Why do some aftermarket intakes have 4 holes at the carb and some have 1 big opening?
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Posting Guru
Joined: Nov 2004
Posts: 1,628
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From: Northeast Nebraska
Why do some aftermarket intakes have 4 holes at the carb and some have 1 big opening?
I understand the dual and single plenum intakes but I havent yet figured out why some intakes have 4 holes, 2 oval opeings or 1 big opening where the carb mounts. If there are 4 holes can a guy use a thick square spacer so the butterflies on the carb clear the intake?
Sort of off the subject....What do you guys think about running dual 500 cfm carbs on a very healthy and well built 429? The truck will be used for towing and I need good torque but I wouldnt mind opening it up once in a while and hear it roar. Would a 500 cfm primary be good for highway speeds and maybe help the milage?
Sort of off the subject....What do you guys think about running dual 500 cfm carbs on a very healthy and well built 429? The truck will be used for towing and I need good torque but I wouldnt mind opening it up once in a while and hear it roar. Would a 500 cfm primary be good for highway speeds and maybe help the milage?
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
On a 4-hole intake, the primary and secondary bores of the carburetor are run separately. This allows the runners for the primaries to be of different size and length than the secondaries. On an open intake (one big hole), one "signal" feeds both the primaries and the secondaries. Fuel and air takes the same path into the cylinder through both the primaries and secondaries. 4-hole intakes tend to be better suited for street use and economy whereas open intakes are performance oriented.
I think a 500 is too small for a 429. I run a 500 on my 300 inline-6 which is a much smaller motor. I think it would starve a 429. I think a 650 is more in the ball park.
I think a 500 is too small for a 429. I run a 500 on my 300 inline-6 which is a much smaller motor. I think it would starve a 429. I think a 650 is more in the ball park.
Moderator
Joined: Dec 2001
Posts: 22,436
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From: Louisville,Ky.
I would run a 750cfm single carb myself, The primaries are only 375cfm which will give you great throttle response and mileage.
The open intakes mix a little mixture between the sides which helps upper rpm power a little while the split dual plane intakes such as the Edelbrock Performer, are divided to the top for better throttle response and torque. I ran an Edelbrock Performer intake and 750 (1407) carb on my 460 and it ran very well.
The open intakes mix a little mixture between the sides which helps upper rpm power a little while the split dual plane intakes such as the Edelbrock Performer, are divided to the top for better throttle response and torque. I ran an Edelbrock Performer intake and 750 (1407) carb on my 460 and it ran very well.
Elder User
Joined: Dec 2007
Posts: 842
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From: royal oak, mich
Go for the dual 500 cfm setup. Make the primary of the secondary carb open up progressively. You get response but if needed you can open up the secondary carb primaries for power. I'm talking Edelbrock carbs. Adjust the AVS to open for your application. You can have your 1000 cfm then. Check the distribution of running on just the primary carb primaries. Don't go leaning things out for mileage to cause problems.
