Timing woes, I wish I wish I hadn't killed that fish! Options

[mike_the_man]

Hi all,

My car was running like piece of poop recently (74 2.0L with F.I.), but backing off the timing a little made it run a fair bit better. Today I took it for a little drive, got it nice and warm, and decided to try and re-time it. It turns out that my timing was correct when it was running poorly, and now I'm very confused. I checked top dead center on the fan and on the fly wheel, as well as looking at the position of the rotor. Everything points to top dead center. I then put a new mark on the fan at 27 degrees as per the PP tech article. I also found the 27 degree mark on the fan, and it lines up with the mark that I made.

When I rev my car up to 3500 rpm and set the timing to the 27 degree mark (I disconnected the vacuum hose from the dizzy) the car runs like crap. But if I set the static timing (not revving the car up, but setting it at idle) to 27 degrees, it seems to run pretty good. I'm totally confused. Could it be that the mechanical advance isn't working? Is there any way to test the mechanical advance? What would the symptoms be?

I hope this all makes sense, and I'm sorry for the long post.

Thanks for all ideas. A (IMG:style_emoticons/default/beer.gif) to the first person that gets it right.

[airsix]

The vacuum retard is only activated at idle when the throttle is fully closed, so this has no effect on the engine above idle.

Mike, try this if you haven't already:
1)Set your advance to 27 degrees BTDC at 3,500rpm per the book.
2) Slowly reduce the engine speed from 3,500rpm while continuing to watch the timing mark with the light. Continue slowing it down and watching until you reach idle.

You should have been able to view the advance being reduced until at idle you can't see the (red) 27 degree mark any more, and you should be very close to the (white) TDC mark now. If the 27 degree mark is still visible at idle then your advance mechanism is jammed up. As you rev the engine you should be able to watch the timing move in a linear manner from somewhere near TDC (white mark) to the 27 degree (red) mark.

If that checks out, the next thing I'd verify is that the timing marks are correct. Put the engine at TDC and get under it. Check the small hole at bottom center where the tranny and engine are bolted together. You will be able to see the bottom of the flywheel through the hole. there is a groove machined into the flywheel indicating TDC when the groove lines up with the seam in the engine case. Use that to make sure your timing mark for TDC is correct. Once you know if the TDC mark is correct you'll also be able to tell if the 27 degree mark is correct.

-Ben M.

ps - I'm just guessing, but I think a likely culprit is the installation of the pertronix. The screws holding the pickup in place, or the wiring to the pickup might be interfering with the advance movement. Just a guess, but you wouldn't be the first that has happened to.