I had a carb selection question and was hoping to get some good advice. I was thinking about running the Holley Street Avenger System on a SBC 406. I was wondering what the better choice of carbs would be between the 770cfm 400+hp and the 870cfm 500+hp models. Our 406 has a a cam with 224/230 duration with .502/.510 lift at 110 degree seperation. The heads are 23 degree Dart Iron Eagles nicely ported with 64cc combustion chamber and 9.6:1 compression. The intake is most likely going to be the Edelbrock RPM Air Gap or the Victor Jr. ( was hopin to get some feed back on that choice also). The cam range is from 1900-5600 and was planning on throwing on a set of 1.6 roller tip Pro Magnum rockers. Any advice would be greatly appreciated. I am unsure of what the power output of the engine is going to be so I was wondering if 870cfm would be too much and if 770cfm would be too small. Any advice would be greatly appreciated.

-Mark

Sounds like a nice, streetable 406 you've got.  Given the specs you spelled out... IMO, you'd be fine with the 770cfm carb (or similar size) along with the E-brock RPM intake.

Unless you're going to be operating above 6,000rpm (which your cam won't do well), stay away from the bigger carb and Vic Jr.  General rule of thumb is that a single-plane only begins to outperform a dual-plane above 5,500rpm.  How often are you going to buzz your 406 beyond that?

Hey, thanks for the info. Not really planning on pushing it past 6 grand becuase 1st the powerband is gone and 2nd dont want to risk the engine. Any estimate on the power output..? I was looking at the ImpersonatorII that CHP built and found that the 406 we are building up is very similar. You think this engine is comparable to the Impersonator?? I believe they were getting some 530ft/lb and 512 horses.

-Mark

I've never been a fan of estimating power output from a sheet of paper (or message board).  There are simply too many variables.  Frankly, there's only two ways to tell and one is better than the other.

1)  Put it on a dyno.

2)  Run it down the strip.  You can directionally calculate power output from the trap speed and vehicle weight.

Stoplight to stoplight would work better with the 770, full race the 870.

If an automatic and on the street definatly the 770. A stick could handle either carb whether on the street or track, simply because you can keep in a better and lower gear selection to keep the Rs up.

But peaking those Rs under 6K really doesn't need 870 cfm.

Bogie