I don't know if this subject has been covered already...but gotta ask. Holley 94 throttle shaft question..how much clearance is to much? I'm rebuilding some carbs and using them in a 6 x 2 application. I know the oversize shafts are .282. I've used plug gauges and some bases that I have are all ready sized at .2845. The. Plug gauge is tight at that dimension. Is that to much clearance? Guys what are your recommendations? I've seen those aluminum bases from Vintage speed. What are the clearances on those? thanks for any help...maybe Dickster or Vintage speed can make some suggestions.....if it's been posted can somebody direct me!...thanks a bunch! Wildman
i think you are ok. buy a couple of the longer length oversize shafts. i think you will find they fit ok w/o drilling. if you need to drill, use a long 9/32" bit so that it will bore all holes in a straight line. manufacturing tolerances will vary on the new shafts. that is why i say to buy 2 or 3 shafts. once you are happy with the fit of the shafts, you can order the throttle plates. I use shafts from Speedy Bill....jack
Thanks Jack, yeah bought a long .282 reamer and it fell right thru. Lol. That's when I decided to try the plug gauge. The shafts I bought were from speedy Bill. Some vary in size? I will try that next.
If it is snug at .2845 then the shaft has one and a quarter thou clearance for a .282 shaft - sounds ok to me. Not too lose. I would shy away from the alum base plate. Where i would spend lots of time is blade fit to seal the carbs off.
This is a subject that we need to cover on the HAMB. I am about to start working on mine so they seal properly. What works best?
Thanks guys...I bought about 12 cores to find six good bases. The cast iron is what I was worried about. Some are pitted in throttle bores also. Any ways the throttle plates I used were the speedy bills. I lapped in the plates. Throttle bores are 1.250? I'm guessing. Don't really know factory specs. OJ, I'm guessing that .00125 (per side....0025 total clearance) good but didn't know. I will check all the throttle shafts monday at work to see if any variance. Wildman
Shafts...Ford published specs for shaft wear on earlier carbs and later carbs but not the 94. The reason is revealed in Ford's overhaul instructions for dealer-level rebuilding...to summarize...visually check blade fit (and don't mix parts) as snugness there is imperative...if wear/looseness found at plates or at shaft..."The complete assembly should be discarded." So...shake the thing! If you can feel movement sideways, do you actually think an air molecule is going to have a problem going on through? No need to measure. So...no damn help there, and the local dealer is plumb OUT of new assemblies. I am just real careful when I buy junk carbs...a surprising number are good and tight, probably due to Ford's exchange rebuild program, and I have NEVER encountered a seller who charged differently for carb cores that were tight and those with 1/4 inch of slop... On the wear...I am suspicious of any use of drilling or reaming without milling machine. You can find the original hole from the unworn side and align on that, but tooling is going to follow the oval hole I think. If I had one done I would want to find someone with a bridgeport, possibly using the unworn sides of old hole to create a proper holding fixture and get the thing centered under the tool. And I would bush the thing...unlike the Stromberg which has OEM bushings that can just be pushed out and replaced you'll have to order something by diameter from industrial supply. Oversize shafts on all carb tests I have seen give the shaft diameter as a very significant factor in flow...you do not want a fatter shaft! Conversely, anything you can do like cutting down shaft, removing casting warts, etc. that improves flow without enlarging venturi gives you improvement without negatives, unlike switching to a model with bigger venturi which will cut and delay main jet response. An olde trick applicable to stock and toodamnfat shafts is SLABBING the shaft. This is doen AFTER fitting shaft, fitting blades, and making sure they move smoothly as shaft is going to be weaker and easy to twist. You scribe where the thing emerges from insides of casting and simply file the shaft flat and as thin as you think safe between the casting and the first blade screw, between the screws, and then over to the next wall. Throttle blades Good fit is needed both for totally closing carbs in progressive systems and for controlling idle in non- progressive one because a tiny amount of extra air in either makes good tuning impossible. 1. Throttle shaft needs to be in pretty good shape...if bad, it leaks air AND closes the blades differently each time it moves, ruining their adjustment erratically. Should be fixed with bushings and standard shaft...fat shafts are a big loss of flow capacity. 2. Loosen screws holding blades very slightly...not a problem even on staked ones, very slight movement only. Hold the throttle body (idle screw OUT!) up to a good light, poke, prod, and shake to find the position of each blade that shuts off the light around edges. always start with everything in its original hole---this stuff was fitted tight at the factory and this will give you a head start. Unlike the Stromberg, Ford did not recommend repairs here because of this...their overhaul instructions written in 1939 said to toss the whole throttle body and replace with new assembly if worn! You may find some throttle bodies cannot close up reasonably, so swap the whole thing or swap blades and see if anything gets better. That's all there is...patiently move the blades around till you get the light pretty well shut off or you go mad... Once all is fitted, I like a dab of grease around each end of the shaft where it enters the throttle body on each side in hope of preventing the entrance of grit that could wear it out.
Wow, talk about info...great job! Have you ever managed to get a torsional spring to work on the 94? to keep the throttle blades closed? I had problems with similar carbs and progressive linkage.
"Man, am I screwed" Mebbe, mebbe not. Maybe you have a magic touch and got the shaft centered... See if the throttle seal well. My thinking is if both butterflies can seal decently, shaft must be about right. If not...it is pretty well impossible to get a multi setup to behave with air getting through beyond your intentions. I would say...borrow or steal a good tight original boltit to a 90 degree bracket to bolt to a milling machine, use stock hole to align the thing bolt on the plum wo' out bases runnem through to a dimension that will take an over the counter bushing (Msc Industrial supply?) that can be reamed to standard I'm not a machinest but I think that is a reasonable course and once setup could do a bunch of bases reallydamnfast.
None. Any bypass air will make your setup impossible to set up as progressive and wonky with straight linkage. I would look for no movement wiggling the shaft sideways, at most the barest suspicion of a hint of movement. Multiples are far more persnickety than a single, as a single can be adjusted to feed idling air coming in at strange places, but a triple cannot really because so little air is needed at idle speeds. You MIGHT be able to tune a leaky primary with air-tight secondaries, MAYBE. Oddities of shaft movement in a worn hole are likely to make the carb seat and seal differently each time throttles close...
Well it should look good parked anyway. I've got a dozen 94's or so to play with. Thanks for your help.
Shoot, man, 6 sloppy carbs...definitely time for desperate improvisation. See if those oversize shafts will fit in there with tight enough fit. If they can fit...two thoughts: Best thought, mark off the bearing and exposed areas, find someone with small lathe, and with either proper tools or just a rat bastard MFer file spin the exposed sections down to about stock size. Should take about a month less than slabbing 6 carbs by hand! Second best...with 6 carbs, whyinhell, assuming your engine isn't gigantic, should we worry about a flow loss from fat shafts??
Bruce thanks for help on this subject. Gotcha loud and clear on the shaft clearance issues, ...so maybe .0024 might be to much total clearance. You can feel shaft wobble by hand. Made a fixture to bore base for throttle bushings. But before I do that what clearance do I need? I can machine bushings if I could get some help on actual measurements. Throttle shafts fom Speedy Bill mic at ....#1. .2815 #2,6 .2818 #3. .2816 # 4,5 .282. So apparently there is a difference! The one carb I rebuilt so far with the secondary throttle plates had .0012 total for clearance. After pokin' and prodin' the new 12* throttle plates around got a perfect seal. At least I can't see light! Will post some pics a little later. Will have to match bases to shafts. Wildman.
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