Leak Down Test On My New 418 Need Help?

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superchargeddrt

superchargeddrt

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Hey Guys,
I have been getting what I think is excessive crankcase pressure. The dipstick is pushing out and I have been getting oil leaks (even on the dyno). I have the PCV connected and I have a breather on the other valve cover. After the installation and modification of the breather (added extra breathing holes) the dipstick isn't pushing out however I still have oil leaking on the exhaust and I notice oil leaking out of the transmission bell housing. Additionally I am seeing a oil film on the rear bumper and trunk panel. When I got the short block from the machine shop I noticed that I was able to rock the pistons slightly in the bores (is this normal for forged pistons?) All of this prompted the leak down test. This was done dry and on a cold engine but the results are troubling, what do you guys think?

1 = 12%
2 = 16%
3 = 3%
4 = 11%
5 = 7%
6 = 4%
7 = 12%
8 = 6%
 
If you aren't hearing piston slap, you are probably ok. How many miles and what kind of rings did you use? How wide are the end gaps? Seems like some of the rings haven't seated well.
 
The numbers don't look very good. Is your leakdown tester well calibrated? Some of the cheapo ones are no good.

Forged pistons usually take .004" piston to bore clearnce...much more than cast or hypers. So the rocking sounds OK....without knowing the actual clearance. Did the shop have the pistons in hand when they did the final bore/hone? New pistons?

What rings were used? What ring gaps were used? Any idea on the hone finish? Did the shop know the type of, or have, the rings too?

With high leakdown AND oil out the back, it sounds like the rings are not seating properly or are very badly gapped (and possibly some improper oil ring setup). Is this thing burning a lot of oil? How was this broken in, as far as the initial driving? I've used forged pistons numerous times for street and racing and never had any ring or oil burning issues, but I take certain steps in the break-in process.
 
oliver said:
If you aren't hearing piston slap, you are probably ok. How many miles and what kind of rings did you use? How wide are the end gaps? Seems like some of the rings haven't seated well.
Click to expand...
Unfortunately I didn't measure the ring gaps as the guy that built my short block came highly recommended. The engine MIGHT have 150 miles on it.
 
nm9stheham said:
The numbers don't look very good. Is your leakdown tester well calibrated? Some of the cheapo ones are no good.

Forged pistons usually take .004" piston to bore clearnce...much more than cast or hypers. So the rocking sounds OK....without knowing the actual clearance. Did the shop have the pistons in hand when they did the final bore/hone? New pistons?

What rings were used? What ring gaps were used? Any idea on the hone finish? Did the shop know the type of, or have, the rings too?

With high leakdown AND oil out the back, it sounds like the rings are not seating properly or are very badly gapped (and possibly some improper oil ring setup). Is this thing burning a lot of oil? How was this broken in, as far as the initial driving? I've used forged pistons numerous times for street and racing and never had any ring or oil burning issues, but I take certain steps in the break-in process.
Click to expand...

Not sure of the bore finish but here is a list of what was used in the build.
Domhoff's_Invoice.jpg
 
The question should be where is the leakage going? you didn't specify that this was all into the crankcase . You could have 4 bad valves at 5/6% and then the ring leakage might all average out to say 5 or 6%, which at 150 miles doesn't sound catastrophic anymore.
So perhaps you have multiple problems, at least one of which might settle down with more miles.
The 2-4 could be a head gasket as could 1 and 7,puking pressure into the CC, as far as that goes, and that could also be the contributing factor to the oil consumption.
So, the point is, your LD test is telling us something, but without qualifiers it is almost impossible to interpret

AS to the rocking, the piston crowns are quite a bit smaller than the skirts and so rocking is normal. You should see pistons in outboard marine engines, they rattle around up there.
 
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I cant read the # of the pistons, are they 1/16" rings, moly 5/64" or just iron 5/64", Iron wont be broke in yet, How hard have you run it, rocking piston is normal, I personally like them on the loose side. Get it hot and redo the test then give it a squirt of oil in the plug hole and do it again and see if there is a difference.
 
Unfortunately, the parts list is too small to read the details and the piston line says 'with rings' so that tells us nothing except that the rings are probably circular.

The questions on the hone finish and rings have a lot to do with how well and quickly the rings will seat. For example, if the rings are chrome, then they may never seat very well, or will take a long time.

The questions on how the break-in was done have to do with the ring seating process. After 150 miles, IF you drove it a variety of RPM's, got it heated up every time, and gradually increased the loading to WOT or near WOT in that time, AND the hone finish was appropriate, then any ring (besides maybe chromes) should be well seated. Plain iron are not all that hard to seat properly.

The questions on gaps are similar: was it done right at the shop?

The other possibilities could be issues too... it is the oil on the back that is pointing to the ring situation, IMHO.

If you re-do the leakdown tests, you might want to make sure each piston is on an up-stroke when tested to simulate the rings being pushed downward by combustion pressure. And if the pressure is going past the rings, you may be able to hear it leaking into the crankcase.
 
All this nonsense about the rings not being seated is just that. Nonsense.

The rings should have been in by the first time it hit running temp of before.

AJ is correct...where is the air going?

Anytime you have a dipstick blowing out you got ring trouble. IMHO, if your rings ain't in by now, you can't fix it unless you take it apart.
 
brian6pac said:
Iron wont be broke in yet,
Click to expand...

?? Most iron rings are broken in by the time you get the thing out of the driveway

Ring gap is not gonna cause this unless somebody somehow shoe horned the wrong BORE SIZE rings into the thing
 
yellow rose said:
All this nonsense about the rings not being seated is just that. Nonsense.

The rings should have been in by the first time it hit running temp of before.

AJ is correct...where is the air going?

Anytime you have a dipstick blowing out you got ring trouble. IMHO, if your rings ain't in by now, you can't fix it unless you take it apart.
Click to expand...
I wouldn't say it's complete nonsense. I've seen plenty of engines with a bad hone job or ring swap burn oil and have lots of blow by for a few thousand miles before it gets better.
 
I am a firm beleaver that break-in should be done standing on the gas pedal just as hard as you can.......it takes pressure on the back side of the rings to seat them. Long drawn out engine break-ins are things of 30's, 40's and 50's due to materials engineering and machining. Things are better now for the most part, no need to draw the procedure out over time.

Something to think about after you do some sort of autopsy to find out what happened would be to put in a crankcase evacuation system, might help ring seal.
 
oliver said:
I wouldn't say it's complete nonsense. I've seen plenty of engines with a bad hone job or ring swap burn oil and have lots of blow by for a few thousand miles before it gets better.
Click to expand...


If it takes a thousand miles to "break in" the rings they are JUNK. They will never be right.

Its F'ing 2018. When will the ring seal lies stop?
 
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brian6pac said:
I found this on Wiseco rings

View attachment 1715190989
Click to expand...


Wiesco is WRONG. The piston has almost ZERO to do with ring break in. If the piston is correctly made, the bore is geometrically correct the rings WILL seat in very little time. Even with no load on them.
I will say this. If what you posted is true, it means their pistons are JUNK.
 
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Another perspective...........NASCAR, Pro-Stock..........they don't take a slow, easy break in on an engine............they put them together, fire them up, check for leaks, set timing and then stand on them..........they seem to run pretty good
 
If it was run on the dyno, the rings should have seated pretty well way before a power pull. I'd be pulling it apart and find out why they DIDN'T seat.
 
I use moly rings in every engine and they seal right away with a 400 grit hone. I haven't used cast iron rings sense the 80's.
 
With it blowing oil when on the dyno theirs no way in hell I would of taken it from them. It needs to be fixed properly and right now. Is it possible the rings were installed upside down? I know **** can happen, but the builder should of never let it leave his shop.i would be so totally embarresed if it were me. Kim
 
oldkimmer said:
With it blowing oil when on the dyno theirs no way in hell I would of taken it from them. It needs to be fixed properly and right now. Is it possible the rings were installed upside down? I know **** can happen, but the builder should of never let it leave his shop.i would be so totally embarresed if it were me. Kim
Click to expand...

I don't see where it was Dyno'ed
 
nm9stheham said:
Unfortunately, the parts list is too small to read the details and the piston line says 'with rings' so that tells us nothing except that the rings are probably circular.

The questions on the hone finish and rings have a lot to do with how well and quickly the rings will seat. For example, if the rings are chrome, then they may never seat very well, or will take a long time.

The questions on how the break-in was done have to do with the ring seating process. After 150 miles, IF you drove it a variety of RPM's, got it heated up every time, and gradually increased the loading to WOT or near WOT in that time, AND the hone finish was appropriate, then any ring (besides maybe chromes) should be well seated. Plain iron are not all that hard to seat properly.

The questions on gaps are similar: was it done right at the shop?

The other possibilities could be issues too... it is the oil on the back that is pointing to the ring situation, IMHO.

If you re-do the leakdown tests, you might want to make sure each piston is on an up-stroke when tested to simulate the rings being pushed downward by combustion pressure. And if the pressure is going past the rings, you may be able to hear it leaking into the crankcase.
Click to expand...
I will contact my engine builder tomorrow to try to answer some of these questions. Thanks for your response. I really appreciate it.
 
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