I have a 71 442 auto that has a 7042251 carb. Is there any difference besides the stamping on this carb compared to a 7041257 which would be correct for my car? CFM? performance?

 

The CFM is the same. That '71 carb originally came with slightly richer rods (e.g. .001 thinner primary rods and "AT" secondary rods which are slightly different than the "CH" rods in the '72). I can take pics of both sets of the secondary rods for comparison if you wish.

 

Ok thanks, So no difference in CFM and slightly different rods but little to no difference in performance due to richer fuel mixture?

 

That's right. For years, i had a '73 carb on mine and once i got the best combination of rods, jets, and power piston spring to work with my engine, i was good to go. I just rebuilt a correct-numbers 7042251 for mine (only paid $50 for it and in great, unwarped condition ).

 

Those two carbs use different castings for their parts,but the cfm is the same.

 

I have the same carb numbers on my 72 CS with 455/400TH.

I read somewhere that the last number in the carb indicated whether or not the setup was for manual or auto trans??? They stated even numbers were for auto trans and odd numbers for manual trans. This has to be wrong as the OP and my car are both auto trans.

Here was the article...

http://www.ehow.com/how_6130381_deco...r-numbers.html

Some good info, but obviously some of it is wrong too !

 

Nice catch Jimmy_B. What that last number represents (i.e. for transmission and whether odd/even for auto or stick) might be typical but doesn't apply to all.