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Discussion Starter · #1 ·
I am having some leaking issues on my 406. Built last year, and has been together for about 8000 miles. She runs good, and has cranking PSI of 175 across all 8. A few were over by about 5 PSI.
The motor has right at 11 to 1 static, so I dont think I'm getting too much blowby. But there is an oil leak I cant seem to fix...
I am running PCV valve to pass side valve cover, and a breather on the left side. The drips are coming down near the starter, and sometimes even on the left side... It seems like it happens more when I am on the highway. I ran the valve lash last week, and found one gasket got sucked in on the firewall side rear of cover. I used The Right Stuff to glue some Rubber Gaskets with the metal insert to the valve covers before install and the leak has really slowed down. I am really thinking it is coming out the breather, and dripping its way down, and also out from around the PCV Grommet.
These are not very expensive parts I have on there now, and I am looking for something with a tried and true design. I dont mind paying for something thats gonna work.

So what is everyones favorite? I am building my 427 SBC and dont want this mess in my Monte Carlo, so I will be buying 2 sets very soon.
Will take pics of current setup this evening when I get home.
There are baffles in my current setup, but I think they could be better.
 

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What are you using perimeter or center bolt covers now and are they, cast, fabricated, or stamped?

I’m rather surprised that a PVC valved system has the power to suck a valve cover gasket in?

Bogie
 

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Discussion Starter · #3 ·
They are stamped, with bolts around the perimeter. They are fairly new, and never been over zealously tightened yet.
I think the back edge fell in, rather than being sucked in. It was a plain, black rubber Cometic brand gasket. I did not glue it to the cover with silicone, so it probably didn't survive installation.
Also couldn't take pictures tonight, its still raining...
 

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I find at least on the center bolt covers that the rubber gaskets are too short. I stretch them over my chest like one of those exercise handles with rows of springs to build up your chest muscles. Then I glue them to the covers with elephant snot (3M door gasket adhesive).

My choice in valve/rocker covers are cast or fabricated. I found that cost has little to do with quality of these things so I use a lot of those offered on Ebay which sometimes are used American brands like Edelbrock, etc. When we had the shop one of my partners had a daughter that loved to shop, didn’t matter what so she was as good at parts as teenage girlie things. So we’d give her a list and a budget, by golly she kept it all straight and got really good stuff at good prices. I hate shopping for parts or anything, I find it tedious. Same goes for trying on clothe, my wife always wants me to try on stuff. I‘m at; if I like looks and it’s the right size buy it, I’ll put it on at home if it’s ugly or doesn’t fit then take it back. Where’s the problem? Besides just how good does a blue or black denim shirt and blue or black jeans need to look? OK I have a dark orange, deep green and a couple very light tan denim shirts and couple pairs of light tan jeans. The dark orange and deep green with a pair of light tan jeans are for spiffy events. The light tan denim shirt and matching jeans are for riding the Harley on the desert side of the mountains ‘cause I may be crazy but I ain’t stupid. OK the stupid part is open to argument.

Bogie
 

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Discussion Starter · #5 ·
I doubt if you would have made it this far being stupid. LOL!
I will be going with cast, or maybe even fabricated. I want to make sure to get some with good baffles. There is a little smoke that comes out of the breather when I set the timing. (3000+ rpms)
Also, that's when I see it dribbling out around the grommets for pcv, and breather. I can only imagine what goes on under there when I lean on the loud pedal.
I was really worried about blowby at first, but I think my cranking pressures are pretty tight still. Thanks for the input!
 

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Smoke out the breathers is normal when setting timing like you do. With no vehicle load on the engine it takes very little throttle opening to spin 3000 RPM so there is not a lot of combustion pressure which is what seals the rings so there is more blow by in the shop than when operating on the road. Also the PCV valve works to close at high vacuum and open when intake vacuum is low so again with the small amount of throttle being used to set the timing the PCV is on its bleed hole and not applying much draw on the crankcase so you will see more smoke than in say at cruise. AGCO Automotive Repair Service - Baton Rouge, LA - Detailed Auto Topics - What are the Symptoms of a Bad PCV Valve

However, if you drive at high RPMs a lot the PCV simply may not have the capacity if the rings are loosing seal at high RPM. This is a clearance issue which can be caused by wear but often is too much or too little end gap clearance and something many builders miss which is vertical clearance between the ring and the land they ride in. This can also be a function of skirt clearance, where when too wide as the piston rocks about its pin as it moves between thrust faces this can upset the ring seal. Here again running with no working load in the shop the piston seldom gets to operating temperature so for whatever the clearance is it will be close to its widest so the piston will be an maximum or near to it thus rocking about the pin to the extremes of its freedom.

The normal Chevy crankcase breather is PCV valve to intake manifold and a hose into the air cleaner. So there is always some form of forced breathing and oil spillage that passes out as droplets and vapor is always trapped. Most if not all valve cover oil separators really aren’t good enough for performance work, guys that run the engines hard use a separate off engine puke tank to separate and collect the oil traveling with the blow by then vent from there atmosphere or to whatever they are using for an extractor which depending on how serious the build can be the vacuum PCV valve, a hose to air cleaner, an exhaust syphon or positive displacement engine driven vent pump.

Bogie
 

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Discussion Starter · #7 ·
Thanks Bogie. Now im outside my box, and looking at something that will work better for my application. This video taught me a little.
The way my truck gets driven, its not wonder I can't keep the oil inside!
I will start looking into a designed system with a catch can, and proper lines.
 

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Felpro 1604 steel core gaskets and AFR cast valve covers over four studs/flat washers seal mine nicely (Mainly due to the really good gaskets and flatness of cast aluminum covers). Use of studs protects the threads in the heads. The washers protect the powder coating on the valve covers. Guaranteed to stay in place - no goo necessary - and can be reused a number of times if you don't crank them down too hard!!
 

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Discussion Starter · #9 ·
Ok guys, now I'm looking for some valve covers with the AN Fitting Bungs already welded in. These remote catch cans look like the way to go, but I'm not seeing a good option to tie them into the breather holes in valve covers. There are options for LS with a bung for the fitting, but I'm not finding any for SBC.
Catch can might even be overkill for my application.
Maybe some taller breathers? Even these are getting soaked with one on each side...

 

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Discussion Starter · #10 ·
Ok, getting close. Thinking of the Fabricated covers now. I can install these without a welder. They require a 1 inch hole, the common breather hole is 1.25.

JEGS 52231: Vented AN Breather Fittings -12AN | JEGS

Not going to pull the trigger just yet, but the gears are turning in my head...

This is an option for catch can.

 

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I've used a couple different sets of the fabricated type, the short bolt style and the long bolt style (both perimeter bolt, not centerbolt) without any problems, with K&N push in breathers....but they all had stud girdles, that seems to help act as a baffle also.

Set of short bolt fab'd I'm getting ready to use I actually made some tubular breather neck/oil seperators using some 1.25" OD 304 Stainless x .060" wall tubing.
Cut 3" long pieces, turned one end to a 1.230" OD for 5/16" length so it would be a tight press fit into the provided punched 1.220" breather holes.
Took two 1.124" circle end caps cut out of flat sheet, then "swiss-cheese'd" those for oil drainage holes and welded those into the end of the bottom of the tube before pressing it into the hole in the cover.
The tubes then take a push -over band clamped style Breather instead of a push-in.

You can buy them pre-fabbed with the breather tubes, but only in circle track style, with both tubes in one cover.
I wanted just a single tube in each cover, so I had to do that myself.

I've used a couple of the white box polished die cast covers too and they worked just fine. One set was Summit house brand, the other I don't remember....Super Sunny or RPC maybe?
 

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Thick covers that won't bend and some good felpro blue gaskets.
I would run some cast ones like the ones below(painted black) on a old sbc without a 2nd thought. Notice how thick it is where the bolts go through? That spreads out the force allowing that gasket to be squished evenly.


As for the inserts that is a rubber bushing. Dont overthink it. The thing just needs to hold a pcv or a hose
 

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Discussion Starter · #14 ·
My engine guys use these a lot and they are good.
Thanks, those look like the set on the first link you sent me.
I went ahead and ordered them already. I'm just going to run with those for now and devise some type of tall breathers, (like Eric mentioned) and see if that solves my problem. They always have wheezed out a little bit of oil from them and my PCV system from the get-go.
But it seems like it's been getting worse lately, and the truck is marking its territory now with drips on the ground...
I will keep you guys posted of how things turn out!
 

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Discussion Starter · #16 ·
A leakdown will tell you everything you'll wanna know on the ring seal
Thanks, bro. But, I did the cranking test first to ease my mind.

I am hoping 175 is good enough for the street.
Actually, I am glad this thread popped up again.

So, all 8 were above 175.
A few were 176-178.
But there was one. 195!!!!! (it was #7)
Granted, I took these numbers before running the valve lash for the first time in about 6000 miles.

there was 2 reasons for my thinking...

#1 was the clacking sound that didnt used to be there...
#2 was a good sized oil leak that was spewing onto hot exhaust.

Hindsight tells me, I have been chasing a Ping I could only fix with race gas for about 6 months now...

Maybe it was an exhaust valve not opening full enough? But the motor runs strong again, no more pinging after vave lash adjustment.

#2 I think I have found my oil leak @ valve cover...
Dammit Johnsongrass, there are 3 more questions I need answered now. Not including why my Idle is high when I cap off the PCV Valve...

So in the end, I am pretty sure I dont want to do a Leakdown test...
Just Yet...
 

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Leak down testing show you the condition of the ring seal which is a good indicator of the oil control problem being the valve cover baffles or the PCV pulling too much oil vapor or excessive blow by overwhelming the venting system.
Cranking test is good for checking the starter speed and for holes in the piston, cylinder walls and missing valves heads.
Cranking testing doesn't hurt anything, it's just the Leak down gives you way way more information and takes the same amount of time.

Idle changing when the PCV is capped off is normal. The PCV is just a controlled vacuum leak. Controlled in a fashion that allows the carb to compensate for it. Idle going up means the idle fuel mix was likely slightly rich to begin with and now is more correct for what the engine wants. The incoming air charge is not longer polluted with oil vapors when capped off so it's tends to be a cleaner burn as well.

When are you gonna stop messing around put that thing on E85?

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