Topic: 75 vacuum problems
in Forum: C3 Electrical
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Okay I actually have 2 problems but it deals with vacuum. My car won't hold an idle when cold and it runs rough after it warms up. it only does this under 1200 rpms. On the street running it's fine. Can't find a vacuum leak anywhere but carb seems to be drawing alot of air and it seems to be running rich. When I close off the top of the arb with my hands it smooths out and runs at a higher rpm and smooths out. But again i can not find any leaks. Could it be the carb leaking internal?? Next problem is when i shut off the car my headlights come up about 2 inches then close back down. Any suggestions???
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Duncanville, TX - USA
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
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#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
You may well have a warped carb base, or even a burned base gasket. You may also have a brake booster leak...those are a bit hard to find! Try blocking the vac. going to the booster, to see if the engine idle changes.
A large enough vac. leak would also cause the headlight wink, as would a marginal check-valve. The check-valve is a small metal can-looking item in the vac. line coming from the intake. It has one nipple on the engine side, and two on the other side. If it leaks, or fails, the headlight will wink, or even raise all the way up. On the '68-72 cars, when the valve fails, the wiper door will raise up.
It sounds like finding and correcting the vac. leak will solve both issues. You can eliminate any external vac. leaks by pinching(or other-wise blocking) all of the vac. hoses coming from the intake/carb. IF none of them smooths out the idle, then you will probably find a carb gasket burned/blown, or a warped base.
A large enough vac. leak would also cause the headlight wink, as would a marginal check-valve. The check-valve is a small metal can-looking item in the vac. line coming from the intake. It has one nipple on the engine side, and two on the other side. If it leaks, or fails, the headlight will wink, or even raise all the way up. On the '68-72 cars, when the valve fails, the wiper door will raise up.
It sounds like finding and correcting the vac. leak will solve both issues. You can eliminate any external vac. leaks by pinching(or other-wise blocking) all of the vac. hoses coming from the intake/carb. IF none of them smooths out the idle, then you will probably find a carb gasket burned/blown, or a warped base.

Joel Adams
C3VR Lifetime Member #56
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Moderator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas



Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
in Forum: C3 Electrical
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