Testing unknown engine

[michel richard]

As I understand it, both a compression test and a leakdown test need to be done on a warm engine.
So what if you have an engine of unknown origin, sitting stone cold on your bench. How can you gain some insight on it's internal condition without tearing it apart.
I figure I can judge valve guide wear by pushing the valves sideways and seeing if they move.
Anything else ?

[BenI]

Here are some ideas to try:

Drain the oil-you will want to replace it anyway and now you can smell it and look at it to gain some insight

CHeck valve lash-check to see if it was last run with correct tolerences

Static timing check

If it has carbs, Id open it/them up to see if you have gas jelly in the bowls, or rust from the tank or something

Check the spark plug conditions

If youre scared to turn it over you can pull the plugs and squirt a little oil into the combustion chamber to lube up the cylinder walls a bit. This is actually one way to prep a car for storage, so they might already be coated.


Im sure there are more clever ideas out there to try too. Good luck!

[Dave at Pelican Parts]

The compression and leakdown tests do not have to be done with the engine warm. The results may not be as accurate as you'd like if you do them on a cold engine, but they can still give you a rough idea of the overall condition of the top end.

Also check the oil and such as Ben suggested.

--DD

[JP Noonan]

Remove the oil screen and the access plate in the front corner of the block. Look for sludge.

Best thing to look for on comp numbers is that they're all even or with 10%. Spray some top end lube (PB Blaster makes one called PB Catalyst) if the numbers are way off and see if that helps.

I pulled out the pushrod tubes and then the lifters to see if the cam or lifters were badly worn, just be sure to put each lifter back in the hole it came from.

While the motor is out clean all the cooling surfaces and replace o-rings, oil cooler seals, front and rear main seals.

Check the crank-shaft end play to see what condition the main bearings are in.

See if the valve springs and area have cooked on oil (overheating) or are a nice brown color. If they look clean the motor has few miles on it.

I don't think you can check the valve guide wear they way you describe with the springs still on. But look and see if the valve tip is concaved or mushroomed, indicating high mileage.