Setting distributor timing without $$$$ scan tool? 1999 5.7 Suburban

You can set the distributor for 99 cent Bluetooth adapter , 10$ obd2 elm 327 bluthooth thingy(or obd2 elm 327 usb) and download scan XL (from TPB).
For 11 bucks you cant go wrong.

east302 said:

Which CMP retard did you use...cmp retard * or cmp retard **?

I get different values for both with CarGauge Pro. But, DashCommand also has two choices that don't use the asterisk and give the same value.

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Interesting. I tried the first one (one * ). I'll try the other one tomorrow after work. If mine varies as much as yours, in the same way, I may have dropped my distributor in closer to perfect than I thought.

If I don't throw codes or notice a change in the way it runs, or mpg, I'll probably leave well enough alone. Truck drove like a dream to church this morning with the whole family and neighbor's kids loaded up in it. A lot more fun to drive since I swapped the 4.10 gears in last month. Just need to get the speedometer fixed lol.

TylerZ281500 said:

base timing HAS to be set with a scanner or somethign that can read it. guessing might have "done the job" and sure the truck can accommodate to some extent some retard and advance to get timing where it needs to be a tthe +/- 2* setting. you may have gotten very lucky, otherwise suggesting stabbing it, regradless if it worked for you is a poor suggestion. The app is a great tool as suggested.

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Tyler, just out of curiosity. If your cmp ends up being a +4 instead of +2, but the truck otherwise seems to run like a champ and the engine light does not come on, what issues is the +4 going to cause?

Definitely not debating you on this, but at least I've seen with my own eyes that it's quite possible for a rookie to set a distributor on a Vortec (from total uninstall, unmarked) and get it close enough that the truck runs like a champ.

I know better than to yank the distributor out without marking it, lol, I've swapped enough caps/rotors to know that, but hadn't ever marked the distributor body itself. And when I removed the distributor from the motor, it was the first thing I did that morning, and just went full dumbass and yanked it out without marking.

From my knowledge the way you reset the timing is this.

Disconnect the ECM Timing advance connector, back of the firewall tan and black wire for 88-94 and its by the blower motor inside the cab for 95-99.

Once you do that unplug cylinder #1 and turn the engine over with a breaker bar until you feel that cylinder # 1 is at TDC (Top dead center)

Then unbolt your distributor point it at cylinder #1.

Then going to the crank and there should be a timing mark there that you can mark with a silver sharpie or white chalk, something that pops.

Then hook up a timing light to the cylinder #1 spark plug wire and start the truck. Make sure the timing looks like its in between the biggest opening (farthest to right) if not adjust the distributor accordingly clockwise to take out timing and counter clockwise to add timing.

Once that is all lined up and the mark is in the biggest gap with the timing light, shut off the truck and bolt down your distributor.

Disconnect battery and reconnect that tan and brown wire you disconnected from before and start the truck.

Voilaaaaaaa your truck is timed properly.

vortecs dont have a timing tab otherwise yes that is how on pre 95 trucks.

TylerZ281500 said:

vortecs dont have a timing tab otherwise yes that is how on pre 95 trucks.

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If you are talking about the tab to align the harmonic balancer so that #1 piston is on TDC, here is a pic I just took of the OE cover on my 97 Vortec 350 or 5.7L and a replacement cover from Orileys They both have a tab. This tab is for putting the #1 cylinder on TDC, and not for a timing light, because the ECM will adjust the timing and a timing light would be useless. Also you are rite about the pre Vortecs, 95 back, timing them by removing the advance wire, then a timing light can be used. That is how I did my 93 WT 4.3L several times.

MikeMc512 said:

This information is NOT correct. If you point the distributor at #1 your truck will not start, and you'll have to start over with aligning the timing marks.

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Congratulations on resurrecting a 3-year-dead thread to tell somebody that they are wrong, while adding no useful information to the discussion and simultaneously being wrong yourself.

Nearly any distributor based ignition system can be set close enough to run by setting the rotor to point toward the cylinder 1 terminal with that cylinder at TDC, compression stroke. This has been true since before the Model A, and is still true of the L31. Will your CMP retard be within spec? Not likely. Will it run well with no codes? Possibly. Personally, I use a scanner and don't leave it to chance.

That's funny, because I just did it and it didn't work. But your THEORY maybe better than actual experience. Also the response itself was useful, in that it will save time by not setting the distributor pointed at #1.

MikeMc512 said:

That's funny, because I just did it and it didn't work. But your THEORY maybe better than actual experience. Also the response itself was useful, in that it will save time by not setting the distributor pointed at #1.

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This will help you to learn what you don't seem to understand.

https://www.bing.com/videos/search?...40668F97C054302085414&view=detail&FORM=VIREHT

MikeMc512 said:

That's funny, because I just did it and it didn't work. But your THEORY maybe better than actual experience. Also the response itself was useful, in that it will save time by not setting the distributor pointed at #1.

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The theory and principles that it's based on are sound and backed up by millions of functioning, distributor driven spark ignition systems, as well my own decades of experience. But if you have an alternate theory, please share it with the class. I'm happy to be proven wrong.