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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
That's one of the reasons I went with a fixed idler gear system. Nothing wears, nothing stretches, timing stays rock solid. I had a dual floating idler gear system in my engine for 1 day before yanking it out.
The crankshaft will always be pulling the chain so the one side will always be under tension however due to harmonics, valve spring pressure pushing back down on the lifters etc, you'll normally see your timing mark jumping around when setting the timing with a chain that loose. Even a high end double roller chain will wear out and doesn't last as long as an OEM chain will.
They came with nylon teeth on the cam sprocket. At least my 86 did. Crank sprocket was steel. And mine was loose like that also. Chain stretch and tooth wear on the cam sprocket.
AlkyIROC, that's what I hope was causing my base timing jumping about 4 degrees, that metallic ball bearings in a can sound at idle, floating idle, and the strange-feeling lower RPM running. With that slack chain, I imagine the cam can float around at lower RPMs causing "strange" engine running.
They came with nylon teeth on the cam sprocket. At least my 86 did. Crank sprocket was steel. And mine was loose like that also. Chain stretch and tooth wear on the cam sprocket.
GD
That's what I thought but I can't see where any nylon was on my gears. I thought it was the crank gear but I can't see any remaining nylon on the cam sprocket instead. The chain sure had a lot of gap between the chain links and sprocket teeth.
You mentioned modifying your timing cover so that you can reinstall it without dropping the pan. My pan gasket looks really good. It a black rubber looking gasket so I think I can reuse it. I am planning on "popping the cover on" by starting at the bottom engagement. Did you trim the top two end corners of the pan gasket rail? Can I leave the pan gasket on the pan or do I need it on the cover during re-installation?
Last edited by Tootie Pang; Aug 4, 2017 at 01:58 AM.
Wow. Not surprised GM tried it but glad they got rid of them.
When I bought my car I knew it would be a project, but I did not think the timing chain, even an all metal one, would be a wearable item. I couldn't believe how loose my OEM chain had gotten.
It wasn't too bad of a job. Two afternoons. I did not need to remove the pan and I reused the rubber cover to pan gasket. I did notch the cover in three places- two along the inside gasket retaining rail (one on each side, to clear the block casting for the lower cover bolt) so that the cover could go straight on and drop in. The other was on the drivers side to clear the power steering and alternator bracket to help with install.
Last edited by Tootie Pang; Aug 6, 2017 at 10:27 PM.
I would say the two maintenance items I have done that made the biggest difference have been the timing set, and the valve stem seals. It's like a new engine - oil consumption is zero, and timing is rock solid. Made a huge difference in performance, idle quality, etc.
Pretty impressive that after 160k mikes and over 30 years that this is all it needed mechanically.
OK, now your just nudging me! Seals and springs is next (No.2 plug fouls but compression is fine), and pretty much the very last thing. The only sensor I have left is the TPS and I'm going to replace it just because. And then the ECM. And then there's nothing more.
Sloppiness in the timing chain does more than fluctuate ignition timing. It also causes valve timing to jump around. If you valve open and close a few degrees from what the cam card says then performance changes. As ugly as it is, a performance engine should be replacing chain and gears every few years.
GM use the nylon teeth for one reason. Sound. In any sort of passenger vehicle, noise is not wanted so one place to reduce noise is in the timing gear system. The chain they use and the nylon gears are inexpensive and very quiet compared to other systems.
