For anybody that are 16V afficianado, my question is my motor is pretty quiet when its cold and when the oil temperature goes up the valves started being noisy. I look at the tensioner it the updated one and the timing chain seems to be new. I guess I have to find out when it was replaced. But I did a valve adjustment via shims since the valvetrain is not hydraulic. Also, when I accelerate and let of the gas i hear valve noise i don't know if its the chain or the valves. any suggestion would help. I ran thicker oil to and thinner oil, its still the same noise.

thanks,
Ernest

Ernest,

Your valve gaps grow as they get hotter. If you set them at the lower range of the factory specs, they should be relatively quiet when hot. They will not be as quiet as a hydraulic lifter motor.

Tinker

The clearance on my Cosworth Vega grows .002" between cold and operating temperature, and I've measured the ramp tops at .016" above the base circle, so a the OE specified clearance from GM of .014" is right on, and the valves are probably a little quieter when cold, but it's tough to tell because the loose clearance forged pistons create a cacophony until the engine heats up, and even when warm the engine still generates a lot of mechanical noise.

Normal mileage accumulation sinks the valves and since changing shims is such a POA on the 16V (the CV has shim over bucket design) I would recommend you set them at the high end of the range and then reset if they fall below the low end, but that should be many tens of thousands of miles.

Most modern DOHC designs with lash should hold their settings very well due to high quality valve and seat materials that erode very slowly.

Duke

Tinker,
You mean I should set my valve lash at the lowest tolerance when its hot? Can I go over the allowable lowest setting? Or will I burn my valves? I notice when I crank my motor the exhaust cam bounce after cranking it. Is that an indication of a bad timing chain? It's really annoying having those valve noises. I don't know why the gap for the valve adjustments is too high compare to Japanese car's vavle gaps. thanks for the help.

thanks,
Ernest

Ernest,

DO NOT set them hot, only cold. The spec I have specifies 0.10 - 0.20mm. I would set it in the 0.10-0.14 range and see if that helps with the noise. Any lower and you will risk burning the valve due to inadequate cooling.

You will need to juggle around the shims and hopefully you will only need to buy one or two.

The timing chain tensioners in the 16v engines are a known weak link. You want to make sure you have the upgraded tensioner. You can get a rough estimation of the stretch by setting the engine at top dead center and checking the alignment of the cams. If the chain/tensioner has not been upgraded and needs attention, you will usually hear a rattle at start up indicating the needed rapair. Don't wait. The longer you wait the more you risk damaging the chain guides or motor by possible chain slip.

Tinker