Timing Chain Already Slipped out?

[Marty Rogan]

My Race car blew the head gasket last time out (240Z with L28 turbo motor). So today I started in on removing the head. When I went to push the timing chain tension tool in, it did not want to go inat all. When I looked closer, the manifold side of the end chanin was already very loose. The plug side of the engine is still tight. Does this mean that the tensioner has popped out? I haven't even removed the cam gear yet.

Le me know what you think.

Thanks,

Marty

[240ZMan]

I just checked one of my old engines to confirm that the tensioner is on the plug side, so I think something else is going on. The rotation of the engine should keep the manifold side tight.

[Marty Rogan]

I know the last time I used the tensioned tool it pretty much slid in easily. This time, I can't even force it in.

Man, I really didn't want to have to take the front cover off this engine!

[mlc240z]

Maybe the tensioner wasn't working/broke/wasn't tight enough to begin with and you jumped a tooth?

Might leave it overly tight on tensioner side and 1 extra link on slack side.

Did the timing shift?

[Marty Rogan]

I went back after a short break and looked at it again. Then I turned the engine slightly in the opposite direction. That took the slack out and allowed the tool to slide in. Sometimes it pays to walk away and get a new pespective.

[mlc240z]

Found that most problems are helped by a "walkaway".

Or at least your mental state. Beats Prozac!

[ozconnection]

Maybe the tensioner wasn't working/broke/wasn't tight enough to begin with and you jumped a tooth?

Might leave it overly tight on tensioner side and 1 extra link on slack side.

Did the timing shift?

A broken tensioner is possible but he'd be telling us about some weird noises up front and power loss due to erratic cam timing. More likely is that when a timing chain 'stretches' because of age and use, the front end of the engine gets very noisy because of the chain slap.

I've never heard of a chain jumping a tooth, even when really stretched, ever.

I don't really get why you couldn't get your tensioner tool into place Marty. Pushing the tool in will just push the chain against the chain guides, the same as normal! The 'y' shape of the entrance in that area lends itself nicely for a tool of similar shape to simply glide in and push the chain against the guides. Am I missing something here? Photos would help, for sure.

Now that you've bumped the motor off TDC to get rid of the slack in the chain, turn the engine back to TDC. You don't wanna take the head off before you do this, save yourself some extra pain later on mate .

Stock valve springs and cams but more so with aftermarket grinds and H/D springs can 'flip back' or 'flip forward' the camshaft when turning the motor over by hand, leaving what looks to be a loose chain on the straight side. It doesn't need to be much at all. Seen that before, many times.

There were no other suggestions as to why you might have a problem Marty were there? I would be surprised to hear that you've done any damage here, you would've had other issues for sure. I just think it's a case of camshaft 'flip forward'.

Edited June 19, 2010 by ozconnection