Question on Header evac tubes/check valves
 

I am considering adding the evac tubes to my headers with the check valves, etc. I am running mufflers. Is it true that if you run mufflers, the venturi effect wont work well enough for the evac tubes to be effective? I was told this is only good with with straight open headers and that evac would be minimal with muffers because of the back pressure.
Let me know your thoughts...

Thanks!

I ran them in my headers before the muffler and it would cause my dipstick to pop out. I changed it to after my muffler and it works great now. Just install it after your muffler.

Draggin,
Base on your response, it looks like it's true that the mufflers are going to cause an issue. My only problem......no tailpipes...just dumps.
Might have to consider a vacuum pump up front. :roll:

I have done extensive research on this. Mufflers will cause back pressure which will never let the valve open up. You have to run straight through design bullet type mufflers. I was just about to get the mufflers put on when I found a pair of Borla Header collector mufflers on RJ. I jumped on them but now I have to run a vacuum pump. The evac tubes only work at WOT so if your car sees even some minimal street time, it will suffer. The pump is the way to go. I have been searching ebay and RJ for a good used pump but they go quick all the time. New is almost $900.

I dont know of any pump that has any kind of life span for the "mostly street " race car... anyone hear of anything ??

FWIW, I just pulled my e-vac system off. It's not the hot setup for street use. And, the valves WILL open at very low rpms if the vacuum is enough. My valves open even in the garage just warming the car up. This will pull oil out while the oil is cold and thick. My car would leave puddles under the tailpipes when cold. Yes, I had baffles in the valve covers and yes I have 40 series flowmasters and tailpipes out the back.