My engine recently started blowing out my valve cover gaskets during normal drive - less than 3000 RPM. First it was my oil dipstick, so I checked the usual: oil level, replaced the PCV valve, forced compressed air through the valve cover lines from PCV to manifold, and also the pass side valve cover line (which is a direct vent line to the TB, before the butterflies). It seemed to be working ok for a few mild drives. Then after about 50 miles of driving, it blew out both valve cover gaskets during a second gear WOT datalog. I then replaced the gaskets and added a breather to the pass side valve cover. Took it for a drive and didn't even make it 3 miles before the drivers side gasket blew out - now I'm mystified! Following this last blowout, I did a leakdown test and compression test (this past weekend) thinking my rings were shot. The worst cylinders were #2 with 10% leakdown, and #7 with 11%, all others were between 4-7%. Compression test revealed all cylinders between 200 and 220 psi. Shockingly, both #2 and #7 were 215 psi. I reassembled it yesterday, added Rislone ring sealer, rechecked the oil level and took it for a drive after work today. Low and behold, the drivers side gasket blew out again...oil everywhere and the smoke show to follow. I'm not sure what I should do next??? Do I simply add another breather to the drivers side - the same side as the PCV or is there something else to look for?

This is a significantly modified 383 with 6" rods and AFR 195 Comp Eliminator heads. If not for the gaskets blowing out, you can not tell it has an issue. The car has tons of power and pulls hard to 6200 RPM. It previously ran 11.7 at the track with a 1.59 60ft. Since then, I upgraded the cam and heads, added a tubular K-member, and installed LS1 front brakes with expectations to pull a low 11.0X this year. Now, I can't keep it on the road because of this.

Any suggestions? What else should I look for? The heads and cam are new, so I wouldn't think the valve guide seals are leaking. Is it easily fixed with another breather on the drivers side valve cover or is something else still amiss? I'm stumped.
~Magman

 

What valve covers do you have? What gaskets are you using?
FTR: I have very good results using the blue silicone gaskets with my cast aluminium covers (GM licenced ProForm centre bolt). I RTV the gasket to the valve cover. No leaks despite plenty of ring seal blowby.

 

If it leakdown tests ok, then I'd bet your oil is too lightweight or getting too hot maybe. Fix the valvecovers and it'll blow out somewhere else, pressures gotta go somewhere! I had a sim issue where I cooled a engine operating temp down too much and had to go heavier weight oil to stop all the blow-by, I tried 4 hi-flow breathers before I figured it out. Oil was still hot enough but not too much and it was a high mile engine. Being yours is a 383 and it's doing it after WOT I'd bet it's oil related. What kind of exhaust does it have?

 

Thanks guys, I appreciate the feedback and other ideas. The valve covers I have are from Jegs, Cast Aluminum, Polished centerbolt mount, PN: 555-50104. Sealed with FELPRO VS50088R gaskets (blue rubber). I clean the valve cover gasket surface area with a wire brush, then isopropyl alcohol, let dry, paint on Permatex hi-tack gasket adhesive and push the gaskets into place on the cover. Then place two 10lb weights on top of them and let setup for 30 mins. After they setup, I install them and torque them to 92in lbs twice and check all corners/sides with an inspection mirror to ensure they are seated correctly.

The oil I'm using is 10W30 Valvoline Max - semi synthetic blend. After it blew my oil dipstick out, I doublecheck the level. I don't believe it has to do with oil PSI though, this is air PSI building up and then blowing out the gaskets which allows the oil to leak everywhere. I'm going to add another breather to the drivers side and replace the gaskets - again. There is no way in hell they should blow with a breather on both sides! The Rislone ring sealer I added was super thick, like 90W, so it should thicken the oil up some. The oil pump is a Melling M-55 with a yellow spring, it gives me 60 psi until it gets fully warmed then drops to a norm of 40 or so at idle.
Nothing has really changed, since I swapped the cam and heads. I have ran it without breathers for years. My only concern is that it sat for ~5 years with my wife starting it occasionally while I did some extended time away from home to finish off my Navy career. That is what made me think the rings lost their ability to seal.
Thanks for the ideas, anything else?
~Magman

 

As it was for me, I found that the centre bolts would bottom out in the head, achieving the requisite torque but not the needed clamping force on the gasket. I used my vernier caliper depth probe to determine how far down the bottom of the bolt boss in the head was down from the valve cover. I had to trim a couple of threads off each bolt to get things right. Just throwing that out there in case that a possible solution for you.

 

Cool, thanks. I'll check to ensure the bolts aren't bottoming out. I just ordered some K&N filters and grommets from Summit. I think with some drive time and some heat back into the engine it should settle itself out. I'll post back up next week and share the progress. I was actually driving it to the paint shop when the gaskets blew out last week. Needless to say, that was delayed. Hopefully better news to come!
~Magman

 

I had a similar problem with my dipstick blowing oil on a stroker motor. Put one of these crankcase evac kits on and it solved all my problems. They say its not for cars with mufflers, but if you have a good free flowing exhaust, it will work fine. https://www.summitracing.com/parts/mor-25900

 

That's something I'd considered as an alternative to the PVC system. It's not necessarily an issue with oil control in my case but more about the compromise the "vacuum leak" has on overall performance and tuning. If this next build leans more towards racing than street driving, I'd probably go with the pan evacuation method.

 

Well I hadn't thought of a crankcase evacuation system, but it looks like it would work well as the next and final solution. How does it affect intake plenum vacuum though? Crankcase pressure (valve covers/oil pan) is completely separate from the intake plenum, the source of vacuum (MAP) for tuning. If I went that route, I'd definitely need to upgrade my exhaust. I'm running Hooker 2055's with a single 3.5" straight pipe back to a Hooker Aero Chamber dual output muffler. It sounds great, but I know it's restricting HP.

I'm going to try 10W40 to help seal the rings and minimize blowby along with installing a breather on both valve covers. I'll leave the PCV on drivers side, the vent line to the TB on the pass side, and a breather to each valve cover to ensure the pressure created has an escape route and stops gaskets from blowing out. Thanks guys.
~Magman

 

No effect on intake vacuum. The evac kit is using the exhaust to create a vacuum to pull the cranckcase pressure out of the block. Another option, but much more expensive, is a vacuum pump. They will both add some power by better ring seal, and keep oil mist from contaminating your intake, valves, plugs, pistons, and combustion chamber.

 

My concern with the pan evac is that using it with an exhaust that has back pressure will result in it being more or less useless wouldn't it? The backfire valves operate as one way valves ( which is my understanding) so if there are several PSI worth of pressure in the collector and less than that in the crankcase, then there's no flow. Perhaps the reason why they are not recommended for systems with mufflers. Now that said, there's no reason why a mufflered system can't be free flowing. Suitably sized pipes and mufflers with sufficient capacity should do it.

 

I'm no scientist, but i think the scavenging effect or low pressure waves create the vacuum in the exhaust? Your correct, there are replaceable one way check valves to prevent exhaust from pushing pressure in the block. Trust me, these things work good. Check out some you tube videos, etc. Theres a lot of info out there. IIRC the PCV system only generates 1" of vacuum when its working?

 

There are certainly low pressure pulses in the collector. And the flow of exhaust past the evacuation tip also creates the siphoning effect that I believe is the principle on which the evac system works. That said, I've also observed siginicant positive pressure in the exhaust as measured with a gauge. So I'm not entirely sure how all of that comes together.
And Joe, I've no doubt you have a functioning arrangement. Pan evacuation has been around for as long as I can remember (which is a long time!) but it's the application on a street driven vehicle that I've no experience with.

 

Problem solved. Looks like I made a rookie mistake using the Fel-Pro rubber gaskets and too much torque. The increased blowby just helped push them out of their seat. No problems now with several miles on it after switching to 10W40, adding ring sealer, replacing the blue rubber valve cover gaskets with Fel-Pro 1604 double thick steel core gaskets, and I also added a breather to both covers for insurance. PCV is retained on drivers cover and the pass cover is vented to the TB. With the blue rubber gaskets, each pass I torqued the bolts to 92" lbs resulted in an additional 1/4 turn, which basically squished the gasket out of place. Without a solid surface they were just getting squeezed and distorted. I'm happy now with the new gaskets and no oil leaks!

Moving on to upgrade the exhaust. My cam/combo is supposed to pull to 6500 rpm, but my best run to date shows 6200 RPM. Hooker Blackeart LT's and full exhaust is in my near future!
~Magman

 

Nothing like a happy ending. WeIl done.
Be sure to post up on your experience with the BlackHeart stuff. I may go the same route myself.