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2006 cammed, carbed L33 with 3 qt Accusump and trapdoor pan in a 1970 240Z. Was at an autox this last weekend, the course was fast and the engine was on the 6250 rpm rev limiter a lot. After the 3rd run I saw smoke, pulled the hood off, and there was oil all over the top of the engine. First impression was that I lost a ring land or a ring, but I did a compression test and everything was OK.
Now I think I pumped all the oil out of the pan and then it leaked from valve cover or valley cover. Was planning on pulling the intake manifold off and having a closer look to see if I could tell where it was coming from. Problem is I just changed the oil so it's hard to see.
I'm aware that people do mods for oil return such as porting the return holes, drilling holes in the lifter trays, adding -10 AN hoses to the rear of the heads and pan to return more oil, changing PCV setups, etc.
Just wondering what the best bang for buck is, and whether there is a solution I could find that wouldn't necessitate removing the engine from the car, or the heads from the block, etc. Basically trying to make this work with as little effort as possible.
Last edited by jmortensen; 10-16-2018 at 12:16 PM.
Talked with some folks and decided on a plan: replace valve cover gaskets, upgrade to LS6 valley cover, and run sealed catch can back to intake to reduce crankcase pressure and make my vented catchcan the air intake. Parts ordered, hopefully that fixes.
What heads? I've heard some pool oil and some drill holes in the lifter trays for quicker drainback. Did pressure ever drop? What oil pump? It seems pretty difficult to starve it at autox especially with accusump but who knows. Also most run a quart high, or over the crosshatch on the stick
I know some have had major PCV issues, one guy on another forum went to great lengths to cure his oil in intake. For mine I did later ls6 style valley cover with "built in PCV valve" to Mike Norris catch can filled with stainless Brillo pad and mounted under headlight for cooling, no external valve, going back to intake. It seems to work and no oil in intake, small amount of oil and water vapor drained from can.
799 heads. Engine has ARP rod bolts and cam/springs/pushrods and the carb, but is otherwise stock. Oil pressure never dropped. Has BIG RED LIGHT on dash, so would have been obvious. I've heard the holes in the trays thing, but I was hoping not to have to pull the heads. If PCV fixes, I won't even have to pull the engine out of the car. Fingers crossed.
What's kinda funny is that I have a 2006 GMC 1500 with the same motor that I use to tow the race car, and it's been consuming a lot of oil and pings even on 92 when it's hot, but runs strong and only has about 80K miles. In researching this for the race car, sounds like my oil consumption problem in the truck might be fixed by the exact same parts list.
If your air pressure in the Accusump is too high it will overfill the crankcase.. If your running it in active mode,,
For road racing I always use the low oil pressure switch to activate. The switch needs to be as close as possible to
the oil pump outlet so it has as fast reaction as possible. I've always had over-oiling issues on cars with the hand
operated ball valve..
With a 3 quart accusump you could easily way overfill the crankcase especially if your sump pressure is too high the
sump will just always dump to the engine leaving you way overfull, I pressurize the sump empty to about 50% of the
full throttle oil pressure, by the time it fills the pressure should be at or above the high oil pressure level.
It takes some fiddling to find the sweet spot for the pressures,
I believe I'm running 15 lbs pressure on the sump as I thought that was the mfr recommendation, and I just run it with a ball valve, no electronics. I know there are arguments for and against the solenoid, but I just figure that it's best to have oil there instantaneously.
Don't want to increase the pressure until I'm sure that I've solved the leaking problem which will most likely be next year.
799 heads shouldn't be a problem so I wouldn't worry about the lifter trays. Does sound like the accusump might be putting too much oil in the system though
If your air pressure in the Accusump is too high it will overfill the crankcase..,
No, it won't (and can't) because oil level is set at whatever pressure you put into your accusump anyway. 0 psi, 5 psi, 20 psi will all net in the same amount of oil resting in your case.
At 15 psi its almost never going to dump the oil, FWIW, I've installed a ton of these,
with the ball valve your pressures will be lower than with the solenoid valve.
One other thing, I typically run the oil level about 1/2 to 1 quart lower with a Accusump
on motors without windage trays. (Assuming about a 4 to 5 quart oil pan.. )
Its a interesting gadget, has saved many engines for me,
but some motors do work better with them than others..
No, it won't (and can't) because oil level is set at whatever pressure you put into your accusump anyway. 0 psi, 5 psi, 20 psi will all net in the same amount of oil resting in your case.
Thats why I was saying if the pressure in the accusump is too high,,
If you have a 4 quart crankcase, and a 3 quart Accusump, and you have a full load of oil in the oil pan, and the pressure in the oiling system goes below the pressure in the accusump the oil in the accusump goes in to the engine,, so for a bit your pan has 7 quarts in it.. its a pressure balance, I've found guys running 50 or 60 lbs in them, the accusump essentially empties any time they let off the throttle. Granted its not for very long,, but submerging the crank isn't usually a great idea ,, the accusump refills in a blink so its a very short period of time.
If the sump is overfilling, the pan, it usually shows up as you exit the turn,, you get a engine bog that clears after a second..
Thats why I was saying if the pressure in the accusump is too high,,
If you have a 4 quart crankcase, and a 3 quart Accusump, and you have a full load of oil in the oil pan, and the pressure in the oiling system goes below the pressure in the accusump the oil in the accusump goes in to the engine,, so for a bit your pan has 7 quarts in it.. its a pressure balance, I've found guys running 50 or 60 lbs in them, the accusump essentially empties any time they let off the throttle. Granted its not for very long,, but submerging the crank isn't usually a great idea ,, the accusump refills in a blink so its a very short period of time.
If the sump is overfilling, the pan, it usually shows up as you exit the turn,, you get a engine bog that clears after a second..
I had always thought it worked slightly differently: if you rev up your engine and close the valve, you'll trap whatever pressure the oil pump is producing in the Accusump. So it might have 80 psi in there total, but it will be 65 psi oil and 15 psi air, in my case.
The other difference is that whenever oil pressure lessens in the engine whether it be from starvation or letting off the gas, the accusump will drain back to the engine. So the way I had conceived of it (which may be way off) is that with the open ball valve there is a lot more oil transferring back and forth, and it's not just the 15 psi going back and forth, it's whatever the engine was making at the time before the pressure dropped. When I open my ball valve with the engine off it takes about 3-4 seconds to move all of the pressure back into the engine. This is my first Accusump so I'm open to the idea that I had envisioned it incorrectly.
If that is right then it seems the problem with running really high air pressure is that you don't fill up the accusump at all until you get past that threshold, so you'd either have to rev the crap out of the engine to get oil into the sump, and you would really pump a lot of oil into the pan anytime that the pressure was less than the air pressure. Seems like a lot of pressure is a bad idea. I can see upping the pressure a little bit, but that's still going to mean less capacity in the Accusump.
Last edited by jmortensen; 10-19-2018 at 11:46 AM.
Thats why I was saying if the pressure in the accusump is too high,,
If you have a 4 quart crankcase, and a 3 quart Accusump, and you have a full load of oil in the oil pan, and the pressure in the oiling system goes below the pressure in the accusump the oil in the accusump goes in to the engine,, so for a bit your pan has 7 quarts in it.. its a pressure balance, I've found guys running 50 or 60 lbs in them, the accusump essentially empties any time they let off the throttle. Granted its not for very long,, but submerging the crank isn't usually a great idea ,, the accusump refills in a blink so its a very short period of time.
If the sump is overfilling, the pan, it usually shows up as you exit the turn,, you get a engine bog that clears after a second..
Your logic is not based in the reality of a race engine. If the pan is full of oil, the pickup will suck it. The imaginary scenario you are dreaming up where the pan is overfull because the accusump is providing the engine (more) oil is not possible because physics says so. The oil isn't in the pan, it's in the top end. I guarantee my car pulls more g-force then his, and turns more rpms. I have 7 qts in the pan, 1 qt in the lines/cooler, and roughly 2.2qts in the 3qt tank at 20psi base pressure with a 70# bypass in the pump and 30psi hot idle/50psi cold idle native oil pressure. Works great, and is supported by datalogs of the pressure around several racetracks because you can watch the accusump work as oil pressure flatlines in the same place lap after lap.
All that aside, puking oil out the top is 100% a windage issue related to an inadequate pressure vent because a stock style pcv can't handle sustained high rpm (especially high rpm decel in gear), and has 0 to do with accusump anything.
I had always thought it worked slightly differently: if you rev up your engine and close the valve, you'll trap whatever pressure the oil pump is producing in the Accusump. So it might have 80 psi in there total, but it will be 65 psi oil and 15 psi air, in my case.
Not quite. So imagine your 3 qt accusump is set to 20psi base pressure. If your engine pushes exactly 60psi of oil pressure, it will fill exactly 2/3 of the way. Why is this? Well, you've compressed your 3 quarts of 20psi air to 1 quart of space, tripling the air pressure. You now have 60psi ambient in your tank, which is 2/3 full, because physics says that 60 psi of oil will compress the air to the same pressure, which levels out at 2/3 of the tank full of oil, or the air at 3x the base pressure it originally started at because your oil pressure is 3x your air pressure.
The way the oil released is on a sliding scale/rate based on how the oil pressure drops. As the tank empties, it will trickle down from 60psi down to the base pressure of 20psi at which point the tank is totally empty, because physics - the oil in the tank pushed by the oil pump has compressed that air, so the return pressure is higher - equal to the ratio the air has been compressed in a linear fashion. Generally when I set my base crankcase oil level I rev the engine to 10psi above idle pressure, and capture that much in the sump tank.
Oil control items needed for road race ls engines. Many small pieces to a larger puzzle that work together in unison to keep your engine reliable and consistent.
Restricted pushrods (~$200 a set). Get them made by trend or some similar company. Well worth the investment for a road race deal - keeps excess oil out of the top end.
Scraper/Special windage tray (Improved racing, a few others). Keeps oil off the crank. Worth a couple hp and saves you from aerating your oil.
Trap door baffle for oil pan (improved racing, a few others). Keeps more oil at the pickup. Prevents sloshing. Worth the investment.
Oil Cooler - not necessary for autocross, 100% needed to road race. 280+ oil temps will kill your engine, period. Added benefit of putting another .75-1qt of oil in your total oil capacity, which further lowers thermal load.
Link-bar lifters - wise investment if the motor is apart. ditch the trays, allows oil to drainback faster out of the topend and back into the pan
EDIT--Interesting on the rev to fill idea. Wouldn't that likely be the same as closing the accusump at idle pressure then adding .5 or 1 qt?
Right, but 15 psi air + 65 psi oil doesnt equal 80 psi, it equals 65 psi. Pressure isnt additive, it equalizes on either side. The exact add for your setup will vary on what your oil pump naturally makes and how much air is in your tank. Best to set it and adjust as needed. I run all the way to the top of the hashmarks.
Right, but 15 psi air + 65 psi oil doesnt equal 80 psi, it equals 65 psi. Pressure isnt additive, it equalizes on either side.
I think I just stated the example badly. I was saying if you revved up the motor to 80 psi and then closed the valve, you'd have 80 in the sump (65 + 15).
I think I just stated the example badly. I was saying if you revved up the motor to 80 psi and then closed the valve, you'd have 80 in the sump (65 + 15).
You'd have 80 in the sump. 80+15, which would actually be 80 oil +80 air, since the pressure will be the same on both sides.
10-16-2018, 12:04 PM
Autox engine leaked oil after extended high rpms 
,, the accusump refills in a blink so its a very short period of time.