thegoon1969

350 with intake, new cap in coil dist. and new holley carb. when i start the engine it goes to 1,700rpms and stays there even after warming up. i hooked up a vacuum gauge to the manifold and it says i get 18-19 hg at 1,700-1,800 rpms. My initial timing is set at 18*. all the numbers i listed above are with the vacuum advance on the dist disconnected and pluged. If i plug in the vacuum advance the rpms go to 1,900-2,000 rpms and 19-20 hg of vacuum.

how do i get the rpms down to where i want around 800-900rpms at warm idle?

LilJayV10

iTrader: (5)

Have you tried the idle set screw? If you have make sure your throttle cable is long enough and isn't keeping it from closing all the way. The easiest way is to disconnect it at the carb.

Give a little more info on your setup and when it started doing these things.

novaderrik

did you hook up the choke? sounds like it's stuck on the fast idle.
did you adjust the idle speed and idle mixture screws? are all the vacuum ports that aren't being used plugged?

i assume that new Holley carbs come with instruction/installation manuals and that there is a troubleshooting section... what does it say?

Edwardgp

All kinds of adjustments to be made. Let us know how it works out.

ibmtech

iTrader: (1)

This could be 1 of a few problems.

1. Large Vacuum Leak
2. Distrib timing way off
3. TPS out of adjustment
4. Idle Set screw
5. Throttle Body gummed up

The 1st thing everyone says is to adjust the idle set screw.. This is set at factory and it 99% of the time it will never or should never be touched again.

I would start at a very large vacuum leak before anything..

thegoon1969

I havent played with any of the carb adjustments yet. I agree i belive it is stuck on high idle. Yes the choke is hooked up. should i disconnect it and see if it still idles high? I am almost positive i DO NOT have a vacuum leak becuase the needle on my guage stays constant at a certain HG. Vacuum leak usually causes moveing vacuum needle.
The carb is new to me but older it was just profesionally rebuilt and the builder is very reputable. I do not have any trouble shooting instructions with the carb.
I will play with the high idle screw and see if that helps. My question is in what order do i mess with/tune all these screws? do i do the high idle first, then curb idle, then back out adjustment screws until max vacuum is reached? I just need to know the order on which to do things. also if i adjust one screw (high idle screw) does that mean that i have to adjust other accordingly or is the high idle screw adjusted "independently"?

kauboy

Definitely not a vacuum leak. Fast idle from a large vacuum leak would only be on an injected car. I would think the fast idle cam is stuck.

novaderrik

a vacuum leak will lead to a high idle with a carb if it's set to run rich.. the extra air combines with the extra fuel to make the engine "think" the throttle is open..


don't unhook the choke- leave it hooked up, but make sure that it actually works.. Holley Carbs are supposed to have a little ground wire that goes from the cap to one of the choke housing mounting screws. if this wire isn't hooked up, the choke coil won't get hot and the choke won't open up.
use your test light to make sure the choke is getting power with the key on- it should be getting a full 12 volts. if you are still running the stock choke wire, then it will be running thru the oil pressure switch and you will have to start the engine before checking for power at the choke.

kauboy

Fine, you don't need my advice Derrik knows everything about vacuum leaks on carburetors.

novaderrik

touchy much? you gave some incomplete info, i completed it. a good way to tell if you are running rich or lean is to pull a small vacuum line to see what the engine does.. if the idle speed goes up, then it's rich.. if it dies, then it's lean. if it just stumbles a little bit, then it's just about right.

kauboy

Not incomplete info just a short and sweet answer. Lets leave criticism of each others advice alone and help this guy fix his problem.
Aloha.

Edwardgp

blackbmagic

Why dont you adjust the idle speed screw to close the butterfly slightly? Any chance the carb is not set 100% ready to run perfectly out of the box?

Also to start with your vacuum advance should be connected to ported vacuum not manifold. So check your diagram on the carb to see which is which. There should be no change in idle when the vac advance is hooked up to the ported vacuum at idle. The ported vacuum is the port coming off the primary metering block.