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Detonating / Knocking When Floored Z24 Carb

1266 Views 1 Reply 2 Participants Last post by  smj999smj
Hey y'all, figured I'd throw this out here and see if I could get any leads. 1985 720 King Cab 4x4 with carb Z24, 5-speed manual. Engine and carb were rebuilt around three years ago by previous owner.
When driving in any gear, if you give it a good amount of gas on an incline or floor it while flat, you'll get varying amounts of knocking/pinging/detonating/static, whatever you want to call it, coming from up front. Only happens when giving it gas. Sometimes it doesn't do it at all, but if you're in 5th gear on a slight incline at 2400-3000 RPM, it is pretty bad. It will disappear most of the time once you hit a certain RPM, around 3200-3400 I'd say.
I've done standard tune-up stuff, cap, rotor, plugs, wires, all good. I've read up a bit on detonation. Could be timing, compression, or something as simple as the gas, plugs, or lugging the motor.
Any tips would be great!
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A lean condition can do it, as well. It would help to get the emissions read with a gas analyzer. Have you tried richening up the idle mixture a little or making sure the accelerator pump is spraying fuel into the bowl? Dirty or clogged carb jets can do it, as well. If they shaved too much off of the cylinder head when it was rebuilt, that can have an effect. Is the EGR system working properly?
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