wabbit

Got a bit of a problem with oil in the rocker covers workig it's way into the air cleaner via the filtered air port on the PCV system.

start of the story.
355 stroker engine has a catch can set up with the D/s rocker cover connected to the air filter and P/s rocker cover to the catch can. PCV between P/s rocker and catch can and to the throttle body from the catch can.
thinking of changing this to bring the clean air to the catch can and PCV between catch can and throttle body.

at the drags last night, the air cleaner got a bit of oil in it via the filtered air port. enough to paint the filter, cold air tray and half of the windscreen. a bit found it's way into the throttle body on one side and oiled 3 plugs. that's not an issue, as all plugs were on one plane of the manifold, so it's obvious what went on there.

the combo was on the dyno for about 10 runs a few weeks ago and had no issues, but a single run down the strip pushed the oil out. minimal driving and no changes apart from plugs since.

we have an aftermarket, non high volume oil pump and enlarged drains in the heads. This issue hasn't surfaced before, so what could it be?
previously on the verge of spewing and not quite getting there?

I don't know what has caused this to happen now. Compression test this morning was good and nothing that would have caused a change in status can be found.

We pulled the D/s rocker cover off to check the status of the baffle and it's where it should be. not real impressed with the standard baffles, though. They vent to the bottom of the rocker cover, so a bit of oil in the heads and crankcase pressure would push it straight into the filter.

Run down the strip was no higher than revs used, with approx 20 secs between burnout and green light. I'm thinking oil may not have had time to drain from heads?

engine is a roller cammed 355 with roller rockers, so restricting pushrods may be the next step. 6500 peak rpm and standard volume pump shouldn't need it though, should it?

I'm just wondering what may have caused this to happen this time, when it's been on the dyno a few times with no issues in this regard.



any thoughts?
this is a bit of a head fornication, as nothing appears out of the ordinary

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Daryn

I'll just add.............I haven't raced it for over a year and previously it just had a filter on each rocker cover. So maybe I've connected the catch can up incorrectly?

ketchup

was your temp right up when this happend? i got the same engine combo but ,have both rocker covers running to one catch can with 1 breather on top works well ,until until temp is high then oil fills the 500ml catch can in around 6 passes ?

ketchup

also with yours on the dyno oil would most likley drain through all holes on heads , when racing foward force would push most of the oil to the back drains only . just a thought

ahk068

I run same set as ketchup and have done before without drama's

Pic of set-up would be nice wabbit. Sounds very complicated. PCV could be stopping oil getting to the catch can too

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Daryn

I've disconnected everything so I can't get a pic of the current setup.

But in a nutshell:

Driver side rocker to base of air filter.
Passenger side rocker to pcv to catch can.
Catch can to manifold side of throttle body.

We're going to change it to something similar to what you guys are running:

Both rockers to the catch can.
Catch can to base of air filter.
Catch can to pcv to manifold side of throttle body.

ahk068

VN type rocker covers will outlets at the front?

If so g-force can be ruled out unless it's happening under brakes. Do you need to use PCV. I'd try to remove can to body link and run a breather on catch can to try to stop the cycle.

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400HPONLPG raped my pet possum
gas84k went sloppy seconds
crunchy nut held the camera

wabbit

yes, VN rockers with outlets at the front.

you're right. G forces would be forcing the oil to the rear on the strip, so wouldn't the issue have surfaced more readily on the dyno with no G forces?
The run down the strip would have been longer at high revs, including the burnout, I suppose.

buggered if I know.
no blown head gasket evident per compression test
I'd like to see the PCV stay if possible. It's working correctly, so I dont see it as an issue unless it's a major restriction.

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76lxhatch

If I understand correctly, at present the driver side cover's only outlet is to the air filter - where else is excess going to go? I think the above will sort it

Daryn

Ok, hooked up the catch can as per below:

Both rockers to the catch can.
Catch can to base of air filter.
Catch can to pcv to manifold side of throttle body.

It went alright the first few runs, but on the last run I overdid the burnout and oil had come up through the air filter. Any ideas on how to fix this?

skidmarx

Iv just a very similer problem with my stroker
but I lost about 1.5ltrs of oil out of the drivers side rocker
cover on decel after a hard run down the strip at 7000rpm most of the way

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GRPABT1

I tried and tried with a complicated PCV system like you are attemping Wabbit and only got headaches and dramas, the factory "flow through" setup isn't designed well enough to work on WOT and you either get oil spewing out the passenger rocker into your intake or if like me you put a check valve in there so are can only flow in passenger side and out drivers side you get a pressure build up and blow your dip stick out.

Just do away with the PCV and vent both rockers to a catch can with a filter on top.

If you want to keep the popo happy try and make the catch can rather large and or drain back to the timing case cover and encase the filter and run a hose from that back to your intake and try that.

76lxhatch

Yes, it's supposed to do that

You don't have to do away with the PCV, just run the filter on the can rather than sending it back to the air cleaner - this is where the excess will go at sustained high rpm/high oil movement

VHPirie

We've got a similar problem with our race car. It's a 308, and we got both PCV valves in the rocker covers going into a t-piece and into the bottom of the carby. After each race there would be oil everywhere in the engine bay. Tried putting a breather oil cap in, but still pisses oil out everywhere and still pops the dipstick up.

Any idea's on why it does it?

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My rides...
1984 VK Exec Commodore Wagon - EFI 5.0L - Project
1983 VH SLE Commodore Sedan - Hot 308 - Race Car

323ci

massive blowby?
whats the ring gaps at, has it always been doing this?

why run pcv anyway, especailly on a race motor?

IMO if a dipstick is pushing out there are some major issues