Do you want to do a 3900 swap? whats stopping you

[geoffinbc]

3900 heads with a 1.87" intake valve flows as good as an LS6 head with 2.0" valves?

[ericjon262]

3900 heads with a 1.87" intake valve flows as good as an LS6 head with 2.0" valves?

LS1 heads have 2.00 inch intake valves and flow more and old camel humps with 2.02 intakes...

[geoffinbc]

Right but your talking valves only .020" different in size and a head casting light years apart. Vortec heads are better than camel hump heads. So it's easy to believe an LS1 or LS6 can out flow old small block heads. But with valve sizes .130" apart that is a huge difference. Along with that bigger valve goes a bigger port so I just can't see a 3900 flowing as much as an LS6. Are there any numbers from the same bench or even the same brand of bench to prove otherwise?

[ericjon262]

I don't have anything to prove it, but I've seen many different flow benches test many different heads, and have similar results. something to remember here, is that 60 v6 heads open into the cylinder away from the wall, LS heads open down along the wall.

[Guest]

canted valves help with flow throughout the entire lift range of the cam. Just need a good cam, to make good power in these LZ engines

[Guest]

bringing this back up. did some research on this and Marc from BCC made a post how the factory vvt was approx 7-9 degrees advanced when the vvt was disconnected from the ecu.

This might be right, as research on the l99 v8 shows the vvt is roughly advanced the same amount.

I am guessing they mean cam degrees, which makes the crank degrees closer to 14-18 degrees yes? I counted the teeth on the lz9 cam gear and it has 50 teeth. That equates to 7.2 degrees per tooth at the cam and 14.4 at the crank.

So retarding the cam one tooth should make the cam in an almost straight up position, if not around 3 degrees advanced at the crank. Most cams are ground with around 3 degrees advanced already so by making this mod, this should help with top end power by not being so advanced.

Lmk if my math is wrong or info that I have read about where the vvt cam is at when deactivated is at.

Keeping the stock cam will allow easy transplants.

[neophile_17]

I have been looking at this for a little while and even bought and tore down the 3900's little brother, the LZ4. What I've determined from research is that the profile of the stock cam is designed to work with VVT. Several people have tried to pin the cam to a specific position or operate the VVT in an 2 position on-off way. The results I saw seemed to be universally underwhelming. I'll either try to get a MS to operate the VVT or get a more traditional profile for my build.

~sam

[Guest]

I have been looking at this for a little while and even bought and tore down the 3900's little brother, the LZ4. What I've determined from research is that the profile of the stock cam is designed to work with VVT. Several people have tried to pin the cam to a specific position or operate the VVT in an 2 position on-off way. The results I saw seemed to be universally underwhelming. I'll either try to get a MS to operate the VVT or get a more traditional profile for my build.

~sam

I've come to the same conclusion from what I've seen as well. It doesn't seem to be a slowly changing cam angle, but something that seems to be happening all the time. There will also be some EGR effects built into this changing cam angle as well.

This is one of the largest reasons I haven't grabbed a 3900 yet, because of the cam issue. Cam bearing spacers are like hen's teeth, and full custom cams are expensive. If there was an affordable off the shelf cam option that didn't require bearing spacers, or the VVT to function, it would make the 3900 an actual consideration.

FYI, DIYautotune has a VVT controller that can connect to the MS, but I'm not sure of the specifics of the functionality. It was developed for the Miata crowd, so maybe taking a look at how their VVT works and see if it might be compatible would be good. This was my first consideration, when I first started looking at using the 3900. The VVT controller can be used stand alone as well.

[Guest]

I have been looking at this for a little while and even bought and tore down the 3900's little brother, the LZ4. What I've determined from research is that the profile of the stock cam is designed to work with VVT. Several people have tried to pin the cam to a specific position or operate the VVT in an 2 position on-off way. The results I saw seemed to be universally underwhelming. I'll either try to get a MS to operate the VVT or get a more traditional profile for my build.

~sam

I only know of one person locking the cam before swapping to a wot cam. it was locked in the full advanced position(default). it still peaked at close to 5500 rpm or so for hp.

It made 206 whp that way. top end fell off of course because of the amount of advance it had. I think bringing it back closer to straight up position will help the top end although it might not need anything done and just run it with the vvt disconnected. Do you know of anyone else who locked it, and has a dyno of it? Here is Reidl's dyno and this was through the auto trans. He had a lz4 upper intake and tb I believe as well.

[neophile_17]

I'm 98% that Joseph Upson was playing with the VVT mechanism before doing a full build including a custom cam. I remember at least 2 other guys playing with it. One was definitely pinned to a traditional angle. Robert Isaar also did some simulations that point to significant power changes based on cam angle.

I would definitely look into it more before pinning the phaser. You can see my change of heart on fixed cam phasing here:

http://60degreev6.com/forum/showthread.php/51996-LZ4-Fiero-Swap

I'm hoping to get back to that project in the fall. Between racing, work, blowing up my LX9, and life I haven't even looked at that stuff.

sam

[robertisaar]

the million ways people choose to break up or spell my name are almost amusing.... anyways.

GM wouldn't have gone through the trouble of making a VVT OHV engine if there weren't some significant benefit to it. the VVT engine's cam profiles are a bit out of the ordinary from what I've seen, they're definitely intended to be used with the cam phaser for peak performance/emissions/economy. you could run it at a fixed angle, but you would probably be far better off getting a custom cam at that point and design in your own compromises rather than work around the stock profile.

[neophile_17]

the million ways people choose to break up or spell my name are almost amusing.... anyways.

Sorry man, I meant to go and fact check that because I remember messing it up before but CRS kicked in.

[carbon]

the million ways people choose to break up or spell my name are almost amusing.... anyways.

Robert IS Always Anal Retentive?

[robertisaar]

Sorry man, I meant to go and fact check that because I remember messing it up before but CRS kicked in.

you're far from the worst of offenders, which I'm certain at times have had stuff as wild as the Cyrillic alphabet to questionable use of umlauts.

Robert IS Always Anal Retentive?

sadly, fact is almost always less exciting than fiction; first, middle initial, last.

[robertisaar]

thought to cast out into the web:

anyone have pictures/information specifically on the gen4 cam reluctor? GM says 4 teeth, variable pulse-width to decode. I'm curious how significant of a difference there are between the teeth. after digging a lot further into the P66 V6 PCM than I ever thought I would, I'm remembering that the LT1 actually uses a similar scheme for its 4X crank sensor... I believe the code in the P66 V6 could be setup to utilize the cam position sensor in the same fashion.

this would allow for a gen4 to be controlled with an unmodified(beyond code patches) OBD1 PCM considering that one of the EGR outputs could be repurposed for cam phaser control.