Whoa Nelly!! Carb linkage stuck?

khansmith · #1 (**permalink**) 10-22-2007, 04:41 AM

Hey Guys:
I have ran my engine about 50 times without issue. My dad finally flies into town and I get ready to start my beast for him (a 428 FE). Plus, he is a chevy guy and I want him to see what a Ford is all about! Anyway, I start the car and as soon as I get ignition the engine shoots up to about 4,000 RPM! I check the throttle linkage and it is returning just fine. I start it again and it revs right up! I ususally pump the throttle a couple of times before starting and I use a manual choke. I had the choke both on and off.

What do you think happened? I have a Holly 750 CFM single carb set up.

I know squat about carbs (or EFI for that matter). Something tells me I will start to learn about this important system on my engine..

convincor · #2 (**permalink**) 10-22-2007, 05:47 AM

Disconnect the linkage at the carb and see which has resistance. Linkage or carb. Take a look at the throttle plates for interference with the intake or gasket. Got a good return spring on it??

Bobcat · #3 (**permalink**) 10-22-2007, 07:52 AM

I had something similar to that happen on my 427 Galaxie ( single Holley carb ) and it was the throttle linkage hitting the rubber hose from the rear crankcase vent on the manifold . Twisted the hose slightly and the problem went away . I second the other suggestions . I had to work the linkage slowely to find the problem .

JCoop · #4 (**permalink**) 10-22-2007, 08:02 AM

After you solve the problem ( I also think it may be sticking throttle linkage), may I suggest also installing a rev limiter if you don't have one already. A cheap preventative to a possibly expensive outcome.

Rick Parker · #5 (**permalink**) 10-22-2007, 08:13 AM

Check the carpet near the throttle pedal.

ROUSHAC · #6 (**permalink**) 10-22-2007, 07:30 PM

Also check for frays in the throttle cable down by the pedal where it enters the cable tube. That could cause the throttle to not return to idle.

Good luck!

khansmith · #7 (**permalink**) 10-23-2007, 12:21 PM

Quote:

Originally Posted by JCoop

After you solve the problem ( I also think it may be sticking throttle linkage), may I suggest also installing a rev limiter if you don't have one already. A cheap preventative to a possibly expensive outcome.

Thank you for the advice. I am running an MSD box with a rev limiter. Best insurance!

khansmith · #8 (**permalink**) 10-23-2007, 12:33 PM

Quote:

Originally Posted by ROUSHAC

Also check for frays in the throttle cable down by the pedal where it enters the cable tube. That could cause the throttle to not return to idle.

Good luck!

This is the weird part. The throttle cable and linkage is returning back to position??? I can move the whole assembly back and forth but nothing happens. It still just reved like crazy.

khansmith · #9 (**permalink**) 10-23-2007, 12:35 PM

Quote:

Originally Posted by Rick Parker

Check the carpet near the throttle pedal.

Great suggestion as I have had that happen before! I forgot to add that I don't have carpet and that the throttle is moving free and that the linkage that the cable connects to is also moving freely as well.

khansmith · #10 (**permalink**) 10-23-2007, 12:39 PM

Quote:

Originally Posted by convincor

Disconnect the linkage at the carb and see which has resistance. Linkage or carb. Take a look at the throttle plates for interference with the intake or gasket. Got a good return spring on it??

I do have a return spring on the throttle linkage. No hose clearance issues. The throttle linkage itself is moving fine and so is the cable. What else could be sticking?

CHANMADD · #11 (**permalink**) 10-23-2007, 12:39 PM

I have had the secondaries stick on me before. Check that they close ..

khansmith · #12 (**permalink**) 10-23-2007, 01:14 PM

Quote:

Originally Posted by CHANMADD

I have had the secondaries stick on me before. Check that they close ..

I haven't check this yet and I bet you are right..... Will check tonight when I get home.

khansmith · #13 (**permalink**) 10-24-2007, 07:17 AM

So I checked the secondaries and they are closed. Are there any other items on the Carb that control idol?

RENEW1 · #14 (**permalink**) 10-24-2007, 08:11 AM

Holly carbs can fail in many ways. Over the years I have had many of them.A high float level along with throttle plates open enough to handle the xtra fuel can result in high RPM. A leaking power valve can also result in high RPM. These conditions can only happen if you have set the idle speed fairly high when the engine was set up. generally these failures result in flooding and low RPM. Sometimes if the carb is set very rich at idle, a vacuum leak anywhere below the carb will add enough air to the fuel to cause high RPM.

LMH · #15 (**permalink**) 10-24-2007, 08:15 AM

Hey Khan
I was wondering if it wasn't some timing issue with the MSD control. Maybe the advance went wild, although I think 4000 revs would be TOO high for an advance problem.
Larry

susan parham · #16 (**permalink**) 10-24-2007, 09:23 AM

Khan-
Call the shop.
Susan

khansmith · #17 (**permalink**) 10-25-2007, 07:25 AM

Susan from Southern Automotive was kind enough to set me up with a tech I talked to their tech and they asked me to see if I could see two rubber nipples on the carb. I only found one. Anyway, they think it is a vacuum issue. Here is the list of possible causes that I have consolidated here (from this board, other folks, etc):

1.) Throttle plates interference with the intake or gasket

2.) Review the linkage movement slowly to ensure proper travel

3.) Secondaries are stuck open

4.) A high float level along with throttle plates open enough to handle the xtra fuel can result in high RPM

5.) A leaking power valve can also result in high RPM

6.) A vacuum leak anywhere below the carb will add enough air to the fuel to cause high RPM

7.) Timing issue with the MSD control, advance went wild

8.) Missing rubber nipples on Carb causing vacuum issues

9.) Fast idle cam on the carb: It is part of the choke and kicks in when the choke is set. Look and ensure that idle stop is resting against the idle screw.

10.) A needle valve not seating fully causing the float bowl to overflow. You can take a hard rubber hammer and tap both float bowls. Sometimes this will free the stuck needle valve.

khansmith · #18 (**permalink**) 01-14-2008, 11:24 AM

Wanted to give an update but waited for servers to come up. So the problem was very simple....My throttle cable jacket pulled out of its retainer....thus reving engine. All works great now.

MCOULTER · #19 (**permalink**) 01-14-2008, 01:51 PM

Great job keeping this thread current. I had the same problem (strangely occured only when shifting from 3rd - 4th) it REALLY gets your attention. Do you happen to have a picture of the cable jacket? I have a Superformance and am wondering how similar their design is. - thanks.

Quote:

Originally Posted by khansmith

Wanted to give an update but waited for servers to come up. So the problem was very simple....My throttle cable jacket pulled out of its retainer....thus reving engine. All works great now.

flipscobra · #20 (**permalink**) 03-07-2008, 11:43 PM

Mine stuck to luckly i have a rev limiter. Its a spf 484 cu. in. So guys with a spf watch out. it sticks where the linkage comes thru the peddle box, it has a nylon bushing there. Keep it lubed with WD40 cause it will stick one day.



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