My new engine is ls3 core. I read somewhere that some guys were reversing the rear main seals on think ls2s for boost as they had problems blowing out if installed normally.Now maybe this was old design or something.
So is just putting in rear main normal on my ls3 any problem.I think ls3 and ls2 use same rear cover????

 

DON'T DO IT!!!!!!! I'm new to the LSX familly of engines but I can say with confidence, "don't put the seal in backwards". Maybe the people who had the seal blow out had crank case pressure issues.

 

I would like to know this too as the later model seals are a reverse lip style, evidently installing them backwards fixes the issue.

 

What? You should never have that much crankcase pressure to blow out the seal. If you have that much pressure, you have bigger issues than your seal popping out.

 

'Im not concerned about them blowing out just weaping, every 2nd ls2/ls3 i put a cam in or tune has a weaping rear main-before it has had a tune of any sort. And they have good leak down numbers.

cheers

 

boosted ls3 here no problems!!!

 

I have a customer with tt ls3 no issues aswell, very random!

 

those seals are specifically designed to work in one direction, ive no experience with trying it backwards but knowing the engineering behind it, id say use it how it is intended.

 

The earlier LS1 design is not a reverse type, could you please elaborate on the differences between the LS1 seal and LS3 type seal and why they changed??

 

The only time I've heard of putting front/rear seals in backwards was when using a vacuum pump.

 

I heard you can lower compression by putting the pistons in upside down..is this true?

 

Yes it is

 

My buddy has a turbo LS3 (forged pistons/rods/ported L92 heads) with custom GTS76 turbo that made 950rwhp. He had a dual catch can setup also which didn't help with the smoking issue.

It would smoke when you let off the throttle in the upper gears with only 8-10psi (medium boost) on the street. At the strip after shutdown (it went 148mph in the 1/4 with baby launch and 6500rpm shifts (low) making around 800rwhp (smaller turbo) and lots of smoke seen. This video was launching off idle and short shifting in the lower gears gently. No power shifting. Car weighs about 3100lbs with driver.
10.03@148mph
http://www.youtube.com/watch?v=bbuNsjMZFAw

With only 4psi we took it to the Mojave Mile top speed event and it blew out the rear main seal after 3 passes. Was smoking excessively after every pass and dripping oil out the seal.... which got worse.

New remedy: GZ Motorsports vacuum pump.... now... now more smoke!

 

I might have to get this guy to build tune my combo(or hand out the green bills to his w/shop like he does )

 

Thats a crankcase pressure issue, and is using the turbo drain as a breather....Daaaaaamn turbos.

 

Seams no experts in here are able to answer a simple question

 

I'm here not to argue, the guy who started the thread popped his rear main out,not mine, in that circumstance he may have to pull his engine down and find a broken ring land or maybe put his pistons in back to front as one guy said lol. My engine has very good leak down numbers and does not use oil, but it does weap a little from the rear main(not even a drip on the garage floor) just some oil stain on the bellhousing and sump.

I have a new seal LS3 reverse lip style.

From GM....

Important: Notice the installation direction of the oil seal. The new design seal is a reverse lip style as opposed to what has been used in the past (LS1). "THIS SIDE OUT" has been marked on the seal as shown in the graphic.

This is the statement that comes with the seal.

From my 15 years in the trade and building engines and gearboxes for race engines , street engines, bike engines and industrial applications.

A standard lip seal uses positive pressure from within the engine and/or gearbox to seal against the shaft/journal. This allows excellent sealing however there is very little lubrication of the seal. As it seals so well the seal lip runs dry and will wear a groove on the shaft or journal. Also if the crankcase is under vacuum at any stage the seal will allow contamination into the sump. This is why if engine builders use vac pumps they use a reverse lip which helps seal the crankcase under vacuum by pulling the seal against the journal and also preventing contamination entering the crankcase.

Manufacturers build engines which are under partial vacuum in the crankcase under 99% of driving conditions. They have adopted the reverse lip seal to prevent contamination entering the crankcase. The sump has partial vacuum which pulls the seal in.

Reverse lip seals are also used in industrial applications where a bearing housing holds grease. Usually they have automatic greasing systems they pump a shot of grease over a certain time. This allows any pressure build up to weap past the seal, keeping fresh grease in the housing, lubricating the seal and shaft(which increases life of the seal) and prevents contamination from entering the gearbox.

These are just a few examples. Put 2 and 2 together. Majority of modified engines have forged pistons and larger ring gaps that breath to an extent and have some crankcase pressure,It is a part of a piston style internal combustion, there is some leakage even in hydraulic systems which use case drains from internal leakage. Using a standard lip seal in this application is effective. The factory updated seal is "double lip". And both face in a reverse direction.