Runs Rich Bad Idle
Thread Starter
Drifting
Joined: Jun 2005
Posts: 1,523
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From: grand prairie texas
Runs Rich Bad Idle
I am in need of serious help. My 77 runs rich enough to burn your eyes in the garage with the doors open and wont idle below 1000 r.p.m. I have a rebuilt 1978 350 in it bored .030 over with overhauled heads and what they call a r.v. cam in it. I thought it might be the carburator and just got back from spending over $200 dollars on a rebuilt q-jet and that did not help. I disconnected all sourses of vacumn from the carburator and manifold and nothing helped. The choke is wide open with engine up to temp. I have a factory cast intake manifold and squirted wd-40 all around the intake with no differance in idle. If you get above idle speed around 200 r.p.m. and wide open throttle it runs like a scalded ape. My cam specs are cam lift int. .281 valve lift exh .296 lobe ctr int. 107 exh 117 lash hot int hyd exh. hyd sae duration 278 int 288 exh .050 duration 204 int 214 exh. I dont know what all that means . The rebuilder said the car should idle smooth.
Thread Starter
Drifting
Joined: Jun 2005
Posts: 1,523
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From: grand prairie texas
Originally Posted by BigBlockk
How is your initial advance set? Timing could be retarded forcing you to run at high idle speed to keep the engine running.
BigBlockk
Later.....
BigBlockk
Later.....
Thread Starter
Drifting
Joined: Jun 2005
Posts: 1,523
Likes: 1
From: grand prairie texas
Originally Posted by wnmech
I am in need of serious help. My 77 runs rich enough to burn your eyes in the garage with the doors open and wont idle below 1000 r.p.m. I have a rebuilt 1978 350 in it bored .030 over with overhauled heads and what they call a r.v. cam in it. I thought it might be the carburator and just got back from spending over $200 dollars on a rebuilt q-jet and that did not help. I disconnected all sourses of vacumn from the carburator and manifold and nothing helped. The choke is wide open with engine up to temp. I have a factory cast intake manifold and squirted wd-40 all around the intake with no differance in idle. If you get above idle speed around 200 r.p.m. and wide open throttle it runs like a scalded ape. My cam specs are cam lift int. .281 valve lift exh .296 lobe ctr int. 107 exh 117 lash hot int hyd exh. hyd sae duration 278 int 288 exh .050 duration 204 int 214 exh. I dont know what all that means . The rebuilder said the car should idle smooth.
Melting Slicks
Joined: Aug 2005
Posts: 2,606
Likes: 5
Originally Posted by big_G
You will need to check/set the timing before any carb. adjustments can be done.
Not to hijack this thread, but sorta related...I'm having similar problems: Will adjusting the timing correct a "running rich" situation? Can a carb mistakenly be diagnosed as running rich if the timing is off?
Thread Starter
Drifting
Joined: Jun 2005
Posts: 1,523
Likes: 1
From: grand prairie texas
Originally Posted by BigBlockk
How is your initial advance set? Timing could be retarded forcing you to run at high idle speed to keep the engine running.
BigBlockk
Later.....
BigBlockk
Later.....
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Thread Starter
Drifting
Joined: Jun 2005
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From: grand prairie texas
Originally Posted by comp
bad gauge maybe ????
Drifting
Joined: Nov 2001
Posts: 1,469
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From: 68 427 4.11s Roadster
The vacuum can be low until it breaks in, but I doubt that low.
Did vacuum advance work at idle? If not then its bad. If it did then vacuum is higher than the gauge is saying.
I don't think wd-40 will do much for affecting a vacuum leak. Its kind of thin to plug one and isn't going to burn for an indicator there.
Has anyone used this for detecting a vacuum leak?
I would double check the vacuum lines too. Mice like them for some reason and the section that fits on the fittings gets a set that can leak.
Did vacuum advance work at idle? If not then its bad. If it did then vacuum is higher than the gauge is saying.
I don't think wd-40 will do much for affecting a vacuum leak. Its kind of thin to plug one and isn't going to burn for an indicator there.
Has anyone used this for detecting a vacuum leak?
I would double check the vacuum lines too. Mice like them for some reason and the section that fits on the fittings gets a set that can leak.
Thread Starter
Drifting
Joined: Jun 2005
Posts: 1,523
Likes: 1
From: grand prairie texas
Originally Posted by Techno
The vacuum can be low until it breaks in, but I doubt that low.
Did vacuum advance work at idle? If not then its bad. If it did then vacuum is higher than the gauge is saying.
I don't think wd-40 will do much for affecting a vacuum leak. Its kind of thin to plug one and isn't going to burn for an indicator there.
Has anyone used this for detecting a vacuum leak?
I would double check the vacuum lines too. Mice like them for some reason and the section that fits on the fittings gets a set that can leak.
Did vacuum advance work at idle? If not then its bad. If it did then vacuum is higher than the gauge is saying.
I don't think wd-40 will do much for affecting a vacuum leak. Its kind of thin to plug one and isn't going to burn for an indicator there.
Has anyone used this for detecting a vacuum leak?
I would double check the vacuum lines too. Mice like them for some reason and the section that fits on the fittings gets a set that can leak.
Drifting
Joined: Nov 2001
Posts: 1,469
Likes: 6
From: 68 427 4.11s Roadster
I have been blessed with never having to find a vacuum leak other than hoses. With a new engine I kind of doubt this is the problem unless you've warped the heads or something else just as dubious.
Assuming your vacuum is too low start at the simple and work up. Check all vacuum hoses and connections. Then check the carb. These are usually the culprits not intake gaskets and all the other obscene things.
BTW don't just look at the hoses. Take them off and put them on. I got tricked one morn from the line off the wiper vacuum motor which killed wipers and headlights. It LOOKED like it was on but wasn't.
Assuming your vacuum is too low start at the simple and work up. Check all vacuum hoses and connections. Then check the carb. These are usually the culprits not intake gaskets and all the other obscene things.
BTW don't just look at the hoses. Take them off and put them on. I got tricked one morn from the line off the wiper vacuum motor which killed wipers and headlights. It LOOKED like it was on but wasn't.
Instructor
Joined: Mar 2005
Posts: 135
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From: Northern NJ
Go back and check your manifold. Some manifolds have the exhaust gas heat exchanger for warm up. There will be a small opening under the carb on the front end of the intake. It is seperate from your regular intake bore but it needs to be separated from your carb. You would have a steel plate sandwiched by two gaskets? The lower gasket is a material made to withstand the heat of the exhaust gas. Do not use the incorrect gasket or you will be sucking exhaust gas directly into the intake manifold when the gasket fails. This may be the cause of your choking exhaust and low vacuum condition. This link will give you a picture of this configuration.
http://www.carburetion.com/images/Ba...ets/bg581a.jpg
http://www.carburetion.com/images/Ba...ets/bg581a.jpg
Drifting
Joined: May 2005
Posts: 1,909
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From: Lake Arrowhead - Georgia > 72 Base Coupe & 74 BB Roadster
My 72 had the same symptoms....NOTHING helped until I finally discovered a vacuum leak inside the car where the brake rod goes through the PB booster. I replaced the booster and ONLY THEN did adjusting the timing and carb make a difference.
Team Owner
Joined: Sep 2003
Posts: 88,393
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From: eville in
Originally Posted by fotyfobravo
My 72 had the same symptoms....NOTHING helped until I finally discovered a vacuum leak inside the car where the brake rod goes through the PB booster. I replaced the booster and ONLY THEN did adjusting the timing and carb make a difference.