Tune necessary for L99 -> LS3 conversion?

[Gunmetal Speedster]

Originally Posted by frankwjr

get with dynoSteve, RDP....he will answer all you q's...look for his Q&A thread...

+1 on DynoSteve. He's a great guy to work with and will hook you up!

[ClawSS]

Originally Posted by fastbroshi

Aren't the LS3s rated a bit stronger on dynos? Every thread I've seen about L99 dyno numbers has them consistently putting down 40hp or so less than the LS3s.

It's the compression. Different pistons. And you aren't touching the pistons in your initial build list. You will still be down HP vs stock LS3.

I think you may be slightly misguided due to missing facts or twisted data.

VVT good.

[xc_SS/RS]

If you really want to swap in a LS3 cam I would at least get the LS9 cam. It's worth about 10-15 hp more up top than the LS3 cam and it holds onto its power longer. Best thing is that it utilizes the same valve springs as the LS3 cam and the LS9 cam is a little cheaper than the LS3

Or the LS7 cam can produce similar results.

You will need a tune for sure

[qcman]

Originally Posted by fastbroshi

Every thread I've seen about L99 dyno numbers has them consistently putting down 40hp or so less than the LS3s.

As mentioned different pistons and compression ratio means with the LS3 cam it will be virtually the same HP as now and the 40 HP less on the dyno has more to do with drivetrain loss through the auto trans and that will still be present.

My L99 was remote tuned by Dynosteve and has had nothing else done to it and it runs way better than before it was tuned. I understand your concern about the AFM lifters but I can't recall anyone having any failures with them on here. Some 2010's needed them upgraded I know by GM but that is all I can recall seeing about them.

[fastbroshi]

Ah, now the pistons being different is good to know. That puts a damper on the LS3 cam switch. I have to admit I haven't seen any instances of outright AFM lifter failure, but man when it was super cold that tapping really had me worried. It hasn't done it like that since thankfully.

[qcman]

Originally Posted by fastbroshi

Ah, now the pistons being different is good to know. That puts a damper on the LS3 cam switch. I have to admit I haven't seen any instances of outright AFM lifter failure, but man when it was super cold that tapping really had me worried. It hasn't done it like that since thankfully.

Yeah I 've heard mine tap a bit now and then too when cold so I turned up the radio lol. I believe when you should be concerned is if they tap when at normal temperature.

I think the L99 pistons have a notch or relief in the top of them IIRC and I think that is what makes the compression a bit less too. I think the VVT in the L99 even stock gives it good torque down low which helps on the launch.

An LS3 conversion as you were intending might give you some peace of mind but nothing performance wise for the money.

[xc_SS/RS]

Originally Posted by qcman

As mentioned different pistons and compression ratio means with the LS3 cam it will be virtually the same HP as now and the 40 HP less on the dyno has more to do with drivetrain loss through the auto trans and that will still be present.

My L99 was remote tuned by Dynosteve and has had nothing else done to it and it runs way better than before it was tuned. I understand your concern about the AFM lifters but I can't recall anyone having any failures with them on here. Some 2010's needed them upgraded I know by GM but that is all I can recall seeing about them.

The different pistons and slight decrease in compression will have a negligible effect on power numbers. Major difference is the cam and lack of DOD/AFM components, heads are the same on both engines. The problem is the L99 cam and valvetrain components are more mild because of DOD/AFM when compared to the LS3

If he goes with a LS7, LS9 or drop in aftermarket cam he will gain power over what the LS3 cam gains. Hell, there's a Lunati cam that is drop in and someone here is running 11's with it

OP there is power to be gained with the LS3 cam and other drop in cams. Go for it!

[qcman]

^ I was assuming just the LS3 conversion would not yield more than the stock LS3 HP of 426 and perhaps a little less than that due to the pistons as that is all he seems to want to do?

[xc_SS/RS]

Originally Posted by qcman

^ I was assuming just the LS3 conversion would not yield more than the stock LS3 HP of 426 and perhaps a little less than that due to the pistons as that is all he seems to want to do?

Oh my mistake. Yes you are correct it will not gain more than what a LS3 comes with stock if all he does is drop in the LS3 cam. It'll have more power than his L99 with the LS3 cam and right valvetrain components. I'm sure the pistons wont affect things too much