So I've been working on my holley 94's trying to put in new shafts and plates. I've got one that is really tight, I drilled it for an oversized shaft but its still tight and ever tighter with the new plates in it!! I emery clothed the shaft a little and that helped but I don't want to wreck anything. Is it ok to see a tiny (very slight while holding it up to a light source) amount of light past the plates on a secondary?
I've never dunnit, but I'm very careful to buy only 94's with tight shafts--none of the vendors knows the difference, so there's no added cost at the swaps, and a core with sloppy shaft may well have a negative value due to cost of parts and extra work needed! I'd get hold of an adjustable reamer and sneak up on right size very carefully. This is a critical area. On the plates, try very slightly backing off screws (this can be done by slightly forcing against the staking) and tapping the plates around a bit. They may be slightly rotated from optimum. restake screws against some sort of improvised anvil, NOT by hammering against your carb! Or mebbe try that green wicking loctite...or back off and loctite one screw at a time. Carb engineers call any air bypassing fuel metering bad air--with good reason. The official Ford cure for this problem, since these carbs don't have bushings like a Stromberg, involved a trash can and a new throttle body assembly, but that's a touch impractical nowadays.
I did a couple of these awhile back. Got the proper dia. reamer, ran it through the base a couple of times and ended up with a nice snug fit. Haven't completed the carbs as yet, they're still sitting under the bench along with the rest of the flathead parts awaiting assembly. So get a reamer and see if that does the trick. If they're still too tight, the oversize shafts may be a little "oversize".
All the previous info is spot on, but one thing re the throttle blades may be of interest. The blades have a bevel to them and must be installed correctly. Something like a 7 degree or so. You may need to get a magnefying glass to check it and be sure that the blades are installed the right way.
So this is what I was thinking: Secondary carbs are not being used at idle so therefore they need to be shut, no air leaks. but the question is how tight do the plates have to be in regaurds to the bore of the carb? And how freely can/should the shafts be? This is what I was waiting for on the HAMB, some good info, rather than somepeople just trying to get high post #S. Some guys the other day were commenting on each others opinions rather than talking about the post at hand!!! Thanx for your input guys!!
I think most of my prob is the tightness of the shaft. I think I'm going to focus on reaming the carb. I've been seating the plates by leaving them slightly loose then turning the shaft a bunch of times to move them in place.
It has been opined elsewhere that .005" was the max gap at the throttle plates, .002" preferred. On the throttle shaft, it is said, that Ford allowed for .008". These would be that "eyebrow" of gap as the throttle plates are ovate and so is the wallering you get at the throttle shafts. This information hasn't been backed up... it is merely part of the stuff I've gleaned over the last few years about these carbs. As noted, the throttle plates are not round and must be installed correctly (correct orientation). Intallation involves setting the plates in place, screwed in to locate... tap the shaft with a screwdriver handle to "seat" the plate in the closed position... tighten then peg the screws.
OK, plates should be as gapless as possible--I dont think assigning numbers here is practical, because once they are close we will be discussing tiny arcs of light here and tere, not a neat gap that can be readily gauged. Design of parts is such that fit should potentially be perfect, but obviously tiny differences in machining angles plus any tiny difference in shaft angle that may have been introduced in oversizing will cause visible gappage. If one side is consistently worse than the other, you MIGHT have aslight edge angle difference and want to go nuts swapping plates. This comes down to a judgement call, as 60 year old carbs tend to have their imperfections...if you have loosened and rotated and shaken the thing down to a few tiny slivers of light, you're probably at the best you're gonna get with the parts you have. On the shaft, you want to keep loosening it until it moves freely with very little effort--friction will cause difficulties with everything you do from here out on a multi carb setup. You are starting from too tight rather than the usual too loose here, so don't blow it by taking off too much and you'll be fine. Use your best bases for secondary carbs, as primary will be open here and feeding gas into the air going by anyhow. Ford's instructions are entirely subjective, with not a number in sight: "Make visual inspection of tightness of fit of throttle plates when closed by holding towards a light and observing amount of light that can be seen around edges of T plates. A very snug fit is necessary (square the "Very" for carbs without idle function!) for proper idling and low speed operation. The complete assembly should be discarded if wear and looseness is encountered around edges of throttle plates; if throttle shaft is worn loose so air will leak into throat, if throttlelever is loose on shaft, or if link 9526 is loose... Remember you are operating on idle and off idle circuits until considerably beyond idle when the venturis start functioning, and trying to compensate for bad air at end carbs with adjustment to middle carb cannot produce very good results, so getthat fit as tight as you can.
One thing you might try is to "lap" the shafts and bases with valve grinding (lapping) compound. I'd try the fine compound first..you are dealing with brass shafts. It sounds like you are close and just need that final detailing. Coat the saft and work it back and forth in and out for a smooth fit. Sneak up on it. Worth a try. I'd be afraid a reamer would cut too much too quickly. At least it would for me.
The bases wear egg shape, the shaft is actually harder than the cast iron. The first thing to do is open up the bases to a true round; dont try this with hand tools. Then try the OS shafts for a fit. You will: A. Be OK B. Need to bore some more. C. Go to the next size OS shaft D. Bore, insert bushings and ream bushings to fit the shaft. If you already have a sloppy .008 fit that thing will be sucking air and you will never balance the carbs. I never turn down a cheap and loose 94 core as the work required is not that hard. Besides 94's will be 97 prices pretty soon!
Just a small related statement. I was the line inspector on the carb assembly line at Chevrolet Bay City Division of GM. Among other 2bbl carbs we manufactured the secondary carbs for the 348 tri-power engines. The specification for light passage around the throttle plates was "0" (no light) no exceptions. If during assembly the result was that some light passed they were put on a repair line to be adjusted to meet the spec. or scrapped. Due to the best manufacturing procedures at the time the end result was a very low scrap rate. Due to the fact that this specification directly affected the idle adjustment and quality this was a strictly enforced condition. When you have to satisfy the general motoring public , most of which haven't a clue what is going on, a component that affects how the vehicle operates is held to a high standard. The fact that most of these cars were ordered by the high performance segment of the population your dealing with people that sometimes have unrealistic expectations that are skewed toward this environment. This only made us as manufactureres especially aware of conditions like this and every reasonable effort was made to produce a quality product. Frank
This is great info guys!! Its good to know the HAMB has people who care about tech, like real detailed tech. This makes me think we could rebuild anything. I was talking to johnnycola about his power window switches in his '64 lincoln, he said there's nothing you could do, but I'd like to look at 'em maybe I could fab somthing to get them working again...anything is possible...well within reason. You guys are the Heart and Soul of the HAMB!
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