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Posted by hemimech on Saturday, July 11, 2009 at 00:30:47 :
In Reply to: Re: Speeking of slant six's,,, posted by David Sherman on Friday, July 10, 2009 at 23:55:07 :
Excessive fuel in one chamber can be a sign of low cylinder pressure and poor combustion. First step is to OHM out the plug wire for the suspect cylinder & compare to the others. Next check the distributor cap terminal for terminal corrosion/ damage/ carbon tracking. If the wire checks good & the S. plug has been replaced then is time to move to mechanical diagnostics. I would do a compression check on the compression of a couple of the good cylinders. If cyl 6 turns out to be lower than the others then it’s time to investigate the valves & camshaft. Pull the Schrader valve out of the s.plug end of the compression gage hose and hook to a regulated air compressor to the gage end. Bring #6 to TDC on the compression stroke and pressurize cylinder to 80-100 psi. Listen for excessive air out of the exhaust, carburetor or oil fill cap. If air is pouring out the tail pipe than a valve is burnt or a valve spring is broken/weak. Similar diagnosis if air is coming out of the carb…something’s wrong with intake valve. If lots of air is present at the oil fill cap then the piston or rings have an issue that needs to be addressed. Finally if the cylinder seems to hold the air pressure reasonably then the valve lift needs to be checked next. In this case I would lean toward an exhaust lobe on the camshaft being worn down. Air & fuel are drawn in & combustion occurs. A poor lift on the exhaust valve leaves some spent exhaust gas in the cylinder as the next intake event occurs. Now the engine has a bit of internal EGR (exhaust gas recirculation) causing poor combustion. At this point you would use a dial indicator on the rocker arms to compare valve lift from cylinder to cylinder. Good luck!