHOracer14]

I know this.

The cam CHAINS however have a different number of links than the SPROCKETS have teeth, so when rotated the marked links on the chain will only line up with the index dimples once every x number of revolutions of the cams.

The same applies to the number of cogs on the timing belt. Haven't you ever rotated an engine after installing a new timing belt and noticed that those pretty little white lines you so carefully aligned with the index dimples no longer match up with those dimples on each rotation?

It's the index dimples that matter, not the marks on the timing chains or belt.

As to the issue with the chain tensioner, what was the condition of the "shoe"? A perfectly functioning tensioner even at full extension can't adapt to a shoe that is too worn.

The plastic shoe was still in pretty good shape... looked identical in wear to the front pad. There were little grooves where the chain has been riding but nothing out of the ordinary. Looked like any of the other amber pads I've seen from the gen II tensioners. The only thing that was questionable was one of the clipped studs that holds the pad to the metal foot of the tensioner was worn out making it very easy to remove the pad. I cleaned everything up and used a tiny amount of RTV on the bottom of the pad (right on the cross hatched "lines" of the pad) to be 100% sure it didn't fall off the tensioner during re-installation.

 

[Mr Anonymous]

Anything deeper than 1/8" or so is usually where they're gonna stop doing the job.

Without oil pressure in the tensioner it's almost impossible to judge how it's going to behave. Best bet now would be to lay the valve covers in place to stop any splashing and crank the motor over for 30 seconds or so to get oil in the tensioner and see how everything is after that.

 

[HotRodKid]

snip

an i get ya now, Ive never noticed the index marks on the chains so your comment came off sounding like it meant cam to cam relationship instead of cam to chain relationship.

 

[SHOracer14]

Anything deeper than 1/8" or so is usually where they're gonna stop doing the job.

Without oil pressure in the tensioner it's almost impossible to judge how it's going to behave. Best bet now would be to lay the valve covers in place to stop any splashing and crank the motor over for 30 seconds or so to get oil in the tensioner and see how everything is after that.

Definately not that deep. I'll have to give it a try... Thank You!

 

[SHOracer14]

Now with video!

OK... after snugging down the rear valve cover I cranked the engine over for a little while and removed valve cover. The following videos will better explain what I have.
http://www.youtube.com/watch?v=xwwKIUgUliw
http://www.youtube.com/watch?v=kLr5cys-0Dc
http://www.youtube.com/watch?v=WF4BXQHqwWQ
http://www.youtube.com/watch?v=fJeU2NqKz-A
The only answers are a stretched chain or the tensioner is weak. What do you all think?

 

[shoon]

I had a set of high mileage chains, and when I compared them with a new set I bought, there was very minimal stretching. The only stretching that did occur, was in the sides of the chains, giving them lateral movement. That was the source of my valvetrain noise!

The pins that hold the links together stretch, which give the chain more lateral movement. You can tell, because some of the links (like pictured below beside the new chain) have rub marks on them.



The tensioner, once primed and full of oil should be fairly difficult to press in. Once initially pressed in, it bleeds off any oil inside the tensioner and the remaining "tension" comes from the spring. If it feels like the spring is the only thing keeping tension on your chain once you crack your valve covers open after the engine has been run, you might have an obstructed oil passage to the tensioner.

 

[vortex2450]

Do know how much help I can be, but when I was still screwing with my 3.0l I had a tensioner issue like you, I never took it out to rebuild but at one point it wouldn't hold any more pressure than what your videos depicted. A

I found it helpful to turn the engine over with the cover off to see if the oil would squirt from the tensioner, for my case no oil came out which led me to believe what shoon just said that the oil passage was blocked.

My rear head was mostly toast at this point so I just dumper a quart of marvel mystery oil into the crank case and let the engine run @ idle for a couple minutes (with the obvious noise of no oil getting into the rear valve train but it cleared up and I regained the tension to that tensioner along with oil flow.

I'm no fan of snake oils so don't get me wrong but if I was you I would gave it a try, all kinds or gunk can build up over time and it only takes a fairly tiny amount to clog a oil galley.

Good luck, let us know.

-Josh

 

[93rev2sev]

OK... after snugging down the rear valve cover I cranked the engine over for a little while and removed valve cover. The following videos will better explain what I have.
http://www.youtube.com/watch?v=xwwKIUgUliw
http://www.youtube.com/watch?v=kLr5cys-0Dc
http://www.youtube.com/watch?v=WF4BXQHqwWQ
http://www.youtube.com/watch?v=fJeU2NqKz-A
The only answers are a stretched chain or the tensioner is weak. What do you all think?

Slack on the top like that is not abnormal for the rear sprocket. Remember, when the engine is running, the sprockets are rotating counter clockwise (looking at it from the same perspective as the video). Therefore, as soon as the engine starts to move, that inboard, driven sprocket will suck up that slack and apply it all on the bottom leg of the chain...where the tensioner is. With the slack on the top there probably isn't any on the bottom (both cams are rolling down lobe hill -in opposite directions)

So...get the slack out of the top leg of the chain (3/4" on crank bolt) and see if when you do that...the bottom leg of the chain flops around (quite hard to do, actually).

Edit: also - remember that only one of the two cams in any head are fixed to the timing belt...the other one is left to wander around within a "slack zone" that goes away when the driven sprocket says so. As long as the engine is spinning faster than the cam can "fall down the lobe hill"..the tension won't jump from the top to the bottom of the chain.

 

[SHOracer14]

Do know how much help I can be, but when I was still screwing with my 3.0l I had a tensioner issue like you, I never took it out to rebuild but at one point it wouldn't hold any more pressure than what your videos depicted. A

I found it helpful to turn the engine over with the cover off to see if the oil would squirt from the tensioner, for my case no oil came out which led me to believe what shoon just said that the oil passage was blocked.

My rear head was mostly toast at this point so I just dumper a quart of marvel mystery oil into the crank case and let the engine run @ idle for a couple minutes (with the obvious noise of no oil getting into the rear valve train but it cleared up and I regained the tension to that tensioner along with oil flow.

I'm no fan of snake oils so don't get me wrong but if I was you I would gave it a try, all kinds or gunk can build up over time and it only takes a fairly tiny amount to clog a oil galley.

Good luck, let us know.

-Josh

Thanks... I'll have to look into the oil passage as I know the pin hole in the bottom of the tensioner is clear. I would be suprised as this engine is still fairly clean on the inside. Of course the rear heads always seem to get more buildup do to lack of a beather like the front.

 

[SHOracer14]

Slack on the top like that is not abnormal for the rear sprocket. Remember, when the engine is running, the sprockets are rotating counter clockwise (looking at it from the same perspective as the video). Therefore, as soon as the engine starts to move, that inboard, driven sprocket will suck up that slack and apply it all on the bottom leg of the chain...where the tensioner is. With the slack on the top there probably isn't any on the bottom (both cams are rolling down lobe hill -in opposite directions)

So...get the slack out of the top leg of the chain (3/4" on crank bolt) and see if when you do that...the bottom leg of the chain flops around (quite hard to do, actually).

Edit: also - remember that only one of the two cams in any head are fixed to the timing belt...the other one is left to wander around within a "slack zone" that goes away when the driven sprocket says so. As long as the engine is spinning faster than the cam can "fall down the lobe hill"..the tension won't jump from the top to the bottom of the chain.

I'll have to look into this but when there is tension to the top the chain did appear to have slack at the bottom even with the tensioner in place. I will need to double check. At this point I am going to see if I get decent oil movement with the valve cover off and I think at this point, since there is no visual problem with the chain, make sure everything is timed, cross my fingers and re-assemble.