RPM problem
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RPM problem
Got a tough one here
My 74 idles at 800 curbed but when I am driving no-matter what gear I am in if I take my foot off the gas my RPM sticks at 1500 until I come to a complete stop and then I takes approx 10-15 seconds to drop back to 800
In my driveway with the hood up and manually working throttle no problem.
Any advice welcome
Forgot to mention 700cfm Holley DP 4 speed
My 74 idles at 800 curbed but when I am driving no-matter what gear I am in if I take my foot off the gas my RPM sticks at 1500 until I come to a complete stop and then I takes approx 10-15 seconds to drop back to 800
In my driveway with the hood up and manually working throttle no problem.
Any advice welcome
Forgot to mention 700cfm Holley DP 4 speed
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When I manually rev the engine the rpm drop right back when I release the linkage.
When I am driving it hangs up
The carb is a couple of years old springs etc the same
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Burning Brakes
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From: Huntingburg Indiana
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If it is a bad gasket and I spray the propane around the base of the carb the engine rpm should increase
Le Mans Master
Joined: Dec 2007
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From: McHenry Illinois
Not likely but easy to check, no telling what bubba might have done to some of these cars.
Melting Slicks
Joined: Oct 2001
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From: Halifax, Nova Scotia, Canada
Is your vacuum advance connected to the "ported" vacuum ? Or is it connected to full vacuum at idle ?
If connected to ported (no vacuum at idle), this sometimes causes some weird idle issues while driving.
You might also want to check the mechanical advance weights/springs in the dist. If they are sticky, they get "advanced" when driving and they slowly return keeping the timing advanced until they return.
(Advanced timing = fast idle)
If connected to ported (no vacuum at idle), this sometimes causes some weird idle issues while driving.
You might also want to check the mechanical advance weights/springs in the dist. If they are sticky, they get "advanced" when driving and they slowly return keeping the timing advanced until they return.
(Advanced timing = fast idle)
Le Mans Master
Joined: Oct 2006
Posts: 6,842
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From: Palmdale CA
I can't right now but the setup has been the same for years and just started acting crazy the other day
When I manually rev the engine the rpm drop right back when I release the linkage.
When I am driving it hangs up
The carb is a couple of years old springs etc the same
When I manually rev the engine the rpm drop right back when I release the linkage.
When I am driving it hangs up
The carb is a couple of years old springs etc the same
And add the fact, that you're running a Holley DP and if you're running the stock cable, that is a problem, as the Holley's linkages puts the cable farther back, forcing the already too-long cable into a tortuous bend (or bends...), that's less than optimal and causes a lot of internal friction inside the cable jacket.
Stock
Holley Carb
My custom cable set up. It is actually a little bit too short. I could've lengthened it a 1/2" and it would've been perfect, but it works well and never hangs up
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I'd say it was the throttle cable sticking. The fact that you can manually rev the engine at the carb and it's easily dropping back, versus going through the cable is the difference that points to the cable, IMHO.
And add the fact, that you're running a Holley DP and if you're running the stock cable, that is a problem, as the Holley's linkages puts the cable farther back, forcing the already too-long cable into a tortuous bend (or bends...), that's less than optimal and causes a lot of internal friction inside the cable jacket.
Stock
Holley Carb
My custom cable set up. It is actually a little bit too short. I could've lengthened it a 1/2" and it would've been perfect, but it works well and never hangs up
And add the fact, that you're running a Holley DP and if you're running the stock cable, that is a problem, as the Holley's linkages puts the cable farther back, forcing the already too-long cable into a tortuous bend (or bends...), that's less than optimal and causes a lot of internal friction inside the cable jacket.
Stock
Holley Carb
My custom cable set up. It is actually a little bit too short. I could've lengthened it a 1/2" and it would've been perfect, but it works well and never hangs up
Why do u have two springs on your throttle?
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Is your vacuum advance connected to the "ported" vacuum ? Or is it connected to full vacuum at idle ?
If connected to ported (no vacuum at idle), this sometimes causes some weird idle issues while driving.
You might also want to check the mechanical advance weights/springs in the dist. If they are sticky, they get "advanced" when driving and they slowly return keeping the timing advanced until they return.
(Advanced timing = fast idle)
If connected to ported (no vacuum at idle), this sometimes causes some weird idle issues while driving.
You might also want to check the mechanical advance weights/springs in the dist. If they are sticky, they get "advanced" when driving and they slowly return keeping the timing advanced until they return.
(Advanced timing = fast idle)
I checked out the springs in dist and one looked a little stretched out so I replaced both of them.
Vet still having idle sticking problems.
I checked everything and still no luck.
I will be installing a heavier throtle spring tomorrow and maybe that will help.
Last edited by SCHOONS; Jun 3, 2014 at 06:36 PM.
