Wanted: Mechanical Throttle Linkage Advice

[DowenS]

I purchased Fortes mechanic throttle linkage and I'm planning to install it soon. I received little instructions and 3 pictures to do the installation. Can anyone familiar with this setup give me any tips, advice, additional photos before I start drilling holes where they don't belong? Thanks in advance.

[japollon]

I have the same question. Mine came with basically no instructions.

[CraigS]

You want to mount the rodend shaft mounts as low as you can to the firewall just above the 2x2 frame member.. If you use a fender washer or other reinforcement, shave off the bottom. You want them just high enough to get a socket onto the head of the bolt. The shaft needs to be low because the bell crank on the inside of the foot box (which pivots ABOVE the shaft) can get close to the top of the foot box. The rod end shaft mount closest to the foot box can be either in the foot box or in the engine compartment. Just depends where you are w/ your aluminum so you have access to drill the hole. The shaft mount toward the center of the car can be on either side of the bell crank that will connect to the carb linkage. The shaft is stiff enough that an over hanging end will be fine. The bell crank should be positioned left to right so the rod going from it to the carb is parallel to the valve covers. This is mine on my old mkII although it is not a Forte kit.
https://farm5.staticflickr.com/4216/35553206130_6f6db9e362_c.jpg (https://flic.kr/p/WaHtwA)linkage two (https://flic.kr/p/WaHtwA) by craig stuard (https://www.flickr.com/photos/152454123@N04/), on Flickr
BTW, I have worked on two MkIVs w/ a forte kit and the only real difference is the style of the bell cranks.

[boat737]

Mine is not Forte's, but a similar design shamelessly copied from EdwardB's #7750 build thread, Post 77 http://thefactoryfiveforum.com/showthread.php?8296-Mk4-7750-Build-Progress-Update/page2

One thing to consider is where to mount the pivots (heim joints) for the rod. I see a lot of folks mounted to the firewall. Some beefed up the firewall where the pivots mounted. I went a different route. I mounted them to the 2x2 crossbar. Absolutely no flex or give mounting to that 2x2. I drilled through the 2x2 tube, then on the inside (under the dash in the cockpit), opened up the hole big enough to accept a allen/hex bit for the socket head bolt from inside the 2x2 into the pivot. Popped in a couple of metal caps/plugs to cover up the holes, even though they are out of sight anyway. One pivot is mounted in the engine compartment behind the carburetor, and the other is mounted in the upper footbox, near the steering shaft. The arm in the footbox clears all the wires and other stuff in there.

Also, I had to do a lot of guessing on where to mount them, because I didn't have the engine yet. I did all the mechanical linkage by looking at pictures and pretty much guessing where everything was going to line up. It turned out perfect, everything is right where it should be. One final thing, I added a throttle stop at the pedal.

[David Hodgkins]

Here's a link to my throttle linkage adventure when I was building my brother's MKIV, complete with a ton of pics a small misadventure for dramatic effect:
http://thefactoryfiveforum.com/showthread.php?13397-15th-Anniversary-MKIV-build-thread-2nd-place-best-in-show-HB2016!&p=194600#post194600

HTH,

:)

[Gumball]

And just to pile on, here's a link to my thread on the subject back in the day when we had to piece the parts together from various sources.....

http://thefactoryfiveforum.com/showthread.php?4539-Any-suggestions-on-length-of-gas-pedal-travel-with-mechanical-linkage&highlight=mechanical+throttle+linkage

[silver_pilate]

If it hasn't been mentioned, the hole in the DS footbox is an oval due the angle of the shaft. I ended up marking where the sides of shaft would enter the panel and started the hole straight-on in the center with a step bit (this created a pilot hole). Then I angled the bit slightly to finish the hole and then finalized fit with a round file. I also did as others have done and added reinforcement behind the firewall. I used a piece of angle aluminum and riveted it to the 2x2 with 1/4" rivets. It's very strong and does the job nicely.

Here's where I am at currently:

70592

70590

70591

--Nathan

[DowenS]

Thank you all for your input/advice. This is very helpful.
One question. I'm noticing that some of you have both pivots (helm joints) located in the engine compartment. While others have one in the engine compartment and the other one in the pedal box area.
Does it make any difference either way?

[boat737]

The closer the push (throttle) and pull (carb linkage) rods are to the heim joint pivots, the better. That way there is little to no pivot rod bending or binding. It just spreads the load out to where the mounts are. Theoretically anyway. In actual practice, I think the thickness of the pivot rod, and the relatively light load that the throttle linkage has on it, bending of the pivot rod will be minimal, if any. If you have the room, putting one pivot in the footbox I believe is the preferable way. At least that's what I think.

[jlfernan]

If it hasn't been mentioned, the hole in the DS footbox is an oval due the angle of the shaft. I ended up marking where the sides of shaft would enter the panel and started the hole straight-on in the center with a step bit (this created a pilot hole). Then I angled the bit slightly to finish the hole and then finalized fit with a round file. I also did as others have done and added reinforcement behind the firewall. I used a piece of angle aluminum and riveted it to the 2x2 with 1/4" rivets. It's very strong and does the job nicely.

Here's where I am at currently:

70592

70590

70591

--Nathan

I was trying to work out where to drill for the rod bearings so that the bellcrank inside the footbox won't hit the top and it was giving me a headache. How far above the 2x2 crossmember did you drill for the rod bearings?

[silver_pilate]

Mine is snug as is and I may have to switch to a smaller bell crank inside the footbox, though I think I can make it work. I haven't finished the install yet and won't for a while since I don't have my engine. I tried to go as low and close to the 2x2 as possible. Unfortunately the angle aluminum added a bit of height. I did cut the washers to get the rod ends as close to the 2x2 as possible.

At this point I'm committed and will make it work. Just get it as low as you can. Every 1/4" counts.

Nathan

[jlfernan]

FYI I mocked it up inside the DS footbox. I bought 1/8" aluminum angle. I drilled through the angle at 3/8" which puts the bolt head(mine came with button heads) a 1/16" above the aluminum. It clears the inside of the foot box top by about an eighth. This puts the center of the bolt 1/2" above the 2x2. FWIW. YMMV.