Stovebolt.com Forums The Shop Area The Engine Shop Leak down test?

I’ve never done one, but I’d like to compare the condition of two engines. One that’s in my truck, and one that’s not.

Is a leak down test similar to the compression test, in that operating-temp numbers are more meaningful than cold numbers?

Obviously, a cold vs cold or hot vs hot would be necessary to compare apples to apples. Rigging up a way to run the stand-alone engine would be a moderate PITA, but I could do it. Just curious how much difference it would really make.

A cold vs cold test would give you an idea of the difference. Especially if the stand-alone one isn't easily fired up. I would still do one dry and a second one with some oil squirted in each cylinder on each engine.

I'd say it's too much trouble to run the stand-alone engine just to get a hot vs. hot test done.

Keeping a warmed-up engine at a steady enough temperature to leak test all the cylinders would be a challenge. I've had better results doing a leakdown test with the piston partway down the power stroke than getting it at exactly TDC- - - -mark the distributor body with the position of the cap towers, and lock the flywheel at approximately the width of the distributor rotor tip clockwise of the actual TDC position to get the same distance after TDC for each cylinder. That puts the rings into the area of maximum taper wear on all the cylinders.
Jerry

Locking the flywheel so the air pressure doesn’t spin the engine? Is that the idea?

Easy to do that in the truck. But with the engine that’s standalone…just have to wedge something in between bellhousing and flywheel?

When we do that on aircraft, we can hold on to the prop to keep the engine from turning!

ED

Use two pairs of vise grips on the flywheel- - - -one on each side of the bottom of the bell housing. Easy-peasey, in or out of the vehicle! With the bell housing removed, just use the engine stand legs as a locking point, or screw a couple of bolts into the back of the block.
Jerry