Excessive crankcase pressure... will this help? is this right?

[herostar]

Will this help cure my extra/excessive crankcase pressure?

http://www.roadraceengineering.com/instructions/catchcaninstructions.htm


I know it's not from the rings b/c I did a compression test and the rings were awesome (adding oil only upped my compression 10-12 psi per cylinder...) My theory is that my stroker creates more pressure, and since the PCV valve closes when the car is under boost the only place it can vent is through my breather on my valve cover. I'm assuming that by eliminating the pcv and having the 2 openings on the valve cover that it will help with my crankcase pressure.



A second related question about my crankcase pressure...:

I have a bad head, and I am losing cylinder pressure through the head (my compression is between 60-65 psi per cylinder). Would this having a bad head cause my pressure in the crankcase and under the valve cover to increase? Also, do you think once I put my new head on it will help with this pressure problem?

 

[Defiant]

Crankcase pressure is from -and only from- ring blowby.
I don't get that you think that "I did a compression test and the rings were awesome" and then explain that "compression is between 60-65 psi per cylinder". That motor's done for.

 

[Big Woo]

The minimum cylinder pressure for a 1G 6-bolt is 121 psi, and a little higher for a 2G, sorry don't remember the exact figure off hand. Never the lesss with compression readings of 60 to 65 psi per cylinder there is a major ring sealing problem.

The fact that it is a stroker motor has nothing to do with, how the rings seal, or the reasons for the blowby in the first place.

 

[4wd-Eclipse]

I'm using RRE oil catch can with my 2.3 stroker and I'm still have a slightly blow-by problem ... I did compression test with 175 psi pressure in all the cylinders. Then I removed the intake manifold and found oil leaking from all valve guides. I ordered a new set off Ferrea valves from SBR and I got a clean N/T head to be installed soon. Then I'll do leak down and compression tests... hoping this will help to reduce the blow-by problem

 

[steve]

The minimum cylinder pressure for a 1G 6-bolt is 121 psi, and a little higher for a 2G, sorry don't remember the exact figure off hand.

According to my manuals the min spec @ 250-400 rpm for a 6 bolt turbo is 114 psi and 137psi for the NA block. The 2G 4G63 service limit is 133psi.

Steve

 

[bigjdog84]

I think he means 160-165. Or atleast i hope so

 

[herostar]

The engine was recently built and yes the compression was stated correctly. Amazingly the car still ran an 8.52 in the 1/8th mile (this was when I found out something was wrong...) Its not that the rings are amazing, but when I did a compression check, well actually I did 5 different checks using 3 different gauges/testers, it was low every time and when I put oil in the cylinders like you are supposed to to check the rings the compression barely changed, leading me to believe that the rings are not the problem. I also am blowing white smoke out my exhaust (coolant, and no, there is no blue tint to it whatsoever...) as well, whic leads me to believe it's a cracked head, or possibly a warped head. Tomorrow I'm getting a leak-down test performaed at 8am so I'll have more results then.


Back on topic though... The catch can, will it help or is it just another waste of money?

 

[herostar]

Crankcase pressure is from -and only from- ring blowby.
I don't get that you think that "I did a compression test and the rings were awesome" and then explain that "compression is between 60-65 psi per cylinder". That motor's done for.

Defiant, normally I agree with you, but if you read in many of the threads about stroker motors, you will find that there IS an increase in crankcase pressure because of the longer stroke of the crank. And yes, what if I had 8 bent exhaust valves and had no compression in my combustion chambers? The rings could still be awesome and the compression could be bad. Think about it.

 

[bigjdog84]

I wouldn't even waste your time with that shit. Just pull the head and see whats going on.
And yeah the catch can is a worthwhile mod. JMfabrications makes a very nice one for about the same price I believe.
Later/joe

 

[4wd-Eclipse]

Back on topic though... The catch can, will it help or is it just another waste of money?

The catch can will help to avoid any the accumulation of oil inside the intercooler and lose some cooling efficiency by the time also to make the interior of NEW intake manifold clean

In my case it didn't help .... I'm keeping the lower catch can lower valve open all the time.

 

[Defiant]

Defiant, normally I agree with you, but if you read in many of the threads about stroker motors, you will find that there IS an increase in crankcase pressure because of the longer stroke of the crank.

How. The stroke is lengthened in both directions. As two go up, two go down. You'd have an increase in the amount of wind going on in there, but the volume won't be changing.