The Ford Barn

Pilotdave · 03-10-2012, 07:46 PM

I have a couple of questions about a compression issue that I hope you guys can help me with.

1. Our '30 Tudor has low compression in one cylinder, okay in the others: 50-55 in #1, 3, 4 and 15 in #2. I had previously found a valve problem and attempted to correct it. After replacing both valves and the head gasket, compression was no better.

Yesterday I performed a leak down test. With 50 psi on #2, I could hear air rushing out #3 spark plug hole. With the plug in place, I could hear air at the tail pipe. My diagnosis is that neither valve in #2 is seating properly.... does this make sense?

2. I did encounter one challenge performing the test. The engine tried to rotate every time I pressurized the cylinder even though we had the car in gear, e-brake on, and wheels chocked. Finally got it to hold still so we could run the test on #2. However, when I tried to run the test on #3 I couldn't prevent the engine from rotating - enough to move the distributor rotor about half way back to #2 terminal. I could hear air slowly leaking from #3 when this happened - is that because a valve had started to open? And is there a way to prevent the engine from rotating when doing this test?

Thanks for your help!

03-10-2012, 07:46 PM	#1
Pilotdave Senior Member Join Date: Oct 2010 Location: Grafton, MA Posts: 1,311	Compression Problem Revisited - Update - See p2 I have a couple of questions about a compression issue that I hope you guys can help me with. 1. Our '30 Tudor has low compression in one cylinder, okay in the others: 50-55 in #1, 3, 4 and 15 in #2. I had previously found a valve problem and attempted to correct it. After replacing both valves and the head gasket, compression was no better. Yesterday I performed a leak down test. With 50 psi on #2, I could hear air rushing out #3 spark plug hole. With the plug in place, I could hear air at the tail pipe. My diagnosis is that neither valve in #2 is seating properly.... does this make sense? 2. I did encounter one challenge performing the test. The engine tried to rotate every time I pressurized the cylinder even though we had the car in gear, e-brake on, and wheels chocked. Finally got it to hold still so we could run the test on #2. However, when I tried to run the test on #3 I couldn't prevent the engine from rotating - enough to move the distributor rotor about half way back to #2 terminal. I could hear air slowly leaking from #3 when this happened - is that because a valve had started to open? And is there a way to prevent the engine from rotating when doing this test? Thanks for your help! Last edited by Pilotdave; 03-11-2012 at 05:01 PM.