time or not to time....that is the question

[billschroeder5842]

Question on the timing for my 383 with electronic ignition, 750 vacuum secondary with headers.

Can I (or is it better) to time the engine with a vacuum gauge than mechanically?

I ask because I seem to get a break up at around 3500 rpms and I really don't trust my mechanical read as the engine is a bit old and probably tired.

According to my timing light, my initial is about 18-20 which pulls 17 very steady on the vacuum gauge although the engine seems a bit wobbly.

Everyone asks about total timing but I have no idea on how to figure that one.

Any ideas?

[b5blue]

Do you run vacuum advance? Set initial @ 12* with no vacuum advance and plug it back in if you do. 

[billschroeder5842]

Okay, so set the timing at 12 with the advance un plugged from the distributor. Set the timing, then plug the advance hose back in? Is that correct?

[billschroeder5842]

Well that seemed to make a big different on the top end--I got it up to 90 with only a little jumping tach, and that occasionally.

Might I have a fuel flow issue? I have a Holley 750 and the fuel lever is set even at the bottom of the site.

[A383Wing]

I don't thinks fuel flow is gonna cause a "jumping tach"....sounds like more of a distributor problem to me

Bryan

[b5blue]

Okay, so set the timing at 12 with the advance un plugged from the distributor. Set the timing, then plug the advance hose back in? Is that correct?

Sorry I was out working on my car..yes. Now were closer, jumping tack could indicate a loose wire/bad connection. Check the blue wire on the bulkhead connector. Be certain it's clean and tight as it feeds ignition. Clean/check all coil/ballast and dist. connections then check the back of the alt. connections and regulator to. 
Verify engine grounds.

[69wannabe]

I usually plug off the vacumm advance completely. I haven't ran a vacumm advance on anything I have worked with in years. Its not a big deal to plug it off and run it. I would set the timing to 14 or 15 initial and plug off the vacumm advance and see how it runs. If it runs better I would leave it plugged off. Still need to check all wiring connections on the bulkhead and around the coil and the ballast resistor too. make sure the engine is grounded to the body also!!! Also mite want to check to see if any of your spark plugs may be fouled, that can cause problems too!!! A 750 may be a tad rich on a mild 383. I ran a 650 AVS on my 383 and it seemed bout right for my mild built combo. If plugging off the advance doesn't work out for you all you have to do is plug it back up, trial and error is best when playing with timing and distributors and vacumm advance's!!!