LT1-LT4 Modifications 1993-97 Gen II Small Block V8

vacuum check valve question!!!!!

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Old 08-22-2010, 08:36 PM
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Default vacuum check valve question!!!!!

So yeah when I removed my evap and all my HVAC crap I noticed that I had broke off the the vacuum check valve so after that I just caped off all the hoses and have run it like that ever since. When I looked at it tonight I noticed that 2 of the lines actually came out of the wiring bundle and I think the other was hooked up some where on the evap box thing. My question is do I need the check valve and the hoses hooked back up or is it perfectly fine to run with out it. Not sure if this played a factor in the whole motor vacuum system stuff or not. It seemed like the car ran fine although at times the car idle weird but always leveled it selve out to run just fine....Any info on the following would be great, Thanks again folks!....Link posted for the picture so you all not what I'm talking about: http://shbox.com/1/vac_check_valve.jpg
Old 08-22-2010, 08:44 PM
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The vacuum check valve is part of the HVAC system and prevents any backflow through the line. Any breaks in the line prior to the vacuum check valve will result in a vacuum leak. Don't just rely on the check valve though - cap everything off.

As long as there are no leaks, you don't have anything to worry about.
Old 08-22-2010, 09:04 PM
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Originally Posted by RamAir95TA
The vacuum check valve is part of the HVAC system and prevents any backflow through the line. Any breaks in the line prior to the vacuum check valve will result in a vacuum leak. Don't just rely on the check valve though - cap everything off.

As long as there are no leaks, you don't have anything to worry about.
Ok so it has to do with all the HVAC stuff then. Right on I have it all capped off and electrical tape around the caps as well. Every last bit of the HVAC stuff is gone. Just wasn't for sure if it actually had anything to do with the engine vacuum stuff it's self. Sweet I appreciate it. So I would assume that all my vacuum stuff is good to go since really all I have is the one line coming from the fuel pressure regulator to the intake. Other than that line most has been deleted and capped from the removal of other parts. **** not sure what other components are involved with the vacuum then really????
Old 08-22-2010, 09:11 PM
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In stock trim, there are several components that are driven by vacuum.

-Fuel pressure regulator
-EGR
-Optispark (95+)
-HVAC (vacuum tank)
-EVAP purge
-AIR recall components (without the recall components there are no vacuum lines to the AIR pump)
Old 08-22-2010, 10:44 PM
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Originally Posted by RamAir95TA
In stock trim, there are several components that are driven by vacuum.

-Fuel pressure regulator
-EGR
-Optispark (95+)
-HVAC (vacuum tank)
-EVAP purge
-AIR recall components (without the recall components there are no vacuum lines to the AIR pump)
Ok so then I have to be good.....I have all air pump injection stuff gone, all EGR stuff gone and all the HVAC stuff as well. The only thing left that I need to remove actually is my EVAP canister from the rear driver side and then I guess I can actually remove the solenoid from the intake. Then I should be able to block off the Throttle body and then remove the EVAP line that runs all the way from the engine bay to the rear.....So in all vacuum aspects I should only have the Fule pressure regulator vacuum line left and that's it!!!!! Mines a 94 so my opti is not vented. I just thought there had to be more to it but apparently not. **** for a bit I thought I had a vacuum isse but all must be with my TPS. I need to get that **** dialed in....
Old 08-22-2010, 11:19 PM
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When you delete the EVAP system, assuming you delete the charcoal canister as well, you need to put a filter of some sort on the line that goes to the tank for fuel vapor to vent. You will get a slight fuel smell at the rear however.
Old 08-23-2010, 12:24 AM
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Yeah that's a risk I'm willing to take with the smell I guess. I bought a filter a few days a go to vent it though. More or less would like to clean the engine bay up a little more and hell drop a couple lbs in the process. How bad is the smell of gas anyhow?
Old 08-23-2010, 12:37 AM
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I have not deleted my EVAP system as of yet, but I would imagine the fuel smell would not be too bad with the amount of people who have done the delete.
Old 08-23-2010, 12:45 AM
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my evap "hardline" broke sometime a long time ago, occasionally I'll get a whiff of sweet smelling e85 when i'm working under the hood, but i've never noticed anything with the hood closed, car running or not.
Old 08-23-2010, 04:23 PM
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Cool ,thanks guys! I'll be ripping that **** out one day this week.



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