Foot box installation versus throttle linkage

[TXJosh]

Hello all

I am building a mkIV complete kit with a blueprint 347. I am just beginning the PS and DS footbox installations (waiting for sharkhide to dry). My intent is to install Forte’s throttle linkage, which I have not yet purchased. I have already purchased the Breeze throttle pedal, which I already have.

My question is whether I should be thinking ahead to the eventual throttle linkage installation while installing the DS footbox later today. I am assuming I’ll need to drill a hole or two on the right vertical wall of the foot box but with the engine not in yet and not yet in possession of the throttle linkage I’m not sure where I would drill those holes.

Does anybody have any wisdom on the sequencing of these various steps? Ideally I’d install the footbox today and then drill the linkage holes down the road unless someone has found that to be much more difficult.

Thank you !

[FDLWproject]

Following this too as I have the same question. I’ve got the mechanical throttle linkage and a 351W from Forte but haven’t installed either yet.

[OSU Cowboy]

I've got a throttle linkage on my MK3.1 - did not buy from Forte, but decided to source my own components and make it from scratch.

Yes - one hole in the right side footbox to accommodate the horizontal shaft. For me - I did have the right side footbox in place but sure it was with cleckos at the time and not yet a permanent install. With the two rod ends in place that the horizontal shaft runs through, I marked locations for the hole from both sides - really in hopes of minimizing error for the hole location. Drilled the hole, slightly oversized, and put things together to insure the horizontal shaft passed comfortably through both rod ends (very unforgiving) along with the hole in the footbox.

This was the way I approached the challenge - I'm sure there are perhaps better methods that others will chime in with.

[OSU Cowboy]

Failed to mention what I think is an important step. When I drilled into the footbox panel, I started with a small pilot hole so that I could review that from both sides of the panel being drilled through - just to confirm it was relatively centered within the markings on both sides ... and proceeded from there.

[TXJosh]

What throttle pedal were you using?

[egchewy79]

the location of the hole will depend on where you want the horizontal bar located. I put mine through the 2" square frame for max stability. putting it too high on the firewall will result in some flexing when you step on the gas. If going through the firewall, try to put the pedestals as low to the frame as you can. cutting one side of the washers allows you to get lower to the frame on the cockpit side of the car. others will put a piece of angled aluminum on the cockpit side of the firewall to stiffen it up. If going through the 2" frame, get longer bolts to secure the pedestals.
When drilling the hole, keep in mind that the bar goes through the wall at an angle. I'd drill the hole the size of the bar first, then slowly enlarge it with a dremel or round file. I put a rubber grommet in the hole and and brass bushing through the grommet just a bit larger than the bar.

as mentioned, cleco the inner wall in place and mark the location of the bar with the standoffs/pedestals against the firewall, remove the panel, and drill/file the hole.

[Bill Elliott]

Wait until engine is installed. No sense guessing where to drill holes. I did mine after engine was installed , very easy. I have mine mounted on firewall just above the 2 inch tube. It is very sturdy with no flexing. I also have the extra thick firewall. I am in Woodway if you are anywhere near here you could always come by.

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server having issues posting pictures.

[rich grsc]

As Bill says, mount the shaft 1-2" above the main 2" frame member. It doesn't need to be any 'exact' height, within that range and the firewall isn't going to flex, just add a fender washer on the inside

[cv2065]

Cleco'd the panel in place, drilled my holes for the support posts, inserted the rod and marked/cut where it touched the panel. I went through the 2" tube and get as low as needed so no interference with the lever arm inside the footbox against the top cover. There is a lot of horizontal and vertical play with the arm and throttle linkage placement, so quite adjustable, even if you do it before the engine is installed. I'll have some exact measurements from panel to support arms in my build thread one of these days.

[OSU Cowboy]

The one from Russ Thompson

[CraigS]

I installed my shaft so the bolts went through the firewall just above the 2x2 frame tube. Some even go through the 2x2. The reason to keep it low is that the bellcrank inside the footbox is above the shaft and it's top end gets real close to the top of the footbox. I would wait to install it. It isn't that terrible to drill the hole after the fact and I'd rather have the parts on hand so I can get a perfect location. If you get it right you drill a 3/8-7/16 hole for a 3/8 shaft and don't need to mess w/ any sealer pieces.

[rponfick]

One suggestion would be to drill and pin your Forte's linkage to the shafts while you can still get at it. My levers have slipped, and I can't get full-throttle movement. I have pinned the under-hood lever (which is accessible), but I am still trying to figure out how to get to the linkage behind the firewall (to drill and pin).
Please don't wait until you get into my situation.
Ralph

[egchewy79]

One suggestion would be to drill and pin your Forte's linkage to the shafts while you can still get at it. My levers have slipped, and I can't get full-throttle movement. I have pinned the under-hood lever (which is accessible), but I am still trying to figure out how to get to the linkage behind the firewall (to drill and pin).
Please don't wait until you get into my situation.
Ralph

I had similar experience while go karting. the set screw wasn't strong enough and slipped. I drilled/roll pinned both arms and left the pin in the footbox about 1/8" out so I could reach up w/ some vice grips if I ever needed to disassemble the thing.

[Theshandman]

TXJosh, just curious if you have considered a throttle cable approach but abandoned that method in favor of Forte’s throttle linkage which is perfectly good. I ask only because I have a BPE 347 and elected a cable (Lokar) system which works just fine and was super easy to engineer and instal.

[TXJosh]

TXJosh, just curious if you have considered a throttle cable approach but abandoned that method in favor of Forte’s throttle linkage which is perfectly good. I ask only because I have a BPE 347 and elected a cable (Lokar) system which works just fine and was super easy to engineer and instal.


I did consider it, but I abandoned the idea of a cable because my reasearch led me to conclude that a mechanical linkage would yield more precise, linear throttle feel. Now, that research was basically just reading a bunch of posts — I have no direct observations whatsoever. So much of my wisdom is crowdsourced here.

Does that seem off, what made you go with the cable?

[rich grsc]

Mechanical linkage is much smoother

[herb427sc]

Mechanical linkage is much smoother

Mechanical linkage also has a lot of moving parts.
A cable is just pull.
The throttle return spring closes.

[rich grsc]

Guess you've never had a cable bind or drag. I've done both, never use a cable again if I can help it

[Mike.Bray]

Guess you've never had a cable bind or drag. I've done both, never use a cable again if I can help it

Are you using a mechanical linkage with your stack setup Rich? I thought about it but I've always run cables and never had an issue. Always used good quality cables like Lokar and made the bends as big as possible. My MKIV setup feels very smooth and solid.

[rich grsc]

Yes Mike I made my own mechanical linkage. One other advantage is you can fine tune how fast or slow you want the throttle to respond. The stacks can be quite aggressive in response, which make driving on the street, in traffic a bit tiring. I'm sure the same can be done with a cable setup by changing the arm lengths too. As I said, very pleased with how smooth it works

[TXJosh]

Late reply here but now I'm going at it myself.
How did you go through the 2" frame?

I'm thinking of grade 8 bolts from the cockpit side into the threaded mounts on the horizontal shaft?

[egchewy79]

Use an appropriately sized drill bit. Just make sure you’re drilling perpendicular to the frame

[rich grsc]

Grade 8 bolts for a throttle shaft???? WHY?

[Bill Elliott]

Grade 8 bolts for a throttle shaft???? WHY?

Spot on Rich!. Also no need to go through the 2" frame ,,,, proven many times, just above the frame through the firewall works fine.

[Jeff_J.]

There isn't a lot of pressure on the SS shaft just mild torque so Grade 8 is a lot more that you'd need here for sure. My approach was to install just above the 2x2 chassis bar through the firewall, I flat spotted 2 fender washers for the inside and installed the bolts/washers/nuts so the shaft was as close to the top of the 2x2 as I could get it. My firewall is thicker than kit supplied & I reinforced it to the 2x2 to better support the stuff attached to it on both sides. Craig S mentioned it earlier if the shaft is installed too high the bell crank on the inside of the footbox will hit the top access lid. I used a felt marker to pre mark all the locations and positions on the shaft before final install. The forte kit works great.
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[tundra2050]

Jeff, I like you ran your hydraulic clutch line. I didn't want to do a hard line and was thinking of running mine out the front of the foot box to simulate a cable line. I like your solution. How long is your line? Any issues think about? I also plan on the mechanical linkage, so your post helps out there as well.

Thanks! James

[Waterman]

I also ran my clutch line out close to the mechanical throttle. As others have said the pivots have to be very close to 2x2" top or the Forte linkage hits, mine does. See small cover for clearance. BUT also see that the 2 holes(linkage/clutch) are in a small SEPARATE panel. I had the linkage slip issue and it is near impossible to drill/fix from under dash. Making the foot box side panel multi sections makes future linkage, brake, electrical fixes easier. I also made the footbox wider at same time. Show quality, not but mine is mainly a driver.
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[jengum]

"The custom built by..." plague adds a nice touch.

[Jeff_J.]

Hi James, I know this is a little off TXTosh's topic here and I don't want to highjack his thread but just quickly; I made most of all my own braided lines for fuel and PS, it's not hard to do but I was able to purchase a premade line (around 30" I think, it was a while ago), the 90 degree coupler and the fitting which screws into the back of the master cylinder from Summit. Then zip tied to the chassis rail to the TKX. Much easier to put the pass through rubber gromet on the line before the fittings are attached......