Hi Igot a stock 62 Tbird with a correctly numbered 4100 carb
The car runs fine at an idle and accelerates good but at a fast idle or small throttle openings it runs very rough. Any help to get it running just fine would be appreciated.
Thanks in advance

First and foremost, those early t-birds were full of options, vacuum run options, from doorlocks to vacuum controlled air vents, even the swing away steering sheel had vacuum tubes. After so long those vacuum tubes crack and then you get an engine vacuum leak. Not big enough to kill the engine but certianly enough to mess with the idle.

Of course the other big hitter is when was the last time it was rebuilt. I always reccomend that a daily driver get rebuilt every two to three years depending upon where one drives and quality of fuel. For a "show or classic car" that is only driven seasonly, I reccomend rebuilding yearly (just like boats, lawnmowers, rv's).
The reason is that wonderful high priced fuel we are getting now is crap, and full of additives that breaks down and clogs passages after only a month or two of sitting in a carb.
I always tell customers who balk at rebuilding so often to take a pint if fuel in a jar and set it next to where they store thier car for one month and look at the bottom of the jar afterwards.

That residue is clogging or blocking those air bleeds and ports and causing the idle to be off.
That is why one always needs to buy good quality gas (fat chance now) use an air cleaner and a fuel filter, and always keep the tank filled or run it dry.

Hope that helps

Bill White
White Automotive

Thanks Bill.
I have blocked off the vacuum lines and dont seem to have any leaks. Looks like I am rebuilding a carb.
I will pracice on a spare carb that came with the car

Steve

Use a really good carburetor cleaner (berrymans works good but the 1 gallon bucket will not allow the 4100 body or top to soak in it). Soak all the parts using the enclosed bucket and get them all clean then transfer the fluid into a roasting pan to soak the top and body.

Make sure you spend lots of time and elbow grease getting the INTERNAL parts, crevices and most importantly all of the internal passages cleaned. Use toothbrushes, bristle brushes, paintbrushes and (my big secret) welding tip cleaners, to make sure all passages are clean. Use air to blow the orofices out when clean.

Let the carb and parts soak generously, allow the cleaner to dissolve and loosen the crud. ( I soak all my rebuilds for 1 week as a rule and I use a much stronger industrial strength cleaner than you can probably get)

ALWAYS USE THE MOTORCRAFT KIT (CT-191A for the 4100) If contains the best quality parts, rarely is missing ony parts (other kits are notorious for this)and most importantly will give you a spec sheet which you will use for bench setting your carb back to factory specs. (Yea, other kits neglect this as well).

Get some good penetrating fluid to help when taking the carb apart (I use Aero-kroil, made by KANO LABORATORIES and its the best) and spray all screws before applying any torque. A frozen screw which breaks quickly takes this rebuild from an amatuer situation to one requiring professional help. Or another way of looking at it: a perfectly good carb to a piece of junk. It happens to all of us, take your time and don't force things or try to hurry, It will bite you otherwise!!!

Be organized and neat and take your time. Spread everything out on a clean towel in order (another nice thing about the spec sheet is it gives you an exploded view with all the parts numbered and sequenced in the way they should be removed and then re-assembled)

Be careful removing the jets, a jet tool here will prevent damage rather than a large screwdriver. A damaged jet from using a screwdriver does not flow as well (or changes the flow)as an undamaged one. A screwdriver is V shaped whereas the jet cut-out is square. The larger the screwdriver the more this is amplified. The V on the screwdriver causes it to slip and damages the soft(er) brass jets. Before I got my first jet tool I modified a cheap large screwdriver by grinding it square on the end and sides. Nowdays jet tools run about 15 bucks at any speed shop.

And be very careful when removing the vacuum secondary diagphram, since the motorcraft kit DOES NOT INCLUDE A NEW ONE, (in fact motorcraft no longer make this) and you will probably re-use the old one but if needed NAPA can get you a brand new one.

Make sure you use the correct settings for YOUR CARBURETOR not your application, EVEN IF YOU THINK IT HAS NOT BEEN CHANGED CHECK IT!!! Get the carb number off of the side (stamped into the drivers front foot. C= 1960's the next number is the year so a C3 means 1963, This changed in 1966 on and they left off the decade code just using the year so a 1966 carb starts with 6.
The next code tells you what car line the carb was used on: A= big car, S=T-bird, Z=Mustang
Between those three, you should be able to tell what carb and then which specs to use.
Don't go by the little tag, most are missing so its not an option anyway but some have been replaced and don't reflect what the carb really is.

Good Luck,

Bill White
White Automotive