Timing Vortec engines

When timing the Vortec 4.3 5.0 5.7 etc. I have read many peoples opinions saying this timing is not adjustable. Why is it that there is a circuit comparitor between the cam and crank sensors. This I was told has to be 0 the give the computer its base to be able to control timing. On my 96 the distributor is adjustable because it has an elongated slot cut in the holder. Can anyone clarify this situation because right now my truck is set at 0 degrees cam retard. Thks

I know the v-8 timing is adjustable, But I believe the v-6 is not. Someone else on here explained to me about the v-6 and I am not familiar with them. The v-8's timing is supposed to be 0 degrees plus or minus 2 degrees and is only adjustable if you have a scanner. A timing light does not work on them.

yup I have a scanner, I was just wondering why the v6 is different or if in fact it is, and if it needs to be set to 0 degrees cam retard.....the principle of the crank needing to know where the cam is should still be relevant. Thks for the info though.

GMMERLIN maybe you can shed some light.

here you go:


TEST PROCEDURE
The ignition timing cannot be adjusted. The distributor may need adjusting to prevent crossfire. To insure proper alignment of the distributor, perform the following:



With the ignition OFF, install a scan tool to the DLC.
Start the engine and bring to normal operating temperature. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM.
Increase engine speed to 1000 RPM.
Monitor the Cam Retard Offset.
If the Cam Retard indicates a value of 0°+/-2°, the distributor is properly adjusted.
If the Cam Retard does not indicate 0°+/-2°, the distributor must be adjusted.
ADJUSTING PROCEDURE


With the engine OFF, slightly loosen the distributor hold down bolt. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM.
Start the engine and raise engine speed to 1000 RPM.
Using a scan tool monitor Cam Retard Offset.
Rotate the distributor as follows:
4.1. To compensate for a negative reading, rotate the distributor in the counterclockwise direction.
4.2. To compensate for a positive reading, rotate the distributor in the clockwise direction.

Repeat step 4 until 0°+/-2°, is obtained.
Turn the ignition OFF.
Tighten the distributor hold-down bolt to 3 Nm (25 lb. ft.).
Start the engine, raise engine speed to 1000 RPM and recheck Camshaft Retard Offset.

Thank u for the clarification. This is how i thought it was suppose to be. Perfect explanation. Thks

Skipr, Were you giving the instructions for a V-6 or V-8 ?? When I did the intake on my 5.7 I set the cam retard to 0 degrees at idle because that is what I was told to do. How much difference will it make ?? When I put the distributor back in I had it marked well and the retard was already at 0 degrees. Should I recheck it ? One more unrelated question, In your post you were able to use the symbol for degrees. At the risk of sounding like an idiot, How do you do that ??

lol good eye! How did I do that? No, really I just scanned the page from my OEM service manuals second edition (4000 pages in 4 volumes). then high lighted the paragraph I wanted copy/cut then paste in reply. Didn't u notice it's worded like a nerd is explaining it? I don't use those fancy words like: IMPORTANT, COMPENSATE and PREVENT....etc.

Neither one of these engines can be "timed" in the way you are used too.
The distibutor housing holds the cam sensor, The PCM calculates the timing by measuring the crank signal and the cam signal.
What you are seting by turning the distibutor housing is the correlation between the 2 sensors.
On the V-6 model, the housing holddown bracket is fixed to the housing so if you return the rotor to the proper position when reinstalling the housing, the engine should be at the correct cam sensor position setting.
Believe me I have seen them installed incorrectly :banghead:
I don't know why they did not fix the holddown bracket to the V-8 models, it would have saved a lot of headaches.

To set the correlation between the 2, you will need a scan tool that can read camshaft position offset.
With the engine RPM over 1200 adjust the offset too 0 degrees.

This is fine for a new engine but a non adjustable disributor on an older engine, I think would cause some trouble. The timing chain stretches, the disributor shaft wears, gear wear causes the timing "correlation" to slowly drift. I just checked a v-6 with 200,000 on it and the cam retard was off -16 degrees. Not enough to put it ahead another tooth and I can't figure out why. Any comments on this situation.

Thunderbolt
On a computer running windows you can go to the start menu, select run, type charmap and click ok. Character map may also be in accessories folder. Once you have the character map running you can select what symbols you want and copy them from there and paste them where you want.

Planedude
Are there any problems with the way the engine runs? I think the cam retard spec on the V6 is 0° +/-20°

Yep my scanner picked up 11000 misfires.

skipr is good he heped me out on my truck.
by the way skipr i still have not had time to get that check engine light off yet. I have to get my hands on a scanner.

Thunderbolt
On a computer running windows you can go to the start menu, select run, type charmap and click ok. Character map may also be in accessories folder. Once you have the character map running you can select what symbols you want and copy them from there and paste them where you want.

Planedude
Are there any problems with the way the engine runs? I think the cam retard spec on the V6 is 0° +/-20°



Thanks Jeremy !!

GMMelin, When I did my intake on my 98 5.7 I had the engine idling when I set the cam retard. How much do you think it would be off and what effects would it have ?? The truck runs fine. Should I reset it ??

I have heard that putting a distributor cap with brass contacts on a 4.3 helps with misfires and the 5.0 and 5.7's have had some problems with distributor gear wear. It could be a possibility on a 4.3 but I haven't heard of it being a problem. You may want to check for slop in the distributor since there is wuite a bit of plastic and the bushings could be worn

"With the engine OFF, slightly loosen the distributor hold down bolt. IMPORTANT: Cam Retard Offset reading will not be accurate below 1000 RPM.
Start the engine and raise engine speed to 1000 RPM.
Using a scan tool monitor Cam Retard Offset."

is Cam Retard Offset the same as spark advance????

no, cam retard is the offsetin degrees from the signal from the crankshaft position sensor and the cam position sensor

http://www.obd-2.com

do you think this software will show you cam retard offset? I was looking on the site But I can't find were it show that value. I even downloaded the evaluation and played the demo. all I saw was spark advance

"List of possible GM Powertrain Specfic Real Time Data
699 items for model years 1995 and beyond.
Updated Nov. 2004 as used in Car Code Vehicle Explorer Scan Tool Browser enhanced data.
Powertrain Control Module address $10 on VPW network. SAE mode $22

Camshaft Reference Signal Missed Counts
Camshaft Retard Degrees
Camshaft Signal Input High or High to Low Counts"

I think I just answered my own question. I need to get this software. Man, I have alot to learn... what happend to the days of just turning the distributor till it ran right?

Wow, there is alot of information going on in this thread that has me believing the answer to my neighbors motor we have recently installed. We have been trying to figure out that 1% that is keeping it from being 100% complete. There have been many of ?'s I have wanted to ask on here, but I have been trying to search through previous threads and have been able to answer some ?'s. However, I am now forced to ask a ? to make sure this info is relevant to our problem. We have installed a rebuilt 350 (5.7L) in his '88 C1500 body. Basically I just want to know if the information here would apply to the vehicle we are experiencing the tecnical difficulties. A simple "yes" or "no" reply will allow me to know if we are on the right path or not. We have been practicing alot of patience and restraint at the point we are at now, regardless of how anxious we may be to hear it fire up. Still diggin' the rich knowledge offered in this thread, no matter if it applies to our application or not, so please keep me learnin'!

Wow, there is alot of information going on in this thread that has me believing the answer to my neighbors motor we have recently installed. We have been trying to figure out that 1% that is keeping it from being 100% complete. There have been many of ?'s I have wanted to ask on here, but I have been trying to search through previous threads and have been able to answer some ?'s. However, I am now forced to ask a ? to make sure this info is relevant to our problem. We have installed a rebuilt 350 (5.7L) in his '88 C1500 body. Basically I just want to know if the information here would apply to the vehicle we are experiencing the tecnical difficulties. A simple "yes" or "no" reply will allow me to know if we are on the right path or not. We have been practicing alot of patience and restraint at the point we are at now, regardless of how anxious we may be to hear it fire up. Still diggin' the rich knowledge offered in this thread, no matter if it applies to our application or not, so please keep me learnin'!

The information in this thread only applies to 1996 - 1999 Vortec Engines (Gen 1 blocks with a distributor).

Your neighbors 88 should be a TBI engine and setting the timing requires that you disconnect the EST wire near the firewall under the black wire cover.

//2000CAYukon

Ok thanks. I was just scrolling through and many things were drawing my attention. I was hoping to have hit the jackpot but....oh well.

Soooo, now that we are still @ square one, could anyone please verify the color the EST wire should be? Is it the tan with black trace wire?

Ok thanks. I was just scrolling through and many things were drawing my attention. I was hoping to have hit the jackpot but....oh well.

Soooo, now that we are still @ square one, could anyone please verify the color the EST wire should be? Is it the tan with black trace wire?

It is either black with a tan line or tan with a black line, I can never remember. It can easily be disconnected and I think it is the only wire like that under the cover.

What exactly is the problem with the 88? Won't start, won't run?

Do you already have a thread going on this?

//2000CAYukon

I'm bringing up this old post, becasue I'm having problems that relate to this.

I recently replaced the distributor on my "97" 350 vortech.

I am getting a code that indicates the correlation between the Cam position and Crank position is out from one antoher.

I'm assuming the scanner that's mentioned in the replies is more than a code scanner and the cost is quite a bit more as well.

Is there a way to set the cam position sensor without a scanner?

I don't think I'm too far out, becasue it seems to run good. I thought about using the code scanner to reset the codes, move the distributor a degree or two, start the engine to see if code comes back. Repeat the process until it doesn't come back on.

Any thoughts?

Just replaced the distributor on my 98 Tahoe as per advice from a local dealer's shop supervisor to cure stalling / misfires / stumbling.

Found that after i've replaced it that it lit up the engine light and spit out a P1345 code.

I marked it carefully and re-installed in the same position it came out. Luckily I have a friend with a Snap-On Scanner "Brick" that I had hooked to this truck previously.

What I remember though was after I had the intake coolant leak fixed and they also replaced the timing chain that the camshaft reading was -3 and I thought that they might have been off a tooth when reinstalling the cam gear on the cam. Can someone let me know if this is possible to find out or if the cam retard reading is only the correlation between the crank and the cam and if negative 3 would have made the motor run rough, stall and all the crap i've been going through with this?

Thanks!

Jay