I wanted to bring some perspective with what I'm experiencing and food for thought. I have a primary track car that does get street driven often. 12K total miles with right at 40 track hours over 2 years. Car ran flawless for myself in every aspect for the time. Until I lost my rear main seal.... twice. Second time two weeks of street driving. Which has lead into a rabbit hole this whole year. Same time a lot of information, information on at least my motor. What caused this? Come to find out the LT2 short block/ crank case is sealed off. It's stated that ring control and the scavenge pump/s help control the pressures and gases. Explanation is seen in this video starting at 3:10. Same time it's a great video overall.


For my car and my driving this is a issue. Serious engine load especially on deceleration doesn't allow this engine to breath properly with the crank case being sealed and depending on ring control and scavenge pumps to really keep up. No. It needs to vent up to the valley and become more equal. First my engine failed compression/ leak down test.
Compression
1) 145 2) 145
3) 165 4) 165
5) 165 6) 165
7) 165 8) 165

Leak down
1) 37% 2) 37%
3) 15% 4) 15%
5) 15% 6) 15%
7) 15% 8) 15%

Cylinder walls looked flawless though. Come to find out from LME from the testing they have done for FI builds on their engine dyno testing found quickly that this motor has crank case issues with breathing correctly. Unknown the issues is applying to my NA engine that is pushed hard. Also it is being seen in other shops where rear seals are letting go. Even from cars that do serious spirited drives like the Tail of the Dragon and such. But staying on a straight line with my build I went to a heads, cam, E85 setup while I was replacing the first rear seal. Why not. Shortly after that rear seal again. Most likely quicker this time from the new power, not to mention the leak down results that turn. This is what lead to the deep search.

So the circumstances is LME was already installing vent tubes from the crankcase to the valley (along with another benefit) on their short block builds regardless to resolve this issue so we can vent to a catch can like normal. Lingenfelter has done the same on their new 427. So it's known out there. Not having this causes all sorts of imbalance of pressure causing ring flutter and who knows what else. My new plans could of been just go with a new rebuilt 377 short block that solves my issues from LME. So using my block being it's still in great shape itself I'm moving to a LME Blueprinted and balanced 416 NA 12.5:1, w/ CID's, custom cam and a few more new upgrades from several shops on board.


I feel a lot better knowing I'll have a well built motor in every way for the future. Straight and narrow with great power for the track/ road course. I want to stress this is what we saw, experienced, and concluded with my setup and scenario. Build is in process.

 

Almost forgot. The dual mass fluid flywheel failed also. It was leaking and moving around too freely once out. Also saw this first hand and a few others. They were FI and other local shops seen this also. I'm hoping with a new build it wont be an issue being new motor will be built well and balanced, it might keep everything in harmony. Then who knows. We learn together.

 

Thanks for the information. Real world results are the final test. Gm makes the motor, the aftermarket fixes the problems.

 

Another discussion about a track Z06 from last year. First his motor seized with just over 600 miles and was breaking it in properly. They did put a new motor in within two weeks. Broke it in 1500 miles. Then the seal went out at COTA. They claim it was from the new engine install but wasn’t leaking before then. Amazing easy to install when there. I had two portions where it blew out. They too know a little bit and believe it’s from the design. Which it is. I’m a little optimistic about the longevity of these two new designs. Time will tell. A quick search here shows another rear seal failure just last month.

 

NoMatter, I agree there is too much internal "unvented pressure" LME and Lingenfelter recognized this issue and have the solution, unfortunately GM has no cure for stock track cars.
I had a rear main seal failure on my 2024 Z06 track car, 3100+ street miles no problem, 60 track miles and failure.

 

So hard to believe this didn’t show in any of their testing which had to be done on an engine dyno measuring all sorts of parameters at some point. I always remind myself every car is build on a budget first. Then engineering is limited to such.

 

"acceptable casualties" might be acceptable to GM but not those of us who buy Corvettes

 

Great info. Pardon my ignorance but what is the Lingenfelter solution to this?

 

Lingenfelter and I think LME use vent tubes in the lifter valley extending down to the lower crankcase, maybe equalizing/relieving the internal engine pressure. I think by doing these vent tubes the PCV can also help purge the excess pressure and maybe prevent seal failure.

 

Same as LME. They have ports/ snorkels in the valley leading to the crankcase. Hopefully I will have soon pics soon enough showing all. The ports are at a certain height to allow oil to build some in the valley or it will drain back too fast. As it was discovered also.Will have 3 ports.

Lingenfelter



LME


Not that it pertains to this issue. Lingenfelter 427 stroker kit uses a particular crank design for clearance within the oil pan.

My 416 from LME will have a CNC oil pan for clearance. And it is beautifully designed with increased oiling functions.

 

That is correct and allows to vent properly for use of a catch can as it should be.

 

WOW, kinda scary

 

Yes, the LT2 valley has a scavenge pump for the dry sump.
Some oil needs to pool there so there is something to scavenge.

I received my LME NA 416 long block after waiting for some time after ordering, it made 700hp without boost.
It also kept making power all the way to 8k RPMs on the engine dyno, hopefully that TCM unlock is around the corner..???

 

Correct.

LME 416 NA or FI block? Being you mentioned before boost. Yes the TCM will help a lot with pressure control and deleting pressure codes that are sensitive at times. So much win will be coming being it keeps building power.

 

To go back to the beginning, if your engine had good leak down numbers, would the seal still have failed?

Thank you for sharing this info.

 

Probably not. Still curious of GM’s balancing act with the pressures in the block.

I’ve been beating on it for just over two years on the track and hard enough on the street. Combined with the stock tune for so long it’s not surprising. I was just hoping for at least three years in some way or form. No different than most other cars that track a lot. On the track with constant acceleration and braking plays havoc on the engine in so many ways. I never had heat issues though. But tracking is brutal on a motor.

There’s so much that can be crossed referenced. Even the flywheel was bad. Did that cause a problem and how long had it been that way. It drove great. But I was always down on power a little. Found out today the ring lands were failing was the issue. So I’m sure over time more pressure was leaking through.

 

My contribution to this thread is My track car also has a blown rear main seal. Seems a common issue. IT would leak profusely on track and not much around town.
I am now worried about engine damage. Is this something Chevy would cover?

 

the stock system works great until it doesn't

gm anticipates a certain amount of blowby, and sized the scavenging system to accommodate it.
because it is actively scavenging vs all the previous passive / hybrid systems, there is not as much grey area
once you go outside of that (especially if changing things that make blowby) you can be in trouble fast

our c8 systems have the ability to pressure release just like the previous corvette build-outs, but because the top side is sealed off, you just can't help it out that much by adding vents to it, until you mod the valley

 

So is your can needed on a stock car that’s tracked?

 

well some track rules require oil spill control, so check your rules
but
most track day cars i bet do not have them
just depends on what level of control/protection you want