Excessive oil after rebuild

[911 Rod]

Details.
3.2 rebuilt to 3.4 with 9.8:1 Je pistons.
Lightened clutch and flywheel
964 Cams
B&B headers and race mufflers
3.4 chip
Brad Penn break in oil for break in
Leakdown test 1% to 5%. Compression 180 lbs all cylinders
3,000 km since rebuild
Car runs well, but I'm using 1 litre of oil (Brad Penn 15W-40) per 500km

My mechanic is stumped.

Any ideas?

[BURN-BROS]

Smoke while driving? decel? Start-up?
Any leaks that are notable?

[911 Rod]

No more smoke than before the rebuild. You would think there should be a blue cloud behind me, but there isn't.
No excessive leaks.

[BURN-BROS]

I would, if possible inspect the intake ports for oil pooling as look for wet exhaust ports for potential valve stem seal issues. It has happened to me in the past. With that kind of oil consumption, evidence should be very apparent.

[cgarr]

what is the cylinder history? you have yours bored and plated? if so who did that?

[lvporschepilot]

JE oil scraper rings are typically pretty light resistance and thin, 12-14lbs if that. Valve stem seals would be the other issue I’d look at. I’d ask the machine shop who did the heads to clarify what stem seals were used.

[911 Rod]

Originally Posted by BURN-BROS

I would, if possible inspect the intake ports for oil pooling as look for wet exhaust ports for potential valve stem seal issues. It has happened to me in the past. With that kind of oil consumption, evidence should be very apparent.

How can I do this?

Originally Posted by cgarr

what is the cylinder history? you have yours bored and plated? if so who did that?

My engine builder sent my cylinders to be bored and plated to a place in Nevada.

[cgarr]

Most likely EBS find out, I hear they are now honing the cylinders much finer because of ring sealing issues. My set after 20k still burn a quart every 400 miles. Someday I will send them back to be redone.


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[911 Rod]

Originally Posted by cgarr

Most likely EBS find out, I hear they are now honing the cylinders much finer because of ring sealing issues. My set after 20k still burn a quart every 400 miles. Someday I will send them back to be redone.


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Would this not show up on a leakdown test?

[lvporschepilot]

Originally Posted by 911 Rod

Would this not show up on a leakdown test?

Not necessarily. Oil burning is what articulates the issue most. Also keep in mind a leakdown test performed at static levels of 100psi are a far cry from the pressures the engine actually operates under. The 'tests' we are able to perform at 10% of the engines normal operation can be worthless without a seasoned diagnostician.

[911 Rod]

My exhaust pipes are very black inside. Because of the condensation, when I start it up it blows out black water droplets all over my garage floor.

[BURN-BROS]

The tune may be too rich. This condition can wash the cylinder(s) of oil and can cause sealing issues.

There is/was a problem on the 996/Boxters in which during startup, the engine would flood and wash the cylinders out. The engines would no longer produce enough compression to start. I heard they smoked quite a bit once they were able to get them started.

[911 Rod]

Originally Posted by BURN-BROS

The tune may be too rich. This condition can wash the cylinder(s) of oil and can cause sealing issues.

There is/was a problem on the 996/Boxters in which during startup, the engine would flood and wash the cylinders out. The engines would no longer produce enough compression to start. I heard they smoked quite a bit once they were able to get them started.

That would be an easy fix.

The car runs very strong. Most of it's life is spent at the track and it's quicker than the 3.2's. I do use more fuel, but I figured it was because of the 3.4.

Still applicable?

[Trackrash]

FWIW. I had an air cooled Vanagan. 2.0 T4. It would burn about a quart every 300 miles if driven on the freeway.

Never smoked. Even passed smog. Good compression.

Tore it down and the oil rings were carboned up to the point of being stuck. YMMV.

[911 Rod]

^^ The oil consumption started after the rebuild.

[Trackrash]

My point I was trying to make is the fact that rings can pass a lot of oil with no smoke or loss of compression.

FWIW, I had another car that never sealed the rings after a deglaze and new rings. According to some experts at the time the crankcase breather was not working correctly and caused the cylinders to glaze over.

Not saying it is your problem, only that probably your rings failed to seat properly for what ever reason.

I have also heard of the second ring being installed upside down, which could cause a problem similar to yours.

[lvporschepilot]

Is it a bad time to praise AA iron cylinders yet haha. I've built 2 motors with them now, both turned out nice and the rings sealed right away, likely due to them not being nikasil. One with 90mm and other 92mm, one twin plugged, both using JE pistons. The 90mm single plug 2.7 engine made 197bhp at the wheels on a dynojet, running carbs. I won't pretend huge mileage can be put on them but for how much these things are driven anyway I don't think it matters. Oh and neither burn much oil or overheat. /ducks and runs

[VFR750]

Originally Posted by cgarr

Most likely EBS find out, I hear they are now honing the cylinders much finer because of ring sealing issues. My set after 20k still burn a quart every 400 miles. Someday I will send them back to be redone.


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This is very true.

It took me three rebuilds to solve the oil comsumption problem. On the third tear down I packed up the P&C and sent them to EBS. They inspected the cylinder bore and confirmed the honing was too deep.


they not only had them replated and honed to a finer surface finish, they applied a coating to the skirt to reduce wear.


What a difference! Seated right away. Oil consumption less than one qt in >1,000 miles. JE pistons. 9.5:1 with Goetz rings.

Also make sure all of the valve guide seals are ok. That’s another story.....

[911 Rod]

Checked my records. It was EBS that honed the cylinders to 3.4

[VFR750]

EBS doesn’t physically do the cylinders. Millennium does the boring, playing and honing for them, at least that was for mine.