3.9L LZ9 engine internal upgrade & performance?

[robertisaar]

i have the GM SAE version...

[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?

[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).

[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.

[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]

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.

[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 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]

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?

[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!

[mrtohil]

Obtained a new stock cam . Had the lobes welded and reground. Work peformed by Racer Brown. Unfortunately the option of Mast wasn't available/known when I farmed the cam out. At the time I was looking for someone to make a cam for this engine, all the "big name" cam manufacturers wouldn't even look at it (out of fear of course). And just blew me off. Even a few British racing cams manufacturers wouldn't even look at it. Racer Brown was the only one who I called/emailed that even agreed to look at and into it.

[ericjon262]

what are you doing about a cam? stock regrind? might try calling someone like Mast motorsports and seeing if they can spec a VVT cam for you, they've been pretty big in the VVT tech R&D, so they might be able to help out...

[trotterlg]

I would think the exaust valve would hit the piston when the cam was fully retarded, advance would get it closed earlier. Hope you aren't making your measurements backwards. Larry

[mrtohil]

So I finished cutting the two pistons for cylinders 2 & 5. Now I have to reset the machine for the remaining four since the angles are different than before (thanks GM). I'll try to upload pics of this ASAP in Photobucket.

[mrtohil]

The latest is checking the valvetrain geometry and clearance. So far I checked the pushrod length to obtain the proper rockerarm to valve contact. The pushrods are going to be significantly shorter than stock. Once I got the length figured out I checked the valve to piston clearance. The first cam position came out okay. But with the cam in full advanced I found the exhaust valves hitting the pistons. The good thing is I have two extra pistons to try the cut with. Which later I would need since I really setup the angles on the machine wrong. I was finally able to obtain the angles directly from the valve guides to match them to the machine cutting head. The second test piston came out alot better. I also cut it deeper to clay and determine what actual depth was needed.