Custom spec cam seems a little big

[stevieturbo]

It really depends. If it was a very tiny blower with lowish goals, maybe not. But if it's a big enough blower moving more air, overlap will help making power/torque.

Although really a lot boils down to the LS really isnt that fussy when it comes to cams. Almost any half sensible cam is going to offer good results everywhere. Some may tailor a little to say mid range or higher rpm, but they'll all be good.
Some however with too much overlap or duration, can hurt lower end performance, and given boost...likely no gain up top. Which makes trying to go for a big lopey type cam just pointless.

And no sense picking a cam with a ton of lift, if your heads/valvetrain arent designed with that in mind. That said, the GT9 I had has a lot of lift, but it really did perform well, and hang on well up the rpm's too. A nice all rounder. But although it never did give any issues...the lift did scare me a little.
I did end up changing the cam for something with less lift. Really though...I've had a few different cams in mine, and none have really shone above another. Hence why I say overthinking it is pointless.

[JANNETTYRACING]

Originally Posted by Big Biscuits

I had a well known cam spec shop spec a cam for my stock ls3 with all the stuff in my sig. Only difference was it is for a Big centri power adder. Plugging the specs in my cam calculator spreadsheet puts the overlap out around 10.5. I understand what the numbers stand for and what setup should run what profile, but it seems a little big. I would not want to lose low end boost in exchange for top end power. Also, DCR is around 8.02 vs my current BTR PD cam of 7.67. Bringing the DCR up would bring in TQ vs dropping it on my cam now, so that's a big plus. Cam specs are 23X/24X 114+4. Real close to this BTR PD stage 3 I run now (wink, wink). I have seen custom cams spec'd for larger motors with less duration and overlap by the same people. Please don't tell me to just run what I have. I am going to run a different cam regardless as the setups will be different than what I was originally hoping to do. A PD cam is very different from centri. Any thoughts?

It is certainly bigger than you need.

The LS3 Heads are so good it doesn't take a big cam to make them work well.

Especially when dealing with blowers, you have a way to force air in to the engine so quite honestly you can just increase the size of the exhaust lobe and get great power gains.

When we port heads for blowers we focus on the exhaust side and do very little on the intake ports. Same concept.

Also like putting a 102 Throttle body on a blow through centrifugal supercharger no gain, no point.

I have been all over the place with cam testing and believe I found the sweet spot for the LS3 head with my Rough and Smooth Idle cams.

I offered and discontinued several cams early on, one of which was copied and marketed under a popular name, that is still around.

That cam is Soggy on the street, needs 4.30 gears and only make 5-10 more PEAK HP than my rough Idle cam in our testing.

My current rough Idle cam has proven time and time again to be a solid performer, runs more MPH in the 1/4 the larger cams, Drives better, you can leave a standing start in 2nd gear but still has the rumpity rump idle.

My smooth Idle cam makes great power with a wider RPM range and maintains perfect street manners but everyone wants the Rumpity Rump, Rump Rump, so I sell 4 to 1 rough Idle to smooth Idle.

When selecting a cam for an LS or any engine for that matter moderate bigger cam gives the largest gain, then as the cam gets bigger the gains get smaller from cam to cam.

Ted.

[Big Biscuits]

Originally Posted by JANNETTYRACING

It is certainly bigger than you need.

The LS3 Heads are so good it doesn't take a big cam to make them work well.

Especially when dealing with blowers, you have a way to force air in to the engine so quite honestly you can just increase the size of the exhaust lobe and get great power gains.

When we port heads for blowers we focus on the exhaust side and do very little on the intake ports. Same concept.

Also like putting a 102 Throttle body on a blow through centrifugal supercharger no gain, no point.

I have been all over the place with cam testing and believe I found the sweet spot for the LS3 head with my Rough and Smooth Idle cams.

I offered and discontinued several cams early on, one of which was copied and marketed under a popular name, that is still around.

That cam is Soggy on the street, needs 4.30 gears and only make 5-10 more PEAK HP than my rough Idle cam in our testing.

My current rough Idle cam has proven time and time again to be a solid performer, runs more MPH in the 1/4 the larger cams, Drives better, you can leave a standing start in 2nd gear but still has the rumpity rump idle.

My smooth Idle cam makes great power with a wider RPM range and maintains perfect street manners but everyone wants the Rumpity Rump, Rump Rump, so I sell 4 to 1 rough Idle to smooth Idle.

When selecting a cam for an LS or any engine for that matter moderate bigger cam gives the largest gain, then as the cam gets bigger the gains get smaller from cam to cam.

Ted.

Thank you Ted. May I ask, how much overlap is too much? I agree with going with less duration intake and a little more exhaust works well with blowers. Centri setups seem to like overlap from research. I have not found a solid do this, don’t do this rule yet.

[JANNETTYRACING]

Originally Posted by Big Biscuits

Thank you Ted. May I ask, how much overlap is too much? I agree with going with less duration intake and a little more exhaust works well with blowers. Centri setups seem to like overlap from research. I have not found a solid do this, don’t do this rule yet.

Overlap affect drivability low speed performance and cylinder filing at low speeds that is what gives the rumpity rump.

At high engine speeds you wouldn't be able to discern overlap affects unless excessive

We have seen that when a car will have low power with boost because it is being blown out the tail pipe.

A little overlap is fine it helps exhaust burnt gasses to make room for new charge.

The fact is there is no math or single number that is good for every application there are far more factors that need to be accounted for.