Hello, I have a stock flattie with a Original 2 barrel Ford/Holley AA-1 carb. I have a feeling it runs rich. I have been adviced to change to power valve from 7.5 Hg to 5.5 Hg that is it stays closed until va*** is 5.5 or lower i.e. opens later than with the 7.5. What do you think about that? Also I have seen that the jets are stamped 57 on the side. I have read at Vintage speed that the 94 has 0.051 jets at sea level stock. 1. Is the Ford/ Holley AA-1 the same carb as a 94? 2. Does the stamping 57 means 0.057 jet size i.e. today it has bigger than stock?! 3- If that is the case I ***ume that I should rejet with number 51?! Best regards NB
yes it is same basic carb. doesn't have vacuum port on back (needed for 8Ba distributor). don't know about the 57 stamp. yes re-jet with 51 jets. rejet b/4 power valve change. 7.5 is correct stock valve....jack
If it is a 2100 model 94 Holley it came with #57 main jets. I have one on the stock '50 Merc flathead in my '40. I thought 57's were to large, changed them to 53's, much too lean, went back to the 57's. Runs good, same milage as the 8ba 94 it replaced.
you are on the right track if it is running rich, 57s are big for a stock flathead ,maybe not a merc (bigger displacement) but what 'feeling?' cons***utes rich running? have you done a plug chop? is it fouling plugs? blowing black smoke? bad milage? heres a tip... be very wary of powervalve seating.. a good way to check if it is leaking is leave the car overnight, then carefully take the top of the carb off the base throttle ****erfly piece,without tilting it much, if there is any wet fuel in the chamber underneath the powervalve, its leaking, either a torn diaphragm or, more likely not sealing on the seat very well. this will cause a huge overrich probelm, as the contents of the fuel bowl can be drawn into the engine through here with no metering..
Hello,Thanks for the tips!The car doesn't run crazy rich plugs are somewhat brown but not extremely so. Maybe staying with the #57's.How about the power valve. Should I change from 7.5 to 5.5 ? I now have a new 7.5 so it is not leaking. RegardsNick
Food for thought, slight over-rich may indicate weaked ignition as well. Unless you have changed cam etc in the engine the ford engineers were pretty sharp about getting the right amount of fuel into the engine, so before i strayed too far i would evaluate the ignition/coil as well.
There are a lot of true 94's and a number of related carbs with bigger venturis and jets... Post the MODEL of the carb...if it is Ford, it'll be on driver's side of Bowl. Step one is always finding out original jet size, what you need should be quite close to that. And "stock flathead" is about as meaningless as most uses of "94"...they made a lot of years with lots of different details.
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