ChadS
06-12-2005 11:05:37
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Re: super m carb serial number in reply to farmall, 06-12-2005 09:33:26
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All of the throttle bodys from the M-MTA were the same, they did have different part numbers, but were basicly the same casting. The 400-450 carbs have the idle screw in the carb flange, where the M-MTA has the idle screw along the lower side of the venturi. The carb bowls are different on the SM and MTA, the choke is on the opposite side of the bowl, M's have them on the left side, Supers had them on the right. (towards the engine) Most differences were main jet size, venturi size, and the choke shaft was a different diameter. Keep you throttle body, and the venturi from the origianl carb off the MTA, just use the carb bowl from the carb you found. That keeps the origianl part number of the throttle body on the MTA. Now as far as jet drilling,,,, If that MTA is a stocker,, you dont have to drill it much,,, maybe 2-3 sizes larger than the original jet size. if you went more than that, you went too far. You also have to remove the brass metering stem when you do this, otherwise you will drill right through the stem, and it will run erratic. Too rich. If the stem is ok, you can still use the bowl you drilled out,,, you just wont have any kind of fine tuning adjustment, 1/8 to a 1/4 of a turn, and its either rich, or lean, like on the usual,, you have to back it out a couple of turns to see a change in the engine's fuel mixture. It will be extremly tempermental on where the main load adjustment is set, cause you may have lost the fine tuning ability by going too big. If you do choose to attempt this again, it wont take much, maybe 2 drill bit sizes from the origianl jet,,,, if you can back the adjustment out all the way, while its under a load, and it does not run rich, then a jet change is nessisary, if it does run richer, and you can notice a change, then the jet size is fine where its at. Hope this helps,,, ChadS
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