69 tri-power idle?

[Wayne P.]

Been working on a 69 model 400hp. The idle is erratic. One time it will be 500 rpm the next time it will be 1500 rpm. I thought return spring tension was too little so I increased that. I checked to verify the fast idle cam wasn't sticking. I looked for vacuum leaks though I figured that would be consistent. Float and seat is new and appears ok via sight plug. Ideas?

[William C.]

Re: 69 tri-power idle?

Check the linkage to the front and rear carbs, if not properly adjusted, they can cause this problem. Check the archives, there was a thread with instructions for setting the tri-power linkage a while back.

[Jerry Clark]

[Wayne P.]

Re: From Jerry Lucks Bag Of Tricks

Thanks for the input. I should have said this one has mechanical linkage. It does not seem to be binding or holding the secondary throttle plates open. Other ideas?

[Jerry Clark]

Re: From Jerry Lucks Bag Of Tricks

Wayne
Mechanical secondary throttle linkages are great for allowing full WOT but often are adjusted with that in mind paying no attention to stop down. You are not talking a huge variation in idle speed and one that could be caused by any of the throttle plates not being completely closed ?
jer

[Brian Monticello]

Re: 69 tri-power idle?

Throttle shaft bushings worn? Is the idle different depending on how you let off the gas? I bet a slow gradual pedal release will give you a high ROM idle and a quick "blip" will give you a low because the throttle plates snap closed.

Brian

[Wayne P.]

Re: 69 tri-power idle?

One secondary(rear)was one turn of the rod from being closed. I think that took care of it. I haven't been able to drive it yet, but it behaves ok in the garage.