If someone has a Sterling Carb and a caliper, or a good steel ruler, I would really appreciate you taking a measurement on your carb for me. I'm trying to figure out how thick Sterling leaves the throttle shafts when he mills them down. I'm guessing it is somewhere between 3/32" and 1/8"?? If one of you guys with a Sterling carb could measure and let me know that would be awesome. I'm going to be milling down my own throttle shafts, but I need to know how thick to leave them. I posted some pictures below of the measurement that I'm looking for.

Thanks!

 

Anybody???

 

I have a yaw and can measure it tomorrow, im sure theyre milled about the same length.

 

That would be great. Thanks! I didn't know that Paul Yaw milled the throttle shafts on his carbs even. If you can measure and let me know that would be awesome.

Thanks,
Jamie

 

if you can wait about a week, we found the 1973 Rx3 competition book, which tells you how to build a sterling carb.... yes its that old and there is a factory book for it!

 

Wow! Maybe that's where Paul Yaw got some of his information from? And then Sterling took Paul Yaw's methods and ran with them? So why the week long wait? Are you watiing for the the book to be shipped to you?

PDF that section about building a competition carb and send it to me please!

 

I'm all in on this rx3 comp book as well. Is it going to be put online (ala foxed.ca maybe) or what.

 

yep, my friend dug it up and was going to scan it in, and then it can be shared. the 73 book is the stock carb/bridgeport in 3 stages of tune (so there are actually 3 carb mod levels), and the 77 book is a P port.

 

Giggity!

 

i know! i've been waiting a year for him to dig it up. he used to have the R100 comp book too, although i think that got sold with the car.

 

mine is sitting on my bench - but: disclaimer: village idiot - where do I see the throttle shaft? Is it what the butterflies are attached too? oy. I am assuming this can be seen/measured on an assembled carb? Think mine is an 83-84 nikki Sterling.

Stu Aull
80GS
Alaska

 

Yes, the butterflies are attached to the throttle shaft.

 

Stu,

Look at the two pictures at the top of my thread. See the one with the two red arrows? That is what I need the thickness measurement for. Separate your carb from the intake manifold. Flip the carb upside down so you can see the butterflies in the bottom of the throttle body. You should be able to get a measurement on the throttle shafts right there with the carb upside down. No need for disassembly. The best way to measure it would be to use the depth measurement feature on a set of dial or digital calipers. Or you could also measure it with a high quality steel engineering ruler that is graduated into 50ths of an inch.

 

Anybody have a chance to measure this yet? I still haven't figure out what the thickness is supposed to be. I'm ready to take these throttle shafts to the machine shop, I just don't know what thickness to tell them to mill down to. If ANYONE has a Sterling carb I would greatly appreciate the help.

J9fd3s, any hope of getting that Rx-3 manual scanned in soon? I'm dying to see what they show in there for carburetor modifications.

Thanks all,
Jamie

 

gonna be about a week or so, its 2 FSM sized books!

the thickness of the shaft isn't actually super critical, IMO. you actually have a small tradeoff, the less you remove the stronger it'll be, but you'd loose a teeny bit of airflow. so for a street car, err on the big side

oh that reminds me, if you cut the throttles like this you should make a throttle stop on the floor of the car. the stock pedal is flimsy, if you get excited while driving it'll bend, and you can bend the shaft. we built one for the race car and tommy pushed it thru the floor!

 

WOW! Got any pictures of the throttle stop that you used? I'd like to see what you came up with. I may copy it for my car, b/c like you mentioned the throttle shafts are prone to bending. If you have some pics of that throttle stop please share!

Thanks,
Jamie

 

well we had to fix it at the track so since the old one failed and left a 1/2" hole in the floor, the only bolts we had were 12mm with a 17mm head (like an FB trailing arm bolt) and a couple of the 19mm head, 12mm thread nuts with washer, so we just used one as a jam nut and the other just holds it to the floor....

if you aren't will to drill holes in the floor the paul yaw one was the same, except he welded a short 1x1" piece of steel to the floor and welded a nut to that.

 

Does this help?
sorry for delay... looks like 2mm but the photos tell the story - hopefully.
regards
Stu Aull
80GS
Alaska

 

About 2mm Jaime

 

whenever you get it all finished, please keep me in mind for a copy.

 

turns out the carb in the early book is a knockoff weber, its still made by Nippon Kikai, but its a 2 barrel downdraft...

the good news is that there is xp64 drivers for the scanner so it'll be up shortly

 

I cut mine to around 2mm (have been building carbs like sterling's for over 2 years in australia).

Few thoughts on this -

If you go with mechanical secondaries, the secondary shaft could go thinner because it doesn't bear any pressure across the shaft (aside from engine vacuum holding them shut).

Another advantage of mech secondaries is you can use the stop on the secondary linkage, which adjusts the WOT position, to stop the primaries at WOT as well - so a heavy right foot doesn't strain the shafts. IMO this would be preferable to using the stop on primary shaft opposite side (the OMP linkage tab) since it's on the same side and would prevent possible twisting across the shaft if too much pressure is applied.

Also don't forget to file the screws flush with the shafts. I apply some threadlocker for extra security too.

Edit: One more thing I forgot is rust. I sand the shafts and polish them to be as smooth as possible but still get some surface rust over time. Not sure how to avoid this, the best I can think of is routinely cleaning them up with the dremel (can be done with shafts installed).

 

Awesome! Thanks for the info! I can't believe that those throttle shafts rust. I thought they were stainless steel? Where do they rust at? Perhaps there is some kind of coating or finish that could be applied to prevent it.

Can you post a couple of pictures of the throttle stops you are talking about that could be used to prevent twisting the shafts? I'm not sure I understand what you mean. If you could show a picture that would be awesome. Thanks for the throttle shaft pictures also. Those look really nice!

 

Also, what color of threadlock are you using to hold in the screws? Red?

 

I don't know much about metals, but the shafts seem to be coated in something that prevents them rusting. But when you cut this away to thin the shafts, it looks like steel underneath. The rust occurs basically anywhere that this finish is removed. I always file, sand and polish the cut-away surface but minor surface rust still shows up. If anyone has any ideas on fuel resistant rust protection I would love to hear them.

These are the stops:

You want to bend them to adjust the WOT position. Note that this is only relevant for mech secondaries. I prefer to rely on the lower one since it's on the same side as the throttle cable. If you relied on the upper one, a heavy right foot could twist the primary shaft, since tension is being applied to opposite sides of the shaft in opposite directions (throttle cable vs. stop).

I use the non-permanent threadlocker, for removable screws. Since the screws are so much smaller than the loctite recommendations, I wouldn't rely on it completely, but it should still help hold them in I think.