any help would be appreciated to break down code ,i have a 780 holley carb list # 3310 gm stamped 3878261-EH ,base plate # 12R 2916 B ,big block ?,small block ? car or truck it was born on ,thanks

over the counter carb

This carburetor number was originally listed for the 1965 Z-16 Chevelle (375hp/396), the date will indicate if an original issue Z-16 carb (rare) or the much more common one sold over the parts counter to half of the Chevy enthusiasts in the US. My experience with MANY dyno pulls on a 406 CID SBC was it was hard to improve on as delivered over the counter. There were some small improvements we made after many dyno pulls, but you really ought to have access to a dyno if you decide to alter jetting/air bleeds, etc. When these were right it was tough to find a better 780 cfm carb at the time. I still look for them at swap meets.

I have one of those on the shelf too.

thanks for info ,are they worth anything ,i have the base plate to

I have one too,we're all gonna be rich .............

Shucks, I'll lower my sale price to $1500.

j/k

I have one that is dated 1972. I picked it up from a buddy in high school, thirty years ago. I've had it on numerous cars with everything from a street/strip 468 to a stock 350, still one of the best carbs I've owned.