Question : Cam degree timing with Turbo

[Schmieder]

I am changing out the timing chain and sprocket, thought it would be a good idea since I'm about to push more power through and the chain is about 60k miles.

Upon close inspection before removing, I noticed the cam was advanced by one gear tooth. 40 teeth / 360 means it was advanced 9 degrees.

This is why my car was such a torque beast and also seemed to flat line at 6000 rpm.

After some consideration, I question if I should leave it advanced with the turbo installed. Knowing the advanced exhaust would help spool up the turbo better. The advanced intake timing should also reduce wasted fuel during overlap, IIRC.

Question is if this is a good or bad idea. It would seem ideal to have lots of torque due to cam degree then have extra power in upper rpm from the turbo, best of both worlds. But I question how safe it may be, due to increases in compression and other possible unknowns I am over looking.

Any advice?

3100 v6 1996 GPse with stock camshaft

[IsaacHayes]

Make sure to use a GM chain and sprocket, the cloyes set has been shown to wear extremely fast. We don't know about the other brands of chain/gears though, so who knows how other brands hold up.

[Schmieder]

Make sure to use a GM chain and sprocket, the cloyes set has been shown to wear extremely fast. We don't know about the other brands of chain/gears though, so who knows how other brands hold up.

Ugh, I bought mine from Advance Auto Parts. I'm going to call them and find out.

My current chain isn't bad, only about a 1/4" play by the dampener. If I'm going to question the chain I have, I might just leave the old one in.


Any advise on the cam timing? Can I keep it at 9 degrees advanced and be safe? Power shifting to low end, robbing high end is another issue. I just want to be sure the 9* isn't dangerous with the turbo set up. As far as knock is concerned, I can tune that out.

Otherwise, I'll just put it stock. But I like to keep the high torque. Plus I read it is good for turbo spool to advance the exhaust valve opening. So as long as the exhaust won't get tooo hot.

Thanks for the pointer about the timing chain.

[TiredGXP]

I'd previously run some simulations on desktop dyno with various levels of cam advance and retard. At least with my cam, the best area under the torque and HP curves happened with the cam 2* retarded....might as well install it straight up since the difference wasn't great.

[asylummotorsports]

Unless you want to spring for the Double Roller set up and the associated machining involved, the only option should be the pre-99 3400 set up from GM!

The aftermarket stuff has proven to be somewhat wanting in quality.

Unless of course the promised billet stuff on here suddenly appears, LOL!

[RedZMonte]

Im running stock timing and happy with it... on boosted apps most people run stock timing (atleast that i know in my area)..

S

[IsaacHayes]

I'd probably go to stock. I know with my sloppy old chain it was retarded and the low end had no power but the top end was insane. After the chain replacement I went "wtf happened to my top end" LOL But the low end was much more torque-y.

With a turbo you will be making more torque and that is what kills trans...

I forget the other brands of chain sets, one was like something "gear" at advance...

I didn't know about the cloyes until too late too, but I just put on the chain as the gears were crappy compared to stock and the stock wasn't worn much. it had more play with the new chain and gears than it did with the old gears and new chain.

yeah yeah gears i mean sprockets.

[Schmieder]

Well, the tubo shouldn't spool until about 3500 rpm, is that correct?

I have two B&M coolers for the trans with temp gauge. I went all out to cool the tranny as 95% of trans failures is heat related.

One is rated at 14k btu and the other is 9k btu. And they rest right behind the intercooler (3" spacing) where it gets excellent air flow. Though, I might use the 9k btu for oil cooling just before turbo feed. I'm considering it but not sure what to do there. Super cool the trans or regular cooling with oil cooling before the turbo.

So, the trans is good up to 280 lb/ft torque. Can't I use the PCM to regulate the torque hitting the trans?

Most of my driving will be city, 25-45 mph.

And, will the 9* advance help with spool up for city driving? If correct, the advance would allow more expanding exhaust gas to hit the turbo spooling it faster at a lower rpm. And the turbo would help cram in air since the intake valve would be opening 9* earlier. And wouldn't the overlap effect be reduced with 9* advance?

I know it is a lot of questions, but I'm that type of guy. I love to learn and I'm always pursuing knowledge. I'm trying to keep more power down low and let the turbo kick in at higher rpm. So I can take off from a red light like a beast out of hell.

But if it is entirely impractical, I understand, just lay it out, I'll listen.

Thanks again guys.

[robertisaar]

Well, the tubo shouldn't spool until about 3500 rpm, is that correct?

depends on the turbine/housing. not too sure of how it would react as-is, but if it spools too soon for you, get a larger setup.

So, the trans is good up to 280 lb/ft torque. Can't I use the PCM to regulate the torque hitting the trans?

yeah, by removing spark advance... heats up the exhaust gases though.

I'm trying to keep more power down low and let the turbo kick in at higher rpm

if you don't play with too much else(mechanically), you would probably get the results you're looking for.

[Schmieder]

if you don't play with too much else(mechanically), you would probably get the results you're looking for.

Ehh, your right and I know it. I'm not wanting to change it to stock right yet. Reason is I had not returned it to normal and installed the timing gasket and cover now. No new chain yet until I can determine if this chain I have is good enough quality. The chain isn't that bad, yet. It's only 58k miles in.

And since I am moving up the street, the car is still in the garage at my old home. My brother and sister moved in there, so I can keep it there for the time being until it's drivable.

I'm going to get nearly all the stuff done I want to get done. Just a few short cuts and I will do the work later in the season when it is warmer out. As I am sure you know, it is A LOT of work installing a custom turbo build.

Just as long as my car isn't going to explode at 9 degrees cam advance. Otherwise I'll have to grunt it out and change it to stock.

Will it be ok for the time being?

I know 9 degrees is a bit much. From what I understand, 6 degrees is considered a max. Not sure if that is due to power shifts in rpm efficiencies or too much stress on the block/trans.