Need info on 3900 variants

[34blazer]

Gathering up info since Im considering the 3900 as a swap candidate. Ive looked through Mars' threads, but I would like any and all information out there. Pictures of the internals, swap contingencies, different variants, if any variant of the 3900 is preferred over another.


Thanks!

[ericjon262]

http://60degreev6.com/forum/showthread.php/41450-3-9L-LZ9-engine-internal-upgrade-amp-performance

lost of pics in here ^

[34blazer]

Yeah I remember that. What ever happened to that build? Was shaping up to be pretty sweet. I didn't see anything talking about the later versions of the LZ9/LGB, because I have my eye on the newer variant. Anything radically different with the newest 3900s? I need to get in touch with Will and see what he has dug up too. Thanks Eric

[ericjon262]

Yeah I remember that. What ever happened to that build? Was shaping up to be pretty sweet. I didn't see anything talking about the later versions of the LZ9/LGB, because I have my eye on the newer variant. Anything radically different with the newest 3900s? I need to get in touch with Will and see what he has dug up too. Thanks Eric

I don't really know of anything special. I think the only differences were options, flex fuel and the like.

[Guest]

they were pretty much all the same. I think the last year or two the ditched the variable plenum and went to the regular lz4 upper intake. There were probably small differences in mounts or brackets pending on what make and model it came out of however but thats all external stuff.

I always wondered why gm used pistons with 4 valve reliefs in a 2 valve head, I never looked into it but I am thinking the pistons shared the same bore as the 3.6 dohc? don't know though. most likely a cost savings thing for sure though.

[34blazer]

Thanks Gents!

Pulled the trigger on a low mileage unit(24K) from a 2009 Montana. Need to beg, borrow, or steal some cam bearing spacers, now.

[Guest]

I'm going to talk to a machinist tonight about the possibility of making some actually.

[34blazer]

I'm going to talk to a machinist tonight about the possibility of making some actually.

NIIIICE!

CNC-GUY still machining parts too?

[34blazer]

Talked to Comp about a cam for this, nope. E mailed delta to see what they can do.

Any suggestions for any other cam grinders?

[Guest]

I spoke with Crane and they pretty much aren't going to touch it. I am sure they will do a regrind but they have no cores, which means no new grinds. I asked them about welding the lobes and regrinding and they said no to that since the cam is iron.

[34blazer]

I sure someone out there would gladly build a cam for this engine, but limited to a CNC billet, and that will get expensive. Other option, custom cam bearings, which most wont touch due to the amount of material needed. If TCE wont make cam bearing spacers, then a budgeted option wont exist.

OTOH, roller cam bearings? But a quick search yielded no options as well, closest size is a 55mm bearing for the SVO blocks, a little too small.

I will probably contact a company that has the capability to build a custom billet piece, and find out how much it will cost.


Last resort would be to figure out optimal cam timing with the stocker and lock it out, which I will need some help with since this is going to be turbofied.

[Guest]

It seems that locking the cam out is a large compromise, since the cam grind is meant for the VVT, which as I understand it, is constantly adjusting, not just by RPM and/or load.

[Guest]

When I was communicating with crane, they too mentioned a billet cnc cam but crane doesn't have that capability.. This is the final email

"IF YOU FIND A CAM COMPANY THAT USES A CNC CAM GRINDER THEN IT CAN BE POSSIBLE. WE DO NOT USE A CNC GRINDER. WE USE LOBE MASTERS THAT RIDE ON A PATTERN. LOBE MASTERS ARE AROUND $1000 EACH TO MAKE. IT WOULD NOT BE COST EFFICTIVE FOR US TO PRODUCE LOBE MASTERS FOR A CAM THAT IS NOT POPULAR."

I saw WOT offered a billet cam so I figured one could be made for the 3900 journal size. paraphrasing Ben but I think he said something about how it still couldnt' be done.

a member here dynod a 3900 with homemade headers, lz4 upper, 75mm TB and through the auto made 206 whp with the cam locked in the default position which from reading on here is the full advanced position. Peak tq was around 4900 rpm even with the stock cam specs which I don't think are too bad.

from what CNC said stock cam is advanced about 14 degrees. Not sure if thats crank or cam degrees.

If its crank degrees then its only 7ish at the cam. there are 25 teeth on the lz cam gear so each tooth is 7.5 degrees roughly. retarding one tooth could pretty much bring the cam close to a straight up position. I thought of going this route.

Costa Mesa RandD might be able to make a billet cam for us. (949) 631-6376

[Guest]

according to this video, which might be oversimplifying, if the bar stock used has a large enough diameter, then the larger journals of the LZ can easily be cut to make a new blank so to speak. It also seems that the 3 bolt pattern of the older style cams can also be machined, allowing use of the cloyes double roller. No I haven't called comp to confirm

https://www.youtube.com/watch?v=sYO0Yp4Ag5g

it seems all that Comp would need to change would be the programming for the journal size for the CNC to cut. Even keeping the single timing chain bolt nothing else in the programming would need to be changed. A call to Comp might be in order.

my thread that got locked.

http://60degreev6.com/forum/showthread.php/51974-WOT-billet-cam

[34blazer]

If they can cut a cam from a blank, then this email I received today is total BS

The length on the cam may be the same, but its the lobe spacing, the VVT and other dimensions on the cam that differ. Per our engineering dept, we do not and will not have any parts for these engines.






Thank you


Jeff

901-375-3416

Remember, you can order direct from us.