Header evacutaion system pros / cons
Thread Starter
Safety Car
Joined: Aug 2001
Posts: 3,892
Likes: 13
From: Pettis Performance 565 with two stages of Nitrous Supply nitrous 1.082, 4.61 at 155, 7.17 at 192
Header evacutaion system pros / cons
I have to make 500 at the wheels :banghead: (just kidding about the head banging part) I am adding a 3/4 in. wood spacer soon also
I have been considering a header evac. system plumbed off each valve cover with a 5/8 heater hose (braided) to the collectors of the headers. I know they are supposed to aid is piston seal, crank case pressure, etc. Any real world experiance out there. I have also heard a little negitive feed back regarding causing too low of a pressure build in the crank case there by causeing oil pump starvation.
Any thoughts ?
[Modified by 69 N.O.X. RATT, 6:12 PM 6/21/2003]
I have been considering a header evac. system plumbed off each valve cover with a 5/8 heater hose (braided) to the collectors of the headers. I know they are supposed to aid is piston seal, crank case pressure, etc. Any real world experiance out there. I have also heard a little negitive feed back regarding causing too low of a pressure build in the crank case there by causeing oil pump starvation.
Any thoughts ?
[Modified by 69 N.O.X. RATT, 6:12 PM 6/21/2003]
Burning Brakes
Joined: Jul 1999
Posts: 923
Likes: 164
From: Hudson NH
Re: Header evacutaion system pros / cons (69 N.O.X. RATT)
Hi John,
Dynatech claim ~ 11 HP gain on an open exhaust 800HP (IIRC) big block w/ their system. I tested this very mod on a chassis dyno and found no difference. In spite of this poor result I still believe they can work w/ a VERY low restriction exhaust system using straight through style mufflers (Borla, Magnaflow, Ultraflow, Dynatech, etc.). If you can drop your exhaust system and match the HP of your full exhaust system, then a pan-evac system will probably work. Given a gain of 11 HP on a nearly 800 HP big block w/ open headers, I wouldn't expect you to gain more then 3-5 HP (assuming you have a great exhaust system).
For the amount of time you'll be drawing vacuum w/ this system (WOT and high rpm) I would not worry about any oiling problems. A dedicated vacuum pump on the street may be a different story. Steve Barker runs a vacuum pump on his nasty 542 so he may be able to share his experiences.
Good luck,
Mark
PS If you have a trick 2 or 3 piece timing cover w/ adjustable chain (or even better a belt) than I'd play w/ intake centerline. Sometimes retarding a cam a couple of degrees compared to the typical 4 degrees advanced can be worth a few ponies up top, of course at a cost of some low rpm torque.
Dynatech claim ~ 11 HP gain on an open exhaust 800HP (IIRC) big block w/ their system. I tested this very mod on a chassis dyno and found no difference. In spite of this poor result I still believe they can work w/ a VERY low restriction exhaust system using straight through style mufflers (Borla, Magnaflow, Ultraflow, Dynatech, etc.). If you can drop your exhaust system and match the HP of your full exhaust system, then a pan-evac system will probably work. Given a gain of 11 HP on a nearly 800 HP big block w/ open headers, I wouldn't expect you to gain more then 3-5 HP (assuming you have a great exhaust system).
For the amount of time you'll be drawing vacuum w/ this system (WOT and high rpm) I would not worry about any oiling problems. A dedicated vacuum pump on the street may be a different story. Steve Barker runs a vacuum pump on his nasty 542 so he may be able to share his experiences.
Good luck,
Mark
PS If you have a trick 2 or 3 piece timing cover w/ adjustable chain (or even better a belt) than I'd play w/ intake centerline. Sometimes retarding a cam a couple of degrees compared to the typical 4 degrees advanced can be worth a few ponies up top, of course at a cost of some low rpm torque.
Drifting
Joined: Jul 2002
Posts: 1,820
Likes: 283
From: Puyallup WA
Re: Header evacutaion system pros / cons (ML67)
Pan evacs are not the way to go when you have an exhaust system hooked up to your headers. In fact, pan evacs are not all that effective on open headers.
A vacuum pump is the way to go. I have been running one for a while with no problems at all.
Steve
A vacuum pump is the way to go. I have been running one for a while with no problems at all.
Steve
Racer
Joined: Sep 2001
Posts: 354
Likes: 0
From: Prineville Oregon
Re: Header evacutaion system pros / cons (69 N.O.X. RATT)
I agree with Steve...
I had a pan evac system on my blown motor and disconnected it because of excessive blow-by. I also found it blowing my dip-stick part way out of the tube on every WOT run. Once disconnected those problems went away. The pan evacs are really only effective when running open headers.
Deen :iagree:
I had a pan evac system on my blown motor and disconnected it because of excessive blow-by. I also found it blowing my dip-stick part way out of the tube on every WOT run. Once disconnected those problems went away. The pan evacs are really only effective when running open headers.
Deen :iagree:
Thread Starter
Safety Car
Joined: Aug 2001
Posts: 3,892
Likes: 13
From: Pettis Performance 565 with two stages of Nitrous Supply nitrous 1.082, 4.61 at 155, 7.17 at 192
Re: Header evacutaion system pros / cons (DeenHylton)
I wanted to see some real world experiance before I said anything. I would think on a mufflered car they would be counter productive. With a full exhaust system you have a degree of back pressure. With a direct link from the back pressure to the pan you are increasing the very thing you are trying to get rid of, pressure in the pan. That is probably when Deans boat was blowing the dip stick out.
I will stick with a breather set up
Thanks
I will stick with a breather set up
Thanks
