Low Leak down

Emo993 · 03-25-2018, 06:01 AM

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, Mark

boosted79 · 03-25-2018, 10:26 AM

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.

Emo993 · 03-25-2018, 11:53 AM

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

boosted79 · 03-25-2018, 11:58 AM

probably just run it and see what happens..

Emo993 · 12:07 PM

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

boosted79 · 03-25-2018, 01:05 PM

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.

Trackrash · Trackrash's Garage

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?

Emo993 · 03-25-2018, 01:43 PM

Yup, two gauge....

Emo993 · 03-25-2018, 01:46 PM

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

Emo993 · 03-26-2018, 05:51 AM

OK, few more pictures. Exhaust valve, looks new, port is a little dirty. Bottom of engine and cam shot. What do you see. Best, Mark

boosted79 · 03-26-2018, 06:01 AM

Very little time on that engine, run it and see if it tightens up. How do the cam lobes look?

Catorce · 03-26-2018, 06:21 AM

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.

Emo993 · 03-26-2018, 06:31 AM

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.

boosted79 · 07:22 AM

"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.

Trackrash · Trackrash's Garage

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

Emo993 · 03-26-2018, 08:32 AM

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

Catorce · 03-26-2018, 11:42 AM

Quote:

Originally Posted by boosted79

"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.

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.

Emo993 · 03-26-2018, 12:25 PM

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, Mark

boosted79 · 03-26-2018, 12:46 PM

"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.

Catorce · 03-26-2018, 01:25 PM

Quote:

Originally Posted by boosted79

"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.