3.9L LZ9 engine internal upgrade & performance?

Why are you going to use LS1 valves?

My guess is the larger valves, didn't see any in the store for the 3900 and I'd like to go larger on the exhaust valve, looks like there may be just enough room for 1.7". Would like to see more pictures instead of words though.

[SappySE107]

Why are you going to use LS1 valves?

[mrtohil]

Hey everyone. Started another quarter. Well, here's the latest developments (issues).
I am going to try to fit the LS1 valves into the heads. This in turn will means I have more than likely have to replace the valve seats. And also widen/unshroud the combustion chamber around the intake valve, especially on the outer edge of the chamber.
Also, discovered that the current LS1 pistons will work for four of the six cylinders. Due to the fact that the other two cylinders have the intake and exhaust places swapped. So, we're going to have to cut the reliefs by hand (not literally, but you know what I mean) onto the non-cut side of the pistons (since I have to match all). But that will have to wait until I have the valve fitting resolved.

[gectek]

cam journal is alot larger....answer = no. just get the oem ones.

[mrtohil]

Does anyone know if the OEM cam bearings are similiar to another GM engine? For example, the 3.1L cam bearings can be replaced with SBC cam bearings which are wider.

[gectek]

they are def 1.7.

[robertisaar]

http://60degreev6.com/forum/showpost.php?p=333209&postcount=9

1.7 according to that...

[torq455]

when i think about it...that sounds familiar.

[robertisaar]

they might be, but for some reason i remember them being higher ratio than a 1.6....

[torq455]

i thought they were 1.6.

[robertisaar]

IIRC its like 1.7 or 1.8:1...

[mrtohil]

Does anyone know what the stock rocker arm ratios for this engine is? Since I didn't measure them before I tore it apart...Doh!

[robertisaar]

i imagine the constant movement is for EGR purposes... that would explain why it doesn't move much at WOT.... idle is probably fairly still as well...

[gectek]

all the tuning valve does is close when it is grounded. i did try a 6 volt battery from a lawn mower on it, but it still opened and closed it with nowhere in between. it is actually a fail intake IMO. the plenum neck up to the top chamber is way small and retarded, as well as the pocket at the front.

you should watch the vvt events with a scan tool and graph it. crazy stuff. it is never a constant at any speed. it moves all the time. during WOT for a while it will stay somewhat static. it could be a good idea for pwm the duration of a lobe too....but that can be a bad thing as well if your homemade circuitry doesnt make it work like it is supposed to and a piston hits a valve due to it hanging open

this is from car craft:

"Advancing the camshaft means that you are starting the opening and closing process sooner in the cycle. It generally improves low-speed torque and mid-range power while sacrificing top-end hp. Conversely, retarding the cam detracts from low- and mid-range power in order to help top-end power. Generally, moving a camshaft a couple of degrees will not make dramatic changes to the engine's power curve."

this is how i understand it, but when you advance it in desktop dyno, EVERYTHING drops like a rock. you don't gain anything anywhere. maybe under 2000, but DD doesn't go down that far. i'm not seeing the trend above though either...

IDK.... i want a 3900 making the power(and fuel economy) of a small port 3100 until i really start getting on the throttle, then for it to turn into the beast it is... its what the LT5 did, i don't see why we can't do it.

it seems through DD i would be better off referencing MAP for the power switching... maybe at 70-75kPa it retards for full power. i''d be happy with that.

VVT cams perform differently than non VVT cams. That's why my reground VVT cam to specs more similar to fixed camshafts, stopped showing the power increase that it did when retarded in stock specs.