Why is it that that I see intake manifolds that are wide open where the carb sits (I believe the term is open plenum?), have four holes (spread bore?) or are split down the middle. What are the differences? Do carbs come in similar configurations?
intakes & carbs
- Thread starter tonyk72
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MaineShark
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Dual-plane (split plenum) intake manifolds favor low-end torque.
Single plane (open plenum) intake manifolds favor top-end horsepower.
The carb will be the same, in either case. The number of carb barrels is related to the diameter limitations of the venturis. Large-diameter venturis don't meter fuel as accurately, so a greater number of small venturis is more precise than a smaller number of large venturis. That's why you end up with carbs like the Q-Jet: it has a pair of small primary venturis to accurately meter fuel in part-throttle conditions and idling, for good driveability, and a second pair of larger bores that open up when you step on it, to flow a large amount of air. With such a great quantity of air, variances in fuel delivery don't have as much effect as they would at smaller flow rates. The "two small, two large" configuration is called "spread bore," since the bore centers of the secondaries are spread to account for their larger diameter (look at the Edelbrock Performer and Performer RPM manifolds, to see the "spread" of the bores in the regular Performer, compared to the "square" alignment of the bore centers of the RPM).
Joe
Single plane (open plenum) intake manifolds favor top-end horsepower.
The carb will be the same, in either case. The number of carb barrels is related to the diameter limitations of the venturis. Large-diameter venturis don't meter fuel as accurately, so a greater number of small venturis is more precise than a smaller number of large venturis. That's why you end up with carbs like the Q-Jet: it has a pair of small primary venturis to accurately meter fuel in part-throttle conditions and idling, for good driveability, and a second pair of larger bores that open up when you step on it, to flow a large amount of air. With such a great quantity of air, variances in fuel delivery don't have as much effect as they would at smaller flow rates. The "two small, two large" configuration is called "spread bore," since the bore centers of the secondaries are spread to account for their larger diameter (look at the Edelbrock Performer and Performer RPM manifolds, to see the "spread" of the bores in the regular Performer, compared to the "square" alignment of the bore centers of the RPM).
Joe
1BAD80
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This site will tell you everything about every intake made and how it flows, plus some on carbs. This is one of the best intake sites I have found, it may say Mopar but covers ALL manufactures.
http://victorylibrary.com/mopar/intake-tech-c.htm
http://victorylibrary.com/mopar/intake-tech-c.htm
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