DANIEL TINDER (2/3/2013)
Ted,
Curious: Is that "optimum intake tract length" across the board, or is either torque or high rpm HP favored when shorter? Also wonder if you have found any difference in height between the carb. brands that make appropriately sized models? Was the height of the 1/4" taller manifold likely limited by hood clearance when using an OEM '57 T-Bird aircleaner?Daniel. Optimum intake tract length is not expected to be the same across the board. And optimum even on the same combination depends alot upon driving characteristics and the rpm range being targeted for. Head flow, camming, exhaust, ignition timing, and other variables all enter into the equation. If one item is changed, then all items typically must be re-examined again. But for a single four equipped Y, a 2” high carb spacer tends to give the best overall results but the spacer design itself may vary. Even with the Blue Thunder and Mummert intakes being very similar in design, each manifold has its own preference to spacer design or style.
The factory has it easy in that all vehicles of a given model have the same engine combination and tuneup. For the hobbyist who is constantly changing up his combination, then a new tuning scenario presents itself with each change.
But beyond all that and as a general rule, torque values increase as intake tract lengths increase while horsepower numbers may go up with decreases in intake tract lengths. My roadster engine is now making 520 ft/lbs torque and much of that is attributed to the sheet metal intake it is running.
Lorena, Texas (South of Waco)