Low Leak down
 

History, bought as a long block six years ago, no history on build other than its a 2.2L E case and heads with S cams and Pistons. It is sealed up nice, chain tensions, oil bypass upgrades. As mentioned I did confirm S cams and can see the S pistons so the story was correct. Now getting to finish engine, new PMO's, going to switch out S cams to Mod Solex-30 cams....Soo, last week I did a leak down test, yup cold, never seen engine run. All cylinders were at about 50/60 percent. I could see leaking around valves with a little oil in them (all the same Int. and Exh.) Could also hear leaking coming from the chain case cover off (rings). As you can see in the photos, valves and head ports look very clean....does this look like a rebuilt engine that has never run or been Broken In?
What should be my next step, I really don't want to have to take heads/cylinders off. Best, Markhttp://forums.pelicanparts.com/uploa...1521985936.jpg
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Probably a dumb question but the piston was at TDC when you did the leakdown right? And valve clearances checked? Put a socket over the adjuster and give each valve a little tap with a hammer at TDC, sometimes it will seat the valve and give a better reading. Then put one bank upright and squirt some oil in the plug hole you are doing leakdown on, turn it over then check LD again.

Thanks boosted79..Yes TDC, I backed off the valves a little to make sure rocker were not on the cam. Did put oil down valves...very even leak all around like a small amount of rust on valve seats. And shot oil down spark plug hole for rings. Popped top of valves with rubber mallet again TDC. Each time on each cylinder it got a little better, maybe 70 percent dropping to 60. Odd thing..all cylinders acted the same, both valves and rings. Not one standing out good and others bad. Again the history, this engine came with a number of early 911 race cars that were being changed back to street 6 or so years ago. The engine may have been built years before that. The gentleman I purchased it from was in Florida around Orlando. Best, Mark

probably just run it and see what happens..

And test gauge used, Longacre with 100psi. I reversed the numbers, leak down showed 30 to 40 percent leakage on all cylinder. Cold

Do you have the type with two gauges, one before and one after orifice? Last engine I got 7% on five and 12% on the sixth before it was run but I use total seal in second groove.

You can't tell anything by looking down the intake. Mine look like that after 30 years.

What do the exhaust valves look like? Plugs?

Yup, two gauge....

Trackrash, original plugs gone. I'll take exhauste valve shots tomorrow. Mark

OK, few more pictures. Exhaust valve, looks new, port is a little dirty. Bottom of engine and cam shot. What do you see. Best, Markhttp://forums.pelicanparts.com/uploa...1522072248.jpg
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Very little time on that engine, run it and see if it tightens up. How do the cam lobes look?

Was the engine ever run afer its rebuild? Really tough to get meaningful leakdown numbers on a cold engine, almost impossible to get them on a newly rebuilt long block.

Cam lobes look great. And I do not think this has been run after rebuild of what ever fashion. There was no dirty oil or carbon on or around heads etc. I did not clean engine, this is how it looked when purchased.

"almost impossible to get them on a newly rebuilt long block."

No, it is not. Depends on how it was rebuilt. If it was rebuilt right and not with oval jugs then good cold pre-run in numbers are very possible.

Do a cam run in then put it in the car and break it in.

Possible that the rings aren't even seated yet. Looks like a new motor.

Thanks Trackrash, boosted79 and Catorce. I feel a little better. Need to finish wiring and cam switch and then get this thing running. Finger crossed. Best, Mark

Say what you like, I'm telling you as a serial engine builder that doing a leakdown on a long block that is newly assembled will yield numbers that are utterly meaningless. I am not sure why this test would be performed in the first place, but if you did, I would bet your numbers would be 30% LOW or more on every single cylinder.

To do a leakdown correctly the motor needs to be warm to account for thermal expansion, which presupposes the rings have been seated correctly on initial run in.

Catorce.....I did the leak down because I'm a 70 year old sports car buff still trying to learn, your comment is well appreciated. Every thing I've read about 911 engines is having leak down done. So, also knowing it should be done warm/hot was not possible. The part new to me (thanks to your experience) is the difference regarding a rebuilt engine verses previous running engines. I've owned this 914 for 40 years, lots of auto-cross's and track time (Road America, Blackhawk Farms) but its been apart for 25 year. Two year ago, final body work and paint. Suspension upgrades done, gear box with short gears and new synchros etc. Now just need a running motor. Best, Markhttp://forums.pelicanparts.com/uploa...1522095851.jpg

"Say what you like, I'm telling you as a serial engine builder that doing a leakdown on a long block that is newly assembled will yield numbers that are utterly meaningless."

Whatever.. Do a leakdown on a newly "assembled" long block that has oval cylinders with new rings and then do one with replated and honed to spec cylinders and new rings and tell me what you find. The do one on a newly assembled one that has old pistons with grooves that are out of spec but with new rings then do one with new pistons and new rings.and see what you find.

The comparison you are depicting is also meaningless. I don't assemble motors with oval cylinders so....

Now do this. Take your newly assembled BUT NOT run in motor. Do a leakdown. Record your readings. Then, run the motor, break it in, do a leakdown while warm. You will find that the first set of numbers you get are bogus.

Only the second set of numbers matter, and those numbers are exclusively what you will base your automotive diagnosis from.

Good, because while your numbers will be totally useless, you STILL learned how to do a leakdown. Now, when you run the motor, you will be able to do an accurate one with a warm engine, then you can compare your numbers.

The exercise itself is not wasted time, even though the numbers won't be accurate.

There is nothing wrong with doing a leak down test on an engine when cold. We do it all the time. We do have a coalition between hot and cold though.

Every time time we rebuild a cylinder head we always vacuum test each valve seal. No different in doing a leak down to test the valve sealing. When testing the valve sealing, cold or hot it wants to be the same. If this engine sat for along time, its quite possible that the valve margins and seats have got some dirt on them. Most of the valves would have remained open while the engine sat.

Although the rings have only their tension and 100 PSI pushing them against the cylinder walls, the leakage past them is normally low. No where near 50%. Typically around 2% - 3%.

Rings can stick in their groove from sitting especially if assembled with engine oil. This is not so sticky and can drain down to the bottom of the piston.

What are your choices. Run it and hope it all sorts itself out or pull it apart and check. Best to eliminate the valve seating. This can be done with the engine assembled and cold.

To check the valve seating, someone already has suggested tapping on the valves. Make sure both rockers on each cylinder have lash, (piston some where close to TDC) and with a plastic drift
and the leak down tester still connected, give the rocker adjuster a smart smack with a dead blow hammer. Don't go nuts here. What you should hear is a loud pop as the valve is lifted of its seat. If the leak down number go down, you are essentially removing any dirt from the seat. If no change, you have a seat issue that probably will not get any better. Remember here, any leakage past the rings will remain constant. What you are trying to do is to seal or see if the valves are seating correctly.

This is all based on your initial findings of some leakage past the valves.

"The comparison you are depicting is also meaningless. I don't assemble motors with oval cylinders so..."

We're not talking about an engine you assembled, the history on it is unknown, thus the LD test.

It is entirely possible to obtain cold LD of 10% or less on a fresh engine. 40% is not good.

He has an indication that there MAY be a problem.

Run it and then check.

Thanks Neil again for the explanation. Did the leak down again...TDC, both valves with lash. Popped valves a few times, also put some oil into cylinder... Did two cylinders, both around 10% leakage slowly going up to 15 or so. From every thing I see, motor has never been run. Thanks for the help. Mark