Yup..depends on the Heads for that one. Stock L92's dont have that problem but ported ones do. I'm sure there is others..I just know them cause that is what I'm running.
Yea I hear ya man.. you start with the simple stuff and eventually have to do the hardest thing that you are trying to avoid..kinda sucks.

 

Thread sealant was not used on the rocker arm bolts, but I believe the L92s are stock and the holes are "blind".

 

One more slight possibility is that a valve guide is letting oil past on the OUTSIDE of the guide where it is pressed into the head. Very rare, but a remote possibility.

 

Update:

With the new routing, the car is still chewing through oil at an alarming rate.

I will take the throttle body off and take another look.

I do not think it will make any difference, but I may put a pcv-eliminating catch can on for a while just for arguments sake.

Is it possible the heads are the culprit? The heads were put on at the same time the shortblock was installed. Too many variables! :-)

Calling the vendor aside, what would the next logical troubleshooting steps be?

Any tips/suggestions on the best approach to work with the shortblock vendor would be appreciated! :-)

 

Try removing all PCV lines and vent to atmosphere. This will eliminate it as a variable.

 

My thoughts exactly. At the rate I am going through oil, it will not take long to know the results. :-)

 

That's what I did and it eliminated all oil consumption. Try it.

 

My uncle had a big problem with oil consumption when he first had his 404ci LS2, it ate about a quart every 500mi or so. After a couple of setups, he finally got one installed that vented both valve covers to a vent tank. The oil consumption went way down.

It still burns some when driven really hard(road course or nitrous use) but most high-performance engines do.

 

I have read most of the thread and a lot of good info and people helping on various PVC set-ups, but I haven't seen if you used a non-synthetic oil for break-in? Assuming that you did use a non-sythetic I would suggest performing a leak down test to see if the rings have seated to eliminate that before chasing the PVC system. This tests the rings at TDC and not at the bottom of the stroke where the piston has a tendency to rock in the std. sleeve length strokers. If they seal at TDC then pusue the PVC system to take care of the rock at BDC. The leak down testers are fairly inexpensive if a local shop doesn't have one.
If the leak down is bad, then a friendly call to the builder with the issues and leak down results would be in order to see how they want to proceed. Realize that a bad valve job or gasket can influence the test, so test as normal then squirt some oil (Small amount!)in the cylinders and crank the engine just a couple turns then re-test to see if it's specifically the rings. The oil will help the rings seal, so it should improve if it's the rings. The same can be done with a compression check to see pressure before and after adding oil in the cylinders.
Not to hi-jack the thread, but has anyone else noticed that hooking the PVC line into the port on the intake just behind the throttle body mount makes the #2 cylinder go lean at idle? We measured all 8 EGT's on our dyno and noticed a +300 degree increase on #2 everytime it was connected. Above idle it would balance out with the other cylinders. We connect prior to the throttle body in the cold air tubing to eleminate this. This provides little vacuum at idle, but increases with engine speed.

 

Lots of good info in this thread.

 

Update:

With the Cartek catch can reinstalled (which is basically a vent-to-atmosphere setup) the following has now been observed.
- No more oil in the intake.
- Spark plugs are now dry (all eight used to be oily).
- Oil consumption has drastically decreased. Oil is still being consumed but it does not appear to be much. I will be performing further tests to measure just how much oil is being consumed.
- I have plans to do a leak-down test tomorrow.

The engine was broke in using Joe Gibbs Break In Oil. Since break in I have been using oils that are high in ZDDP.

 

Is the can accumulating any oil?

 

It did not appear that the catch can was collecting any oil.

Update:

With the Cartek catch can installed, and if the car is not driven hard the amount of oil consumed is "not much". I do not have exact numbers.

When the car is driven more aggressively, the oil consumption rate is 1 quart per 350 miles. :-(

A leak-down test was done and the cylinders were 10%-11% each.

I have contacted the company the shortblock was purchased from, and immediately the tech stated the PCV routing should be as follows.

- Crankcase valley cover port --> throttle body port.
- All other ports closed off.

The PCV system has been rerouted as per the technicians instructions and I should soon have enough mileage on the car to know the results.

 

I find this topic/issue fascinating, and am still working away on it. A big thank you to everyone for providing their insight, knowledge, and experience.

The engine vendor has stated that a vent-to-atmosphere system is indeed bad, and that such a system may also cause oil consumption due to such a system not being able to relieve enough crankcase pressure. I am going back to my RevXtreme setup. :-)

- When the car is driven hard, the engine consumes 1 QT of oil every 250 miles.
- When the car is driven in the city (a lot of stop and go traffic) with an occasional "romp", the car still consumes oil (I do not have exact numbers) but it does not appear to be anywhere near 1 QT per 250 miles.
- When the car is driven on the highway, it does appear to burn any oil. 275 miles of highway driving equals no noticeable oil loss.

- I have performed a number of leak-down tests on the car. Rather than testing at TDC (I did not have a way to access the crank bolt), I removed the rocker arms before performing the tests. The results were inconsistent and considering Quick Carl's statement (see above) I now believe my leak down tests should be thrown out.
- I have performed a static compression tests and the cylinders were between 195 and 197. The cam I use closes the intake valve, later than the stock cam, so I think 195-197 is good?
- Multiple times I have replaced the spark plugs. The longer the spark plugs are in the engine the more soiled with oil they are. When the spark plugs are removed the plugs always look identical. There is no way to tell them apart. Whatever is causing this oil consumption issue, it does not appear to be specific to a single cylinder.

I took a valve spring off today, and as the air compressor was disconnected from the spark plug hole the tip of the valve was held (so it would not fall in the cylinder). The valve was then moved up and down. For the first time ever, I saw a valve-stem-oil scraper in action. Two things surprised me. The amount of oil that is removed by a valve-stem-oil scraper, and how the rubber seal that actually contacts the valve stem, flexes a bit as the valve moves downwards.

If valve-stem-oil scrapers were not working properly, the amount of oil that could be consumed, appears to be quite large.

If the rubber ring on a valve-stem-oil scraper flexes when the valve is moving downwards, I am left wondering if it would flex even more when under vacuum?

I have always assumed that as long as your valve-stem-oil scrapers were seated, that any oil consumption issues must be caused by something else. Perhaps there is more to it than that?

My short-term plan is to take an assortment of valve-stem-oil scrapers (different brands, different models, etc), a set of spare heads, and a set of spare valves, down to a local engine shop and perform some tests. If nothing much comes out of this research, the heads that are on the car now, can be removed, and taken to a local engine shop to be professionally inspected (valve guides, etc) and then pressure tested. If the heads look good, the next step will be to pull the motor.

 

Man I sure hope you get this solved.....this has been one headache of a mystery, and there has been alot of good advice from several that know what they are talking about. Your compression tests show good IMHO, so that would lead me away from piston ring issues, but not 100%. Keep us all updated and good luck!

 

MrDrezzUp,
Any further updates on your troubleshooting effort?

 

With the RevXtreme can hooked up, the can does collect a bit of oil. :-) At the same time I installed the can, I wiped the interior of the intake manifold dry. I will inspect the intake manifold again, just to make sure no oil is making it in there (via the catch can or from the engine).

I have spoken at length with the company I purchased the shortblock from. Everything I have heard/learned from them sounds like the shortblock was properly built, and built to tight tolerances.

I am going to replace the valve seals next. Considering the next step will be to pull the heads and then the motor...I figure it would not hurt to replace the valve seals first!

 

When you replace the valve seals, be sure to do two things:

1) if any of the rocker bolts pierce into the air passages, use liquid teflon to seal them.
2) Set your compressor at 100psi and use a leakdown gauge when you pressurize the cylinders (to keep the valves seated). Make extra sure that you're getting good leakdown numbers.

-ch

 

The rocker bolt holes appear to be blind holes. Regardless, I am going to seal them when the valve seals are replaced.

I have done a few leak down tests, but the crank bolt is so close to the steering rack I can not get at it. Without the piston being at TDC, I have been getting skewed results.

 

That's a good point, although the only thing you're missing at BDC is possible grooves in the cylinder wall that are only at the top. Ring and piston issues should be apparent at any angle.

However, something to consider: there have been documented cases where damage to the cylinder wall at some point between TDC and BDC creates compression and oiling issues. The only way to check for this is to do a leakdown where you start at TDC and slowly let the piston fall to BDC. Needless to say if you don't have a really firm grasp on the crank and a long lever arm, things can get dicey...but the bottom line is that if you do find an issue during that test, you're tearing down the motor anyway!

-ch