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Crankcase Vacuum Pressure
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DRR Trophy
posted
Recently installed a vacuum relief valve on my valve cover, and also recently installed a pan vac raceapk sensor to my racepak dash. At idle the dash reads 0 for vac. Looked at a recorded 1/8 mile run and my vacuum started at 1 on 2-step and going down track ended up on a -4? Can anyone shed some light on what this means for me? This was the only run I recorded so I haven't attempted to adjust the relief valve.

This message has been edited. Last edited by: CTRacing,
 
Posts: 33 | Location: Staging Lanes | Registered: March 30, 2009Reply With QuoteReport This Post
DRR Trophy
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Try adjusting the relief valve all the way for high vacuum and see what happens. Did your engine have a rear main seal for a vacuum pump? I just in stalled a vacuum pump on a new engine and it has 4-5inchs at idle and is adjusted for 12inchs going thru the 1/4 mile. The engine needs to be pretty air tight.
 
Posts: 7 | Location: Maryland | Registered: March 16, 2002Reply With QuoteReport This Post
DRR Trophy
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Something doesn't seem right. I also pull 5-6 at idle with a moroso 3 vane enhanced running at 50%. It's also usually pretty safe to set your vacuum relief at 3000rpm.


Denis LeBlanc
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Posts: 111 | Location: Manchester, NH | Registered: February 03, 2006Reply With QuoteReport This Post
DRR S/Pro
Picture of Curly1
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I am pulling 10 or more at idle and 17 down track. Are you sure the logger is calibrated correctly?
I do not like the relief valve on the valve cover because when it opens it draws air through the motor. As air goes through the motor it will pull a lot of oil with it. I like the return mounted on the pump or line going into pump.
Leaks can be a pain to find, check around distributor shaft, valve cover gaskets, crank seals, intake gaskets, timing cover and even oil pan gaskets.

First thing I would do is remove and block the relief valve and see if it changes anything.


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Posts: 1203 | Location: United States of Texas | Registered: April 02, 2011Reply With QuoteReport This Post
DRR Sportsman
Picture of Slick Vic
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Either the valve is too far open, or you don't have a good sealed engine. Either way, i don't like the relief valve anywhere installed on the engine. This allows it to suck in dirt etc from the outside air. Star makes a nice relief valve made to screw into the moroso or aerospace pumps that puts the valve at the pump, so the only dirt you are getting goes through the pump. Still not good but better than the engine.


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Posts: 103 | Location: Delaware | Registered: June 12, 2008Reply With QuoteReport This Post
DRR Pro
Picture of Mike Beck
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I use the one from Star also. It does have a screen on it.

The terminology used above can be confusing.

I do have my relief valve on my valve cover, but it is on the cover which feeds the pump. Too much vacuum and the pump starts pulling from under the hood and not as much out of that cover.

DO NOT put the valve on the OTHER side of the engine where it WOULD be pulling air through the entire engine!

I pull next to nothing at idle but it quickly rises with RPM. I have never had any issues.
 
Posts: 1703 | Location: South River, NJ | Registered: June 19, 2007Reply With QuoteReport This Post
DRR Trophy
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quote:
Originally posted by Mike Beck:
I use the one from Star also. It does have a screen on it.

The terminology used above can be confusing.

I do have my relief valve on my valve cover, but it is on the cover which feeds the pump. Too much vacuum and the pump starts pulling from under the hood and not as much out of that cover.

DO NOT put the valve on the OTHER side of the engine where it WOULD be pulling air through the entire engine!

I pull next to nothing at idle but it quickly rises with RPM. I have never had any issues.


The hose that runs to my vacuum pump is on the passenger side cover. Are you saying my relieve valve should be on that same side? Or the opposite driver side valve cover?
 
Posts: 33 | Location: Staging Lanes | Registered: March 30, 2009Reply With QuoteReport This Post
DRR Sportsman
Picture of 23taltered
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It sounds like you have a big air leak or a calibration issue. I would disable the vacuum control valve by taping it up or something similar, and install an analog gauge. Start the engine and see what you have. Rev it up and see what you have. If you really have nothing, you either have air leaks or a bad pump.
You can check for air leaks by pressurizing your crankcase to 1-2 psi (I use my leakdown tester to control the amount of air), or you can use a smoke machine. Listen and spray soapy water. If you need more help, give me a call at 209 296-3793


Bill Huntington
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Posts: 129 | Location: Northern Cal | Registered: January 06, 2000Reply With QuoteReport This Post
DRR Trophy
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quote:
Originally posted by 23taltered:
It sounds like you have a big air leak or a calibration issue. I would disable the vacuum control valve by taping it up or something similar, and install an analog gauge. Start the engine and see what you have. Rev it up and see what you have. If you really have nothing, you either have air leaks or a bad pump.
You can check for air leaks by pressurizing your crankcase to 1-2 psi (I use my leakdown tester to control the amount of air), or you can use a smoke machine. Listen and spray soapy water. If you need more help, give me a call at 209 296-3793


Thanks everyone for your insight. If my pump was bad would I still be getting stuff in my puke tank?
 
Posts: 33 | Location: Staging Lanes | Registered: March 30, 2009Reply With QuoteReport This Post
DRR Pro
posted Hide Post
quote:
Originally posted by CTRacing:
quote:
Originally posted by 23taltered:
It sounds like you have a big air leak or a calibration issue. I would disable the vacuum control valve by taping it up or something similar, and install an analog gauge. Start the engine and see what you have. Rev it up and see what you have. If you really have nothing, you either have air leaks or a bad pump.
You can check for air leaks by pressurizing your crankcase to 1-2 psi (I use my leakdown tester to control the amount of air), or you can use a smoke machine. Listen and spray soapy water. If you need more help, give me a call at 209 296-3793


Thanks everyone for your insight. If my pump was bad would I still be getting stuff in my puke tank?


Low vacuum is either caused by a leaking gaskets like valve covers, oil pan, seals etc or it could be the pump or it could be the rings or a combo of all... If your cause is mainly a leak(s) then it is likely that oil would be carried into the puke tank since actual air flow would be high vs a seal motor with high vacuum/low air flow.

Smoking the motor is probably the easiest way to find leaks also.
 
Posts: 1218 | Location: Tewksbury, MA,USA | Registered: November 03, 2000Reply With QuoteReport This Post



DRR Trophy
posted Hide Post
quote:
Originally posted by TOP38:
quote:
Originally posted by CTRacing:
quote:
Originally posted by 23taltered:
It sounds like you have a big air leak or a calibration issue. I would disable the vacuum control valve by taping it up or something similar, and install an analog gauge. Start the engine and see what you have. Rev it up and see what you have. If you really have nothing, you either have air leaks or a bad pump.
You can check for air leaks by pressurizing your crankcase to 1-2 psi (I use my leakdown tester to control the amount of air), or you can use a smoke machine. Listen and spray soapy water. If you need more help, give me a call at 209 296-3793


Thanks everyone for your insight. If my pump was bad would I still be getting stuff in my puke tank?


Low vacuum is either caused by a leaking gaskets like valve covers, oil pan, seals etc or it could be the pump or it could be the rings or a combo of all... If your cause is mainly a leak(s) then it is likely that oil would be carried into the puke tank since actual air flow would be high vs a seal motor with high vacuum/low air flow.

Smoking the motor is probably the easiest way to find leaks also.


Is there a way I can check to see if pump is working properly? Maybe taken off hose to valve cover and seeing if vacuum is there? Or anything else? Pump is few years old set up for about a year when car wasn’t ran. I didn’t do anything to maintenance it so to speak.
 
Posts: 33 | Location: Staging Lanes | Registered: March 30, 2009Reply With QuoteReport This Post
DRR Pro
Picture of Lenny5160
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quote:
Originally posted by CTRacing:
Is there a way I can check to see if pump is working properly? Maybe taken off hose to valve cover and seeing if vacuum is there? Or anything else? Pump is few years old set up for about a year when car wasn’t ran. I didn’t do anything to maintenance it so to speak.


Every week or 2 I take the vac hose off the valve cover and spray brake cleaner into it while the car is idling. You can tap the fitting to your palm and you should be able to feel the suction. For me, there is a big difference before and after the brake cleaner spray.

After cleaning, I'll usually have 5 inches of vac on the gauge at idle. After a pass or two I won't show any at idle, but it will still pull good vacuum during the pass.

I also get a ton of oil in my puke tank, so I'm planning to put some air pressure to it this week to check for leaks.


Tony Leonard
 
Posts: 2419 | Location: Inver Grove Heights, MN | Registered: March 18, 2004Reply With QuoteReport This Post
DRR Pro
Picture of Mike Beck
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If you have oil in your puke tank, the pump is probably working.

There are a LOT of places for vacuum to leak.

Some were mentioned, distributor mounting gasket, distributor slip collar if you use one, the actual valve cover bolts, fuel pump block off plate, etc....

A smoke machine will find ALL OF THEM!

I am lucky to have a friend that has one I can borrow when I need it. Smile
 
Posts: 1703 | Location: South River, NJ | Registered: June 19, 2007Reply With QuoteReport This Post
DRR Pro
posted Hide Post
quote:
Originally posted by Lenny5160:
quote:
Originally posted by CTRacing:
Is there a way I can check to see if pump is working properly? Maybe taken off hose to valve cover and seeing if vacuum is there? Or anything else? Pump is few years old set up for about a year when car wasn’t ran. I didn’t do anything to maintenance it so to speak.


Every week or 2 I take the vac hose off the valve cover and spray brake cleaner into it while the car is idling. You can tap the fitting to your palm and you should be able to feel the suction. For me, there is a big difference before and after the brake cleaner spray.

After cleaning, I'll usually have 5 inches of vac on the gauge at idle. After a pass or two I won't show any at idle, but it will still pull good vacuum during the pass.

I also get a ton of oil in my puke tank, so I'm planning to put some air pressure to it this week to check for leaks.


I will add this, cleaning the vac pump with brake clean is only needed if your getting water/condensation out of the crank case. When I ran alky I needed to do this but not on gas. Sometimes on cold mornings at startup the vac was low or 0 but once I got a little heat in the deal it was normal so the cold oil can hold the vanes in at low rpm until it warms up. Also pump speed has a much larger vac impact at idle vs WOT. I went from the 2.5" crank pulley to a 4" and it stabilized the idle vac big time.
 
Posts: 1218 | Location: Tewksbury, MA,USA | Registered: November 03, 2000Reply With QuoteReport This Post
DRR Pro
Picture of Mike Beck
posted Hide Post
quote:
Originally posted by CTRacing:
quote:
Originally posted by Mike Beck:
I use the one from Star also. It does have a screen on it.

The terminology used above can be confusing.

I do have my relief valve on my valve cover, but it is on the cover which feeds the pump. Too much vacuum and the pump starts pulling from under the hood and not as much out of that cover.

DO NOT put the valve on the OTHER side of the engine where it WOULD be pulling air through the entire engine!

I pull next to nothing at idle but it quickly rises with RPM. I have never had any issues.


The hose that runs to my vacuum pump is on the passenger side cover. Are you saying my relieve valve should be on that same side? Or the opposite driver side valve cover?


Put that relief valve on the valve cover leading to the pump. Don't use the other side. That would allow air to be drawn through that valve cover, through your entire engine (while carrying oil) and out of the other cover into your pump.

Look at the hose coming off my drivers side valve cover. The Star relief valve is right there, it turns upside down on it's own all the time, but you should see it hanging there.

 
Posts: 1703 | Location: South River, NJ | Registered: June 19, 2007Reply With QuoteReport This Post
DRR Pro
Picture of Lenny5160
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I put a little air into the vac pump fitting yesterday, and I could immediately hear a leak from the distributor base.

What's the best play here? Ultra Black on both sides of the gasket and under the slip collar?


Tony Leonard
 
Posts: 2419 | Location: Inver Grove Heights, MN | Registered: March 18, 2004Reply With QuoteReport This Post
DRR Sportsman
Picture of 23taltered
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CTRacing, you can unhook the pump from the valve cover and check vacuum at the hose. Either put a gauge on the hose, or just put your thumb over the hose end and rev the motor. you'll be able to tell if it's working.
Lenny, Make sure you get silicone in the slot of th slip collar, thats where the air usually comes through


Bill Huntington
GZMOTORSPORTS.com

gzmotorsports.com/video/PRI2010.wmv
 
Posts: 129 | Location: Northern Cal | Registered: January 06, 2000Reply With QuoteReport This Post
DRR Pro
Picture of Lenny5160
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quote:
Originally posted by 23taltered:
Lenny, Make sure you get silicone in the slot of th slip collar, thats where the air usually comes through.


Thank you, Bill!


Tony Leonard
 
Posts: 2419 | Location: Inver Grove Heights, MN | Registered: March 18, 2004Reply With QuoteReport This Post
DRR Pro
Picture of Mike Beck
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I have a normal distributor mounting gasket under my slip collar plus put RTV all around the slip collar and distributor shaft. I can still turn it if I need to.

Since it is only a cam sync which never has to be turned once it is set, I could RTV the whole mess, but it doesn't leak so I just leave it alone.
 
Posts: 1703 | Location: South River, NJ | Registered: June 19, 2007Reply With QuoteReport This Post
DRR Sportsman
Picture of TD3550
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Had the same issue with the slip leaking. Found a rubber type band and slipped it around the outside, put the collar on, tighten away, no leaks
I have seen other guys use an o ring under the slip and sealed as well.
 
Posts: 385 | Location: Under a Truck | Registered: August 23, 2013Reply With QuoteReport This Post



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