06-02-2009, 09:40 AM | #1 |
BoomerSchooner75
Join Date: May 2009
Location: Mountain Home ID
Posts: 96
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not enough vacuum????
does anyone know of a way for me to get more vacuum to my engine. I have a performance camshaft and it is not gettng enough vacuum so when i idle the truck run bad?
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06-02-2009, 10:20 AM | #2 |
Registered User
Join Date: Apr 2005
Location: Austin, TX
Posts: 1,223
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Re: not enough vacuum????
You don't offer a lot of information.... so how about some basic detailed engine specs, like CID, compression ratio, what heads, what cam, what intake, what carb, etc.
How is your distributor set up? Need initial timing and the total advance and the RPM it is all in by. And are you using vacuum advance? Where is it getting vacuum from and how much timing does it add? Also what do you have you idle speed set too, and have you tweaked the idle mixture screws for max vacuum? And have you checked for vacuum leaks?
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- Greg |
06-02-2009, 10:27 AM | #3 |
BoomerSchooner75
Join Date: May 2009
Location: Mountain Home ID
Posts: 96
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Re: not enough vacuum????
ok well here is what the truck is doing. When i first start driving it and i come to a stop sign or have to stop and idle the truck wants to die but once i get the temp up above 180 it runs fine unless i floor it than it after the engine revs up it kind of hesitates to catch back up. i also have to let it warmup to 165 before i can shift into gear or else it dies when i shift. the mechanic also said that the cam is a little to big for the engine which is a 350 sb. and i am not sure on all of that info i just bought the truck and i have not have the chance to get inside of her to see what she is packing.
Last edited by rlcasey75; 06-02-2009 at 10:27 AM. |
06-02-2009, 10:56 AM | #4 |
Registered User
Join Date: Apr 2005
Location: Austin, TX
Posts: 1,223
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Re: not enough vacuum????
So then you need to start with the basics.
First thing is to check for obvious problems like unused vacumm ports that are not plugged, rotted vacuum lines that are leaking, bad brake booster, intake manifold gasket sealing issues, etc. Fix all of these issues first. Next you need to get the ignition sorted out. For a performance cam, you probably need at least 16-18° of initial timing. And most Chevy V8 like 36-38° for total timing. But you will need to experiment and find what your engine likes best. For this you will need a timing light and accurate tachometer. I would also suggest using full manifold vacuum for the vacuum advance instead of ported. This will add additional timing at idle and help smooth it out. If you don't know how to set all this up, there is a FAQ thread in the engine section, here is a direct link to it - Timing FAQ Once you have the timing sorted out, you can start on tuning the carb. If you do not have a hand-held vacuum guage, I suggest you buy one. You will need it to set the idle mixture, and it will also help with finding the optimum initial timing. My guess is once you get everything tuned properly you will be okay.
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- Greg |
06-02-2009, 11:25 AM | #5 |
BoomerSchooner75
Join Date: May 2009
Location: Mountain Home ID
Posts: 96
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Re: not enough vacuum????
ok thanks for the replies and help i really appriecate it.
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06-02-2009, 06:55 PM | #6 | |
just can't cover up my redneck
Join Date: May 2004
Location: Columbus OH
Posts: 11,414
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Re: not enough vacuum????
There was no mention of transmission either. I am assuming that we're talking automatic by your discription of having ilding problems. If so, this can greatly add to the troubles that you have here. If you don't have the torque converter matched to your cam, it can give you lots of trouble trying to get a reasonable idle....even with all of the other previously mentioned tuning.
If the converter is too "tight", it will be very hard to get it to idle in gear, because of a large drop in RPM. Then if you speed the idle up so that it will stay running in gear, it will be really high in park. There is no way to tune around this. A new higher stall torque convertor is the only fix.
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06-02-2009, 07:38 PM | #7 |
BoomerSchooner75
Join Date: May 2009
Location: Mountain Home ID
Posts: 96
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Re: not enough vacuum????
ok thanks for the info i will look at that too than. it also has th350 turbo tranny.
Last edited by rlcasey75; 06-02-2009 at 07:39 PM. |
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