3.9L LZ9 engine internal upgrade & performance?

[ericjon262]

I'm probably going to use an LX9 in my fiero, then swap to an LZ9 later when I have more time to complete a build, this build of yours should be pretty potent, mine should include an offset grind on the crank though, (4.3 Liter!) and maybe a custom intake if I want to go crazy!

[NateD4]

Have a bunch of questions on this thread...

I'm doing a LZG swap into my Fiero. I'm essentially a bit behind where you are, however we are on parallel paths.

I'm curious if you flowed the entire intake assembled. I am looking at having my local shop flow the entire assembly before and after port work is done.

How has the build progressed since your last post?

[paramount]

I agree with Nate D4, this thread needs to be re-opened because I would like to know more about the cams you had in the works. I have a LZ4 and have big plans to stroke it to 3.9 liters with the 3.9 crank.
I want to do cams as well and this thread has been a big help but I would like to know more. What are your regrind specs MRTOHIL while still retaining VVT and how did it work out?

[NateD4]

From what I can tell the VVT cam isn't anything special. Just a hydraulic roller profile. Displacement on demand is a different story though. It has special ramps on the cam profile for the DOD profile.

What other info do you need?

[paramount]

I just want to know how everyone's cam situation worked out. A lot of people said just to void VVT but I think with the right regrind on the stock cam (maybe weld to lobes since they are pressed on)
you can make VVT work a lot like honda's vtec system. Keep it so until 3500 rpm your loaded with torque then the cam is retarded and you get high end hp. I just wanted to know if anyone made
any progress on the cams.

[robertisaar]

VTEC is more along the lines of an on/off switch, the HVV6 VVT can and is used by GM as continuously variable. and while being on/off would be simpler, it wouldn't be optimal.

[paramount]

People were having a hard time creating a cam that suited both the advanced cam and retarded cam. I wanted to know if this problem was solved.

[NateD4]

I just want to know how everyone's cam situation worked out. A lot of people said just to void VVT but I think with the right regrind on the stock cam (maybe weld to lobes since they are pressed on)
you can make VVT work a lot like honda's vtec system. Keep it so until 3500 rpm your loaded with torque then the cam is retarded and you get high end hp. I just wanted to know if anyone made
any progress on the cams.

The lobes are actually swedged onto the 'barrel' of the cam. In my case I plan on running much higher springs and decided to go with a billet cam since one of the 3400's I bought a few years ago had a cam that came out in the pieces. I figure why risk it on a built engine.

In any rate, I suppose as with all of my other posts, you need to define your goals.

I'm sure some tweaks to the cam profiles would work well. However I think tuning in the case of a VVT will be a bit tougher as you'll need to find the sweet spot for the various timings which may not be the same for a modified cam compared to stock.

What tuning software do you have? Does it allow you to alter the cam timing?

What are your specific goals?



To answer your question. The only progress I've made is a fairly exact profile of the lobes on the stock LZG and I'm about to cut a billet cam from either 8620 or 9310 to get ground. I'm in the process of creating my own profiles, though it may be a few weeks before I finalize them (still waiting on flow data for the heads and intake).

[NateD4]

I can understand that finding the right cam balance is tough. I'm tempted to say the stock 3.9L cam isn't too bad. The G6 I drove with one in it felt like it wanted to run to 7K. The dyno graphs I've seen appear to show a torque curve fall off around 5900 RPM. But the curve looks fairly flat overall...

Anyone else have any dyno results on VVT engines they can post?

[robertisaar]

i have the GM SAE version...

[paramount]

I plan on bringing the car to a dyno tuner in SW florida. Says he has experience with G6's and uses HPtuners software on his tunes since he works with GM tunes only really (specializes in corvettes).
I don't need it to rev to 7K or anything, just 6500 would be nice. Have some nice low end grunt and then a little more high end. Just a little gain on both ends would be nice. Remember the engine
I have is really the LZ4 but I plan on stroking it to 3.9 with a 3.9 crank and custom pistons/rods.

[NateD4]

Not to shabby a torque curve. How much torque do we want/expect from a NA pushrod engine?

Certainly some cam changes, a bit of compression and a higher redline would give more power and slightly better torque.

[paramount]

The problem is finding someone who can do this cam for me. I plan on running somewhere around 11 compression on 93. Nothing crazy just would like to see a little gain on both ends.
I just posted here to find out if anyone found a solution to the VVT advance/retard woes.

[Kenova]

After looking at aftermarket cams for VVT LS engines I have noticed that as lift and duration increases the amount of advance and retard with the VVT is reduced substantially.
With enough Lift and duration the VVT would become useless.

Ken

[robertisaar]

With enough Lift and duration the VVT would become useless.

why? VVT is used to boost torque at all RPMs by advancing or retarding the cam to shift the powerband around. adding more lift and duration will favor high RPM power while sacrificing low RPM.