Any suggestions on length of gas pedal travel with mechanical linkage

[Gumball]

Here's a picture of my mechanical throttle linkage mocked-up with wooden dowels. Since I have quite a range of adjustment at the gas pedal with this set-up, I'm looking for recommendations as to a good length of travel for the gas pedal. Do any of you have preferences? Given the high horsepower and low weight of these cars, I'm thinking more travel is better, but I don't want it to be too much. I'll tweak it once it's in go-kart stage, but I'm looking for a suggested starting point.

http://i845.photobucket.com/albums/ab15/CCRsAC/FFR7074MechanicalThrottleLinkageMockUp.jpg

[PhoneGUy]

No input, just drooling...

[Richard Oben]

Not having done one. Logic (bad word) say that from just below the brake pedal (so you can heel and toe) to the floor should be idle to full throttle. JMHO, Richard.

[ArcticSnake]

As Richard said above, lower than the brake pedal. I set mine up based on where the brake pedal is. I have the throttle pedal set deeper than the brakes as I dont want to hit the throttle and brakes together. As it is, you should have more than enough room to scare the %%^$@ out of you. I have full throttle response with plenty of rppm to spare before the pedal hits the metal. You "may" sense that from this pic. Nice mod, you wont regret it.

http://i325.photobucket.com/albums/k385/schubertdr/My%20Cobra%20Project/IMG_7911.jpg

[Jeff Kleiner]

I placed my Russ Thompson pedal slightly forward of the brake as Richard & Dan have mentioned. From idle to WOT the travel is 2.25" at the pedal. I find it comfortable and easy to modulate.

Jeff

[Gumball]

Thanks for the feedback - Jeff hit the nail on the head regarding my concern about ease of modulation.

For those interested in doing something similar, here are the specifics: The wood dowels will be replaced with a stainless axle shaft along the firewall and two threaded rods (right/left threads for adjustability). The pedal is from Russ Thompson, with a fabricated pad to mimic the originals and the carb is a Holley 650DP in an old turkey pan that I got from another forum member. Most of the parts came from McMaster, but the lever arms were sourced from Midwest Control Products. It's a very simple mod to do and gives a great range of adjustment between throttle plate movement and pedal travel. The only real challenge was making sure that all three holes (2 in the firewall and 1 in the driver's footbox sidewall) were level and in alignment. Total cost for parts was around $75.

I'll be happy to share more details if anyone is interested.

[Gumball]

For those looking for a parts list, here's what I used - the small rod-ends for the pushrods are the captured-stud version.

McMaster-Carr:

3/8” stainless steel shaft (parallel to firewall) / 1141T253 / $37.64 for 36” (only need 10” or so)
¼” hardened steel rod for pedal and carb pushrods / 6061K61 / $14.76 for 36” (only need 24” or so)
¼” rod end – left hand female 28 tpi / 6072K311 / $6.87 ea / Qty. 2 (one per pushrod)
¼” rod end – right hand female 28 tpi / 6072K31 / $6.87 ea / Qty. 2 (one per pushrod)
3/8” rod end – right hand female 24 tpi / 6072K175 / $5.47 ea / Qty. 2 (firewall)

Using one-each of the left/right hand threaded rod ends for the pushrods allows you to change the length of the span by simply turning the rod one way or the other, then secure with jamb nuts.

Midwest Control Products:

Lever arm / Part# MCA-6 / Stock# 4106 / $8.61 ea / Qty. 2

Misc. hardware sourced locally:

(4) ¼” x 28 tpi nylock nuts to secure rod ends at pedal, lever arms, and throttle w/star lock washers.
(4) ¼” x 28 tpi jamb nuts (2 left-hand / 2 right hand) to secure pushrods once adjustments are made.
(2) 3/8” x ¾” x 24 tpi bolts to secure rod ends to firewall.

As mentioned above, you’ll have to stiffen the firewall a bit to ensure that it doesn’t flex – I’m using 1 ½” angle behind the 3/8” bolts that go through the firewall – the angle is then riveted to the top of the 2” square tube at the bottom of the firewall.


I was asked about pictures regarding the connection at the top of the pedal lever, which is a Russ Thompson part, and clearance of the clutch quadrant - here are a couple of detail shots of that area.

http://i845.photobucket.com/albums/ab15/CCRsAC/7074MechThrottleLinkageatPedalLeverTop.jpg

http://i845.photobucket.com/albums/ab15/CCRsAC/7074MechThrottleLinkagefromBelow.jpg

[Gloveman]

Hey Gumball,

Your post is timely as I was just about to start sourcing parts!

Thanks

FYI, here are a couple shots from an original, yours looks much better!

68166817

[Gumball]

Gloveman - I like the spring on the original; I may have to try to incorporate that.