Leak Down Procedure (Pic Heavy)

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seabee

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Did a leak down test on the 273 today and took some pics on how I did it for the next guy that searches it. Please add any , corrections, advice, or tips.

1. Find Top Dead Center on Piston #1. I used a piston stop to make sure the balancer hadn't shifted.
IMG_0478_zpsfe5a5f95.jpg

IMG_0486_zps9188d296.jpg


Using a small level I made horizontal and vertical marks:
IMG_0474_zps218ebac1.jpg

IMG_0472_zps77e802e8.jpg


Each 1/4 turn of the crank will put the next cylinder in the firing order at top dead center. Firing Order: 1 8 4 3 6 5 7 2
IMG_0512_zps49df8ba6.jpg

IMG_0477_zps2ed8651b.jpg


Next I checked the gap (solid, non hydraulic lifters) to make sure the valves were fully closed. I could also just remove the rocker arms completely.
IMG_0481_zpsc079089a.jpg


Then I used the piston stop on the cylinder opposite the firing order to prevent the crank from turning under the air pressure. Opposite pistons: 1:6, 2:3, 4:7, 5:8
IMG_0494_zps35b665e2.jpg


Then Applied 100PSI to get the first reading. Number 8 cylinder is losing 20%.
IMG_0498_zps29bc8b1b.jpg


Then I put the spark plugs into the neighboring cylinders to help rule out a head gasket breach between cylinders.
IMG_0496_zpse0c42cbf.jpg


Next I use a piece of hose to my ear and listen to locate where the 20% of air is going to.
Carb: Intake Valve
Exhaust:Exhaust Valve
Dip Stick (Crankcase): Past the piston rings (Normal)
Radiator: Cracked head or cylinder wall.

I wrote down all the results:
IMG_0513_zpsf9d0b7a7.jpg


Might be time for a rebuild, what do you think?
 
Curious, what's up with the retainer next to the valve you're checking gap on?
 
Only thing I know to add:

With valve gear in place, you must check piston at TDC. If you have something like a rough/ cracked cylinder wall, this wont' show up. Better to run at TDC, then pull rockers and run again all cylinders at BDC

Also, this test will show different results hot and cold.
 
Marks from manufacturing I guess. Several of the retainers have them, which is why I didn't notice.
 
Only thing I know to add:

With valve gear in place, you must check piston at TDC. If you have something like a rough/ cracked cylinder wall, this wont' show up. Better to run at TDC, then pull rockers and run again all cylinders at BDC

Also, this test will show different results hot and cold.

Del, just curious as to what the difference would be BDC vs TDC?

Great thread, thanks Seabee!
 
Question. Is the test performed when the engine is cold or after warming to operating temperature?
 
First, excellent post ! THX added.
Second, I (with Your permission Sir). would like to add an note on the hot/cold test
parameters.
Pistons are, always have been, and always will be of an 'cam ground' design--- read the larger mass across the pin bosses , when heated, 'pulls' the smaller mass of the casting/forging into a circle.

Apologies, suffice to say, do the test no more than 10 min after normal operating temp has been reached.

Now Sir on to My humble answer on Your rebuild 'Q'.

I wrote down all the results:


Might be time for a rebuild, what do you think?


Left bank total % = 56.
Right bank total %= 60.

total variance 4%...bank to bank anyway. further,

#1-#2 delta , 4%.
#3-#4 delta , 4%.
#5-#6 delta , 5%.
#7-#8 delta , 1%.

'Delta' an term used for 'total' overall engine 'sealing' health. as it were.

In Your case Sir 14% total delta = changing #8 when it oil fouls, probably
after 3-4k miles

Thx to the board for My long winded reply !!!!
 
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