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Exhaust air sound.?


Cokekid
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I decided it was time to turn the engine over. The first thing I heard was a puffing sound as the engine turned. I again started the engine to try and locate were it was coming from and while doing this my hand passed over the carburetor and I felt the air was coming out the top of it.

 

I am at a loss as to what would cause this to happen.

 

Gerry

 

 

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C.Douglas

 

The engine has been turned over a few times by hand in the last month while installing the distributor. I will do a compression test as you and 19tom40 have suggested

 

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  • 2 weeks later...

Cylinder 6 is probably the culprit. One or both valves may need an adjustment. If the engine is not broken in, the other low readings are not a disaster, but a concern.

 

You should try adding about a spoon full of oil to each cylinder as you try for a wet compression test. That will tell you if your low readings are from rings not seated or from too tight a valve adjustment.

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19tom40

 

I did another dry test and followed up with a wet test. The reading for the dry test  went up a little not sure why. I was also interested as to why you pointed out #6 as possible the culprit. 

 

Here are the readings .

252438557_COMPRESSIONTEST03914.JPG.a31bc5f09aeb80bf3b3eade1b6eb2fd8.JPG

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Doesn't look good, you might need an overhaul and valve job to get the compression up to where you can drive the car safely.  They should be over 100.  If you pull the heads you might find burnt valves/seats and such.  Any idea the actual mileage on the engine?   It will probably need new pistons also  or at least new piston rings if the pistons are good.  Need close examining.  And the block really needs tanking/cleaning to check for any cracks.  Probably needs some boring too.  With that low compression it will never make power.  Not sure who to recommend to get it overhauled, perhaps some members on the Club here might know of anyone in your area.  Good luck with it!   At least parts are available!   

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WoW!   Long time, so it needs investigating.  If it hasn't run in 10 years after a full overhaul then something must have happened.  You're gonna have to pull the heads and see if the valves are seating properly.  Do you remember any readings after the rebuild?  What I use is a gauge that has a hose attached that screws directly where the spark plug is installed.  That way you can get an accurate measurement.  On the compression stroke it should show you the maximum pressure and hold unless one of the valves is leaking off if not seated properly.  It should be over 100.  Mine read if I remember about 110-125 # .   You might want to investigate your gauge to make sure you're reading it accurately.  High compression engines read a lot higher than that, but for the V12 that range should be sufficient.  Also head gaskets can be a problem.  I'm sure you can find out what's going on if you keep checking.  

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Are you cranking the engine until the gauge does not increase the reading? Your readings are not consistent, leading me to believe that you are not getting a good seal  with the tester or not cranking the engine long enough. Try again with the throttle pulled all the way out, all spark plugs removed, a fully charged battery and cranking the engine long enough for at least 4 compression strokes on each cylinder being tested.

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19tom40

 

When I used the compression gauge I removed the plugs ,had the throttle open up wide and had the battery fully charged. I even left the trickle charger connected to the battery while doing the test.

I hand tightened the cable into the plug hole and was turning the engine over eight times for each cylinder.

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Here are my results for using the Cylinder Leakage Tester. Before starting the test on each cylinder, I brought them up to top dead center. 

 

Here is the starting sequence I had to do for each cylinder. 

Turn on the compressor to read 100 psi

Each cylinder had to be brought up to top dead center

Then connect the hose into the plug hole The other end is connected to the tester

Connect the compressor hose to the tester

Turn the left hand gauge up to 60 PSI 

Listen for any air escaping from either of the four places as shown in the photo.

Take the  psi reading from the right side and subtract it from 60 psi and this the percentage loss for that cylinder

98085413_LEAKAGEREADINGS03918.JPG.807ae0b9be282322687a62c515a7c6c4.JPG

 

Here are my readings

#1 Loss 6% through Crankcase

#2 Loss 12% through Crankcase

#3 Lost 24% through Crankcase

#4 Lost 18% through Crankcase

#5 Lost 28% through Carburetor

#6 Lost 14% through Crankcase

#7 Lost 12% through Crankcase

#8 Lost 50% through Carburetor

#9 Lost 48% through Carburetor

#10 Lost 48% through Carburetor

#11 Lost 8% through Carburetor

#12 Loss 10% through Crankcase

 

Did I do both test correctly.? I'm no sure but both reading seem to indicate I have a problem.

 

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When I test, I just use a pressure gauge like the one you're using.  Top Dead Center isn't the issue, it's that amount of pressure each cylinder will pump up with a few cycles of the engine.  I put a little light oil in each cylinder as I run them to make sure there's some adhesion among the valves and the rings if the engine has been sitting for a while.  The idea is when you remove a spark plug and attach the gauge you want a good seal.  Give it a little extra turn with a wrench so there's no leaking in your gauge.  That goes for both ends of the hose on the gauge.  Then I crank it several times and watch for the highest reading on the gauge.  Then I wait and watch to see if it bleeds off which could mean valve issues, or as stated before a bad leaking head gasket.  If you stop the engine rotation past compression, a valve will open and bleed the air off.  So do the test till you can stay in the compression cycle to get a good idea of what's going on with the valves.  

 

Once you've done all 12 cylinders, written down the results of each cylinder under test, you will get a bigger picture of any issues with compression.  And don't overlook putting new head gaskets on the engine just in case there's a leak and retest all 12 cylinders.  Make sure you get the copper head gaskets to properly reseal the heads.  Make sure you use the recommended tightening of the head nuts with a with a torque wrench to insure proper head gasket installation.    You will need to pull the heads and inspect what's going on and take photos of the exposed engine under the heads.  Bottom line is if there is ANY low compression from your tests you're gonna need to do an overhaul if you expect the V12 to perform as originally intended.  The dual gauge setup you're using, not sure.  No reason to compare reading with #1 cylinder, just measure each cylinder and look at the values.  They should be close unless there are wear problems.  The last time I did mine they registered from 110-125 lbs. of compression.  These engines aren't 'high compression', but they do need a goodly amount of compression with pistons and valves working properly.  You could just do a valve job if the valves are a problem, but like any other engine with miles and wear, just grinding the valves will increase the pressure/vacuum in each cylinder and with worn piston rings the engine will suck oil from the crankcase and you'll have a nice oil burner!  Let us hear how you do on your testing!

 

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You must have each cylinder on top dead center of the compression stroke to do the leakdown test. There are 2 reasons for top dead center. One is the worst ring wear is at top dead center. The second is the air pressure is likely to turn the engine if the piston is not at perfect TDC, so much that you can't accomplish a test at all.

 

I like to start at #1 and follow the firing order, turning the crank just enough to get to the next cylinder that would be firing. I believe that is 60 crankshaft degrees on the Lincoln, but correct me if I am wrong.

 

If you were on TDC overlap for some of those, maybe that explains the leakage through the carburetor. If not, and you were on TDC of the compression stroke for every one, your intake valves are stuck open or not seating on those cylinders.

 

Air escape through the crankcase is normal, and though some people will tell you anything over 10 percent is bad, my experience says otherwise. There are plenty of perfect running (if a little worn) engines running around with 25% or more ring leakage. That goes double for you because the engine is fresh and the rings presumably aren't seated. For now, they are going to leak.

 

High leakage through the valves is always bad, but engines that sit get rust and crud on the valve faces, and a little running time could be a miracle. That said, 8,9, and 10 are ridiculous and if they were truly on the compression stroke when the test was made something is wrong, like intake valves stuck or clearance set too tight.

 

The across-the-board low and similar compression numbers don't jive with 3 stuck intake valves. I can't explain that. I would double check the valve timing.

 

 

 

 

 

 

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I don't remember if you converted your engine to adjustable valve lifters. If you did, I would expect that you have a valve adjustment problem. If your lifters are still hydraulic, you should remove the intake manifold and observe the valve operation as you turn the engine over. You could have stuck valves, guide keepers not installed correctly or bad lifters.

 

Check the gap between the lifters and the valves when the cylinders that had leakage through the carburetor are at TDC and both valves are closed. Check the valve positions also. They should be at the bottom of their travel, if not check to see if the lifter is holding it open or it is stuck in the guide.

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