cant find the vacuum leak?
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Car: 1987 Gta Trans Am
Engine: 383 Stroker
Transmission: t-56
Axle/Gears: 3.47 02 SS rear end
cant find the vacuum leak?
Ive tried everything and cant seem to find it. I had to swap my old intake manifold back on and im only getting about 6 vacuum again. Ive tried starting fluid everywhere with no luck. I adjusted my valve lash and the vacuum dropped since ive put the intake back on. I was getting alot of hesitation and popping on heavy acceleration. Now thats gone since ive adjusted the valves but cant find the vacuum leak. It idles at 1200 rpm and i cant get it below 900 even i back the idle screws all the way in. is there some other way to find a vacuum leak?
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From: Enschede, Netherlands
Car: 82 TA 87 IZ L98 88 IZ LB9 88 IZ L98
Engine: 5.7TBI 5,7TPI 5.0TPI, 5,7TPI
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Axle/Gears: 3.08, 3.27, 3.45, 3.27
Re: cant find the vacuum leak?
go over very nook, cranny and hose with an unlit torch
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Car: 87 IROC Z "ZZ4"
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Re: cant find the vacuum leak?
my leak was the bottom of the intake gasket couldn't find it any other way without removing the manifold. just an idea.
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Car: 1986 Trans Am
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Re: cant find the vacuum leak?
Disconnect all sources of vacuum form the carb and intake. Then try all over again.
Seems to be a decent sized leak. Might check out the brake booster
Seems to be a decent sized leak. Might check out the brake booster
Thread Starter
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Joined: Feb 2010
Posts: 258
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From: in my car
Car: 1987 Gta Trans Am
Engine: 383 Stroker
Transmission: t-56
Axle/Gears: 3.47 02 SS rear end
Re: cant find the vacuum leak?
ive tried everything. i disconnected and plug everythig off from the carb and still the leak. maybe its in the carb? the intake is sealed on there permenantly... lol. i have another question in the engine swap section..
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Car: 1986 Trans Am
Engine: 5.0
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From: Fairview Heights Illinois
Car: 1986 Irocz
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.25:1
Re: cant find the vacuum leak?
You should stop yanking everyone's chain here and take your car to a mechanic ASAP. Seriously.
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Thread Starter
Senior Member
Joined: Feb 2010
Posts: 258
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From: in my car
Car: 1987 Gta Trans Am
Engine: 383 Stroker
Transmission: t-56
Axle/Gears: 3.47 02 SS rear end
Senior Member
Joined: Nov 2009
Posts: 419
Likes: 1
Car: 1986 Trans Am
Engine: 5.0
Transmission: 700r4
Axle/Gears: beats me
Thread Starter
Senior Member
Joined: Feb 2010
Posts: 258
Likes: 0
From: in my car
Car: 1987 Gta Trans Am
Engine: 383 Stroker
Transmission: t-56
Axle/Gears: 3.47 02 SS rear end
Re: cant find the vacuum leak?
thanks for the replys blind driver. i didnt mean any offense to what i said in the other thread. when i re read it, it sounded like i was meaning to be a douchebag
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From: Fairview Heights Illinois
Car: 1986 Irocz
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.25:1
Re: cant find the vacuum leak?
I gave you the best advice you've gotten on here to date.
Every engine problem cannot be blamed on a carburetor or a vacuum leak.
That's a fact.
In numerous threads you've posted that you are experienced with engines, then right after that state something that makes you sound completely clueless. The best thing you could do is to find a good mechanic and hope it's not too late.
Every engine problem cannot be blamed on a carburetor or a vacuum leak.
That's a fact.
In numerous threads you've posted that you are experienced with engines, then right after that state something that makes you sound completely clueless. The best thing you could do is to find a good mechanic and hope it's not too late.
Thread Starter
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Joined: Feb 2010
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From: in my car
Car: 1987 Gta Trans Am
Engine: 383 Stroker
Transmission: t-56
Axle/Gears: 3.47 02 SS rear end
Re: cant find the vacuum leak?
Im a certified mechanic you douchebag, i graduated from wyotech.
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From: Fairview Heights Illinois
Car: 1986 Irocz
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.25:1
Re: cant find the vacuum leak?
Then you should probably get off this forum and go out and fix your car.
You have a Chevy smallblock with a Carter style aluminum AFB, about the simplest carburetor out there, and a simple non-computer controlled distributor. It doesn't get any simpler for a mechanic.
You have posted that you had two bolts holding on a header, then complaining about popping in the exhaust and asking why and what could be wrong with your carburetor besides that it sucks. You say something about your engine oil being milky, and then what? suggesting that it might have needed a valve adjustment, but that didn't help. Then you ask about trading your engine for something else.
"Ive checked the valvetrain and re-adjusted the valve lash."
im getting a pretty steady reading of 15 vacuum."
Was it 15" before you messed with things?
"Needle bounces a bit but that should be normal because im running a pretty large cam and i have roller rockers.
I rebuilt the carb (600 cfm edelbrock) and the car runs great its just the popping at wot. Only thing i know with the carb is a slightly bent fuel float. So the only other things i can think of to replace is a hotter coil or a bigger carb. Any advice would be appreciated."
I rebuilt the carb (600 cfm edelbrock) and the car runs great its just the popping at wot. Only thing i know with the carb is a slightly bent fuel float. So the only other things i can think of to replace is a hotter coil or a bigger carb. Any advice would be appreciated."
So it runs great? Then why all the posts about running problems? Which is it? This is just one example of why I made the statement about not yanking people's chains on here. Did it run good before you messed with it?
I have posted for you before that exhaust leaks will cause popping in the exhaust, but you may have ignored it and called me a douchebag.
Could it be that the exhaust leaks at the cylinder heads were the only problem you had before you pulled the distributor and carburetor and started messing things up?
Yes, exhaust leaks near the heads will cause bad running, rough idle, weak part throttle power, low vacuum, and popping in the exhaust at pretty much any time, but especially so at a steady cruise or on deceleration. Exhaust leaks WILL prevent a carburetor from functioning properly.
From the posts I've seen, it appears that you really don't know what you have as far as parts and specifications, besides being able to identify the carburetor and suggesting that it's crap because you can't figure it out. You keep saying over and over that you need a bigger carb, which suggests that you think its small size is causing your problems. You said the engine stumbles or hesitates when you hit the gas. A mechanic would know that this isn't a sign that the carburetor is too small.
You said you rebuilt the carburetor, but made no mention of the details, or real reason that you had to do so, as in a particular symptom you observed from the carburetor, or the result of exhaust testing with a wideband O2 sensor.
If you don't know how to work with the Carter style carb you have, then you could have easily made your problems worse, for instance by reversing the booster gaskets, or leaving out the check valve for the accelerator pump because it fell out during disassembly, or reinstalling the check valve backwards because you didn't see how it came out.
You have done a ton of complaining:
https://www.thirdgen.org/forums/sear...archid=2626049
but actually post very little relevant information about what you have and/or what you have observed as symptoms. For instance, the milky oil. Was this observed on just the dipstick or did you drain the oil-pan and it was all milky?
Low vacuum - Well, what are the specs on the camshaft? Was this a dirt-track engine installed into a street-car?
Did you pull the timing cover to verify that the camshaft timing was correct? If not then that would be a good time to degree the camshaft and find out the exact specs of it if you don't know for sure.
Are you 100% certain that the distributor isn't installed a tooth off? You said that you reinstalled it and that could explain a lot.
What do the sparkplugs look like? all of them. Post a picture or something.
Does the carburetor fit on the intake manifold properly? The Carter AFB is a squarebore. What intake manifold are you running? and does it have a squarebore plenum?
People have told you to perform a compression test and this was your reply:
"new engine.. high compression."
You're too lazy or don't know how to do a compression check and post the results, but you keep creating posts asking for help.
Are you also too lazy to pull the timing cover and put a degree wheel on your cam to check its specs and phasing?
Too lazy to pull all your sparkplugs?
Too lazy to install your headers properly with ALL of the bolts & gaskets?
Seriously, you can't do this and then claim you're a certified mechanic.
Also, don't try to suggest that all of these problems are because you don't have fuel injection, or that you are some kind of mechanical wiz with fuel injection. From the problems you have posted here with what you have now, you shouldn't even think about swapping to fuel injection.
If anyone ever needed to find someone who really knows what they are doing and ask for help, it's you.
Find a real mechanic and beg for help.
If you really want to get help here, then you need to:
1. Know what you're talking about, or don't keep pretending to.
2. Post up ALL information you can, and specifics about symptoms and test results from troubleshooting.
3. Don't ignore good advice and keep on asking the same things with no attempt of suggested troubleshooting or said results.
Otherwise, your posts are going to be ignored for the most part.
After all, most people here aren't certified mechanics, so why would they try to help you, knowing that you are?
Also, saying that you're a mechanic or that you think a certain carburetor is garbage doesn't help your case at all as they aren't relevant. The fact that you think your engine should make 500 horsepower is also not relevant.
Calling someone who is trying to help you a douchebag is not relevant to fixing your problem, except that it looks immature, tacky, and could discourage others from offering advice to you.
Thread Starter
Senior Member
Joined: Feb 2010
Posts: 258
Likes: 0
From: in my car
Car: 1987 Gta Trans Am
Engine: 383 Stroker
Transmission: t-56
Axle/Gears: 3.47 02 SS rear end
Re: cant find the vacuum leak?
Then you should probably get off this forum and go out and fix your car.
You have a Chevy smallblock with a Carter style aluminum AFB, about the simplest carburetor out there, and a simple non-computer controlled distributor. It doesn't get any simpler for a mechanic.
You have posted that you had two bolts holding on a header, then complaining about popping in the exhaust and asking why and what could be wrong with your carburetor besides that it sucks. You say something about your engine oil being milky, and then what? suggesting that it might have needed a valve adjustment, but that didn't help. Then you ask about trading your engine for something else.
From this a mechanic would assume that you are running a solid or mechanical lifter type camshaft. Are you? Mechanics know that a hydraulic camshaft requires preload, not lash.
You later say that you're only getting 5 or 10" of vacuum, so which is it?
Was it 15" before you messed with things?
Yes a large cam will cause vacuum fluctuation at idle due to misfires and reversion, however just saying "large cam" doesn't provide much helpful information to those who would try to help you. Roller rockers have nothing to do with it.
So it runs great? Then why all the posts about running problems? Which is it? This is just one example of why I made the statement about not yanking people's chains on here. Did it run good before you messed with it?
I have posted for you before that exhaust leaks will cause popping in the exhaust, but you may have ignored it and called me a douchebag.
Could it be that the exhaust leaks at the cylinder heads were the only problem you had before you pulled the distributor and carburetor and started messing things up?
Yes, exhaust leaks near the heads will cause bad running, rough idle, weak part throttle power, low vacuum, and popping in the exhaust at pretty much any time, but especially so at a steady cruise or on deceleration. Exhaust leaks WILL prevent a carburetor from functioning properly.
From the posts I've seen, it appears that you really don't know what you have as far as parts and specifications, besides being able to identify the carburetor and suggesting that it's crap because you can't figure it out. You keep saying over and over that you need a bigger carb, which suggests that you think its small size is causing your problems. You said the engine stumbles or hesitates when you hit the gas. A mechanic would know that this isn't a sign that the carburetor is too small.
You said you rebuilt the carburetor, but made no mention of the details, or real reason that you had to do so, as in a particular symptom you observed from the carburetor, or the result of exhaust testing with a wideband O2 sensor.
If you don't know how to work with the Carter style carb you have, then you could have easily made your problems worse, for instance by reversing the booster gaskets, or leaving out the check valve for the accelerator pump because it fell out during disassembly, or reinstalling the check valve backwards because you didn't see how it came out.
You have done a ton of complaining:
https://www.thirdgen.org/forums/sear...archid=2626049
but actually post very little relevant information about what you have and/or what you have observed as symptoms. For instance, the milky oil. Was this observed on just the dipstick or did you drain the oil-pan and it was all milky?
Low vacuum - Well, what are the specs on the camshaft? Was this a dirt-track engine installed into a street-car?
Did you pull the timing cover to verify that the camshaft timing was correct? If not then that would be a good time to degree the camshaft and find out the exact specs of it if you don't know for sure.
Are you 100% certain that the distributor isn't installed a tooth off? You said that you reinstalled it and that could explain a lot.
What do the sparkplugs look like? all of them. Post a picture or something.
Does the carburetor fit on the intake manifold properly? The Carter AFB is a squarebore. What intake manifold are you running? and does it have a squarebore plenum?
People have told you to perform a compression test and this was your reply:
Seriously?
You're too lazy or don't know how to do a compression check and post the results, but you keep creating posts asking for help.
Are you also too lazy to pull the timing cover and put a degree wheel on your cam to check its specs and phasing?
Too lazy to pull all your sparkplugs?
Too lazy to install your headers properly with ALL of the bolts & gaskets?
Seriously, you can't do this and then claim you're a certified mechanic.
Also, don't try to suggest that all of these problems are because you don't have fuel injection, or that you are some kind of mechanical wiz with fuel injection. From the problems you have posted here with what you have now, you shouldn't even think about swapping to fuel injection.
If anyone ever needed to find someone who really knows what they are doing and ask for help, it's you.
Find a real mechanic and beg for help.
If you really want to get help here, then you need to:
1. Know what you're talking about, or don't keep pretending to.
2. Post up ALL information you can, and specifics about symptoms and test results from troubleshooting.
3. Don't ignore good advice and keep on asking the same things with no attempt of suggested troubleshooting or said results.
Otherwise, your posts are going to be ignored for the most part.
After all, most people here aren't certified mechanics, so why would they try to help you, knowing that you are?
Also, saying that you're a mechanic or that you think a certain carburetor is garbage doesn't help your case at all as they aren't relevant. The fact that you think your engine should make 500 horsepower is also not relevant.
Calling someone who is trying to help you a douchebag is not relevant to fixing your problem, except that it looks immature, tacky, and could discourage others from offering advice to you.
You have a Chevy smallblock with a Carter style aluminum AFB, about the simplest carburetor out there, and a simple non-computer controlled distributor. It doesn't get any simpler for a mechanic.
You have posted that you had two bolts holding on a header, then complaining about popping in the exhaust and asking why and what could be wrong with your carburetor besides that it sucks. You say something about your engine oil being milky, and then what? suggesting that it might have needed a valve adjustment, but that didn't help. Then you ask about trading your engine for something else.
From this a mechanic would assume that you are running a solid or mechanical lifter type camshaft. Are you? Mechanics know that a hydraulic camshaft requires preload, not lash.
You later say that you're only getting 5 or 10" of vacuum, so which is it?
Was it 15" before you messed with things?
Yes a large cam will cause vacuum fluctuation at idle due to misfires and reversion, however just saying "large cam" doesn't provide much helpful information to those who would try to help you. Roller rockers have nothing to do with it.
So it runs great? Then why all the posts about running problems? Which is it? This is just one example of why I made the statement about not yanking people's chains on here. Did it run good before you messed with it?
I have posted for you before that exhaust leaks will cause popping in the exhaust, but you may have ignored it and called me a douchebag.
Could it be that the exhaust leaks at the cylinder heads were the only problem you had before you pulled the distributor and carburetor and started messing things up?
Yes, exhaust leaks near the heads will cause bad running, rough idle, weak part throttle power, low vacuum, and popping in the exhaust at pretty much any time, but especially so at a steady cruise or on deceleration. Exhaust leaks WILL prevent a carburetor from functioning properly.
From the posts I've seen, it appears that you really don't know what you have as far as parts and specifications, besides being able to identify the carburetor and suggesting that it's crap because you can't figure it out. You keep saying over and over that you need a bigger carb, which suggests that you think its small size is causing your problems. You said the engine stumbles or hesitates when you hit the gas. A mechanic would know that this isn't a sign that the carburetor is too small.
You said you rebuilt the carburetor, but made no mention of the details, or real reason that you had to do so, as in a particular symptom you observed from the carburetor, or the result of exhaust testing with a wideband O2 sensor.
If you don't know how to work with the Carter style carb you have, then you could have easily made your problems worse, for instance by reversing the booster gaskets, or leaving out the check valve for the accelerator pump because it fell out during disassembly, or reinstalling the check valve backwards because you didn't see how it came out.
You have done a ton of complaining:
https://www.thirdgen.org/forums/sear...archid=2626049
but actually post very little relevant information about what you have and/or what you have observed as symptoms. For instance, the milky oil. Was this observed on just the dipstick or did you drain the oil-pan and it was all milky?
Low vacuum - Well, what are the specs on the camshaft? Was this a dirt-track engine installed into a street-car?
Did you pull the timing cover to verify that the camshaft timing was correct? If not then that would be a good time to degree the camshaft and find out the exact specs of it if you don't know for sure.
Are you 100% certain that the distributor isn't installed a tooth off? You said that you reinstalled it and that could explain a lot.
What do the sparkplugs look like? all of them. Post a picture or something.
Does the carburetor fit on the intake manifold properly? The Carter AFB is a squarebore. What intake manifold are you running? and does it have a squarebore plenum?
People have told you to perform a compression test and this was your reply:
Seriously?
You're too lazy or don't know how to do a compression check and post the results, but you keep creating posts asking for help.
Are you also too lazy to pull the timing cover and put a degree wheel on your cam to check its specs and phasing?
Too lazy to pull all your sparkplugs?
Too lazy to install your headers properly with ALL of the bolts & gaskets?
Seriously, you can't do this and then claim you're a certified mechanic.
Also, don't try to suggest that all of these problems are because you don't have fuel injection, or that you are some kind of mechanical wiz with fuel injection. From the problems you have posted here with what you have now, you shouldn't even think about swapping to fuel injection.
If anyone ever needed to find someone who really knows what they are doing and ask for help, it's you.
Find a real mechanic and beg for help.
If you really want to get help here, then you need to:
1. Know what you're talking about, or don't keep pretending to.
2. Post up ALL information you can, and specifics about symptoms and test results from troubleshooting.
3. Don't ignore good advice and keep on asking the same things with no attempt of suggested troubleshooting or said results.
Otherwise, your posts are going to be ignored for the most part.
After all, most people here aren't certified mechanics, so why would they try to help you, knowing that you are?
Also, saying that you're a mechanic or that you think a certain carburetor is garbage doesn't help your case at all as they aren't relevant. The fact that you think your engine should make 500 horsepower is also not relevant.
Calling someone who is trying to help you a douchebag is not relevant to fixing your problem, except that it looks immature, tacky, and could discourage others from offering advice to you.
whaa whaaa whaaa. go do your bitching somewhere else.
Member
Joined: Aug 2009
Posts: 332
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From: AZ
Car: 1978 Chevrolet impala
Engine: 350ci 300hp/356tq pace crate
Transmission: 700r4
Axle/Gears: 3.42 Yukon posi
Re: cant find the vacuum leak?
He's not bitching friend. He's made several, several valid points and for some reason is still attempting to help you by providing you with a list of information you need to find in order to diagnose the problem. He was also very civil, which is surprising considering how impolite you've been.
Question for you 305SBC, how can you be sure your dizzy is on the correct tooth? May need to pull the mani again soon, this info will be a life saver.
Question for you 305SBC, how can you be sure your dizzy is on the correct tooth? May need to pull the mani again soon, this info will be a life saver.
Supreme Member
iTrader: (3)
Joined: Nov 2001
Posts: 2,428
Likes: 2
From: Fairview Heights Illinois
Car: 1986 Irocz
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.25:1
Re: cant find the vacuum leak?
He's not bitching friend. He's made several, several valid points and for some reason is still attempting to help you by providing you with a list of information you need to find in order to diagnose the problem. He was also very civil, which is surprising considering how impolite you've been.
Question for you 305SBC, how can you be sure your dizzy is on the correct tooth? May need to pull the mani again soon, this info will be a life saver.
Question for you 305SBC, how can you be sure your dizzy is on the correct tooth? May need to pull the mani again soon, this info will be a life saver.
This all assumes that the cam sprocket is in proper phase with the crankshaft position. If the sprocket is off a tooth, then both rotor phasing and valve timing will be off.
When the cap is so out of phase with the spark it normally makes starting and running very difficult or impossible.
Some people cover up this symptom by running oddball timing figures and/or offsetting the order of the plug wires on the cap.
For example if the distributor is 180* out of phase, then you would offset your plug wires by 180* of rotation around the cap to get it to run.
If the cam is out of phase it normally shows up as odd readings during a compression check (usually low), backfiring, and mechanical sounds if the valves are contacting the pistons.
Member
Joined: Aug 2009
Posts: 332
Likes: 0
From: AZ
Car: 1978 Chevrolet impala
Engine: 350ci 300hp/356tq pace crate
Transmission: 700r4
Axle/Gears: 3.42 Yukon posi
Re: cant find the vacuum leak?
So basically just set it to TDC and make sure your cam and crank dots line up. Gotcha :]
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iTrader: (3)
Joined: Nov 2001
Posts: 2,428
Likes: 2
From: Fairview Heights Illinois
Car: 1986 Irocz
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.25:1
Re: cant find the vacuum leak?
It's always best to make sure the piston is actually at exact TDC to make sure the dampener or timing pointer isn't wrong.
I thought you were asking about the distributor, which would be rotor phasing, a separate issue.
The camshaft does determine rotor position in relation to the crank position, so if the cam is off, then the rotor will be too.
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