I was looking at my 12a engine today, and found what seems to be very strange. The ports are HUGE, much bigger than stock 12a ports, yet they are not smoothed at all. It doesn't look like they were ported, just like they came bigger. They have all casting roughness, etc. I had to cut holes twice as big in the stock 12a intake gasket. They are still 4 port, and the holley 12a intake fits fine. Could I be using 13b plates with 12a housing? I am running a streetport 465 holley with great success. I'll post some pics of stock 12a and what I have soon, but I would love some opinions.

 

what is a streetport 465 holley? according to the racing beat site, the 465cfm holley is for stock port engine. 600cfm holley, what i'm using, is for the streetport engine. and 650cfm for bridgeport. your engine could posibably be ported. intermediate housings, wheather 12a or 13b, are interchangeable thru '85, it's the rotor, rotor housings and e-shaft that make it a 12a or 13b. i tried it one time, if you've driven it long enough to get used to how it runs with the 465, put a 600 on it and see if it's better or worse. the stock 12a i had ran much stronger with the 465 on it.

 

There are different side plates for different years and where the car was sold. If you are street porting it, it really doesnt matter what you start with, the end result is what matters!