Carborator popping
05-03-2019, 09:16 PM
#1
Carborator popping
350 200HP 1972 manual transmission. Starts and idles fine runs nice until 3000-3500 RPM's over 3500 it runs fine. Just the sweet spot 3000-3500RPM's the Carburetor starts popping. Here is what I've done with no success; New wires, plugs, distributor with electronics(no points), rebuilt Carb, new fuel pump, new valve springs. All cylinders 155-163 compression vacuum 19-21 lbs. I am stumped! Any ideas? .
05-03-2019, 09:22 PM
#2
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Who did the carb rebuild?
How much initial timing are you running and what's the total? At what rpm does the total come in?
How much initial timing are you running and what's the total? At what rpm does the total come in?
Last edited by lars; 05-03-2019 at 09:23 PM.
05-03-2019, 09:34 PM
#3
Timing 8* TDC. The carborator that was on the car was doing the same thing and that is why I purchased a rebuilt one. It is a ROCHESTER Quadra jet. Not sure what size jets it should have. What do you mean by total?
Last edited by Silent Thunder; 05-03-2019 at 09:35 PM.
05-03-2019, 09:53 PM
#4
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St. Jude Donor '05
Run your engine to 3000 with the timing light pointed at the mark, see what number it reads.
Popping when you rev it or holding it steady? Its not an ignition miss?
Any gas vapor or mist coming out of the carb when this happens?
Popping when you rev it or holding it steady? Its not an ignition miss?
Any gas vapor or mist coming out of the carb when this happens?
05-03-2019, 09:56 PM
#5
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Your timing is very low, and may be contributing to the issue. Depending on the timing curve and the rpm where your total comes in, it could be a factor.
Popping up through the carb is normally a sign of a lean condition. If you bought a "rebuilt" carb, you bought a big can of problems - you can e-mail me for my paper listing all the common problems I typically see with "rebuilt" carbs - your carb has multiple issues. You may have a secondary tip-in problem at that rpm, which may be caused by several issues related to secondary setup and tuning.
Lars
V8FastCars@msn.com
Popping up through the carb is normally a sign of a lean condition. If you bought a "rebuilt" carb, you bought a big can of problems - you can e-mail me for my paper listing all the common problems I typically see with "rebuilt" carbs - your carb has multiple issues. You may have a secondary tip-in problem at that rpm, which may be caused by several issues related to secondary setup and tuning.
Lars
V8FastCars@msn.com
05-04-2019, 08:30 AM
#7
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set your timing initial timing to 14* and see if it gets better. And Email Lars. He wont steer you wrong
05-04-2019, 04:57 PM
#8
Well I got into it today. Found a worn cam so I ordered the parts and will be replacing the cam, timing gears and chain, water pump etc. might as well recore the radiator while it’s out to!
Last edited by Silent Thunder; 05-04-2019 at 04:57 PM.