So I recently bought a new holley 4bl carb, and when I installed it last weekend (on my 460 engine) I had around 3000 rpm in park, so I lowered the idle screw (counter-clockwise) and it seemed to bring it down to around 800.

Well I took it for a test drive and in gear I was sitting around 550 before acceleration, but the second I went to put it into park at the gas station I spiked to 2000.
Also once I accelerate to 45 mph it will not go any higher, when you hit the accelerator I can hear and see the rpms go up but no increase in speed.

Truck broke down last weekend due to ignition, and I replaced the whole ignition (coil, dist, wires, plgs, and duraspark.) and decided I wanted to throw on a new carb with it all. If anyone has some idea of how to fix it I would appreciate it

 

Carbs aren't really plug and play. There should be some instructions that are included with a carb or a .pdf online. To dial it in correctly check the linkage isn't binding, and the fast idle cam screw is adjusted. Have an assistant floor the pedal and verify the butterflies are perfectly vertical. Make sure the fuel pressure is correct, set the float level, and the lean idle mixture, and idle RPM. Check spark plugs for reasonable color, may have to jet a little higher or lower tho should be close if the carb is correct for your engine.

 

Can you provide a little more info?

What year truck and engine?
What Carb?
Is the Carb new or used?
Is it manual or electric choke?
I'm assuming you have an automatic since you mentioned putting it in park. What Transmission?

Did you adjust the Holley? Idle/Air Screws need to be set and adjusted to ensure maximum vacuum along with quite a few other things.

Do you have any smoke coming from your exhaust?

 

Thank you Ted,

The linkage didnt seem to be binding. And according to the tuning guide it came with the float levels and lean idle mixtures are set but I can always take a double look and play with it some

 

Silar,

Its a 86 f250
has a 7.5l 460
Brand new carb
electric choke
and I cant remember the trannys name but its the stock one

I adjusted the idle screw and got my rpm down to 800 or so in park and when I test drove it after I put it into park I was sitting at 2000 again
and no smoke from the exhaust

 

They are supposed to be, yes. Does your engine have a mechanical or electric fuel pump? That's really the first step. If the fuel delivery isn't in the ballpark it will never run right. Make sure any solenoids and all that is hooked up correctly, and vacuum hoses are on the right ports, etc.

 

its an electrical fuel pump,
owner before me took out the two tank pumps and mounted just one electrical on the frame rail

based off of how my old carb was the pcv hose was ran to the spacer, and just a hose with a plug on the carb where the pcv port was.
When I installed this carb I ran the pcv to the carb and plugged the spacer. I dont know if that would help any

 

It would be wise to make sure the aftermarket fuel pump is within the carb spec requirement. Everything else flows downstream from that.

 

Check your vacuum advance hose from your distributor. Make sure it is connected to a ported vacuum source.

(That means no vacuum at idle.)