L92 engine with LS3 intake - high crankcase vacuum
Thread Starter
Staging Lane
Joined: Sep 2007
Posts: 81
Likes: 1
L92 engine with LS3 intake - high crankcase vacuum I made a post about low oil pressure yesterday but didn't get any response. I found some of the problem today. I pulled the oil cap when it was running and it was hard to pull off because of all the vacuum in the crankcase at idle. Then the oil pressure also came up to 20psi at idle with oil temps around 250.
The L92 only has ports on both valve covers, not on the valley. The LS3 intake manifold has one port right after the throttle body which I have hooked to the passenger side valve cover. The driver's side valve cover was blocked off but I tried running it open just to test and still tons of vaccum.
This engine has new rings which are not broken in yet & a hone job, new 230/236 cam & cam bearings, new lifters & pushrods, reused main & rod bearings, only gaskets reused were the valley cover & intake manifold because they looked brand new.
So what's going on here? How can I fix this? When I put my oil cap back on my oil pressure drops. My MAP at idle is 48-50kpa.
The L92 only has ports on both valve covers, not on the valley. The LS3 intake manifold has one port right after the throttle body which I have hooked to the passenger side valve cover. The driver's side valve cover was blocked off but I tried running it open just to test and still tons of vaccum.
This engine has new rings which are not broken in yet & a hone job, new 230/236 cam & cam bearings, new lifters & pushrods, reused main & rod bearings, only gaskets reused were the valley cover & intake manifold because they looked brand new.
So what's going on here? How can I fix this? When I put my oil cap back on my oil pressure drops. My MAP at idle is 48-50kpa.
Thread Starter
Staging Lane
Joined: Sep 2007
Posts: 81
Likes: 1
I messed with it a bit tonight. I hooked the line from right after the throttle body to the driver's rear port on the valve cover and it no longer sucks the oil cap down when trying to pull it off. I put the breather on the passenger front port to test this. Is it ok to run it like this? I'll add a line to the intake tube, can it be from the passenger front port to the intake tube? My oil pressure is staying around 20-21psi at 950 rpm now. I'm seeing 30-32 at 2000rpm and goes up from there.
Thread Starter
Staging Lane
Joined: Sep 2007
Posts: 81
Likes: 1
Ya it's just a 08 l92 truck engine with ls3 intake manifold. New rings and honed, not broke in yet as it's just been idling while I figure this out. Stock rods & pistons, stock rod and main bearings. Roughly .0015 clearances on mains and rods.
The crankcase usually gets pressure from blow by not vacuum.
Is the motor running rite only vacuum area is the intake manifold.
I think your oil pick up tube is socking both air and oil so check see if you left the O ring out from the connection of your pick up tube to the oil pump.
Check see if oil pick up tube is cracked or broken somewhere, cause the only pump you have inside the motor is the oil pump, she is only suppose to pick up oil.
Is the motor running rite only vacuum area is the intake manifold.
I think your oil pick up tube is socking both air and oil so check see if you left the O ring out from the connection of your pick up tube to the oil pump.
Check see if oil pick up tube is cracked or broken somewhere, cause the only pump you have inside the motor is the oil pump, she is only suppose to pick up oil.
