Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - More Cam Tech, close LSA
View Single Post
  #12 (permalink)  
Old 02-02-2007, 08:27 AM
454C10 454C10 is offline
Last photo:
Join Date: Dec 2004
Location: San Antonio, Texas
Age: 53
Posts: 4,023
Wiki Edits: 0

Thanks: 0
Thanked 26 Times in 26 Posts
Cylinder filling is the key.

Poor flowing heads prefer a tighter LSA. Exhaust scavenging from overlap helps the intake pull in more cylinder charge. Therefore, helping the intake port flow more.

Carbs prefer a tighter LSA. A carb needs more signal from the engine to deliver the intake change and exhaust scavenging increase the signal. An efi system can deliver fuel no matter what.

Not all efi's use manifold pressure to determine the amount of fuel required. Therefore, using wider LSA to increase vacuum for a MAP sensor is not the only reason to do so. EFI just doesn't need a lot of signal (air flow) from the engine to deliver fuel.

Rod/stroke ratio also effects the amount of LSA required. The location of the piston in the bore relative to the crank angle and valve timing can make big changes. Typically higher ratios prefer tighter LSA.