Superformance Throttle Cable / Pedal not reaching wide open

[Lee Patterson]

Setting up my SPF throttle cable connected to a Holley 4150. Not getting to wide open throttle position. Removed the pedal box pedal stop bolt which got me more, but pedal still bottoms out short of WOT by a bit. Curious if others have encountered same.

 

[Lee Patterson]

I do see that the pedal attachment to the bell crank is by an adjustable threaded link.

 

[Roger40]

Show us a picture of the cable connection at the carb.

 

[Lee Patterson]

Ignore the zip tie on the return spring. That is temporary. I believe the pedal assembly rod needs to be lengthened between the heim joints. I have plenty of moment arm on the lower end of the carb throttle arm with my extension. And the Cable is perfectly aligned to the arm Lokar fitting. Cable looks loose, but there is zero free-play in actuality. Carb curb idle screw set correctly at 1.5 turns in from throttle plates closed.

 

[JP Verweij]

Throttle cable on the carb needs to be closer to the pivot point so you have more movement on the lever.
Usualy you set this first to the point where the carb is fully open but the pedal does not bottom out. Then you adjust the pedal stop so you wont overstretch your cable.

 

[Lee Patterson]

thanks JP.

 

[Lee Patterson]

Problem has been resolved. Full deflection to WOT now.

Question - SPF uses a very strong spring on the throttle pedal itself. Between carb spring, return springs and throttle pedal spring, pressure seems excessive. Thoughts on the need for the pedal spring? Seems like it would be far more responsive to the foot without that strong pressure at the pedal. thanks for your assistance JP.

 

[Fred W Ballinger]

If you are tempted to remove the pedal return spring, or use a lighter one, make very sure that the throttle still closes well. Without the pedal return spring the weight and / or stiction in the throttle pedal or cable may be enough to overcome the carb end springs and cause the throttle to hang open. Also think about what happens if one spring fails. Their is a reason racing bodies mandate more than one throttle return spring.

I know personally several people who have suffered damaged cars and injuries, in one case fatally, due to stuck throttles.

 

[DaveM]

Keep a pedal spring, but either replace with a softer one or modify the existing one. I do have a double spring arrangement at the carb as Fred mentioned.

 

[Cameron Parsons]

I agree that the factory spring setup is too strong/heavy. It also makes throttle blipping on downshifts more of a stomp than a nuance. I also found the throttle cable itself had a lot of internal friction. I used Kable ease to decrease friction and lighter spring on the pedal. But i do have redundant springs on the carbs(s) for safety. Made the car so much more drivable/fun for me.

 

[Lee Patterson]

Thanks all. Will look at a lighter spring on the pedal and lube.