Re: Header evac tubes- how do they compare to vac pumps?
[Re: tjmarcus1]
#624314
02/25/10 09:39 PM
02/25/10 09:39 PM
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Joined: Dec 2008
Posts: 603 Central Oregon
Rodney
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3-5" is about all I've been able to get out of our Areospace vacuum pump we are running on the 572. While running a vacuum pump the engine has to be meticulously sealed. I was talking with tech @ areospace last week about the pump he said the larger engines may not get much more than 5" which is ok with me the main reason we are running it is to control the engine from oil leaks due to the larger stroke. It's doing that no serious leaks last year... well almost no leaks. plugging the hole where the dip stick went, a Charlies custom oil pan and a new set of Indy valve covers with NO holes except the port for the vacuum made the difference in the pump working or not for us. we also run the evac tubes on the 500 in the GTX they work great for that application.
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Re: Header evac tubes- how do they compare to vac pumps?
[Re: tjmarcus1]
#624315
02/25/10 10:32 PM
02/25/10 10:32 PM
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Joined: Jun 2004
Posts: 1,496 Sask, Can.
72demon416
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Quote:
they don't work well with exhaust pipes and mufflers.
Really? I would have thought that a well designed exhaust system with x/h pipe would actually help due to a greater vacuum created by the extra exhaust pulses compared to open headers that only see one bank of cylinders.
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Re: Header evac tubes- how do they compare to vac pumps?
[Re: 72demon416]
#624316
02/25/10 10:51 PM
02/25/10 10:51 PM
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Joined: Nov 2004
Posts: 2,116 sc
tjmarcus1
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Quote:
Quote:
they don't work well with exhaust pipes and mufflers.
Really? I would have thought that a well designed exhaust system with x/h pipe would actually help due to a greater vacuum created by the extra exhaust pulses compared to open headers that only see one bank of cylinders.
it's been my experience that mufflers and exh. systems create back pressure.
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Re: Header evac tubes- how do they compare to vac pumps
[Re: tjmarcus1]
#624317
02/25/10 11:25 PM
02/25/10 11:25 PM
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Joined: Jun 2004
Posts: 1,496 Sask, Can.
72demon416
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Did you notice any mph difference?
Last edited by 72DEMON416; 02/25/10 11:26 PM.
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Re: Header evac tubes- how do they compare to vac pumps?
[Re: 72demon416]
#624318
02/26/10 12:23 AM
02/26/10 12:23 AM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Quote:
Quote:
they don't work well with exhaust pipes and mufflers.
Really? I would have thought that a well designed exhaust system with x/h pipe would actually help due to a greater vacuum created by the extra exhaust pulses compared to open headers that only see one bank of cylinders.
In all my testing of the evac systems, the most I could produce was 5"hg and if you run a exhaust system that has ANY back pressure it will reduce the effect of the evac by the same number as the back pressure, in other words, if your exhaust has 2" hg back pressure it will reduce the evac by that amount 5"- 2" = 3" and if the exhaust system is greater than 5" hg it will back up and burn out the check valve at the collector and start to pressurize the crank case
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Re: Header evac tubes- how do they compare to vac pumps?
[Re: 72demon416]
#624320
02/26/10 09:42 AM
02/26/10 09:42 AM
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Joined: Oct 2004
Posts: 8,165 Left Coast
BobR
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Quote:
Quote:
they don't work well with exhaust pipes and mufflers.
Really? I would have thought that a well designed exhaust system with x/h pipe would actually help due to a greater vacuum created by the extra exhaust pulses compared to open headers that only see one bank of cylinders.
It doesn't help. In fact, like stated, it will render your evac system completely useless. IMO they are basically useless anyway. Our vacuum pump pulls 19" of vacuum. All VP's are not created equal.
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Re: Header evac tubes- how do they compare to vac pumps?
[Re: Crizila]
#624322
02/26/10 10:37 AM
02/26/10 10:37 AM
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Joined: Oct 2004
Posts: 8,165 Left Coast
BobR
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Quote:
Quote:
thanks Raff, It looks like it's almost pointless to run a header evac system when running a exhaust system. the good part is you just saved me some time and money
I'm sure a pump is the way to go for the serious racer with an engine making big HP, but I'm not sure you can't have your cake and eat it too with an exhaust evac system. I will have my own answers to that question when I'm able to run my car instead of my snow blower - hopefully in a month or two. For now, I know I can pull 10" of H20 at idle with my exhaust system in place. Assume I can pull more vacuum than that with open headers at all engine speeds. Don't have any numbers yet though. Also no info on what will happen at speed with the exhaust system in place - crankcase pressure will likely go positive. I understand the benifits of running a vacuum in the crankcase, but not sure if there is a measureable HP gain between running 5"HG and 15"HG. The only thing sucking around my garage right now is the weather
First, in order to realize any significant power gain the ring pack hass to be optimized for the vacuum-usually a real low tension oil ring. Second, at wot, even on a mechanically sound motor, there will be some blow-by that will quickly overcome the evacs initial vacuum. This even happens with a good pump but the pump has much more capacity than the evac and can handle more blowby before the crankcase gets pressurized. Look at the pro stockers and comp cars. They all use vacuum pumps even though there is a small amount of parasitic loss. For maximum HP there just isn't any comparison.
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Re: Header evac tubes- how do they compare to vac pumps?
[Re: 68LAR]
#624325
02/26/10 10:59 AM
02/26/10 10:59 AM
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Joined: Dec 2008
Posts: 603 Central Oregon
Rodney
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Quote:
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As far as how much vacuum is created... It really doesn't matter. Any vacuum is better than pressure. With that, a vacuum pump will use up some horsepower. A tube type evac system doesn't.
Again, my
you got that right. even tho my vacuum pump only creates 4-5 " I scraped the oil pan and ground a pretty good hole in it after a pass. didn't realize I did this until I shut the engine off in the pit. The vacuum pump was holding the oil in the pan I guess since the leak didn't start until the engine was shut down once I parked the car. After I discovered I was pouring oil out of my pan and got a drain pan under it I retraced where I may have hit something. I found the spot in the return lane over 100 yards away my only guess was the vacuum was holding the oil in the engine What ever caused the oil to not leak until then I was sure glad
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Re: Header evac tubes- how do they compare to vac pumps?
[Re: Crizila]
#624327
02/26/10 02:45 PM
02/26/10 02:45 PM
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Joined: Jan 2003
Posts: 2,902 A shed in England
Tig
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We developed a leak at the last race of the season last year. We couldn't get anywhere near our -12in/hg. Car dropped off 1.5mph and 1 tenth, It was all we could put it down to
'74 Challenger..9.46 @ 145.9 1/4, 6.001 @ 118 1/8 so far. 4023lb !!! # N/A, Marsh performance 655ci, Indy Maxx, T/R, Indy 600-13 X's, Street legal, pump gas, full interior, Cal-Tracs, mufflers, 3:73's and real 10.5 radials. 9.51 @ 142.4 1/4, 6.003 @ 114 1/8 with our old mule KB, 572-13, 580 wedge. RHD '68 Barracuda Fastback 323ci street/strip. Best ET 13.88 @ 99.03
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Re: Header evac tubes- how do they compare to vac pumps?
[Re: Tig]
#624328
02/26/10 03:01 PM
02/26/10 03:01 PM
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Joined: Jun 2009
Posts: 644 Minnesota
Barnstorm
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Diff on the dyno[my 2in Hooker super comps] was 11 hp...500in 440-1 motor. No vac readings. Will pull a little oil thru, but I want plenty of oil uptop. I think headder evacs work well. Cheap 11hp.
The little old lady from Pasadena is back!
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Re: Header evac tubes- how do they compare to vac pumps?
[Re: 68LAR]
#624330
02/26/10 05:07 PM
02/26/10 05:07 PM
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Joined: Oct 2004
Posts: 8,165 Left Coast
BobR
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Quote:
Just curious... Why would any evac system create horsepower? Would it be because the rings seal better? Or the intake? Or is it something else that I'm not seeing or understanding? Help me understand. Thanks,
Crankcase vacuum stabilizes the ringpack and allows a better seal. You should also use a low friction oil control ring and that frees up some more. If the crankcase is pressurized there will be some resistance against the piston bottom as well.
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Re: Header evac tubes- how do they compare to vac pumps?
[Re: 68LAR]
#624332
02/26/10 05:23 PM
02/26/10 05:23 PM
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Joined: Jan 2003
Posts: 20,645 So Near, Yet So Far
topside
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Ring seal improves, especially with lower-tension (lower-drag) rings. It's also arguable that as positive pressure increases in the crankcase, it's harder for the undersides of the pistons to compress on the downstroke; note that the underside of a piston is shaped like a scoop. My experience with my 368" drag-race SB with low-tension rings: Open headers, standard rt & lt pan-evac hoses, minor blowby Adding Dynomax bullets & short 3" exhaust, more blowby Changing to electric pump system, zero blowby Mine is a simple GM electric pump, pulls about 7".
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Re: Header evac tubes- how do they compare to vac pumps
[Re: 72demon416]
#624335
02/26/10 07:57 PM
02/26/10 07:57 PM
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Joined: Dec 2007
Posts: 10,542 BROOK PARK, OH
WILD BILL
Senior Member of the Junior Dragster Club
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Senior Member of the Junior Dragster Club
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BROOK PARK, OH
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Quote:
Topside- what is this electric GM pump off of? Any pictures of it?
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Re: Header evac tubes- how do they compare to vac pumps
[Re: WILD BILL]
#624336
02/26/10 08:09 PM
02/26/10 08:09 PM
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Joined: Jan 2003
Posts: 20,645 So Near, Yet So Far
topside
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'80s GM F-car (Camaro/Firebird). Corvettes, Mustangs, and several other cars use them; my '97 Mustang GT has one. A little bigger than palm-sized. You'll need a relay, a switch, a puke tank & related hoses & wiring. Total weight maybe 8 lbs. Doesn't pull as much vacuum as the "real" pumps, but I'm in the whole deal maybe $75 including the used pump, and it works for my setup. I measure the vacuum using a fitting on the opposite valve cover. Crank end seals & anything that can weep needs to be sealed as tightly as is reasonable, so no pop-off breathers.
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Re: Header evac tubes- how do they compare to vac pumps?
[Re: emarine01]
#624337
02/26/10 08:09 PM
02/26/10 08:09 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Quote:
Hey Mr P, ya got a pic of your evac with the e vac tube square with the header tubes, we found the most vac 5.5" that way
I think I have a pic at home but I'm not home, you might have a little better sealing rings or a less accurate gauge but its still close to my findings
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Re: Header evac tubes- how do they compare to vac pumps?
[Re: MR_P_BODY]
#624338
02/26/10 09:02 PM
02/26/10 09:02 PM
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Joined: Jun 2009
Posts: 644 Minnesota
Barnstorm
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mopar
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I know some SS/AH guys are pulling vac thru the fuel pump plate. Good "quiet" part of the motor. No valve cover hoses.
The little old lady from Pasadena is back!
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Re: Header evac tubes- how do they compare to vac pumps?
[Re: 72demon416]
#624340
02/26/10 09:59 PM
02/26/10 09:59 PM
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Joined: Nov 2004
Posts: 2,116 sc
tjmarcus1
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Quote:
thanks Raff, It looks like it's almost pointless to run a header evac system when running a exhaust system. the good part is you just saved me some time and money
didn't i say that?
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Re: Header evac tubes- how do they compare to vac pumps?
[Re: tjmarcus1]
#624342
02/26/10 10:16 PM
02/26/10 10:16 PM
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Joined: Jun 2004
Posts: 1,496 Sask, Can.
72demon416
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didn't i say that?
Yes you did, thank you for your input! Actually- thanks to all contributors!
Last edited by 72DEMON416; 02/26/10 10:21 PM.
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Re: Header evac tubes- how do they compare to vac pumps
[Re: tjmarcus1]
#624345
02/27/10 08:29 AM
02/27/10 08:29 AM
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Joined: Jan 2003
Posts: 4,852 KENTUCKY
69CHARGERMD
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Good thread.... Question: 1) WHERE do you mount the fitting on the header ? ( is there a measurement to use,,certain distance down the header ? any tips/tricks/troubles/ people have had installing them) The instructions i have say on the TOP surface of the header, just beyond the TRANSITION area. 2) NO MORE POP OFF BREATHERS ? ( this is what i have now,,Moroso sells a "screw" on type deal,,,would that be ok ? ) 3) BAFFLES ? (just for the inside of the valve cover?) 4) HOSE TYPE (what are you guys using ?,,,is there a particular type recomended?) I have the motor out of the car,,,so the headers can be worked on,,,, I have the Mr Gasket Evac kit ( sitting on the shelf ),,, Might be a good time to install them.... thanks. DOUG............ Moroso sells these,,,which i was thinking of getting,,, Just noticed they are about $50 EACH !! (yikes) they are the screw in style,,, i have seen some other styles that look super nice,,billet,,etc,,,
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Re: Header evac tubes- how do they compare to vac pumps
[Re: 69CHARGERMD]
#624347
02/27/10 11:19 AM
02/27/10 11:19 AM
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Joined: Dec 2008
Posts: 603 Central Oregon
Rodney
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Quote:
I have the motor out of the car,,,so the headers can be worked on,,,,
you may want to mock up the headers in the car so you weld the pipe in the correct place to not interfere with things under there I've used both steel braided, black rubber hose and push lock hose
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Re: Header evac tubes- how do they compare to vac pumps
[Re: Todd]
#624355
03/03/10 02:40 PM
03/03/10 02:40 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Quote:
what is the best position for the tubes in the headers? Ive seen them installed a couple of differnt ways.
I prefer the flat of the tube to be parallel with the exit of the collector
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Re: Header evac tubes- how do they compare to vac pumps
[Re: Todd]
#624356
03/03/10 02:42 PM
03/03/10 02:42 PM
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Joined: Jan 2003
Posts: 24,562 Brookeville, Md
Mr.Yuck
Not enough dumb comments...yet
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Not enough dumb comments...yet
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Posts: 24,562
Brookeville, Md
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Quote:
that is the one way ive seen it installed and the other way looks the same but the tube is rotated around 180 degrees so the angled end faces the exit of the pipe. I would like to know what is the best way.
not sure I understand you, the tube is placed at a 45* towards the exhaust. I think as long as you have the tube towards the rear of the car you are ok. Not everybody has room right on top of the header like that.
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Re: Header evac tubes- how do they compare to vac pumps?
[Re: Spode]
#624359
03/03/10 05:59 PM
03/03/10 05:59 PM
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Joined: Jan 2003
Posts: 24,562 Brookeville, Md
Mr.Yuck
Not enough dumb comments...yet
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Not enough dumb comments...yet
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Posts: 24,562
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Quote:
Some tech answers for guys like me who didnt know thing about this subject web page
you're sooo right forgive us stuuupid folks.
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Re: Header evac tubes- how do they compare to vac pumps?
[Re: Mr.Yuck]
#624360
03/04/10 12:31 AM
03/04/10 12:31 AM
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Joined: Dec 2009
Posts: 242 Upland, California
Spode
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Quote:
Quote:
Some tech answers for guys like me who didnt know thing about this subject web page
you're sooo right forgive us stuuupid folks.
anytime
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Re: Header evac tubes- how do they compare to vac pumps?
[Re: emarine01]
#624362
03/11/10 01:18 PM
03/11/10 01:18 PM
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Joined: Sep 2006
Posts: 1,139 West Tennessee
rbstroker
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super stock
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This question will probably sound really dumb, but how much vacuum would a stock PVC setup and the stock breather to air cleaner tube put on the crancase in comparison with an evac setup on the headers?
This is the land of the free
because of the brave
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Re: Header evac tubes- how do they compare to vac pumps
[Re: Todd]
#624366
03/11/10 05:51 PM
03/11/10 05:51 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Quote:
Have you ever syphoned anything with a blow gun and compressed air? What way is it most effective? My guess would be to have the angled cut of the evac tube paralell to the collector. I would turn the tube 180 degrees and leave the 45 degree entrance angle and see what happens.
Did you get yours in?
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