Helping a friend tune his off topic 305 S/B. The timing tab has something I'm not familiar with and I know somebody here has the answer. On the tab is a tube about 1" long and 5/16" in diameter fastened to the tab, what is the purpose of this thing?? and is TDC under the center of this tube or is it at the larger notch before the tube?? Thanks, Ralphie Sorry I can't get a picture of this it's just about buried behind the accessories.
it's to put a timing probe, I think used at the factory to set the timing on the engine? there's also a big notch in the damper, that the probe detects. Totally useless in real life.
Thanks Squirrel, I knew you would come through for me (us) yes it does seem totally useless but I had to know!! Still need to know about TDC. Ralphie
Usually TDC is the largest notch in the tab. A little googling finds this helpful picture, which you could not take on your engine. The text says notch 7 is TDC.
In the late ‘80s I worked in a shop where we had a Sun oscilloscope/diagnostic machine. It had the correct probe to set the timing using that tube.
I'm thinking that most scopes made after the late 70's had the probe The Sun scope in the school shop that we got in the early 80's had it and there might be one for my Marquette Scope in the cabinet with the other wires and pieces. Those came about when they started putting so many accessories on the front of engines you couldn't see the timing marks with a light.
Yep..Went to Allen scope school. I was under the impression that GM put the tab there because it was hard to see in the old location, with all the belt driven stuff at that time.
Monolythic timing, Chrysler made the dealerships buy an expensive machine to use it back in the late 70's.
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