RetroRanger

Im looking at some specs posted on 442.com and in some cases the 350ci carb main jet and primary rods are the same as those listed for some 455s like the toro.

my question is aside from the secondary rods which always appear to be leaner for the 350, are the carbs essentially the same?

_same power piston too?

what about the secondary rod hanger ?

MDchanic

They are mostly the same.

You can compare the other specs to see which parts are different, but in some cases, they used exactly the same carbs.

If I recall, one of the aftermarket carb. parts suppliers listed original specs for all of the components, but I don't remember which one.

- Eric

joe_padavano

If you are talking about the run-of-the-mill Qjets for 1970 ('250 for the SBO and '251 for the BBO) then the differences are primary and secondary metering rods and choke housing and thermostat. Everything else is the same (including 070 primary jets) according to my foot-thick Rochester Carbs parts book.

Interestingly, the MT W-30 carb ('258) and W-31 carb ('255) use the same secondary metering rods as '251 but the same choke housing and t-stat coil as '250. Both of these carbs use a different air horn from other 1970 Qjets. Each uses a unique float bowl and of course no power piston or primary metering rods. Each also uses a unique throttle body assembly and unique jets (057 for '255 and 058 for '258).

dualgate1968

take things on 442.com with a grain of salt. there is a TON of bad info there

quaddriver

I would not put much emphasis in the actual carb numbers, since service replacement parts off the shelf units were used - brand agnostic. the actual fuel circuits were for all intents and purposes identical. the real wild cards were the chevy replacements because of the plethora of cam/head/axle tranny combos. yes, the airhorns for the 4mv and the m4m carbs were different, but it really didnt matter outside of the parts list for THAT carb. you could grab a complete m4m and it be perfectly fine. I refer to the carbs as the simplest and perfect mass air flow device...the motor will use what it needs, no more no less meaning you could fit the carb off a 455 onto a 4bbl intake for a buick v6 and it work perfectly fine. now emission wise, the air velocity might be a little low but that was typically endemic of ALL the motors