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Discussion Starter #1
Cross-posting from GTV6 forum....

I'm about to do compression and leak down testing on the engine I pulled out last week. This engine had its oil drained about a year ago and has sat this entire time except for a few turns to allow me to remove the driveshaft bolts.

Should I squirt some oil in each cylinder through the spark plug hole to avoid scraping the cylinder walls and have a more realistic scenario? Or how can I turn the engine for this test without harming it considering its lack of use and no oil for so long?

Thanks!
 

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Maybe a tiny amount, but too much oil will give you a falsely high reading on how the rings are. Maybe a little WD 40 in the cylinders. Or better, make sure the engine has oil in it, turn it over on the starter til you see oil pressure on a gauge or in reality, then do the compression test after that. It'll have as much oil on the cylinder walls as if running at that point.

Andrew
 

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Discussion Starter #3
Thanks Andrew. Adding the oil and cranking sounds like the most sensible approach. Too bad I drained the oil, removed the flywheel and mounted the engine. Anyway seems worth the time to do this right.
 

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I doubt these tests will offer any useful information on a cold engine, though....
 

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I just tested the new (5 miles) 1750 engine I built for my Duetto, showed cold/dry 190ish all four after first ring break-in drive.
Andrew
 

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Discussion Starter #6
Thanks all.

I squirted a bit of oil in the cylinder and tried the compression test but got very low values that seemed to be nonsense considering the engine ran strong. The leak down almost looked like it could work but I couldn't get consistent readings. Keep in mind this is the first time I've ever done a leakdown test, so could be human error.

In any case, at this stage I'm thinking Pat Braden's method might be best since I have the heads off now. This is where you turn the head upside down and fill the top of the combustion chamber with gasoline...leave it overnight to see leaks or just blow air through the ports to see if any bubbles are seen. Anyone try this before?
 

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...In any case, at this stage I'm thinking Pat Braden's method might be best since I have the heads off now. This is where you turn the head upside down and fill the top of the combustion chamber with gasoline...leave it overnight to see leaks or just blow air through the ports to see if any bubbles are seen. Anyone try this before?
Often. Obviously you want the head level. It sure beats finding out after the head is on that you've got issues.
 

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A machine shop that does heads can do a vacuum test pretty easily on the valves to see how they hold.
Andrew
 

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Don't turn the head upside down and fill it with gasoline. Brake Kleen or Mineral Spirits works better. And you won't have to wait over night. Set the head on it's side and fill the port with fluid then just look to make sure none leaks out from around the closed valve. Then set the head up on it's other side and fill the 4 other ports and look at those valves.

Also if it does leak I would clean the seats and valves and lap them lightly and try it again. Sometimes a valve leaks just because it has a little carbon or something under it on shut down and won't leak after just a run cycle.
 

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Discussion Starter #10
Thanks everyone for the tips - I appreciate it.

I was talking the other day with a very experienced Alfa person who has been around them for a while and he said that leak down tests on Alfa motors never seem to work right (we were discussing V6s but seemed to imply all of them). He said compression tests are useful, though.

This really puzzled me since I can't see how an Alfa engine would fundamentally be different enough to make a leak down test unreliable (assuming its on a warm engine and done properly).

Do you guys agree with this opinion?
 
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