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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Harmon on January 21, 2013, 10:26:41 am

Title: What is this part in my carb?
Post by: Harmon on January 21, 2013, 10:26:41 am
What is the part called that is to the left of the seat that im holding in my pliers.  I no the seat, and the piston with metering rods are there but the middle hole does not show up on my break down of my carb.

I saw online a guy said to count the number of turns to tighten to bottom.  I however see no instructions on what it is, and if that is the correct thing to do.

I have an 86 1/2 ton with 350 and carb 17085226 electric choke
Title: Re: What is this part in my carb?
Post by: rsandusky on January 22, 2013, 11:12:07 pm
??????? a better picture????????
Title: Re: What is this part in my carb?
Post by: rsandusky on January 22, 2013, 11:21:31 pm
Best guess is an adjustable stop for the power piston. I wouldn't adjust or remove it.
Title: Re: What is this part in my carb?
Post by: 454Man on January 23, 2013, 04:25:30 am
There should be a part throttle screw there. 76 carbs have an adjustable part throttle.
Title: Re: What is this part in my carb?
Post by: bd on January 23, 2013, 03:04:20 pm
Quote from: Harmon on January 21, 2013, 10:26:41 am
What is the part called that is to the left of the seat that im holding in my pliers.  I no the seat, and the piston with metering rods are there but the middle hole does not show up on my break down of my carb.

I saw online a guy said to count the number of turns to tighten to bottom.  I however see no instructions on what it is, and if that is the correct thing to do.

I have an 86 1/2 ton with 350 and carb 17085226 electric choke

That screw adjusts the depth to which the primary metering rods penetrate the jets.  It provides limited adjustment of metering rod timing and mixture at specific manifold depressions (slope of the fuel delivery to vacuum signal curve).  Changing the setting will alter cruise and deceleration fuel mixture and might introduce drivability issues.  Best to leave it as set from the factory.