Carb recomendations for BBC
Thread Starter
Burning Brakes
Joined: Jul 2001
Posts: 905
Likes: 1
From: New Bern NC
Carb recomendations for BBC
I know the 600cfm Holley that I have is way too small but what is a good replacement? `There is a Holly 750 and an Edelbrock 750 on EBAY (yes, I know what happened to me there!) for just over $100 each. I was thinking of an 800cfm.
What do the experts say???
What do the experts say???
Racer
Joined: Oct 2000
Posts: 487
Likes: 1
From: Aloha, OR, USA
Re: Carb recomendations for BBC (tworottiedogs)
On my 73 big block, the stock carburetor was a 750cfm quadrajet. 750cfm is good for up to about 5700 RPM with 100% volumetric effeciency (VE), which you are unlikely to get. At 85% VE, which is probably more typical although you may be getting better than that, you should be good to about 6500-6700 RPM. If you have really good flowing intake manifold, heads, and headers, and you want to run above 6000 RPM then you probably want something bigger than a 750. By the way, you calculate CFM by the following equation:
cubes*.5*RPM*VE/1728
So, a 1000 cfm dominator simply isn't needed (and is undesirable) on your engine unless you put on a big blower :D
cubes*.5*RPM*VE/1728
So, a 1000 cfm dominator simply isn't needed (and is undesirable) on your engine unless you put on a big blower :D
Safety Car
Joined: Jun 2001
Posts: 4,004
Likes: 2
From: Severna Park Md
Re: Carb recomendations for BBC (tworottiedogs)
I recomend the Holley 750. There are two types, double pumper and vacuum secodary. Either one will work good on your BB. Both are easy to modify so you can fine tune for your application. If you buy a used carb I would recomend pullung the bowls and verifying what jets are in it. Its good to start with the stock size holley jets and go up from there if needed. Also on a used carb, check for blown power valve. The newer carbs have a brass restricter in the base to protect the power valve. The part is available to add to the older carbs as well.
http://WWW.mortec.com has a list of all the original jets based on carb list #.
http://WWW.mortec.com has a list of all the original jets based on carb list #.
