[ericsmith881]

Looking at some of the upgrade packages offered by various tuners, I see many of the cam or cam+heads builds include (require?) a cam phaser lockout.

Call me crazy but I thought one of the keys to the amazing low-end driveability AND high-RPM power at the same time of the 6.2L LT1 was the variable cam phasing on the stock motor? Why would you want to do away with this? I get that a radical cam might be too difficult to accommodate, but I'm seeing this lockout on mild (<100hp gain) NA build packages. Clearly not all-out race stuff...so why the lockout? This feels like going backwards in technology just because it's the easy choice.

My last ride ('96 Camaro SS) had a big, lumpy aftermarket cam and made great top-end power. It also idled poorly which made daily driving in traffic annoying. I'm hoping there are options where this can be avoided with today's technology? These guys (https://www.texas-speed.com/p-4312-t...-camshaft.aspx) seem to have done it.

[Joshinator99]

Originally Posted by ericsmith881

Looking at some of the upgrade packages offered by various tuners, I see many of the cam or cam+heads builds include (require?) a cam phaser lockout.

Call me crazy but I thought one of the keys to the amazing low-end driveability AND high-RPM power at the same time of the 6.2L LT1 was the variable cam phasing on the stock motor? Why would you want to do away with this? I get that a radical cam might be too difficult to accommodate, but I'm seeing this lockout on mild (<100hp gain) NA build packages. Clearly not all-out race stuff...so why the lockout? This feels like going backwards in technology just because it's the easy choice.

My last ride ('96 Camaro SS) had a big, lumpy aftermarket cam and made great top-end power. It also idled poorly which made daily driving in traffic annoying. I'm hoping there are options where this can be avoided with today's technology? These guys (https://www.texas-speed.com/p-4312-t...-camshaft.aspx) seem to have done it.

KingLT1 and others can explain in greater detail, but the AFM/DOD stuff is not reliable at higher RPMs and the larger duration can cause an interference issue depending on how the cam gets phased. You can keep the AFM/DOD stuff with an aftermarket cam but it will be a very conservative cam (which isn’t necessarily a bad thing). Edit: I meant AFM/VVT.

[Ryfly05]

Originally Posted by Joshinator99

KingLT1 and others can explain in greater detail, but the AFM/DOD stuff is not reliable at higher RPMs and the larger duration can cause an interference issue depending on how the cam gets phased. You can keep the AFM/DOD stuff with an aftermarket cam but it will be a very conservative cam (which isn’t necessarily a bad thing).

That's not what he's asking about. AFM/DOD is not the same as variable valve timing.

OP, sorry I do not have a good answer to your question, I've been wondering the same thing. The link you posted mentions the constantly changing piston to valve clearances as the main challenge, which makes sense with more duration AND lift with an aftermarket cam.

[95 imp]

It has to do with VTP clearance.

Higher lift and longer duration mean that, at the extremes of VVT, there can be contact.

[Joshinator99]

Originally Posted by Ryfly05

That's not what he's asking about. AFM/DOD is not the same as variable valve timing.

OP, sorry I do not have a good answer to your question, I've been wondering the same thing. The link you posted mentions the constantly changing piston to valve clearances as the main challenge, which makes sense with more duration AND lift with an aftermarket cam.

Sorry, I meant AFM/VVT. Sorry for the typo. But I have both deleted for the reasons I mentioned.

[UnknownJinX]

I don't mod my cars, but I do remember reading about VVT on LT1.

Aren't there limiters that can limit how much the cam can phase if the lift and valve/piston kissing ends up being an issue? Supposedly, stock ECU isn't even using up the physical phasing limit of the VVT system.

I do recall there is an HP limit on when VVT will fall apart since the phasing is supported by oil pressure. Basically, the actual cam and the sprocket/timing gear are kept apart and regulated by oil pressure, so at high HP, the force on the gear will be greater than what the oil pressure can provide which will cause issues.

[ericsmith881]

Originally Posted by Joshinator99

KingLT1 and others can explain in greater detail, but the AFM/DOD stuff is not reliable at higher RPMs and the larger duration can cause an interference issue depending on how the cam gets phased. You can keep the AFM/DOD stuff with an aftermarket cam but it will be a very conservative cam (which isn’t necessarily a bad thing). Edit: I meant AFM/VVT.

OK that at least makes a little sense now. Thanks for the info! Still feels like this is something that can be accounted for in the cam design, and obviously has by at least some folks. The thing that still doesn't sound right is these lockouts are coming along with mod packages that are adding maybe 50hp-75hp. That doesn't sound like a radical cam. You can nearly get there with just a CAI, some long tubes, an LT2 intake, and a good tune from what I've heard.

[SOCAL.M6.ZLE]

Originally Posted by ericsmith881

OK that at least makes a little sense now. Thanks for the info! Still feels like this is something that can be accounted for in the cam design, and obviously has by at least some folks. The thing that still doesn't sound right is these lockouts are coming along with mod packages that are adding maybe 50hp-75hp. That doesn't sound like a radical cam. You can nearly get there with just a CAI, some long tubes, an LT2 intake, and a good tune from what I've heard.

I dont think anyone is comparing CAI/LT to a cam...as a phase.1 step.
I can only speak for LT4's but it looks like most guys are starting with bolt ons... getting use to the power bump... then a cam makes sense for the lumpy idle, HP gain and 38% fuel lobe, which gives your high side another 100rwhp +/- or headroom for more boost, or E.


As for the VVT phaser lockout... i will be doing the Katech VVT delete and using the LS3 sproket.. see below.

[Joshinator99]

Originally Posted by SOCAL.M6.ZLE

I dont think anyone is comparing CAI/LT to a cam...as a phase.1 step.
I can only speak for LT4's but it looks like most guys are starting with bolt ons... getting use to the power bump... then a cam makes sense for the lumpy idle, HP gain and 38% fuel lobe, which gives your high side another 100rwhp +/- or headroom for more boost, or E.


As for the VVT phaser lockout... i will be doing the Katech VVT delete and using the LS3 sproket.. see below.

Yep, I used the Katech VVT and AFM delete covers, and they’re both really nice pieces.

[Tim M]

I understood it to be about spring pressures. High spring rates (due to the upgraded camshaft) will result in the phaser no longer working as designed.

Cam Motion recommended mine to be locked out as well...not an overly large camshaft either.

[Stroker548]

When I did the cam in the Denali, I ordered the kit from TSP. It came with a complete lockout and I believe an 8 degree swing. I put in the 8 degree cuz it was only a stage 2 cam. The first time I sent the ECM out for tuning they tuned out the VVT completely. It was a total pig off the line. Sent it back and told them I had the limiter in it and not the lockout, so he retuned accordingly. It was a nite and day difference. I’m a big believer in keeping the VVT if you possibly can.

[BlackbeastSS2]

You mainly use a phaser lockout in a high horsepower builds and especially with high cylinder pressure that require you to prevent the VVT retarding your timing.
VVT will change the cylinder's ability to build pressure, camshaft timing is then retarded, the intake valve will close later usually sometime during the compression stroke. This will cause a drop in cranking compression and that hurts low-rpm power.

There is obviously pros and cons about either limiting your VVT timing swing or totally locking it out. It really depends on your builds. My first build with the Lt1 Gen 5 engine I used a phaser limiter and this build it was recommended by my builder to lock it out.