460 idle issue

[19Kona]

ok, finally had a chance to take the Spectra 20 that I bought over a month ago out to the lake. The Berk G pump from my kona definetly is a good fit in the Spectra. The only hitch was in the idle department. I tried both the Holley 650 mech 2ndary from my Kona and the stock Vacuum 2ndary that the spectra came with. Same issue.
After a good run, the idle stays at 1k for about 2-5 minutes than drops to 800 rpm. If I leave the boat turned off for about 15 min, I have to give it 1 pump of gas to restart, when it does the idle is at 500-600 rpm and engine is about to die.
I checked all the cables, linkage, etc... everything seems ok.
The only thing I saw different on the Spectra from the Kona was that this Spectra has a brass plate (very thin) between the carb and manifold. The setup is: thin gasket, brass plate, thin gasket, carb (from the manifold up). Is this normal (stock)???
Thanks in advance.

[Jetdriver]

Have you tried to adjust your idle set screw?

[1978 Rogers]

The brass plate could have been to keep the carb from heating up. I have 1" thick phinolcic(no idea on spelling) carb spacer. When the carb heats up the gas to vaborize causing you to have to pump the gas a few times on start up, when the engine is warm.
As for the rough idle. You could play with the idle screw a little and see if this fixes you problem. What kinda of condition is the carb in? You need to have it rebuilt.

[19Kona]

I kept adjusting the idle screw, out to lower the idle and in to raise it. But like I said it kept changing on its own. I was thinking that the brass plate was to keep the carb cooler, does everyone with a stock Spectra still run this???
The condition of the carb is good. It looks clean and other than idle seems to work just fine. Could this be worn points or a bad plug or???

[OMEGA_BUBBLE_JET]

check your throttle cable close. sometimes they get a little sticky and the return spring is not enough to pull it all the way back. maybe try running a stiffer return spring or if you have an open engine have someone reach around and make sure the throttle is fully closed when idling.
Omega

[19Kona]

cables all work and the throttle on the carb goes all the way back to the idle screw.
I am just wondering if anything inherent in the stock Spectra 20 Holley vacuum 2ndary 650 carb would cuase such a problem on my BBF. BTW had the same problem with the mechnical 2ndary carb I tried (that carb I know works fine).
Thanks again.

[AngryJosh]

Try readjusting the air/fuel screws. Usual rule of thumb is 1-1/2 turns out from closed. There should be one on each side. There is also such a thing as 4 corner idle air/fuel. So make sure you check for them back by the secondaries. The accelerator pumps should have a play between the accuator rod and the adjuster screw of about .010 of an inch.
And I agree with checking the cable and spring. With it idling high, go back to the carb and manually push the throttle closed, if idle comes down then you have a cable or spring issue. These are just thing I would check, and in no way am I an expert. Free advice is worth what you pay for it!! :eek!:
Good luck-AngryJosh

[GM Killer]

Have you checked for vacuum leaks.

[jstwkd]

I agree with gm check for vaccum leaks.....

[mgar_red]

How old are your carbs? I rebuilt the original tagged Holley on my BBF after some idle issues. It died on me a few times when idling to dock, but it had worked fine all last year. Turned out the area of the throttle shafts were worn/leaking. I've heard Holleys are notorious for base plate leaks ( fuel and vacuum ) when they get up in age, and I don't have the special tools needed to renew the bushings and such. Put a new carb on and haven't had problems since.

[Cheap Thrills]

If youre running a stock intake with an adapter plate .
I had the same issues with mine the problem was with a phenolic (composite) adapter, it was creating a vacume leak within the venturies above the butterflies . It idled perfectly when I changed back to the aluminum one .
the phenolic adapter had a passage from both front venturies that ran forward . the aluminum one doesn't have any.
Just a thought .
C.T. :wink:

[Hotcrusader76]

Since both carburetors experienced identical results...how about fuel pressure? Do you even have any? Also what is your timing at?
~Ty