Header evac with mufflers

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gumper

gumper

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I bought a crankcase evacuation system that welds up to headers a few years ago, and never got around to putting it on because my mopar valve covers didn't have the right hole. Now I'm feeling less lazy, and will drill the hole I need for the breathers. I've read, however, that running the evac system with Flowmasters (chambered mufflers) will cause backpressure at higher rpm which can counteract the vacuum I want, and actually pressurize the crankcase. I've read several forums, and it seems hit or miss. Anyone have experience with this? Right now I'm running regular twist in breathers that like to leave a few drops of oil on my valve covers after a full weekend of racing. My main reason for this is to maybe gain a little power, but I will not sacrifice my mufflers. Maybe an evac system won't do anything for me, I don't know, but this is why I'm asking the professionals here.
 
Extend it past the flowmasters if it's reasonable to do.
 
I run the headers into an x-pipe then the mufflers. Would that be too far back to make a difference?
 
Needs to be appropriately placed in header collector with free flowing exhaust to see benefits from a header evac system. Also I recommend a good sized baffle spaced at least 1/2" from valve cover because they also like to evac oil.
 
Reason you want the baffle spaced away that much is so oil can't gain velocity around the baffle if you didn't know.
 
This won't work with full exhaust, designed for open headers. I would just run a pcv valve or run hoses from rocker covers to a vented puke can. Mount it on fire wall above rocker covers. Be sure your rockers have baffles to control the amount of oil puked out. Be sure to put a drain in bottom of can to drain.
 
67cudafb said:
This won't work with full exhaust, designed for open headers. I would just run a pcv valve or run hoses from rocker covers to a vented puke can. Mount it on fire wall above rocker covers. Be sure your rockers have baffles to control the amount of oil puked out. Be sure to put a drain in bottom of can to drain.
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Any place in the exhaust that pulls a vacuum on a tube in the exhaust flow will work.
Before the baffled mufflers will cause a backpressure instead of vacuum, but after the mufflers will work just fine.
The vacuum won't be as high, but that could be a good thing if sucking oil droplets could be a problem.
 
Don't believe everything you hear on an open forum like this.... Guys talk out their asses is all I can say.

[ame]http://youtu.be/LzaBV1DUnb0[/ame]
 
My buddy Jerry has the same Evac set up on his Nova 364 CI and a 400 Hit of NOS. He has fender well headers and mufflers about 4' away from the collector. Evac is in the collector. The system works xlnt. He has NO Vac Pump and running that much juice. Car runs 5.80's in the 1/8, it is no slouch.

My lil 340 before I pulled it had the same set up. It worked great. My mufflers were in the standard place and exhaust dumped at the axle.
 
My buddy used a crankcase evac system his 455 Pontiac. It cured his leaky rear main seal, and seemed to find him a little more power. On his car it worked just fine with mufflers, but he did run Dynomax bullets, or Flowmasters and no tailpipes...
 
Well I guess I can give it a shot. If it causes much back pressure it'll blow oil out the standard breathers.
 
gumper said:
Well I guess I can give it a shot. If it causes much back pressure it'll blow oil out the standard breathers.
Click to expand...

If it causes any backpressure it could cause seal and gasket leaks, so it's pretty easy to tell if it's working right or not.
Also you'll see it venting out the vents under the hood if it's not working.
 
The hoses would be 7 feet long if I ran them behind the mufflers. Probably defeat the purpose.
 
gumper said:
The hoses would be 7 feet long if I ran them behind the mufflers. Probably defeat the purpose.
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Not at all.
It will have the same vacuum at 7 feet that it would at 4 feet with all other details being equal.
You can't just T it into the pipe though (didn't know if you knew or not)

There are three way of putting the tube into the pipe, and I always prefered number 2 over the others.
1 works fine
2 is my personal favorite
3 seems hacked in to me, but works fine too.

Notice the angle on 1 and 3 ends inside the pipe.
All three will generate plenty of vacuum for case evac.
 

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I was trying to figure out how to do it like #2 in that drawing. Looks to me like it'd pull better vacuum. I also should make a baffle for my valve covers. Naturally mopar has some that'll screw in, but they weren't kind enough to give them with the valve covers when I purchased them 15 years ago.
 
gumper said:
I was trying to figure out how to do it like #2 in that drawing. Looks to me like it'd pull better vacuum. I also should make a baffle for my valve covers. Naturally mopar has some that'll screw in, but they weren't kind enough to give them with the valve covers when I purchased them 15 years ago.
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It's always something isn't it? :)

start with a round hole the size of the OD of the tube and egg out the hole towards the front and back till the tube fits nicely.
Then weld er in there, but make your tube so it gives some room between the hose and the exhast pipe so it doesn't burn it.
 
Run one way valves like stock air pump setups use; TRhe ones that add air to the exhaust manifolds. They only open when under a vaccumn.
 
That's kind of what the valves that screw onto the piece that goes into the exhaust are aren't they?
 
I only use vacuum pump or header evac when running low tension oil rings but that's what I was taught when young. If you're using standard ring pack I'd quit sweating it and use factory pcv especially if you're worried that back pressure might be an issue.
 
Orangepeel said:
I only use vacuum pump or header evac when running low tension oil rings but that's what I was taught when young. If you're using standard ring pack I'd quit sweating it and use factory pcv especially if you're worried that back pressure might be an issue.
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Some good advise right there!
 
I believe we are running a little wider ring gap for nitrous use. I don't really think it has much pressure, it has 4 valve cover breathers now.
 
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