Moparts

Header evac tubes- how do they compare to vac pumps?

Posted By: 72demon416

Header evac tubes- how do they compare to vac pumps? - 02/25/10 11:54 PM

I know that the vacuum pumps are capable of producing more vacuum- but how much more is really necessary or beneficial? Do the header evac tubes even provide enough vacuum to see any benefit or HP gain?
Posted By: tjmarcus1

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 01:17 AM

the evac kits have to be installed correctly in order to work!!!!!!. i'm amazed at how many i see that are not right. they don't work well with exhaust pipes and mufflers. they usually will only pull 3" to 5" vac. lastly i have gained .05 in the 1/8mi.
Posted By: Rodney

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 01:39 AM

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.
Posted By: 72demon416

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 02:32 AM

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.
Posted By: tjmarcus1

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 02:51 AM

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.
Posted By: 72demon416

Re: Header evac tubes- how do they compare to vac pumps - 02/26/10 03:25 AM

Did you notice any mph difference?
Posted By: MR_P_BODY

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 04:23 AM

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
Posted By: 72demon416

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 04:38 AM

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
Posted By: BobR

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 01:42 PM

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.
Posted By: Crizila

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 02:10 PM

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
Posted By: BobR

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 02:37 PM

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.
Posted By: 68LAR

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 02:41 PM

Quote:

know that the vacuum pumps are capable of producing more vacuum- but how much more is really necessary or beneficial? Do the header evac tubes even provide enough vacuum to see any benefit or HP gain?


Here's my worth.
I run an evac tube system. It's been on for well over ten years. I also have a full exhaust system that runs all the way to the back bumper. Through trial and error, I found out that you can not use a "mouse trap" type muffler with a tube type evac system. These mufflers create too much back pressure. You need a "straight thru" type muffler. I use Dynamax but any "straight thru" muffler should work. As far as horsepower gains...I don't know of any gains in this area. I do know that engine oil leaks have stopped. Maybe it's a coincidence, but I have also noticed that my oil stays cleaner longer.
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
Posted By: BobR

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 02:46 PM

"With that, a vacuum pump will use up some horsepower. A tube type evac system doesn't."

I've seen 30+ HP gains with a properly engineered vacuum pump.
Posted By: Rodney

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 02:59 PM

Quote:

Quote:


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
Posted By: Crizila

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 05:37 PM

Not my thread, but trust me, I'm taking notes.
Posted By: Tig

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 06:45 PM

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
Posted By: Barnstorm

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 07:01 PM

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.

Attached picture 5831695-mopar_resize.jpg
Posted By: 68LAR

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 09:02 PM


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,
Posted By: BobR

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 09:07 PM

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.
Posted By: 68LAR

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 09:17 PM

Quote:

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.



Thanks Bob
Posted By: topside

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 09:23 PM

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".
Posted By: emarine01

Re: Header evac tubes- how do they compare to vac pumps? - 02/26/10 11:14 PM

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
Posted By: 72demon416

Re: Header evac tubes- how do they compare to vac pumps - 02/26/10 11:23 PM

Topside- what is this electric GM pump off of? Any pictures of it?
Posted By: WILD BILL

Re: Header evac tubes- how do they compare to vac pumps - 02/26/10 11:57 PM

Quote:

Topside- what is this electric GM pump off of? Any pictures of it?





Posted By: topside

Re: Header evac tubes- how do they compare to vac pumps - 02/27/10 12:09 AM

'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.
Posted By: MR_P_BODY

Re: Header evac tubes- how do they compare to vac pumps? - 02/27/10 12:09 AM

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
Posted By: Barnstorm

Re: Header evac tubes- how do they compare to vac pumps? - 02/27/10 01:02 AM

I know some SS/AH guys are pulling vac thru the fuel pump plate. Good "quiet" part of the motor. No valve cover hoses.
Posted By: MR_P_BODY

Re: Header evac tubes- how do they compare to vac pumps? - 02/27/10 01:12 AM

Quote:

I know some SS/AH guys are pulling vac thru the fuel pump plate. Good "quiet" part of the motor. No valve cover hoses.



That is a good place to pick up from but you need to
put a BIG hose on it if its a single hose coming off
that point, you have 2 hoses coming off the V/C, you
need to move a fair amount of air
EDIT
it would take a 1 1/8" to give you the same sq in of
area as the 2-3/4 hoses... so your looking at a
tube of maybe 1 1/4" to weld to the cover and I would
put a baffle on the inside of the plate
Posted By: tjmarcus1

Re: Header evac tubes- how do they compare to vac pumps? - 02/27/10 01:59 AM

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?
Posted By: 602heavy

Re: Header evac tubes- how do they compare to vac pumps? - 02/27/10 02:11 AM

I've yet to get the motor running to see if the ex evacs are going to work (fire up tommorow) , i'm using the Moroso ones with the 'bird beak' cut out of the tube , i thought this was 'an aid' to create more vac across the evac tube , i also heard a few others mention this , i was trying to get my head around how this 'bird beak' would help , turns out it is just a refference point when welding the evac tubes into the collectors , the instruction shows it to be flush with the outside wall thickness of the exhaust pipe to aid in correct protrusion of evac pipe into exhaust.
Posted By: 72demon416

Re: Header evac tubes- how do they compare to vac pumps? - 02/27/10 02:16 AM



didn't i say that?



Yes you did, thank you for your input!
Actually- thanks to all contributors!
Posted By: chryco

Re: Header evac tubes- how do they compare to vac pumps - 02/27/10 02:18 AM

Quote:

'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.






Attached picture 5832513-IMG_5771.jpg
Posted By: tjmarcus1

Re: Header evac tubes- how do they compare to vac pumps - 02/27/10 03:46 AM

i had one customer that wanted to run evacs on a street truck. i recommended if he were to try it he should put the valves downstream past the mufflers and run longer hoses. but, i stick to my guns and say they don't work too well with full exhaust. what we have to remember is this: they pull 3 to 5" of vac EACH. so that is more volume than you might think
Posted By: 69CHARGERMD

Re: Header evac tubes- how do they compare to vac pumps - 02/27/10 12:29 PM

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,,,

Posted By: mopar dave

Re: Header evac tubes- how do they compare to vac pumps - 02/27/10 12:48 PM

i tried one of those electric vac. pumps last year. did'nt pull enough vac. for me and pulls alot of amps. i tried it with and without it on the chassis dyno and lost a few hp with it on. these pumps came on s10's and corvettes that i know of. jegs sells this very same pump for $250, i'll sell mine for $75, used one season.
mine pulled 3.5" vac.
Posted By: Rodney

Re: Header evac tubes- how do they compare to vac pumps - 02/27/10 03:19 PM

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
Posted By: tboomer

Re: Header evac tubes- how do they compare to vac pumps - 02/27/10 03:27 PM

Doc...I made my own..I used 5/8" heater hose..MrPeabody sent me the check valves...Maybe he had a part#..I used a pair od Moroso valve covers from Summit that already had baffles in them...Also make sure that the pipe nipples are welded in the right direction...I put mine in backwards! Lonemopar noticed that and re did them for me!!
Posted By: Mr.Yuck

Re: Header evac tubes- how do they compare to vac pumps? - 03/03/10 05:26 PM

Dumb question maybe, but what if one were to either run cut-outs or space the exhaust back from the collector? I have seen guys that will run full exhaust then unbolt at the collectore (like un-capping) then use a nut to space back the pipes. This would seem to help reduce the back pressure problem.
Posted By: Todd

Re: Header evac tubes- how do they compare to vac pumps - 03/03/10 05:58 PM

what is the best position for the tubes in the headers? Ive seen them installed a couple of differnt ways.
Posted By: Mr.Yuck

Re: Header evac tubes- how do they compare to vac pumps - 03/03/10 06:09 PM

I think it's in the instructions...I've always seen then welded into the collector either on top or on the side depending on clearance.
Posted By: Todd

Re: Header evac tubes- how do they compare to vac pumps - 03/03/10 06:12 PM

I was wondering about the angle of the tube.90 degrees and down in the pipe or flush with the pipe?
Posted By: Mr.Yuck

Re: Header evac tubes- how do they compare to vac pumps - 03/03/10 06:25 PM

Quote:

I was wondering about the angle of the tube.90 degrees and down in the pipe or flush with the pipe?



click the link.

http://static.summitracing.com/global/images/instructions/mor-25900.pdf
Posted By: Todd

Re: Header evac tubes- how do they compare to vac pumps - 03/03/10 06:33 PM

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.
Posted By: MR_P_BODY

Re: Header evac tubes- how do they compare to vac pumps - 03/03/10 06:40 PM

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
Posted By: Mr.Yuck

Re: Header evac tubes- how do they compare to vac pumps - 03/03/10 06:42 PM

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.
Posted By: Todd

Re: Header evac tubes- how do they compare to vac pumps - 03/03/10 06:58 PM

I think thats the way im going to install them. Makes much more sense than the angle paralell to the pipe and not the collector.
Posted By: Spode

Re: Header evac tubes- how do they compare to vac pumps? - 03/03/10 08:37 PM

Some tech answers for guys like me who didnt know thing about this subject
web page
Posted By: Mr.Yuck

Re: Header evac tubes- how do they compare to vac pumps? - 03/03/10 09:59 PM

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.
Posted By: Spode

Re: Header evac tubes- how do they compare to vac pumps? - 03/04/10 04:31 AM

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
Posted By: emarine01

Re: Header evac tubes- how do they compare to vac pumps? - 03/04/10 03:31 PM

Last winter we messed with our moroso header ev system because we had a problem with the check valves rusting and gettin stuck, I cut the weld holding the tube in the collector < open headers> and played with moving the tube around while running the engine @ 2500 rpm to find the spot with max vacuum, I also booted the check valves and found some more vac with out them, With the morosso system installed as per their instructions we made around 2 to 2.5 inches, I posted last year about anyone not running the check valves cause I was not sure if this was gona be a problem and for the most part had not found anyone blowing up on a back fire. Raff posted a pic of a curved e vac tube that was square with the collector tube so I tried it out and found some more vac that way, I also found that the breather cap tube was too close to the baffle in the valve cover and found some more there, So by the end of messin around we more than doubled the vac @ 2500 rpm, I have seen as much as 5.5 inches and have not blown up yet. As far as power goes I cant tell any difference but no more oil leaks
Posted By: rbstroker

Re: Header evac tubes- how do they compare to vac pumps? - 03/11/10 05:18 PM

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?
Posted By: 68LAR

Re: Header evac tubes- how do they compare to vac pumps? - 03/11/10 06:27 PM

Quote:

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?


It depends on the cam being used. But at full throttle, there should be >3" hg.
Posted By: Crizila

Re: Header evac tubes- how do they compare to vac pumps - 03/11/10 08:05 PM

Quote:

I think thats the way im going to install them. Makes much more sense than the angle paralell to the pipe and not the collector.

This is what I am trying right now. 45 degree entrance about 1/2" in. End is parallel to the pipe and 1/2 of it is capped and the trailing 1/2 of the pipe is cut flush with the pipe.

Attached picture 5858643-evacpipe2.jpg
Posted By: Todd

Re: Header evac tubes- how do they compare to vac pumps - 03/11/10 09:45 PM

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.
Posted By: MR_P_BODY

Re: Header evac tubes- how do they compare to vac pumps - 03/11/10 09:51 PM

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?
Posted By: Todd

Re: Header evac tubes- how do they compare to vac pumps - 03/11/10 10:03 PM

Not Yet. But im definatly going to take a picture and post it.
© 2024 Moparts Forums