Crankcase Ventilation - How much is needed?

568 CID BBC, 14-71 SSI. 26 PSI @ 18% OD

Wet sump Moroso pan, titan pump.

Wizard Burn down tubes with 1.25" hose going to separate puke tanks, with K&N 1.25 shielded breathers.

On our last pass, it built up so much crankcase pressure that it blew out the oil filler plug and spewed oil all over the windshield. We also lost oil pressure for a few seconds after the stripe during shut down.

How much darn ventilation do I need?

I've always run oil restrictors on the top end until this motor. Switched from Isky Endurance lifters over to Isky Red Line and Isky said to NOT run oil restrictors.

The only thing I can think of is that its pumping so much oil up top that the pressure is building as the oil tries to drain back down.

Any thoughts? Should I put the oil restrictors back in? Add in some old style Hemi valve cover vents?

 

I have similiar problems on my BBC's, similiar cid, similiar psi but tractor pulling.
I've tried several things.
Dykes rings, hellfire rings etc, breathers in different spots on valvecovers, different baffles, Ø1 1/4", etc.

My next thing to try is oil pans. I think the crank hits the oil upon deceleration and create a hurricane of oil, forcing it to exit out the breathers.
We've had GM 12 qt, 10 qt and pans that I've made and baffled, but I've always been concentrating on keeping the sump covered, not about deceleration.

 

Mine has Diamond pistons, 10.4:1 compression, with Total Seal AP Stainless rings. .043 - .043 - 3/16. The pistons have 12 top gas ports.

4.614 bore, gapped at .025" top, and .030" 2nd, per Ron Smith Motorsports (friend of Wizbang on here) recommendation.

I would have put a dykes in it, but Total Seal didn't make one in that bore size, so we had to go with plan B.

I'm certain a dry sump would fix it, but I'm just not going to spend that kind of money. I'm thinking about putting the oil restrictors back in and see if removing some oil from the top end of the motor fixes both issues.

But, if anyone else has better ideas, I'm all ears.

 

oil drain back

now that you are not running any restrictors there is going to be a lot more oil building up in the valve covers and that will then start to fill up your puke tanks because that is an easy spot for the oil to go and then when the puke tanks fill up it will create lots of pressure in the valve covers and could spew oil all over. i agree with you i would try putting the restrictors back in but put in some that are bigger than what you were previously using because you don't want to reverse the situation and start burning push rods. that was what came to mind as i was reading this hope it helps but i don't want to see you go burn push rods up trying to fix this but try the restrictors but try a few sizes

 

If you think the cause is when you decelerate, put a tee fitting in the puke tank line or put bulk head fitting in valve cover and run it back to the oil pan, I worked on some CJ Batten B4 motors and he had two # 12 an lines runinng from the head back to the pan( they have no valve covers)

 

We run restrictors even though not many recommend in our situation.
I would like to take them out for more pushrod, rocker etc oiling, but I have this puking situation already. I figured even with restrictors I was filling up the valvecovers with oil, that it was getting pumped up there faster than gravity was taking it down. I considered "porting" the return passages in the heads to remedy this. But opted to move the breathers first.

When I moved the breathers I put them directly over the large hole in the heads towards the top and centered front to back. One would assume there is a lot of air blowing right up that passage, but yet I only get oil coming out upon decel, which is why my next attempt is to keep the oil off the crank while decelerating.
After doing this I'm well convinced that the valvecovers are not "filling" with oil.

 

That's exactly where my Wizard breathers are at. Top center of the valve cover, over the big ass opening in the Dart 360 heads.

But, when moving to the Wizard burn down breathers, I simply bought 2 Chevy push in oil plugs to fill the stock holes up.

Like I said, on our last pass, it built up enough pressure to blow out the plug and sent this huge mass of oil across the windshield/firewall. I'm assuming it did it based on the smoke at the closing of the throttle. So I know the valve covers are filled with oil.

You can see the smoke in the video: http://ca.youtube.com/watch?v=QIz2bSo8ScY

I think I'll take the risk of burning some pushrod balls and put the restrictors back in from my old motor.

 

oil problems

when you install oil restrictors it still only restricts oil on one side of the motor. Try STEPF,s stainless ones. I beleave they are .060 orffice. Drill and tap your cyl. heads, run -6/ -8 lines back to your pan. Weld some mail fitting in the pan. maybe a small baffle inside. Place the fitting in the head low and were the oil will flow and puddle. I ran BBC -14-71 30% over etc, etc, never had a problem.like that. Hope it helps Don

 

Thought you were gonna start your own website?

http://www.yellowbullet.com/forum/showthread.php?t=80027

 

Go grind your axe somewhere else Danny boi.

 

Hi not sure if this will help you or not but we always had a similar problem til we moved the breather outlets to the middle of the inside of each valve cover with the new moroso drill nuts we welded them in not bolted as they didnt have the clearance stock and took a 90 deg -12 male end to half inch pipe welded that to the valve covers . we have a two quart tank that we run our -12 lines to with a large kn breather on top . before we did this use to fill that tank up every run now no more than a paint lid cap comes out .never run your breather outlets off the front of the valve cover or the rear as G forces dictate that is where the oil will be . Had this happen on many vehicles in the past . I build Chassis for a living and the Engines we used to order just had the breathers there so never questioned it til we got sick of this problem happening and this solved it .

 

agree with that

x2 down with that go get em wj!

 

WJ,
What type of block are you using? In my experience most bow tie chevy blocks will not hold the cyl wall straight above 4.600 bore filled or not. The cnc bowtie, dart, and world products block are the only three that have a chance. With an out of round cyl bore your blow by will be of the chart. Have you leaked the engine?

 

RB;

Not leaked it yet, but that's on the 'this week' to-do list.

Yes, it's a filled Bowtie block. It's filled high enough to block about 1/3 of the water inlet passages off.

http://ca.youtube.com/watch?v=QIz2bSo8ScY

On our last pass Saturday, we wound up leaning out the #2 plug too much, burning almost all of the electrode off, thus tulipping the exh valve. So I have to pull it down anyway to check for piston/bore/rod bearing damage.

2 passes before that, and my driver thought he could peddle it with it out of the groove. He did a nice save that could have been a roll over, but in saving it he grazed the right rear fender on the wall. He should have just got out of it and aborted, rather than trying to save the run.

Right now, I'm thinking I'll add a couple -12 lines from the rear of the valve covers to the oil pan, add the restrictors back in, leak the block, and inspect/repair any damage done from the lean cylinder.

 

make sure the breathers are not right over the rocker arms it will push the oil off the rocker arms right out the vent tubes put it between the rocker arms i ran a blown chevy before and we moved the breather holes over away from the rocker arms and i did run the restrictors so that not so much oil went to the top of the motor

 

All cylinders leaked at ~8%. Compression test showed them all between 155-165 PSI (but that's probably because of where the camshaft is degreed in at).

The hurt cylinder has 40% leak.

Puke tanks measure 3" diameter by 8" tall.

Starting to think that it blew out the oil plug when it hurt the cylinder and he snapped the throttle shut, causing excessive crankcase pressure.

 

Years ago I ran a super eliminator dragster with a Chrysler B-1 motor. We had problems with it blowing oil on deceleration and bulging the oil pan and valley cover. It leaked down ok and I couldn't find any reason for the problem till I talked to the guys at McCandless Dodge who told me the B-1 heads were notoriously porous and that excessive blowby was common with them. Their suggestion was to keep adding filtered vents to the valve covers and the valley cover until it fixed it. I ended up with 5 filtered vents and the problem was fixed. I never had another problem with it after that.
Dave Germain

 

Thanks Dave...

After taking the rocker arms totally off, the leakdown is reading dead on par with the other cylinders (~8%). Seems the one rocker might have been holding the valve open causing an erroneous reading.

I've got the head off it now, and it looks perfect. Going to drop it off at the machine shop Monday and have them check the valve lengths to make sure one isn't stretched.

Oil is currently draining out, and I'll pull that piston/rod out too and check the ring land, then drop off the rod and have both ends checked for diameter and roundness.

With any luck, maybe it just stretched a valve a little. Maybe even luckier, it's human error in setting the valves and there's nothing wrong at all.