I bought 2 fbs for $350, one super straight gsl and a parts car so. Both have been robbed of a carburetor, main thing keeping it from running. My grandfather is a welder and a fabricator he can make me an intake manifold. What I need to know is what cfm should I go with? I'm going to bridge port it and probably end up darn near straight piping it, so I can push some air through it. I'll go with a 4 barrel holley. I'm looking at a 390cfm traditional or a 570cfm street avenger. I'm not sure, guide me on this, but it is still a long way from getting a carb.

 

Unless you know rotary combustion and exhaust behavior really well, you may be disappointed
by the results of fabbing your own intake and tuning the carb right. Especially for a bridgeport.

A stock 12a maxes at about 365 cfm. With a bridge the number goes up.

 

I'm new but I'm trying to do my research. I didn't know the max cfm for stock, I'm more of a fuel injection 13b kind of guy. I'm pretty sure I can do a good job with fabrication and I'm not looking for a heaping amount of extra horsepower, I'm just saving my money and seeing what I can get out of it.

 

For the money, your best bet is a Holley manifold rather than fabbing your own. You can probably find a used complete Holley setup with carb and all, for less than the cost of a new carb, in the classifieds here on the site.