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EFV-8 Club Forum / 1940 Ford Discussion / 48 Ford Missing on 2, 5, 8 on crab cap distributor

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Posted By Discussion Topic: 48 Ford Missing on 2, 5, 8 on crab cap distributor -- page: 1 2     carcrazy 06-01-2021 @ 9:14 AM reply profile send p.m. Senior Posts: 1680 Joined: Oct 2009 It is possible that, even though new, three of your spark plugs may be defective and not firing! I recently bought a set of Autolite plugs that were made in China and one of them had a visual defect with the center electrode not being properly located. TomO 06-01-2021 @ 7:32 AM reply profile send p.m. Senior Posts: 7263 Joined: Oct 2009 When you check the resistance, do it from the inside of the cap to the boot end. The best test is to check the spark at the end of the wire as I described in my post. Sticking valves are still a possibility, but I would not work on that until I had proved that there was good spark at the plugs. Tom dknechtly 05-31-2021 @ 8:19 PM reply profile send p.m. Member Posts: 8 Joined: Mar 2021 Really appreciate everyone's input. He has electric wipers; that tube is plugged. The carb to manifold gasket is new but we will do the starting fluid test to see if it makes a difference. I'll check the resistance of the brand new wires from C & G (I would think they would give us the right wires but who knows). We did swap 7 & 8 wires but no difference in number 8; 7 still worked fine. Engine also runs the same hot or cold. TomO 05-31-2021 @ 6:05 PM reply profile send p.m. Senior Posts: 7263 Joined: Oct 2009 Because you did not have a miss before you installed the new cap and wires, the problem is most likely in the cap or wires. Wet plugs indicate that fuel is getting into the cylinders. Pulling a plug and checking the spark can fool you. The plug can fire in the atmosphere but a weak spark will cause it to fail under compression. I pull the plug wire and insert a screwdriver into the opening of the boot for the spark plug and then hold the screwdriver near a head nut. You can also use a spark tester like this on available at Amazon or an auto parts store. https://www.amazon.com/OEMTOOLS-25069-Adjustable-Ignition-Tester/dp/B0014WDFLY With 3 out of 8 plugs not firing, the reading of 5 inches could be normal, the fluctuating needle is probably due to the miss. A new set of correct wires for the 48 V-8 is probably a very good investment at this point. The resister wires could have enough resistance to cause a miss and are easy to break the core with the tight bends in the Ford's system. A sticking valve gives a ticking or a light knocking sound. The MMO should have given some relief from a valve sticking, so that would be lower down on the trouble list. Tom 40 Coupe 05-31-2021 @ 4:39 AM reply profile send p.m. Senior Posts: 1683 Joined: Oct 2009 Did you install the distributor correctly? in some cases it can be installed 180 degrees off usually the case will crack and break. I suggest you remove the distributor and check. Also check all the plug wires are in the correct spots. carcrazy 05-29-2021 @ 8:40 PM reply profile send p.m. Senior Posts: 1680 Joined: Oct 2009 If you have only 5" of manifold vacuum at idle, you have some serious problem causing this. Is there a tube going to the manifold that is open to atmosphere like the tube to the windshield wiper motor? Are there any leaks between the carburetor and the intake manifold or between the intake manifold and the block? What are the resistance values for each of the ignition (spark plug) wires and the coil wire? I have had carbon core ignition wires test OK when they were at room temperature but would go to infinite resistance when hot. If your resistance values are more than about 1 ohm for each wire, I recommend replacing all of them with solid metal core wires. dknechtly 05-29-2021 @ 8:15 PM reply profile send p.m. Member Posts: 8 Joined: Mar 2021 The plug wire boot is too long to hold up a head bolt however, we pulled every plug, they all had great spark. When my buddy (this is his 48) changed the plugs, they 2,5,8 were wet. We do hear noises that are not normal for the engine. I know what loose rockers sound like. I know what a rod knocking sounds like but I don't know what sticky valves might sound like in a flathead V8. The engine did not have a miss before the crab cap, rotor, wires where installed. The old spark plug wires would give a shock and the coil wire was intermittent; we'd have to jiggle it (this was all the dome distributor). Yes we have the 21A rotor installed. I put my vacuum gauge on it and amazingly, I only got about 5 pounds. needle going back and forth to zero pounds. It has a new carb to intake gasket. The car missed before the carb rebuild. We changed his oil (it was not pretty) and put new VR1 50W plus a quart of MMO. We also squited some down the carb. 40 Coupe 05-26-2021 @ 4:54 AM reply profile send p.m. Senior Posts: 1683 Joined: Oct 2009 Early Fords and their original ignition system use copper core spark plug wires with nearly zero ohm resistance from end to end. The more modern resistor type plug wires can cause high RPM missing. TomO 05-25-2021 @ 8:34 PM reply profile send p.m. Senior Posts: 7263 Joined: Oct 2009 When you pull a plug wire on 2, 5, or 8 and hold it near a head nut, do you get a nice blue spark? When you pull the plug on one of the failing cylinders is the plug wet with fuel? Do you hear any noises that are not normal for a good running engine? Did the engine run without a miss before you installed the crab cap? Do you have t 21A rotor installed? Tom dknechtly 05-25-2021 @ 7:49 AM reply profile send p.m. Member Posts: 8 Joined: Mar 2021 Thanks for the replies. These are non-metallic wires. They are what C & G sent with the crab cap and crab rotor. We swapped #7 and #8 wires (at cap and plug). #7 still worked and #8 still did not work. That tells me the wire is good (plus we get strong spark). We will double check the inside of the cap and connections for excess plastic. So I have compression; I have spark; I have gas (since #7 works). Would sticky valves show up in a compression test?

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