Other question I have is if this is a new distributor or not (is the distributor gear worn?). I don't think it would make sense to correct the cam sensor retard if the distributor gear is worn out, and there are plenty of those on these Blazers.

 

It is not a new distributor but actually, the little gear looked to be in very good shape.
I felt like I got it back in the correct tooth but my marks are off a little. I'm going to try to adjust that this afternoon. I'm assuming the clamp will slide off the distributor without removing the whole unit...

 

You can turn the crank by hand with a 5/8 inch socket and ratchet or breaker bar.

There are two marks on the harmonic balancer, and two matching features on the front cover. One mark matches to the notch on the ridge on the cover above the crank pulley at about 1 O'clock as you look straight on from the front., The second mark matches to the tab sticking off the edge of the lower cover and it's at about 4 O'clock as you look at the front of the pulley. When the marks align, #1 and #4 are at TDC, one in firing position and one between exhaust and intake strokes. You can set the dizzy by either one. If #1 is firing, center the metal electrode of the rotor to the 6 mark on the base plate. If it's at the firing position for #4, there are several (3 or 5, depending on who made your cap, AC-Delco has 5) raised ridges on the opposite side of the rotor. The center ridge should line up with the 6 mark on the distributor base plate. I actually think you can be more precise with it at #4 TDC.

Mine is a new metal frame dizzy, and the clamp was really, really snug, and I loosened it some before installing the dizzy. You should be able to get it off. You might need to spread the open side of the "wrench" section to get it loose. I haven't got mine running yet. I'm doing the front cover today, and waiting on some O-rings for the fuel lines to arrive. I put the dizzy in to "test fit" and to make sure I had the oil pump drive lined up, but I have it out to get more room to tighten the fuel lines when my O-rings get here. My gasket kit included two of the O-rings, my spider injector kit had none with it, and I needed new ones at the back of the manifold, as well as where the lines connect to the spider.

 

You can check the gear by trying to turn the rotor back and forth. There should be no movement.


My experience was that I had to remove the distributor in order to spread the clamp enough to get it off.

 

Ah...bummer

 

Graveyard, is yours a metal replacement dizzy? Or do you still have a stock plastic unit?

For the metal bodied dizzies, I'm pretty sure you can use the jaws of some needle nose pliers to spring the clamp apart and slip it off. I'd be scared of breaking a plastic dizzy trying that, though.

 

Hey Guys, I got the clamp off fairly easy. Even without removing the distributor.
I filed the inside for a little while and loosened it up, at least till it would slide on and off.
Then drilled the clamp out to about .422 or so and got my marks lined up. went back to O'reilly's and got the retard checked again. Last night it was around 19 to 20 negative.
After this afternoon's mods, I'm down to 5.5 negative. Just need a little bit more.
I'm happy with the way it's running now, Can't wait till its just right...
Later Everyone!

 

OK, then the O'Reilly's scan tool does read CMP Offset/Retard.

You know they at have least one version of the old style, fully adjustable clamp at O'Reilly's. They sell the Mr. Gasket one for about $6 or $7. Mr. Gasket # is 1009. They might not stock it, but they can get it in a day or two.

When we finally got home today, I got my fuel lines hooked up with fresh O-rings from CarQuest, my dizzy installed (with the Mr. Gasket clamp), and ran out of daylight. I have a full day away from home tomorrow, so I might not get back in time to finish tomorrow. Still need to pull the balancer and replace the plastic front cover and seal, put the new water pump, new fan clutch and all new hoses on.

I wish I could find a metal front cover that was set up for a crank position sensor. The old style ones without the crank sensor mount are common in the "dress up" parts, but I can't find a new style one with provisions for a crank position sensor that will work on the Vortec engines that isn't plastic.

I also have a few other miscellaneous parts to put on and connect. I got the new throttle cable in under the hood and pushed through the firewall, but I haven't dived under the dash to hook it to the pedal yet.

 

Okay, I just downloaded the user manual for the Bosch 1300 scan tool and all it says about the test in question is "ignition advance" It says nothing about cmp offset or retard.
With that said, the first test showed a -19 to -20 degrees when I was about an 1/8" from my scribe marks on the distributor. After reworking the clamp and aligning my scribe marks, it test -5.5 degrees yesterday. It also smoothed up the idle at the -5.5 degree setting. Now I'm wondering if I need to keep going till I reach zero degrees?
Any suggestions?

 

Often the scan tool documentation doesn't say much about "Manufacturer specific data."

Were you the person operating the scan tool? When you went down the list of data items (PIDs) to monitor in the live stream, did you select "CMP Retard" Or "CMP Offset"? If you weren't the one operating the scan tool, ask whoever is operating it to explain what they are doing and which data they are looking at.

Also, never, ever ask to adjust timing. Tell them you need to adjust the cam position sensor positioning (retard or offset).

Turning the dizzy doesn't change ignition advance at all! If you moved the dizzy, and something changed from 19°-20° down to 5.5°, you had to be looking at CMP offset (unless your front timing cover melted or your crank position sensor magically moves 15° when you turned the dizzy). CMP retard/offset is all that changes when you move the distributor.

A quick "how to" here, from memory and from the user manual you probably downloaded from Bosch. The meat of the process starts in section 5.6 of that manual, page 32. I think you get to that point from selecting "Vehicle diagnostics" at the main menu (after going through the process of selecting your vehicle and connecting), and when you get to the diagnostics menu, you select "Datastream" which brings you to the datastream menu shown in section 5.6. Then you select "View data" and the scan tool gets the list of PIDs from your car. Then you select "Entire data list" and you see the list of PIDs this vehicle has that this scan tool can understand. Scroll down, you're looking for "CMP Ret", with the long PID at the bottom reading "CMP Retard." It might be "CMP Ofs" with a long PID at the bottom of "CMP Offset."

Graph or view that "CMPRet" or "CMPOfs" PID in real time as you operate the vehicle. At 1200 RPM's, it should be zero +/- 2°. Closer to zero is best. There is no advantage at all to being at either limit.

The rotor electrode is so narrow on these dizzies, being off by more than 2 degrees can definitely lead to rotor/cap electrode wear from arcing at the extremes of the timing curves. You want to be in spec, and as close to zero as you can get it.