help a girl out......easy question :)
Thread Starter
Launching!
Joined: Mar 2002
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From: Houston, Tx
help a girl out......easy question :) how much vacuum is good on our ls1s with the vortec...i have only the 4lb now (the 6-8 was too much and crapped my motor)
i've heard 10 is good....
i also have a sheet metal intake and the heads/cam.
any info would be great1
thanks
trish
i've heard 10 is good....
i also have a sheet metal intake and the heads/cam.
any info would be great1
thanks
trish
TECH Fanatic
Joined: Mar 2002
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Re: help a girl out......easy question :) </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by trishy:
<strong>what's so funny</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">You should be pulling 20" of vacuum minimum, with a stock intake/cam at idle. You specified the intake, but haven't specified the cam, so any guess is just pure crapola, at best.
As far as boost, it should be the same as the kit is rated with the pulley on the car... 4lbs.?
SC-
<small>[ December 20, 2002, 03:09 PM: Message edited by: SS00Blue ]</small>
<strong>what's so funny</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">You should be pulling 20" of vacuum minimum, with a stock intake/cam at idle. You specified the intake, but haven't specified the cam, so any guess is just pure crapola, at best.
As far as boost, it should be the same as the kit is rated with the pulley on the car... 4lbs.?
SC-
<small>[ December 20, 2002, 03:09 PM: Message edited by: SS00Blue ]</small>
Re: help a girl out......easy question :) Sorry Trish I misunderstood what you were asking for. My bad.
6-8 lbs crapped out the motor? I would think it should've been able to handle that. Was it stock compression? What was done to add fuel? FMU? Programming?
Just curious.
6-8 lbs crapped out the motor? I would think it should've been able to handle that. Was it stock compression? What was done to add fuel? FMU? Programming?
Just curious.
Tire Smoking Tranny Blowing Director
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From: Barto PA
Re: help a girl out......easy question :) Hmm I think she talking about boost. I run 7psi but I have #42lb injectors which should be a must on all boosted cars if not higher.
Re: help a girl out......easy question :) "vaccum" is air pressure that is below atmospheric pressure and "boost" is air pressure above atmospheric.. that help?
i do think the whole question is about boost though.. how much air pressure above atmospheric you can push into an engine.. well the more.. the better <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> but much over 8 or so and odds are you are on the thin end of reliability... on a stock ls1 anyways.
i do think the whole question is about boost though.. how much air pressure above atmospheric you can push into an engine.. well the more.. the better <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> but much over 8 or so and odds are you are on the thin end of reliability... on a stock ls1 anyways.
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Re: help a girl out......easy question :) You see I thought she was asking about boost and had mistakingly used the word vacuum. But then I saw the post after mine and figured I was the one confused and she actually meant vacuum like she said not boost.
I was able to run 6PSI of boost all day without any trouble. Not even in the high 80's did I have any problems. However we had someone tune a guys car that was suprcharged and the motor let go from detonation. You really need to make sure you have enough fuel and that the timing is where it should be. Otherwise even 4lbs can cause you problems.
I was able to run 6PSI of boost all day without any trouble. Not even in the high 80's did I have any problems. However we had someone tune a guys car that was suprcharged and the motor let go from detonation. You really need to make sure you have enough fuel and that the timing is where it should be. Otherwise even 4lbs can cause you problems.
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Launching!
Joined: Mar 2002
Posts: 288
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From: Houston, Tx
Re: help a girl out......easy question :) sorry been busy w/the holidays
nope i'm talking about on the left side of the gauge...u know at idle and cruising....no vacuum leaks and good motor is higher vacuum it is pulling...i dunno if it is measured by pounds or what...a guy w/a stang told me he had 10 or so and that was good for his car.
i have the sheet intake, heads, cam, 38 lb injectors, computer tuning, etc etc...
i think i might have a kink in the line..that is what the hubby says....i notice at start up when the engine is cold and when it is really cold outside that the vacuum is really low.....and once driving around it gets 12-15 or so.
so the question i had was what is a good vacuum number to have to ensure no vacuum leaks and a good running motor...
i hope that make sense and thanks for the replies....u guys always help me out
thanks!
trish
nope i'm talking about on the left side of the gauge...u know at idle and cruising....no vacuum leaks and good motor is higher vacuum it is pulling...i dunno if it is measured by pounds or what...a guy w/a stang told me he had 10 or so and that was good for his car.
i have the sheet intake, heads, cam, 38 lb injectors, computer tuning, etc etc...
i think i might have a kink in the line..that is what the hubby says....i notice at start up when the engine is cold and when it is really cold outside that the vacuum is really low.....and once driving around it gets 12-15 or so.
so the question i had was what is a good vacuum number to have to ensure no vacuum leaks and a good running motor...
i hope that make sense and thanks for the replies....u guys always help me out
thanks!
trish
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Joined: Dec 2002
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From: Newark NJ
Re: help a girl out......easy question :) When cranking a motor should have (stock)
2 to 4 inches (motor in good condition)
At a idle a motor should have (stock)
17 to 21 inches of vacuum
A motor with a non stock cam I've usually seen at about 15 - 17 inches of vacuum
Heads and intake will bring it lower so 12-15inches should be okay <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
2 to 4 inches (motor in good condition)
At a idle a motor should have (stock)
17 to 21 inches of vacuum
A motor with a non stock cam I've usually seen at about 15 - 17 inches of vacuum
Heads and intake will bring it lower so 12-15inches should be okay <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
Re: help a girl out......easy question :) which vortec are you running? s-trim? aftercooled? how did it crap out your motor? Only problem would be detonation, and with about 7-8 lbs of boost, that is usualy by to little fuel.
Re: help a girl out......easy question :) now that i read the post again, i have no idea what is good. I have always cosidered vacum, boost when the throtle is shut. Since you say you have a fabricated intake, i have no idea what you should be running vacum wise. At 4 lbs. of boost i wouldnt worry about it.
On The Tree
Joined: Mar 2002
Posts: 117
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From: York, PA
Re: help a girl out......easy question :) Trish,
Vacumn is normally measured by inches of mercury...in/hg...10 inches is WAY TOO LOW!!!
Even for a supercharged engine. Normally asp. engines should run between at least 17 inches to about 20 or 21 inches. Of course a lot has to do with the cam...the bigger the bump stick the less vac. At 10 inches you would have one HELLUVA intake leak or really crapped out valves or a cam designed for a Pro-stocker. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> I would have to guess you might be ok with 15 or more inches of vac. hope this helps!!!
Jason
Vacumn is normally measured by inches of mercury...in/hg...10 inches is WAY TOO LOW!!!
Even for a supercharged engine. Normally asp. engines should run between at least 17 inches to about 20 or 21 inches. Of course a lot has to do with the cam...the bigger the bump stick the less vac. At 10 inches you would have one HELLUVA intake leak or really crapped out valves or a cam designed for a Pro-stocker. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> I would have to guess you might be ok with 15 or more inches of vac. hope this helps!!!
Jason
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Re: help a girl out......easy question :) Trish,
Like I said before, without knowing the cam timing and because you have a sheetmetal intake, ported heads, etc. ANY guess at idle vacuum is pure crapola. No one can possibly know.
My 347, 12.5:1 Ford had a .680/.680, 280/280 @ .050 cam and the thing only pulled 5". I built a 455 for my friend with a reasonably small cam with lots of exhaust timing and it only pulls 10".
It's just not possible to tell without info. I will say that if you are seeing a rise in vacuum of much more than 1 or 2" between start up and full warm, you are likely fighting internal engine wear. The heat is sealing up some leakdown most likely.
Just can't tell from more than 3' away from your car. Sorry.
SC-
Like I said before, without knowing the cam timing and because you have a sheetmetal intake, ported heads, etc. ANY guess at idle vacuum is pure crapola. No one can possibly know.
My 347, 12.5:1 Ford had a .680/.680, 280/280 @ .050 cam and the thing only pulled 5". I built a 455 for my friend with a reasonably small cam with lots of exhaust timing and it only pulls 10".
It's just not possible to tell without info. I will say that if you are seeing a rise in vacuum of much more than 1 or 2" between start up and full warm, you are likely fighting internal engine wear. The heat is sealing up some leakdown most likely.
Just can't tell from more than 3' away from your car. Sorry.
SC-
Thread Starter
Launching!
Joined: Mar 2002
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From: Houston, Tx
Re: help a girl out......easy question :) </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by SS00Blue:
<strong> Trish,
It's just not possible to tell without info. I will say that if you are seeing a rise in vacuum of much more than 1 or 2" between start up and full warm, you are likely fighting internal engine wear. The heat is sealing up some leakdown most likely.
SC- </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">what exactly does that mean...i don't know too much about cars..u saying there is a leak of some kind somewhere u think?
and thanks for the help on this
<strong> Trish,
It's just not possible to tell without info. I will say that if you are seeing a rise in vacuum of much more than 1 or 2" between start up and full warm, you are likely fighting internal engine wear. The heat is sealing up some leakdown most likely.
SC- </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">what exactly does that mean...i don't know too much about cars..u saying there is a leak of some kind somewhere u think?
and thanks for the help on this
TECH Fanatic
Joined: Nov 2001
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From: Centrifugal City
Re: help a girl out......easy question :) They're saying it's hard to be sure unless you compare it to someone else's setup and it's exactly the same as yours.
Why the sheet metal intake?
That alone will make your car hard to compare to other's normal vacuum.
Why the sheet metal intake?
That alone will make your car hard to compare to other's normal vacuum.
On The Tree
Joined: Aug 2002
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From: Crossville, TN
Re: help a girl out......easy question :) Comparing vacuum on a blown car to vacuum on n/a car is useless. At idle even though the s/c isnt turning fast enough to creat boost, its still turning fast enough to move some air into the engine. FYI, my moms Bonneville SSEi with the blower on it reads about -8 at idle -2 to 0 crusing,(left side of the guage) and sees 7 psi of boost max.(right side of the guage) This is the factory roots blower which makes a little more boost down low so I would expect your numbers to be a little higher than these since a centrifugal blower doesnt make as much down low. The left side of the guage on her car only goes down to 10.
Thread Starter
Launching!
Joined: Mar 2002
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From: Houston, Tx
Re: help a girl out......easy question :) maybe i should tell about the gauge....
it says boost in the middle
left side says vac and goes to 30 or something like that and the right side says press and goes to 30 also i think.
i dunno why we got the sheet metal....i was told it would work good w/my blower. my husband is the one who builds it and i never have understood how the car works or what combinations are good or anything about tuning and the cars needs.
thats why i come on here and try and understand it if i can.
<img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
trish
it says boost in the middle
left side says vac and goes to 30 or something like that and the right side says press and goes to 30 also i think.
i dunno why we got the sheet metal....i was told it would work good w/my blower. my husband is the one who builds it and i never have understood how the car works or what combinations are good or anything about tuning and the cars needs.
thats why i come on here and try and understand it if i can.
<img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
trish
Re: help a girl out......easy question :) you should run more vacum than you should boost, vacum varies with rpm's just as boost does, i believe it about doubles with a stock intake, but i have no idea what your intake looks like and what the diameters are internaly. Your vacumm should be fine, bc vacum is just boost when your throttle is shut (your foot is off the pedal). What vortec are you running, if you don't have an intercooler, without proper timing it could have caused detonation. I believe vacum is mainly a consern when you got a turbo.
Re: help a girl out......easy question :) oh and as your foot is off the pedal your vacum should slowely go to zero, once the motor take in all the air that was stored in the intake since you let off the throttle.