302 valves rattles at highway speed ?
#1
302 valves rattles at highway speed ?
I have a 79 with a 302 with the original 2 barrell carb. The carb started acting up so I took it apart and cleaned it. Now the valves rattle when it shifts into high gear and at steady highway speed. it doesnt do it any other time. Do I need to adjust the carb some or what. I hate to mess with it to much because it runs great but I want to get the valves right. The motor never done this before I took the carb off so I know its something I have done. I'm not a real good carb guy but I will try anything if you guys can help me out. Thanks Scott
#4
What you're hearing is 'ping' (pre-ignition) which is not good to hear. Could be because of the rebuild you are running the carb leaner, which will cause the ping, or the timing is off. Check timing first, then look at maybe backing the idle screw out a bit. All vacuum hoses correctly hooked up?
#5
Join Date: Nov 2005
Location: Charles Town, W bygod Va
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pinging aka detonation aka valve rattle (thats a really misleading term) while under light throttle can be caused by too much vacuum advance. Check base timing first as suggested above. If thats ok try unhooking the vac advance, plug the hose and drive it. Adjusting the idle mixture richer to compensate for a lean higher rpm condition wont work... it would have to be way rich at idle.
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