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question my truck is spark knocking when accelerating i have been using ethenaol free guel 89 octane with 104 race octane booster. i have changed the plugs to the autolite 605, set the timing to 10 degrees, and put in a 180 degree thermostat. the truck doesn't have the egr system on it. what elese could be making it spark knock? its a 5.8L mild cam bored 40 over. i thought about putting the egr system back on it. any ideas would be welcomed.. Thanks!!
timing light on engine and watch how far your ignition is advancing. 30 degrees or 45 degrees? if you distrib is sticking or advancing to quick could be some issues. have to rev up engine and watch see how far timing is moving. also look closely on possible vacume leaks and causing a lean conditions. possible lean condition during hard acceleration needing bigger shot of fuel at beginning. things to check.
If it's doing it under a load that would lead one to believe it's not the vacuum advance. Unplug the vacuum advance, plug the hose & put a light on it and see just how far it mechanically advances and what rpm it starts to advance and what rpm it stops advancing then get back to us. If you have removed the smog stuff you will need to put the advance plates limiting arm in the short slot, it's probably in the long one for the smog, that alone might fix it good enough.
great info guys.. yes i use 89 octane with 104 race octane booster the 89 is ethanol free.. the smog stuff is gone i've never re-curved one before so i guess i need to take it to the local performance shop huh!