mark21742

It's always been my understanding that with a tighter lsa and more overlap you would get a higher peak power, the power would come in earlier, but the powerband would be narrower.

With a wider lsa you would have lower peak power, it would peak later in the rpm range and over all you would have a longer, flater torque curve.

Also with FI you don't need the overlap to pull the charge in because it is already being forced in at pressure.

I have been wrong before, so please correct if or where I am wrong on this. I'm always ready to learn more

88silvergt

iTrader: (8)

I went ahead and paid Pat G to spec me a cam. Will see how that turns out.

matt477

I think you guys are getting lobe separation and centerline confused. that LS9 cam has a 122.5 centerline. the lobe separation is just that, the intake to exhaust spread. centerline is how far it is advanced or retarded. I am new to this sight and don't want to step on toes so Please don't hate on me.

Kip Fabre

I will explain LS and LC so it is not confusing. Lobe separation is the the degrees between IN and EX max lift in cam degrees. So on a cam that is 222 in 232 EX- 112 the Max lift between IN & EX is 112. But if you install this cam 4 degrees Adv. the IN Center line is 108 and the EX Center line is 116. So 108 + 116= 224 crank degrees.

codyseals

Yes please keep this going. I've read nothing but conflicting info on lobe separation for FI.

Kip Fabre

Lobe separation is only a derivative of a cams opening and closing points. There are 4 events to make up a cam. First in the cycle is firing of the cylinder then comes cam events. 1 EX opening BBDC next comes the IN opening BTC this happens before the EX closes so this is call Overlap when both IN and EX are open at the same time. Overlap is measured a TDC so if you have IN open at 4 BTDC and if the EX closes 4 degrees ATDC then you will have 8 Degrees of overlap. After the EX closes the IN is already open the piston is going down now after BDC the IN will close. There are the 4 events. So we will have numbers like EX open 52BBDC EX closes 4 ATDC IN opens 4 BTDC IN closes 44 ABDC so our cam will be 228 IN 236 EX 112LS + 2 Advanced. Here are a few rules for cam timing these DO NOT apply for all applications. Opening the EX earlier makes more top end power . Opening the EX later makes more torque. The later you close the IN gives the engine more time to take in air and fuel which makes higher RPM range and power. The earlier you close the IN the more torque. Over lap is dictated by compression, heads flow RPM range FI or Carb, Turbo, Supercharged. Many variables but mainly by RPM range.

SNLPerformance

iTrader: (15)

I agree, we just finished up a TT 365 with a Texas Giant on a 114lsa that made 980rwhp SAE and table top torque from 5-7k rpm

I believe the LS9 is the most popular because it is cheap and more readily available than the LS6 now, but not necessarily better in a boosted 5.3.

SNLPerformance

iTrader: (15)

Well said