Confirm purpose of fast idle screw on twin SU's

[sdyck]

I'd like to confirm that the only purpose of the fast idel screw is to set a higher RPM (1500-3000) while balancing your carb airflow.  That's my interpretation from eveything ive read. 

Is that right or is there another purpose?

Thanks,

Steve

[Jarvo2]

Correct 

 

[siteunseen]

I'm excited that I'll get to use that for the 20 minute run-in on the first start up after a rebuild. When I built my 280's motor I had to jimmy rig a wire on the throttle rod to maintain 2,000 rpms.

[zKars]

The complexity of adding all those pieces to just raise the RPM to the "high" sync level during an infrequent service, makes me think there just HAD to be more to it. But it's clearly stated in the FSM and maybe even on the air cleaner housing that this is just for this one test. 

Now I have to admit to using it as a idle setting device.. Since there is an interaction between the two on-carb idle setting screws and the inter-carb sync screw, that makes you go round-and-round tweaking all three to get both the sync and idle right. Then you put the air cleaner on and later decide the idle is too high. Here we go again.... Bahhh..

So back the two carb idle screws off, and use the high idle screw to get idle, balance flow using only the inter-carb link screw, then set the idle where you like. and tweek it later without affecting the idle

Feel free to call me lazy. I prefer to think I'm giving a piece of generally un-used and un-appreciated equipment a moment in the spotlight. If it had a thumb it would be under its nose, saying, "I can hold idle just as well as the two of you, all by myself!" 

[sdyck]

Excellent thanks. Good thought on the 20 minute breakin on a rebuild engine. I'm hoping to never use it for that purpose! 

I'll also admit to using it to bring my idle up when I first got the car and it was ideling too low. I've got the timing right and the valves adjusted and it didn't need the extra help.

Steve 

[siteunseen]

14 hours ago, sdyck said:

I'll also admit to using it to bring my idle up when I first got the car and it was idling too low. 

I did the same when I didn't know any better!