How accurate is a leak down test done on a cold motor? Can you get useful results? I'm getting pro & con opinions from local wrench heads.

I'm considering just repairing the head problem on my 928 motor, installing the heads with the old gaskets and preforming a leakdown test to see if I really need to re-ring the bores. The bores look to be in great shape, no vertical scoring.

Lets here the flames. I want it all!

My uneducated understanding is that a leak down test is not accurate unless the motor is warm, all the metal has expanded...

But, I would also expect that if there is a glaring problem, it would be similare readings regardless if its cold or hot.

Rich

The leakdown test allows you to compare the cylinders to one another, therefore, although you might get more leak from a cold engine you will still get a cylinder to cylinder comparison which should locate any problems.

This is often the only choice for someone buying a car that hasn't been run in a long time, or an engine sans chassis.

agree with all the above. the "actual results" may not be as good as when the engine is warm....but the cylinder to cylinder comparison should highlight issues. If all fairly close to each other..good sign that at least things have worn normally across all 8!

QUOTE (jim912928 @ Jan 29 2006, 10:04 AM)

agree with all the above. the "actual results" may not be as good as when the engine is warm....but the cylinder to cylinder comparison should highlight issues. If all fairly close to each other..good sign that at least things have worn normally across all 8!

That's what I thought, as well as a friend of mine that teaches at a BMW training center. The 928 motor is well known for it's high mile service life. I don't see any reason to un-torque anything that I don't have to. If it aint broke don't fix it.

well, there is always the reason to add more HP...

Get some of the Devek heads...that would wake you up.

Rich

QUOTE (r_towle @ Jan 29 2006, 10:16 AM)

well, there is always the reason to add more HP... Get some of the Devek heads...that would wake you up. Rich

My goal is to freshen up the motor I have, correct some of the things that I found need further development and not re-invent the wheel. The money I save in the lower end and block I can spend in other areas.

I think I have more power (even running on 7 cylinders) Than I can get planted to the ground via the current contact patch. I think by the time I correct the throttle linkage so it opens up fully I won't have any use for bigger heads.

Sway bars, that's what I need!

Show a couple of pics of your throttle linkage...

I think I may have just the ticket for you...

Rich