240Z SU Throttle Cable Kit

[KenFirch]

I've been looking for a good throttle cable kit for my 73 240Z with SU's, but couldn't find any. I heard MSA had one, but no luck finding any links or info.  There's an ArizonaZCar instructions link I kept seeing, but link is broken.

So, seeing nothing available, I decided to build my own.  Actually, I put together a few kits (9 more left) thinking maybe others might also be interested. You provide the cable kit, but you decide if you want to spend more for a Lokar cable, or a cheaper $20 Amazon knockoff.  

The design objectives were:

•   Use of readily available 24" universal throttle cable kit (you provide).  No junkyard rummaging needed.
•   No welding or modification to gas pedal. Stock ball is used. No drilling of firewall.
•   Completely reversible if you want to return to stock setup. Only 1 hole needs to be drilled in the carb linkage.
•   Cable runs from carb linkage all the way to gas pedal so you can completely remove old linkage.
•   High quality parts. Plasma cut, yellow zinc plating, and CNC machined bushing.

Circled parts are included.  You provide the 24" Lokar TC-1000HT (braided), Lokar TC-1000U (black), or a cheaper knockoff.  The Lokar is better, but any will work, as long as the adjuster threads are 5/16-24.

Just so you get a taste of the install process, here are abbreviated instructions.  I'm working on a more detailed set for purchasers.

Remove the 4 nuts from the rear SU carb, slide away from engine and remove center linkage.  Slide carb back on studs to hold, you don't need to remove any cables or hoses from the SU.  The only modification needed is drilling a 3/16" hole in the stock lever so a new lever can be bolted in place.  New ball is placed further away from linkage centerline to help give better off idle control of rpm's. 

Reinstall center linkage and place bracket onto the 2 lower studs of the SU and tighten carb back into place.  At this point you could reinstall your old linkage if want to finish project later, or test to make sure your SU's are still happy.  Slot provided so you can pull cable away from engine without loosening the cable set screw.

On the firewall/gas pedal side, remove gas pedal by removing the 3 screws.  You'll need to make the ball end of the cable smaller in diameter so it will fit inside the socket's M5 thread. I twirled mine on the side of a grinding wheel, but a file could work.  Then run the Allen head set screw (it has a hole drilled through it) onto cable and into socket to lock cable in place.  Red thread locker or small center punch on threads to lock set screw in place if needed (after checking fit at gas pedal).  Discard the adjusting nut and replace with firewall bushing after cutting the threads to about 3/8" in length so they don't stick out of the firewall bushing.  Tighten cable sheath to firewall bushing, large diameter side facing to rear.  Slide cable back into sheath and attach socket to your gas pedal linkage ball.  Feed cable through firewall throttle hole until bushing is against inside of hole. I found it easier to feed cable through sheath now, leaning gas pedal against trans tunnel, instead of trying to feed that small wire through that tiny hole afterwards.  I hate working under dashes and definitely didn't want to have a nut to tighten above the gas pedal.

From engine bay side of cable, slide washer down over cable and gently pull on bushing until you can get the E-clip in groove.  Be careful with these braided sheaths that you don't pull the braiding out of the ferrules, it's a pain to put back together.  I put duct tape on mine to help prevent unintentionally pulling apart.

Screw gas pedal back in place.  The rod should stop against the rubber stop with a nice thud without the socket hitting the aluminum bushing.  I glued the rubber stop on, it kept falling off.  You can cut the socket down in length if it hits bushing.

The hard part is done, now you just need to mount cable adjusters onto new bracket, and mount new socket from your cable kit onto 1/4" ball.  Cut cable to length and set Allen screw.  Adjust as needed.

Remove old linkage parts and store away.  One nice thing is the cable is hardly noticeable coming up to the carbs instead of over the top.

Still working out the price.   I've only worked on a 73, but I think the spacing of the center linkage lever is pretty much the same for earlier Z's.  I need some feedback on that.

Anyway, let me know what you think, if you're interested, or if you have any questions.

Thanks, Ken

 

Edited June 7 by KenFirch
Fixed link

[Patcon]

I would be interested

C

[SteveE]

Looks great!  Would be interested

Steve

[grannyknot]

Brilliant!

[davewormald]

Count me in!

[zKars]

Love it! 

I’ve been tinkering with a cable throttle for a long time for SU’s and triples and this is the cleanest solution I’ve seen. I love the bracket that bolts to the carb mounts to provide the under-carb pull cable mount. Brilliant. 

Three things to check and be aware of.

Cable key seating. If the gas pedal ball position isn’t “just” right, the cable won’t be pulled through the exact center of the sheath it will eventually wear into the sheath lining and will lock up at some point, or wear through. Carefully inspect how the cable moves as the pedal is pressed through its full range of motion. Add lubrication to the cable to prevent premature wear as well.  I have had to relocate the ball on the top of the pedal or bend the end of the pedal rod to tweak it into an ideal location.

The hole in the firewall on 280’s is larger than the 240, so as you make and sell these, you might have to make a larger OD version of the firewall bushing. SU conversions on 280’s is pretty common. 1.125 comes to mind, but I can check.

With the change in actuator arm length, advise to set the pedal stop after installation to ensure the throttle blades are not being stressed at full throttle. Gotta hit that stop just before the blades are full open. 

[KenFirch]

Thanks all for the positive comments, especially since you guys know these cars inside out.  I've run this setup for the last few months for testing, and can honestly say I haven't had to touch it since installed.

zKars, good advice and info.  Early on I put a long M5 bolt or threaded rod in the gas pedal socket and watched how centered it was through the range of motion.  It did appear to keep pretty horizontal in the center of the hole.  That's one reason why I really wanted to keep the factory ball since they surely went through that same design exercise.  As good as the factory linkage worked, I still don't understand why they didn't use a cable.  It's not like it was uncommon in that era.  I didn't grease my cable, I should pull it out and rub some grease over it.  Not sure what type grease, don't want it to eventually gum up.  The Lokar instructions don't mention it, maybe it's the liner they use.  

Yes, I need to take a good look at a 280 and get some measurements.  If demand is there, I may put out a 280 version.  The thing about machining small parts is the first one will cost you $150+, but the next 10 could be $30 each.  And I wanted to avoid having some guy on his garage lathe cranking these out manually.  Best to automate.

I gave a real short 2 sentence version of adjusting the cable. LOL.  Yeah, you definitely don't want to stress the butterfly valves, or risk pulling the cable out from the set screw.  What I did was put the gas pedal against the floor stop, set the adjusters midway on the bracket, measured where to cut cable end while carbs are full open, then tighten set screw while in that position.  Used adjusters to fine tune.  Still working on detailed installation instructions, they need to be concise.

Ken

Edited June 7 by KenFirch
spelling

[KenFirch]

Pricing....$125 for full kit, plus $15 shipping (US only).  I've got 9 of these.

For our Weber/Mikuni carb friends, you can get just the firewall/gas pedal end of the kit for $65, plus $10 shipping (US only).  I've got 10 of these.

Hopefully this sounds reasonable for what you are getting.  I'm not making much, just trying to recoup for now.

I've got 3 full kits reserved for Patcon, SteveE, and DaveWormald if you still want it.  I still need to order a few small parts before I can ship, and drill some set screws.

Thanks,

Ken

[Yarb]

This is great knowing there are still fellow Z enthusiasts out there willing to help others by designing and offering options and opportunities to help others. I applaud you friend.

[KenFirch]

For this first batch of the kits, payment can be sent via PayPal (Friends & Family), ApplePay, or Venmo.  I'll refund if kit doesn't work for you, if you send it back.

PM me for 'send to' info since I'm not sure if it's proper to post that in this thread.  I can also send you my phone number if want to talk it over first.

Also, the cable hole on the bracket is 3 3/8" from the center of the SU stud.  Make sure that works for your setup.  The bracket is made of 14 GA (.074") steel, and the lever is 11 GA (.120").

Thanks,

Ken

[Captain Obvious]

Really neat implementation. Certainly simpler than the complicated silver soldering thing that I did.

So why didn't you just grab onto the original existing ball on the linkage?  Is it simply that the Lokar* cable didn't come with the correct sized ball socket?

 

* Ummm.....  of the Hill People?     Anyone?

[Captain Obvious]

Too late for me, but complicated. And it still pulls up, which I don't like as much as what you did.