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mach0415 · 05-23-2012, 08:47 PM

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My 2 cents here, but there are base engine issues to look at here. You have established that #1 it is getting spark, #2 it is probably getting fuel and air, and #3 it is getting some sort of compression. To the average tech, he would say that the cylinder should be firing. He should also ask a few more questions and reassess.

Question #1 Was there anything unique that happened, leading up to this? (i.e. Is it a regular driver? or Was the engine sitting for a period of time? - I am having visions of corn and wheat berries, nesting material, etc. blocking the intake port because of critters making #2 intake port/area home sweet home, as found in dad's '29.

I know 2 and 3 share the same intake runner, but 2 and 3 split in the block.)

Question #2 Is it a dead miss? I would recommend hooking her up to a vacuum gauge and see what it says. A vac gauge will tell a lot. http://www.fordgarage.com/pages/vacuumtune.htm

Question #3 depends on the answer to Question#2, but How did you conduct the compression test? Intermittent compression will still show up at 68 psi even if it produced that on only 1 good compression-producing stroke, because the schrader valve on the tester would not show an intermittent absence of compression, as it acts like a check valve on the tester.

If there is a result to Question #3, you could do a running compression test on that one cylinder to observe if it is intermittently hanging a valve open on a down stroke, due to a weak/broken spring. If its an exhaust valve hanging, the ole paper cup on the exhaust pipe trick will show it also. The cup will be sucked back to the pipe if the exhaust valve inadvertently opens on a power or intake stroke (sucked open). I have done this many times with great diagnostic success.

This happened on a MoPAR flat head six of mine. A weak valve spring was causing an intermittent loss of compression and a subsequent miss on #1. The tester did not show it for the same reason as above. A cylinder leak down test also did not point to it. Valve springs in these things are pretty low tension as it is. It wouldn't take much more weakness to make it leak.

Hope this helps. These mysteries intrigue me. What can I say? I am a nerd.

05-23-2012, 08:47 PM	#6
mach0415 Senior Member Join Date: Jul 2011 Location: Chester, SC Posts: 162	Re: #2 missing Sponsored Links (Register now to hide all advertisements) My 2 cents here, but there are base engine issues to look at here. You have established that #1 it is getting spark, #2 it is probably getting fuel and air, and #3 it is getting some sort of compression. To the average tech, he would say that the cylinder should be firing. He should also ask a few more questions and reassess. Question #1 Was there anything unique that happened, leading up to this? (i.e. Is it a regular driver? or Was the engine sitting for a period of time? - I am having visions of corn and wheat berries, nesting material, etc. blocking the intake port because of critters making #2 intake port/area home sweet home, as found in dad's '29. I know 2 and 3 share the same intake runner, but 2 and 3 split in the block.) Question #2 Is it a dead miss? I would recommend hooking her up to a vacuum gauge and see what it says. A vac gauge will tell a lot. http://www.fordgarage.com/pages/vacuumtune.htm Question #3 depends on the answer to Question#2, but How did you conduct the compression test? Intermittent compression will still show up at 68 psi even if it produced that on only 1 good compression-producing stroke, because the schrader valve on the tester would not show an intermittent absence of compression, as it acts like a check valve on the tester. If there is a result to Question #3, you could do a running compression test on that one cylinder to observe if it is intermittently hanging a valve open on a down stroke, due to a weak/broken spring. If its an exhaust valve hanging, the ole paper cup on the exhaust pipe trick will show it also. The cup will be sucked back to the pipe if the exhaust valve inadvertently opens on a power or intake stroke (sucked open). I have done this many times with great diagnostic success. This happened on a MoPAR flat head six of mine. A weak valve spring was causing an intermittent loss of compression and a subsequent miss on #1. The tester did not show it for the same reason as above. A cylinder leak down test also did not point to it. Valve springs in these things are pretty low tension as it is. It wouldn't take much more weakness to make it leak. Hope this helps. These mysteries intrigue me. What can I say? I am a nerd. __________________ Thanks, Mark in SC "We the unwilling, led by the unknowing, are doing the impossible for the ungrateful." -- By society, who is still arguing over who said it. Last edited by mach0415; 05-23-2012 at 09:10 PM.