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I can't find it now but at some point I remembered reading that the longer steering arms didn't need to be used by Shelby on later model cars because Ford changed the steering gear ratio in the steering box. Since there are so many comments about headers not clearing the longer steering arms on the early cars (65-66) I'm wondering if the header clearance problem could be solved by using a later steering box. Anybody know?

The later cars have shorter steering arms on the spindles, which quickens the steering the same way longer pitman arms do, although to a lesser extend (about 5% vs ~15%). 

According to the 1966 Shelby American Performance Equipment parts catalog, the competition  GT350 road racing engine (PN S1CR-6003-3) had the following cam installed:

Valve lift: 0.445 in
Intake Opens: 29 deg BTDC
   "       Closes: 75 "    ABDC
   "        Duration: 284 deg

Exhaust  Opens: 75 deg BBDC
    "        Closes:  29  "   ATDC
    "         Duration:  284 deg

Intake /Exhaust tappet clearance (hot): 0.018 in

Specifications taken at 0.001 in valve lift

That cam has rather wide lobe separation angles at 113/113. The LeMans cam had much narrower angles at 107/109 while the Hipo cam had both narrower (intake) and wider (exhaust) angles at 109/119.

The only other thing that you haven't mentioned that you looked at is the metering block.

The block has emulsion tubes in it for both the idle circuit and the main circuit. I don't think they were ever intended to be serviced after manufacture.

Drew has a video on his Facebook page that shows you how to service them.
since you are having issues with the idle circuit, you need to consider servicing them.

There are also air bleeds in the main body and need to be cleared out with a numbered drill bit. They are small and clog easily.

It wouldn't be a bad idea to ask Drew to go through that carb for you, set it up and test run it for you? The issue is he's a very busy guy and it might take a while for him to get to it?

For what it's worth, this carburetor is hardly used and everything inside looks brand new and clean, including the air bleeds. I don't know about the emulsion tubes though.

I'm sure Drew could get it right. I do live in Sweden though, so shipping it back and forth would be a bit of a hassle. Also, I had this carb intended for a new engine build I have planned (if I ever get to it....) so if I can't get it right, I might have Drew look at it for that application instead.

You'll find the difference is negligible....
Specific gravity of .748 vs .756 etc. the range from E0 to E10 is well within the range of gasoline variability.

Fuel pressure variation and needle/seat diameters have a much greater impact.

Yeah, you're right. Density is probably not much affected by the ethanol.

I wondered about the (strong) influence of fuel level on the mixture. Initially I thought that the pressure of an inch (or thereabout) of fuel would be negligible, but when looking into the vacuum created in a booster venturi, I found that the vacuum at cruising speed for a 289 is probably only 1-2" of water or so (~40CFM per venturi at 2000 RPM/half load). Compare that to an inch of fuel (~3/4" of water) and it becomes obvious that the influence of the fuel level will be significant at low airflow levels.

When running on the idle and transfer circuit, the holes are directly exposed to the manfold vacuum (or whatever the vacuum will be right at the tip of the throttle blade) so it is much higher than in the venturi booster. Could there be an effect of the exposure of the different emulsion tube holes, with the holes being under or over the fuel level under different operating conditions? Thereby affecting the amount of air that enters the emulsion?

I had set the float levels set to the (somewhat confusing, see first post) recommendation of 3/8" front and 1/2" rear. Now the fronts are a little lower due to the float interference with the bowl. Since the engine ran much better I thought I was on to something, but it's still running rich. I guess I can give it a try and set the floats lower. All this fiddling with the floats sure makes me long for externally adjustable floats and side plugs I'm still considering drilling and tapping my bowls for side plugs: there's a patch on the bowls already.

I wonder if the ethanol fuels require a lower fluid level in the bowl or if  the fluid level should be the same but that the density of the fuel requires a lower float dry setting? Or maybe a combination of both.

The needles in seats are in like new condition and the power valve tested as OK, but will replace it anyway and see what that brings. I will also check for any signs of fuel dripping at idle.

Thanks for the suggestion but that doesn't seem to be the case. Although Now that I look it it, it does seem possible to bend the tab and the float bracket in such a way that a 3/8" setting can be achieved without the float hitting the bowl.

I lowered the primary floats a little to prevent them from bottoming out, but the engine runs just as rich as before: 12,5 at idle (tuned for best idle setting, ~3/4 turns out, 18" vacuum), ~10 at light cruise, ~11-12 at highway cruise and ~12,5 under acceleration. It idles smoothly and doesn't run bad otherwise but smells fuel and fuel consumption is high.

It seems that something is leaking fuel but I can't figure out what. A leaking power valve could be a possibility but it worked fine when I tested it with a vacuum tester (pulling vacuum on the membrane side) and all gaskets seem fine (the blue non-sticking type on the metering blocks). I didn't have any new ones handy but I guess I'll buy some and see if that helps.

Unless the specific calibration of this carb works ONLY on a GT350 engine and not at all on my 289 (short duration but .533 lift roller cam, Shelby Hirise manifolds, 351W heads with mild porting, headers, 10:1 compression), but that seems unlikely.

Yes, I noticed the difference (spongy vs clunk). Any tips on how much lower?

Odd that the official setting is 3/8" then, or is that specification for a different/older float design?

The same Drew as above? I don't have Facebook so I hope he'll answer here

I finally got a wide band AFR sensor hooked up which showed that it's still running (much) too rich: ~10-11 at idle and ~12,5 at cruising speed. My first thought was a leaking Power valve but vacuum testing it showed that it was OK. I then noticed that front float was bottoming out against the bowl. I had set it at 3/8" (see first picture) but that is apparently is right where the float hits the bowl. It is hitting at the edge just below the upper bolt holes (see second picture)

The probably means that the float valve wasn't closing properly and the actual fuel level in the bowl could have been anything. The engine actually ran surprisingly well despite this (although rich at idle).

I guess that means that I have to set the float a little lower (as was already recommended for modern fuels).

Thanks for your answers. I agree that 715 cfm is more than necessary for a street driven 289 and if I were to buy a generic Holley for it, I would have picked a 600. But I had this one and figured that since Shelby used it for several years it can't be all bad and that I at least could try and make it work as good as on a 65-67 Shelby.

I have now driven it a little more with the readjusted float settings. ~50 miles to and from work including city, freeway and stop-and-go driving plus some spirited driving on country roads. It starts easy, idles smoothly, smells much less, has much less hesitation and when I took out a spark plug, the tip and porcelain were light tan/beige (while the metal was still covered with thick black soot, from earlier I guess). Don't know about the fuel consumption yet.
I may try lowering the float settings a little later on, but I think I first will hook up my wide band AFR sensor and see how things look.

Hi,
I have a question about some adjustments of the 715 cfm Holley carburator. My car is just a regular Mustang but I hope you allow me to ask this question here anyway. My main concern is the float level height.

Quick background:
Engine: 289 with ported 351W heads, Shelby Hiriser intake, 10:1 CR, short duration high lift hydraulic roller cam, headers
I used a 600 cfm Holley 1850 previously, which ran OK but developed a lean stumble that I probably could have fixed if I had spent some time on it but I decided to try my Holley 3259 (reissue) instead. It started right up but didn't run right. After some reading I set the float levels and it ran decent, but very rich (sooty exhaust pipes, fuel smell), still had some stumble and required the idle screws to be closed much more than the typical 1.5 turns out. Fuel consumption was high.

I decided to recheck the float levels and check if the power valve doesn't leak. When trying to find the correct float setting, I found the following:
1.   1/2" front, 3/8" rear
2.   3/8" front, ½" rear (to the top of the bowl), confirmed by the same person who confirmed setting #1 was correct in another forum post 
3.   13/32"
4.   Float arms parallel to the bowl
5.   Set floats 1/8" lower than stock to compensate for modern fuels

Needless to say, I was a bit confused. I decided to go for #2, since it was recommended twice by people who seemed to have clue and because somebody with a Cobra 289 said that the correct levels were sensitive to the angle of the engine in the car. Since the engine leans backwards in a Mustang, I figured the front float had to sit a little higher to compensate.

The float levels turned out to be much too low. I probably measured from the bottom instead of the top, last time I set them. Half an hour of tinkering later, I considered them close enough to 3/8" and ½" and put the carb back on the car. It started right up, idled OK and ran good with considerably less stumble (a little remains) and the fuel smell seemed to be less. Back home and the engine warm, I adjusted the idle screws and had to turn them in more (not sure how much). Vacuum ended up at 18" but the RPM is too high at 950. I guess I need to close the secondaries a little, because the primary blades are right where they need to be, relative to the transfer slots.

Before I go on and fine tune this carburetor further, can anybody confirm that these float levels are correct? I'd like to avoid to tune and adjust it based on the wrong float level. Also, do you think that the float type makes a difference? Mine are the Nitrophyle type and I figured their setting may differ from a brass type? I don't know what was original though and if the 3/8" and ½" float settings apply to brass or nitrophyle floats.

It would sure be easier to have some side plugs (and an internal adjuster!) to check the level.... The bowls have flat areas where a side plug would normally be mounted . I'm considering to drill and tap them for side plugs.

Well, a long story but I figured that visiting this forum means you like reading about Mustangs, so you probably wouldn't mind 

BEAUTIFUL CAR, BUT IF YOU ARE GOING TO RESTORE A 1965R OR EVEN A REGULAR 1965 SHELBY, YOU SHOULD A LEAST USE THE RIGHT FUEL PUMP.  NOT A 1966-1967 BUTTON TOP.  3.8 MILLION SHOULD GET YOU A 100 POINT RESTO!  JUST SAYING.

KEN H.

I see a canister.  Something so trivial would not have been overlooked on this car.  Also, there were several engine variations, they chose what was thought to be correct when the car was raced at Green Valley, which if I remember right is a 5 bolt 289.

Since the car must have come with a 6 bolt engine from Ford, they had installed an earlier engine? I can imagine they just took one from their inventory of already race prepped Cobra race engines and spent their time and effort on getting the rest of the car ready instead.

Right, the 67 and later Shelbys had the standard size rear drums. I did not know the prop valves for Shelby were readjusted for the 2 1/2" rear drums but it sure makes sense. Those would lock up big time without a proportioning valve.

Thanks for straightening me out!

    Doug ,
       NOT the same valve as a Corvette. They had bigger fitting/tubing sizes. True both versions were made by K/H and used the same raw casting.

    Royce , YES same valve as C5ZZ "except" the S1MS version was "preadjusted" for use with 2-1/2" metallic rear lining. The C5ZZ valve was set for 1-3/4" organic lining. If you had an original C5ZZ and S1MS side by side , the difference in adjustment is obvious. This is also noted in the partial blueprint Jeff S posted earlier in this thread.
    For '67 and later , metallic shoes were dropped and standard inline , non adjustable prop valves were used.

Royce,actually 67 had 2 1/2 inch rear drums too. 68-70 had the smaller regular Mustang drums.

I seem to recall that the 428 CJ cars got the rear drums upgraded to 2,25". Is that correct and does that apply to Shelbys too?

I know. I had to laugh the first time I looked at a 66 Shelby and noticed the "tire coolers"

Ive pulled apart many 65/66 GT350s that the rear metallic shoes had virtually no wear  so most bias on the from t brakes

And yet they needed cooling in 1966