I have a 86 iroc 305 carb. getting a lot of valve clatter going up grades. have been told this is timing even possibly changing the thermostat to a lower temp may help. (may be runnng hot) Car idles a little rough. I have checked crancase pulley and block for marks and degree numbers and can't find anything to reset timing with a light. Is this done via computer inside distributor?. I'm new to cars as you can tell. Your opinion needed. Thanks

 

there are marks on the dampner and the timing cover, keep looking i bet you'll find them. look in your manual for a pic of the location, most manuals have them, you'd use a light to set base timeing, not something the ecm controls

 

Have you checked your computer for any codes? That's the first thing I would check. If you go to your local Autozone, they'll check them for you.

Pretty cood instructions on doing this...

http://sethirdgen.org/dtc.htm

 

as for your problem it sounds like preignition to me. try changing the timing or octane, maybe even both

 

Yeah, forgot to mention that too... Pre-ignition or detonation.

Found this helpful article that has some suggestions.

http://www.federal-mogul.com/cda/con...9_7525,00.html