Secondary throttle plates not opening completely
#1
Member
Thread Starter
Join Date: Jun 2016
Location: Upstate SC
Posts: 137
Likes: 0
Received 1 Like
on
1 Post
Car: 1985 Pontiac Firebird Trans Am
Engine: 305 LG4
Transmission: 700R4 Automagic
Axle/Gears: No clue
Secondary throttle plates not opening completely
So I've noticed after rebuilding my carb that when I open my linkage to WOT that my secondary throttle plates appear to barely open up, probably like 15-20 degrees open. It has to be something with the linkage, because I can twist the secondary spring by hand and then easily open up to 90 degrees. I made a video of the linkage action:
As you can see at WOT the secondary spring mechanism still has a ways to travel to let the plates go completely vertical. I can't see what I can actually adjust though to make it travel further without making the blades open at part throttle instead of only at WOT. I don't have 3 arms in order to show you down inside what the plates are doing, but I can assure you when the metal piece sticking out of the secondary spring is straight up, the blades are closed properly and when it is turned about 90 degrees, the blades are 90 degrees. Is there something I'm missing here?
#2
Moderator
iTrader: (14)
Join Date: Mar 2000
Location: Littleton, CO USA
Posts: 43,169
Likes: 0
Received 35 Likes
on
34 Posts
Car: 82 Berlinetta/57 Bel Air
Engine: LS1/LQ4
Transmission: 4L60E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
Re: Secondary throttle plates not opening completely
Is the choke open when you're doing this? There is a lock-out tab on the other side of the carb that is disengaged by the green weight/lever behind the choke thermostat housing - when the choke thermostat heats up, the green weight drops down, and holds the lockout tab away from the secondary throttle blade pin.
#3
Member
Thread Starter
Join Date: Jun 2016
Location: Upstate SC
Posts: 137
Likes: 0
Received 1 Like
on
1 Post
Car: 1985 Pontiac Firebird Trans Am
Engine: 305 LG4
Transmission: 700R4 Automagic
Axle/Gears: No clue
Re: Secondary throttle plates not opening completely
Yes I manually hold the choke open, like I said i can look down into it and see the blades opening all the way if I manually rotate the secondary spring
#4
Re: Secondary throttle plates not opening completely
there is an actuator tab on the linkage which js on the primary shaft that actuates the linkage and rod to the secondary shaft spring assembly. Your primary actuating tab appears bent forward toward front of carb.If you can bend it back ,it should actuate the secondary shaft sooner and thus get more travel. I'm assuming all linkage was not removed or adjusted during the rebuild.
#5
Member
Thread Starter
Join Date: Jun 2016
Location: Upstate SC
Posts: 137
Likes: 0
Received 1 Like
on
1 Post
Car: 1985 Pontiac Firebird Trans Am
Engine: 305 LG4
Transmission: 700R4 Automagic
Axle/Gears: No clue
Re: Secondary throttle plates not opening completely
there is an actuator tab on the linkage which js on the primary shaft that actuates the linkage and rod to the secondary shaft spring assembly. Your primary actuating tab appears bent forward toward front of carb.If you can bend it back ,it should actuate the secondary shaft sooner and thus get more travel. I'm assuming all linkage was not removed or adjusted during the rebuild.
#6
Re: Secondary throttle plates not opening completely
That tab doesn't engage the start of secondary actuation until primary is already open approx. 30-40 % . then secondary starts opening and both end up fully open together at same time with wot of linkage.
Thread
Thread Starter
Forum
Replies
Last Post
89irocz355
Engine/Drivetrain/Suspension Parts for Sale
26
09-12-2016 01:28 PM