Set Timing Tip 4.3L GMC Vortek
 

A shortcut / tip which I found ( after much trial and error ) on the 4.3 L vortek is
THAT YOU CAN locate TDC of # 1 cylinder by removing the Oil Filler tube in the drivers side valve cover, place a mini mag pickup tool on the # 1 intake valve rocker - which is viewable and accessable thru this filler hole. ROTATE Engine clockwise with Crank pulley center bolt. Watch for this rocker to open then start to close all while watching the timing mark on the harmonic balancer.
I found thus much easier than removal of valve cover or piston position thru spark plug hole.
I imagine some pros simply can use a compression guage on number 1 spark plug hole and determine when compression stroke is happening and the timing mark on harmonic balancer.

The only problem with that, is #1 cylinder is on the left side of the engine ;)

Correct - Captain Hook.
The orientation you are suppose to use is the view or direction originated from the Vehicle Driver's Seat , correct ?
You seldom use the orientation from the Front of the vehicle ?
So all orientation is viewed from the Rear of the Engine, seems backwards common sense wise,
all maintenance manuals in first few pages remind us that the view is always from the driver's seat viewpoint ?
I wrote "right valve cover" - should be left valve cover.

Hand Drawn Pic
 

Engine Rear

Cylinder # 6 | | Cylinder # 5
Cylinder # 4 | | Cylinder # 3
Cylinder # 2 | | Cylinder # 1

Engine Front

4.3 L Vortek 6 Cylinder rough picture

That's correct. Left hand drive vehicles, (USA) the driver side is the left side of the vehicle. Just wanted to clarify because your image does show the left cylinder head, #1 cylinder is the front cylinder.

Another way to determine if you're on the compression stroke, (as opposed to the exhaust stroke) is remove #1 plug, disable the ignition, and crank the engine with the starter. You will hear/feel two noticeably different air "pushes" coming out of the spark plug hole. Every other "push" is noticeably stronger than the other.** The weak one is the exhaust stroke. Weaker because the exhaust valve is open when the piston is going up, and part of the compression is blown out the exhaust valve. The stronger one is compression. Stronger because both valves are closed when the piston is going up. If you "time" it right, stop cranking the starter just as the compression stroke begins, then manually rotate the crank clockwise until the timing marks line up. Takes a little practice, but very fast and easy once you get the "hang" of it.

** If you've ever done a compression test, you know what I'm referring to, you can see the different pulses on the gauge.

Could the Forum Administrator move or copy this Thread to the "Tech Articles (DIY)"
Forum subsection ?

cferry7

PS, I corrected the mistake where you said "right valve cover" to "drivers side"

Well...you all have done a fine job of confusing the hell out of me. ;) My filler tube is on the passenger's side over #6 cylinder. With the hack job the PO did on my truck I thought maybe he put the rocker arm covers on backwards. But when I look at the "before" pics I don't see how the filler tube would even fit over #1 (see pic). So, I look at the Technical manual and it shows the filler tube in both locations. I'm confused. :(

I don't see anything here that isn't already covered in the EDI Engine Timing article.

So, since you all decided to leave me confused...;) I figured out the answer to my question. Correct me if I am wrong. On engine where the throttle body is at the front of the intake (CMFI engines)('96 and earlier?), the oil filler tube is located on the drivers side over cylinder #1, so the method OP described will work...

https://blazerforum.com/forum/attach...ine=1391662075

On '97 & later (?) (CSEFI engines) the throttle body is on top the intake, the rocker arm covers were switched and the oil filler tube was moved to the passenger side over cylinder #6 to make room for the air flow housing and the power steering fill tube...

https://blazerforum.com/forum/attach...ine=1391662075
I was about to go to my engine stand and switch the rocker arm covers after reading the original post. :)

If I could make a suggestion that the title to the thread be edited to add "(CMFI Engines)". Or am I out to lunch?