Idle RPM goes up and down.

[Pauly1119]

Hello, I have a 383 Stroker, Carburetor and MSD ignition that runs strong. I’m getting a variation in idle speed though. I’ll dial in the idle speed and then it will start to drop for some reason. Main vacuum at this point is from my PCV, I’m going to add another vacuum line to my carburetor from the manifold tomorrow to see if that helps. Could I maybe need to change the springs on the weights on the distributor? Looking for ideas. I also just finished installing my AC and that definitely makes it worse when it’s running at idle. I did add a solenoid to kick the idle up some when the AC is on.

 

[docstoy]

So did you build this yourself . What truck ? Auto or manual ? What cam and carb ? When you tell me cam , I'm wanting to know lift and idle characteristics

 

[Pauly1119]

So did you build this yourself . What truck ? Auto or manual ? What cam and carb ? When you tell me cam , I'm wanting to know lift and idle characteristics

Hello, the engine was fully built and installed when I bought it. I just had to finish the accessories and miscellaneous parts on the truck. I do have all the paperwork though. The cam is 224/236@050 .554/.554. Carburetor is a Quick fuel technology. MSD ignition.

 

[Pauly1119]

I know I’m already lacking in vacuum and the brakes run off my power steering but the only vacuum line to the carburetor is from my pcv on the valve cover. I was going to add a primary from the intake manifold today and see what changes I get. Could this be my issue? When I’m on the accelerator I have zero issues. Lots of power. I have the dyno it’s 490 rear wheel HP.

 

[docstoy]

What is base timing and timing recommended by cam grinder, never told me what truck specs are a I know is carbed stroker that makes nearly 500 hp and don't run right.

 

[Pauly1119]

What is base timing and timing recommended by cam grinder, never told me what truck specs are a I know is carbed stroker that makes nearly 500 hp and don't run right.

My timing is set at 35. Specs say between 34 and 36. So today I ran the intake vacuum to the distributor timing advance, it was originally set from the carb block. This made a huge difference, idling much better and driving under throttle seems slightly stronger now as well. After I switched it over I had to play with the idle speed and fuel mixture a little but seems 100 times better. Even with the AC on now it seems to be happy. I watched a few engine builders say this was the right way and a few say it was wrong but my engine evidently likes it. I originally tried to run the intake vacuum to the carburetor but it was actually worse than before. I took her for a 30 miles ride with cold AC and no issues so hopefully I got it sorted out. Idles nice at lights. I just have to make the connections permanent now I reran all the vacuum lines temporarily, a little sloppy. I’ll clean it all up next week.

 

[docstoy]

Glad you got it .