Pre-Tuner

iTrader: (2)

Is there any way to tell where the "all in" timing should be set? Reading around the threads, I've seen people use 2400 through 3200 as their "all in" timing mark, but I don't know how they got to that decision.

dimented24x7

iTrader: (2)

3200 - 3600 is a common area to bring in all the timing. Youll have to experiment, though, to find out where the proper place is.

Pre-Tuner

iTrader: (2)

OK, any idea how one will perform over the other (earlier vs later)?

One other question, if I'm adjusting the timing for WOT, do I just raise the max timing at 100map and "smooth back" from there?

As soon as there is a day around here that it doesn't rain, I'm headed to the track to sort out the WOT fuel, and obviously timing is part of that.

Thanks

dimented24x7

iTrader: (2)

Its hard to say. The engine may want more sooner, or less later. With timing, its about having just the right ammount so that the mixture is fully burned after the piston has just passed TDC. Too little will cost power and heat up teh exhaust and heads needlessly. Too much will cause the engine to run rough and also will lead to detonation. Its defiantly one of those things youll have to experiment with. 30-34 degrees all in by 3600 RPM starting at around 10-12 degrees at 800 RPM is a good place to start in my experience.

HaulnA$$

Those numbers are good for a 3000 lb. car but are a bit on the high side for a 4500 lb. truck. 6-8 degrees at 800 RPM and 26-30 at 3600 RPM is a good place to start on a mildly modded truck to keep it out of detonation. HTH

Pre-Tuner

iTrader: (2)

OK, thanks guys.

The truck weighs 4008 lbs without me in it according to the scales. Don't call my baby fat!

One more thing, you say 6-8 degrees at 800rpm. The chip is set at 20.04 right now, so do I lower it? I'm running the distributor at 0 degrees if that matters.

HaulnA$$

Ah, o.k. it must be a RCSB. When you say the 800 RPM timnig is 20.04, one of two things must be wrong. Either the main spark bias is not bieng subtracted or you are not looking at the WOT (100kPa) cell. When we talk about "all in" timing we mean WOT timing. It stems from the old days when setting the mechanical timing on an engine. We would disconnect the vacumm hose from the vacuum advance, set the base timing, then play with the springs and cams so that we had the timing we wanted and it was "all in" by the desired RPM. We would then connect the vacuum hose and adjust the vacuum advance to achieve the "total" timing desired. HTH

Pre-Tuner

iTrader: (2)

Oh ya, duh.

I was looking at the timing where it idles (45-50kpa). The chip is set at 6 degrees at 800rpm@100kpa. I'll adjust the table to what you guys and use that as my starting point.

I was reading somewhere that there is something you can do with the timing table to help keep the tires from blowing away. With the weight of the truck at the wrong end, it's hard to keep the ***-end from breaking loose. Any idea what that is so I can dial it in better at the track? I have 275's in the rear and it still smokes the tires.

Sorry for all the questions, but everyone and their brother shows up to the only track in the area, so the tuning runs are very limited. I'm trying to get a plan together to make the most of my time. There's just too many people on the streets around here to get in any street runs

RBob

iTrader: (1)

This thread has a pic of a Vortec truck timing table. Also some discussion of the same:

https://www.thirdgen.org/forums/atta...rtecspktbl.jpg

It doesn't show PE/WOT added spark, so add 4 to 6 degrees for that.

To control tire spin off the line can pull some timing out. Also note that the launch mode SA table comes into affect here.

RBob.

Pre-Tuner

iTrader: (2)

I'll check out that thread, and the launch SA (didn't even think about it) thanks.

By "pull some timing out", where are you talking about? From Idle, TC stall speed?

HaulnA$$

What ECm are you runnung? EBL or the '7747 because the '7747 doesn't have "Launch Spark". Are you running Vortec heads on your '91? It would have been nice if you mentioned this stuff because i assumed a '7747 with swirl ports.

Pre-Tuner

iTrader: (2)

Sorry about that. The thread sort of started out real general, so I didn't bother posting what I have. It's in my signature though in the first thread. I am running the EBL with the vortec heads. Is there something you would change about what you told me earlier?

Thanks again

RBob

iTrader: (1)

Not at idle. Will want to change the timing is the area that is used during the throttle stomp. Look at a data log of a run and note the RPM & MAP that is transversed as you apply the throttle. Then pick the area(s) that are prior to the tire fry to pull timing.

Try pulling some timing and see how the engine reacts. On the other side of the coin it could be said that you just need better traction

RBob.

HaulnA$$

My bad! My dain bramage is flaring up. I usually pay attention to sigs but I missed yours. Sorry!