1998 Tahoe W/Rebuilt Engine & Tranny W/PCM4Less Tune - Update suggestions

[juniorwatson]

Hey fellas,
I have finished rebuilding the engine in my 1998 Tahoe, and I would like to get some suggestions on updating my PCMForless Tune. I have a JET programmer, and have been reading the forums, but would like to get some suggestions from y'all with more experience than I have.


The engine component specifications are: Comp Cams 212/218 .488/.495 112 LSA camshaft, Sealed Power lifters, stock pistons and sealed power rings, Comp 7808-16 (Magnum) .080" wall tube pushrods, Melling 10550 oil pump and tac weld pick up, Howards 98215 single springs, ARP rod bolts & resized connecting rods, new SCAT crankshaft & bearings, Sealed power timing chain Set to 4' advanced, 3 angle valve job W new umbrella seals, resurfaced cylinder heads, new cam bearings, new oil galley plugs & freeze plugs. New spider injector assembly.


The transmission is a new GM replacement with a 2,000 RPM Circle-D stall converter.


To help, I can output my current tune here in a PDF. The biggest thing in my mind is wondering if I have to tune for the 4' advanced cam timing chain setup?


Thanks!

[Fast355]

Hey fellas,
I have finished rebuilding the engine in my 1998 Tahoe, and I would like to get some suggestions on updating my PCMForless Tune. I have a JET programmer, and have been reading the forums, but would like to get some suggestions from y'all with more experience than I have.


The engine component specifications are: Comp Cams 212/218 .488/.495 112 LSA camshaft, Sealed Power lifters, stock pistons and sealed power rings, Comp 7808-16 (Magnum) .080" wall tube pushrods, Melling 10550 oil pump and tac weld pick up, Howards 98215 single springs, ARP rod bolts & resized connecting rods, new SCAT crankshaft & bearings, Sealed power timing chain Set to 4' advanced, 3 angle valve job W new umbrella seals, resurfaced cylinder heads, new cam bearings, new oil galley plugs & freeze plugs. New spider injector assembly.


The transmission is a new GM replacement with a 2,000 RPM Circle-D stall converter.


To help, I can output my current tune here in a PDF. The biggest thing in my mind is wondering if I have to tune for the 4' advanced cam timing chain setup?


Thanks!

Comp Cams are almost always ground 4* advance for a small block chevrolet. Are you saying you advanced it another 4* for 8* total advance. 104 *ICL. Given the results from using various cams, I feel you would see better results only running the 4* ground in advance. That would be the cam on a 108 ICL.

That being said nothing out of the ordinary needs to be done for the cam advance. Just set the distributor CMR within spec and start the actual tuning. The actual ignition timing is controlled by the tone ring on the crank and the crank sensor. The cam could be 20* advanced and the PCM could care less, provided the distributor was 20* retarded so that the Cam/Crank correlation angle was Zero.

[juniorwatson]

Comp Cams are almost always ground 4* advance for a small block chevrolet. Are you saying you advanced it another 4* for 8* total advance. 104 *ICL.

Yes, I set the timing chain to have 4' advanced, since I had always heard that doing so would help with low end torque. I figured why not, let this be the first engine I build to see if it actually makes a difference.


Given the results from using various cams, I feel you would see better results only running the 4* ground in advance. That would be the cam on a 108 ICL.

That being said nothing out of the ordinary needs to be done for the cam advance. Just set the distributor CMR within spec and start the actual tuning. The actual ignition timing is controlled by the tone ring on the crank and the crank sensor. The cam could be 20* advanced and the PCM could care less, provided the distributor was 20* retarded so that the Cam/Crank correlation angle was Zero.

Okay, I just wanted to check since this is the first engine I've rebuilt that uses a PCM. I've rebuilt a few dozen traditional Chevy, MoPar, and Olds engines, as well as Hondas, but this is the first 'newer' engine that's controlled by a PCM. The cam retard is set to 0.

I monitor a few different things while I'm driving with torque pro too.

I've played around with some of the PCM stuff like increasing alternator output for lower RPM since I have a stereo system installed, as well as reducing the kickdown TPS setting. Everything runs very well right now, but tI thought I'd ask the forum for any other suggestions for tuning since it's all new to me.

[THEFERMANATOR]

You always want to degree your camshaft, not just set it 4 degrees advanced. It is better to set it straight up if you're not going to degree it because I've seen some chains with advance built into them. And I hop you machined your heads to work with that much lift. Otherwise you've got bigger issues to worry about.

[juniorwatson]

You always want to degree your camshaft, not just set it 4 degrees advanced. It is better to set it straight up if you're not going to degree it because I've seen some chains with advance built into them. And I hop you machined your heads to work with that much lift. Otherwise you've got bigger issues to worry about.

I used to work as an automotive machinist, so I'm more than familiar with everything involved. I did degree the camshaft using the Comp Cams kit I bought 25 years ago.

I did have the installed spring height set for the new valve springs and camshaft too. I plastigauged the rods and mains, checked piston ring end gap, piston to wall clearance...etc

[THEFERMANATOR]

I used to work as an automotive machinist, so I'm more than familiar with everything involved. I did degree the camshaft using the Comp Cams kit I bought 25 years ago.

I did have the installed spring height set for the new valve springs and camshaft too. I plastigauged the rods and mains, checked piston ring end gap, piston to wall clearance...etc

What I'm talking about is the well known lift limitation on stock vortec heads without machining the guides down. Even with comp 648 locks you only have about .500-.505 of clearance between the top of the valve seal, and the lock. It's not recommended going over .450 lift on stock vortec heads, the 648 locks with the ls6 retainers gets you another .030 without machining.

[Fast355]

What I'm talking about is the well known lift limitation on stock vortec heads without machining the guides down. Even with comp 648 locks you only have about .500-.505 of clearance between the top of the valve seal, and the lock. It's not recommended going over .450 lift on stock vortec heads, the 648 locks with the ls6 retainers gets you another .030 without machining.

Every set of stock vortecs I have messed with have had .490 to .510" clearance in OEM form after the seal was fully seated. Most are actually .510" clearance. With the 787 retainers it gave me clearance for 0.510" lift with 0.050" to spare.

[THEFERMANATOR]

Every set of stock vortecs I have messed with have had .490 to .510" clearance in OEM form after the seal was fully seated. Most are actually .510" clearance. With the 787 retainers it gave me clearance for 0.510" lift with 0.050" to spare.

I've done 3 sets now and each one only had .500-.505 after fully seating the seals and using the 648 locks. Had lots of clearance to the retainers, it was the seal to lock clearance that was the problem. These were all untouched heads, so a set thats had the seats ground would have more clearance.

[Fast355]

I've done 3 sets now and each one only had .500-.505 after fully seating the seals and using the 648 locks. Had lots of clearance to the retainers, it was the seal to lock clearance that was the problem. These were all untouched heads, so a set thats had the seats ground would have more clearance.

I am scratching my head here as to how you are having a seal to lock clearance issue??? The locks sit above the lowest point of the retainer. What retainers were you running?

[THEFERMANATOR]

I am scratching my head here as to how you are having a seal to lock clearance issue??? The locks sit above the lowest point of the retainer. What retainers were you running?

It's been awhile, but it was a Crane set of beehives, and I believe they were LS6 style retainers. The stock locks protruded out of the bottom of them.