What would be the right LSA to use on a truck? From what i understand, the lower the lsa, the more power you get in the lower rpm range, right? so, if i had a choice between a 112 LSA cam and a 114 with the same duration/lift numbers, which would be better? open to any opinions,

 

A 112 lsa will have a noticeable lobe and will be harder to tune. I'd say keep in the 114/115 range.

 

I've heard that with a auto use the 114 and the manual you can use the 112. I think the 112 doesn't work as well with the auto trannie.

 

It depends ... if it's the typical size cam that most truck guys have been using (relatively small), then it won't matter much. The 112 will have more overlap so it does move the powerband up and have a more noticable idle to it. Tuning can usually work out any drivability issues with an auto on the more radical cams.

If you are planning on going forced inducted, then keep it on no less than a 114. Any lower and it will bleed off boost which is a bad thing.

 

Good info I was wondering if that was the case! Thanks!

 

My understanding was that the lower LSA cam will have a slightly "peakier" powerband, meaning, it'll make more power in the midrange and peak, but also fall quicker 'past' peak. Where the cam is in the heart of it's RPM range, it'll make great numbers. The (extreme?) lowned is supposed to be a bit softer than a 114.

The 114 spreads the love out a bit... It won't have the same peak HP numbers. It will fall off slower after peak. It'll take back some of that meaty midrange, and give it to the lowend and idle quality. So you end up with a slightly broader RPM range compared to the 112.

So, the lower the LSA, the more 'supercharging' effect or scaveging you get from the cam, with the cost of a peaky power-range.

The higher LSA will give up a bit of that power, but make it more user friendly.

I guess you could liken the two to a two-stroke and four-stroke motorcycle. The two stroke as 'narrow' valve events and peaky power, while the four stroke has 'wider' events, making power all over.

 

I was thinking more along what Marc said ... I don't know if I would agree with the 'supercharging' affect though. No way is a cam going to force feed a motor with air.

The lower the lsa number is, the more valve overlap that there is. It will have a softer bottom end, which is why a lot of people say use it with an auto and a bigger stall than stock. The valve overlap is where the intake and the exhaust valve is open at the same time, that being the reason it is bad for boosted engines.

 

Yeah, sorry, I don't mean actual forced induction...

I read that the lower LSA (more overlap) allows the exiting exhaust gasses to pull in the fresh charge of fuel, just before the downstroke of the piston. I guess it's technically the opposite of what a supercharger does, but it does allow more fuel to enter the cylinder, than if it was operating on the stop-go-stop-go valve events of a wide LSA.

 

what about 119lsa

 

The lobe separation is the number of degrees separating the peak lift on the intake and exhaust lobes of the cam,in theory the wider the lobe separation the smaller the valve overlap and the greater the low and mid range torque your motor will produce.In actuality the amount performance increase made by widening the lobe separation is limited by head design and the power range you are intending to use.Traditional SBC generally don't benefit from exceeding 110-112 degrees,because they begin to lose lots of power after the midrange.On LS1 motors it's common to see LSAs as high as 116-117,because of the superior head design.Generally supercharged motors like more LSA to maintain higher boost levels and NA motor like lower LSA to build power at higher revs.