The Ford Barn

ronchamblin · 03-31-2017, 08:28 AM

I'm a decent troubleshooter but this confounds me. A just rebuilt 239 cu. in. runs on 7 cylinders, but No. 7 seems to have never fired in spite of changing the plug, the wire from the crab distributor, and ensuring that compression equals the other cylinders ... all being around 100 to 110 at good cranking speed. And when I set at idle and remove the plug on No. 6, and then No. 7 to check the compression reading, they both read 45 lbs. ... indicating a normal valve activity. Clearly, when it is idling, each of other cylinders drops the RPM slightly when their spark plug wires are removed ... but No. 7 cylinder wire removal makes absolutely no difference in the RPM. When the plug on No. 7 is removed and set upon the head, it has a good spark. Does anyone have any ideas? I've been on this problem for a week.

03-31-2017, 08:28 AM	#1
ronchamblin Junior Member Join Date: Aug 2013 Location: Jacksonville, Florida Posts: 13	No. 7 Cyl never gives evidence of a power stroke on '46 Flathead I'm a decent troubleshooter but this confounds me. A just rebuilt 239 cu. in. runs on 7 cylinders, but No. 7 seems to have never fired in spite of changing the plug, the wire from the crab distributor, and ensuring that compression equals the other cylinders ... all being around 100 to 110 at good cranking speed. And when I set at idle and remove the plug on No. 6, and then No. 7 to check the compression reading, they both read 45 lbs. ... indicating a normal valve activity. Clearly, when it is idling, each of other cylinders drops the RPM slightly when their spark plug wires are removed ... but No. 7 cylinder wire removal makes absolutely no difference in the RPM. When the plug on No. 7 is removed and set upon the head, it has a good spark. Does anyone have any ideas? I've been on this problem for a week.