Cam Timing, What is best for 8psi turbo stock cam?

[Schmieder]

1996 Pontiac Grand Prix se 2-door
3100 v6 L82 Automatic 4-Speed
T40E Turbo 5-8psi

I am replacing the camshaft sprocket, crank sprocket and chain today. The cam sprocket has the 4 tooth configuration so I can fine tune the cam timing. So I am hoping some of you can share your cam timings and experiences with them to help me make the best degree choice.

The chain is being replaced as it jumped timing during crank and idle for 2 seconds. It wasn't a load interference but there was some noticeable tapping. I am positive it isn't detonation and used a rod to find cyl 1 TDC through cyl 4. The intake valve is opening late, heavy retardation of the timing. Car is well tuned so that also leads me to believe there was no detonation pinging. I once made the mistake of thinking it was detonation. I ended up really working the piston and valves good. haha.

So there was some light piston valve impact for a very brief amount of time. I have spare valves and rods so I am not concerned about them if bent. They are being replaced, well at least the rods are being replaced initially. I'll pressure test the chamber later to see if valves aren't bent bad.

Give a man a hand guys, I need some professional advice from the best of the best.

Camshaft timing for turbo?

Advise concerning the interference from timing jump?

Thanks guys, you all rock.

[RedZMonte]

Stock. advance timing or retard it electronically in the Tuning software.

S

[SappySE107]

You don't adjust cam timing electronically.

Couldn't tell you what is best for boost, sorry.

[robertisaar]

yeah, i tried advancing and retarding in DD2003 w/boost.... that software might show boosted stuff, but it's wildly inaccurate.

[Joseph Upson]

As was indicated if the timing chain has jumped you will not be able to correct it with a change in the spark table because the timing events between the crank and the cam will still be incorrect. As for a good cam for turbocharging, stick with the stock cam unless you're building a competitor. I struggle with the urge to upgrade the camshaft for boost despite the fact that I favor low end torque and 0-60 acceleration. It's hard to squash the idea of high hp numbers instead of camming the engine according to my driving habits, stop light to stop light tire chirping shifts. A big cam will all but take that away or most of it in exhchange for poorer fuel economy and idle quality. If it's a daily driver keep it friendly, you can always turn up the boost.

[SappySE107]

He didn't even mention spark timing once.

[Joseph Upson]

He didn't even mention spark timing once.

No, but RedZmonte suggested an electronic adjustment and that's what my post was referring to if it helps.

[Schmieder]

No, but RedZmonte suggested an electronic adjustment and that's what my post was referring to if it helps.

I guess I should have typed cam degree instead of cam timing. I see where the error lies.

I agree with stock cam after much reading. If it isn't a big deal, the money is better spent somewhere else on the block. Now, if I run out of stuff to mod I may consider a cam with a little more lift and tweaked ever so slightly for boost.

[robertisaar]

solid-core(as opposed to the factory hollow-core) would help with ease of mind as well.

[Schmieder]

solid-core(as opposed to the factory hollow-core) would help with ease of mind as well.

Yeah, that too. If I decide to go double timing chain getting a solid core cam would be best. Here is an interesting question....have you ever seen a hollow cam twist? As in pistons 5/6 delayed to pistons 1/2.

[bszopi]

have you ever seen a hollow cam twist? As in pistons 5/6 delayed to pistons 1/2.

Possibly, although I'm not sure you would know before it snaps in half. If something is causing it to twist, its going to eventually cause it to snap. And we've seen plenty of snapped ones...

[Schmieder]

Possibly, although I'm not sure you would know before it snaps in half. If something is causing it to twist, its going to eventually cause it to snap. And we've seen plenty of snapped ones...

Ha, I guess I overlooked the obvious.