help with fouling plug

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440marv

440marv

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I need some help my 340 fouls # 8 plug with fuel. Working on tune and # 8 plug comes out with gas on it looking like its doing nothing . Any ideas would be great.
 
Start with the basics! Wires, Compression, Compare #8's compression to the rest.. Then work your way up to the more in depth stuff like cam & Valves. Let us know what you find each step of the way. GL
 
What he said... Get a compression gage (under $20 at any parts store) and get a compression readings with the engine hot, all plugs removed, and the throttle blocked wide open. If it's similar to the other cylinders move on to ignition - Is the wire's insulation intact completely? Any cracks or burns in it, especially the plug boot area? If the wire's in good shape (pull it off to make sure the terminals are intact and better inspect...) move on to the plug. If you clean the plug off with brake cleaner and a wire brush will it fire? If you replace it with one from a "good hole" will it fire in the new one? If it does fire in the new location, swap the wire from 5 or 7 with #8 and see if the skip follows it. If so - replace the wire set. Fuel fouled plugs can be hard to make work again, so it may be to your advantage to replace the plugs too... but diagnose with the old ones... Once you find and fix it, stick in the new ones.
 
Quickie check to see if it's getting spark, hook up an inductive timing light to the #8 wire near the spark plug end and see if you get a pulse/flash.
 
Ok plug is firing per timing light compression is 150-155 all cylinders. Could it be something with the rear carb on the sixpack?
 
I might look at the carb throats that feed that side for a fuel drip. IIRC, the rear carb venturi sits almost on top of the #8 port. That's the first one I would look at for dripping.

There are some idle mix adjustment screws in the baseplates of the outboard carbs. If somehow those got out of calibration, especially the rear carb, it could cause issues. Does #5 plug look wetter than #7? If you don't have them exposed so you can adjust them, might be something to consider.

There is a nice 6 pack tuning guide on moparts in the tech section.
 
Definitely fuel . I was told to set the outboard carb screws 1/8 turn out . It won't run at that setting I have them out 3/4 turn .
 
IMHO, 3/4 is too far out. I do remember the most I ever ran the outboards was 1/4 turn out. The center carb is where the main adjustment comes from for idle quality on those set ups. The outers just need to have some fuel from them so it's not coming from a "dead zone" when they begin fueling.
 
crackedback said:
IMHO, 3/4 is too far out. I do remember the most I ever ran the outboards was 1/4 turn out. The center carb is where the main adjustment comes from for idle quality on those set ups. The outers just need to have some fuel from them so it's not coming from a "dead zone" when they begin fueling.
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Why won't it run on the center? How far out are they on that one? What is your timing set to? Idle speed? What is your engine package? What is the vacuum level in gear (if auto) or in nuetral (if manual)?
 
center carb is 1-1/2 turns out , timing at 18 deg idles at 850 rpm in gear. vacuum in gear is 11 inches. Its got a 60403 voodoo cam ported 2.02 j heads , crane gold rockers ,
dougs headers , accel stock replacement billet distributor, with orange box. Its just a flattop piston motor about 9 - 1 compression . Nothing special.
 
850 in gear is ok. Timing sounds fine... Seems to want to be a little rich tho. What is it idling at in nuetral? What power valve is in the center? When was the last time you checked/set the floats?
 
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