17058263 carb

[17058263]

  ok been woking on 17058263 carb 72 jets 50 m rod  ildes great nice off idle transtion to primary circut but on med acceration i will get a stumble for a sec then goes it does not allways do it on highway no surging plugs dont look lean float at 15/32 apt 3 turns ilde 1and a half out power pistion moves freely did tip in test did not increase good highway mpg but poor city mpg timing 14 intial 23 dist 13 vacuum can ported pontiac 301 60 over stock

[17058263]

also my fule psi is 7-8.5

[comp]

also my fule psi is 7-8.5

 psi may be a little high,,,not sure ??

[Cliff Ruggles]

We have prepared hundreds of those carburetors here, and street, dyno and track tested them.  I even use a nearly identical unit on my own low 11 second daily driver.

The .072" jets combined with the 50M metering rods will not provide enough fuel during low vacuum situations.  Basically, when the engine is heavily loaded, and the power piston moves to it's highest position, there will be a .036" metering rod tip located in a .072" main jet.  This will provide the carburetor with difference of .036".  The original set-up for that carburetor was closer to .044".

The 50M rods have enough taper on the second section to provide adequate fuel for part throttle/high vacuum situations, but will not provide enough fuel for heavy/full throttle driving.  The result(s) will be hesitation, stumble, bog, lack of power, engine feeling "flat", etc.  The lean condition can and will cause poor transition onto the secondaries as well.

If you choose to use the "M" series metering rods in that carburetor, I would move up to jets in the .075-.076" range, and make sure that the carburetors main airbleeds fall within the "range" provided in the "recipes" from our book.

I would also make sure that the carburetor is using the correct fuel inlet seat.  It may also help to raise the float level some in conjunction with the tuning changes........Cliff