Re: Runs better with vacuum leak
[Re: wally426ci]
#1981040
01/01/16 01:50 PM
01/01/16 01:50 PM
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Joined: Nov 2006
Posts: 1,074 Manitoba Canada
67autocross
super stock
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super stock
Joined: Nov 2006
Posts: 1,074
Manitoba Canada
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I had a late 70's Chevy 4x4 that ran better with a leak, drove it like that for years. I'm sure someone here will have some ideas on how to fix your car ....but if it runs with the leak and you really just want to drive close the hood and go.
A new iron curtain drawn across the 49th parallel
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Re: Runs better with vacuum leak
[Re: wally426ci]
#1981158
01/01/16 03:54 PM
01/01/16 03:54 PM
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Joined: Dec 2003
Posts: 4,951 northwest USA
NANKET
master
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master
Joined: Dec 2003
Posts: 4,951
northwest USA
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OK so it idles better with a vacuum leak, how about cruising down the road? It may be too lean and damage things. Is you vacuum hose coming off carb base affecting all 8 cylinders, or just the #8 intake runner affecting only one cylinder?
What do you have for a carb, camshaft, compression ratio, leak down numbers, tell us about the whole engine.
Is you power valve bad, cam to big, idle speed too low, fuel pressure too high, ignition system all goofed up? here we go, the snowball is picking up speed.
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Re: Runs better with vacuum leak
[Re: wally426ci]
#1981199
01/01/16 04:45 PM
01/01/16 04:45 PM
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Joined: Aug 2003
Posts: 43,127 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,127
Bend,OR USA
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It sounds like you may have a issue of hot fuel boiling over into the motor when you shut it off, that will make them hard to start You will have to grind on the starter and hold the throttle wide open to get it to start and run if that is the problem. I've had that problem recently with todays crud they call gasoline One way to verify that problem is to remove the air cleaner after driving it far enough to get the motor up to temps. and heat soak the engine compartment and watch for fuel mist coming out of the top of the carb. from the boiling fuel. Have you tried leaning the idle mixture screws down enough to get the motor to sart to die? If not I run my motors as lean as possible on the idle circuits, adjust the screws slowly inwards. closing them, to make it start to slow down on the idle RPM and then add 1/8 to 1/4 out to make it richer richer A leaner motor is way happier than a rich or fat motor will be
Last edited by Cab_Burge; 01/01/16 04:47 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Runs better with vacuum leak
[Re: wally426ci]
#1981292
01/01/16 06:38 PM
01/01/16 06:38 PM
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Joined: Jan 2003
Posts: 15,315 Omaha Ne
TJP
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 15,315
Omaha Ne
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New distributor runs fine but I was checking vacuum for timing at the brake booster. When I pull the cap it smooths out.
I've never noticed that before and trying to figure out the issue. Could the carb be too rich? New plugs helped previous hard start and smoothed it out but I just want to drive this friggin car! If you are running the vacuum advance, AND depending on where it is hooked up ( IE: manifold or ported)_you may have too much timing at idle thereby creating a misfire. The distributor change may have impacted this. Creating a large enough vacuum leak would lower the manifold vacuum there by retarding the timing Other wise I would go for thee mixture adjustment.
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