400m performance
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
400m performance
The 750 is way big for a 400. Try a 600 CFM Edelbrock 1406.
Just a quick rule of thumb that works for everything except racing apps:
1.5 times displacement in inches is the carb size in CFM you want.
1.5 X 400 = 600
1.5 X 300 = 450
1.5 X 351 = 525
1.5 X 460 = 690
Works every time! Just pick the carb size that is closest. If in doubt for a street engine go smaller, for a race track vehicle go larger. If you are going to see extended use at high RPM's for power... -Get a bigger engine :-)
Just a quick rule of thumb that works for everything except racing apps:
1.5 times displacement in inches is the carb size in CFM you want.
1.5 X 400 = 600
1.5 X 300 = 450
1.5 X 351 = 525
1.5 X 460 = 690
Works every time! Just pick the carb size that is closest. If in doubt for a street engine go smaller, for a race track vehicle go larger. If you are going to see extended use at high RPM's for power... -Get a bigger engine :-)
Freshman User
Joined: Aug 2002
Posts: 40
Likes: 0
From: U.S.A.
400m performance
I have never trusted that rule. The 1.5 times the displacement is something for guessing. I have a holley 750DP on it and it keeps the lowend but also has it up top.The 600 strangled it up top.
Laughing Gas
Joined: Jul 2002
Posts: 843
Likes: 1
From: USA
400m performance
The varieables here are endless. Everything from the temperature of the day and humidity to tires and gears, to the quality of the tank of gas you last bought have an impact on the way the engine will perform on any given day. The 1.5 rule works pretty good with a close to stock/slightly modified motor. When you start messing with cam profiles, exhaust and intake flow patterns timing, type of ignition, all these things bear on just how much air you can get through the engine. A general rule of thumb for the 351M/400 motors is a 600CFM carb works quite well for the average "Joe" going back and forth to work and a little off-roading. If you spend a lot of time with you hampsters wound up tight than a 750 would probably be a better option. Just my opinion.
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