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69 350 timing?

896 views 2 replies 3 participants last post by  BogiesAnnex1 
#1 ·
I had some problems with my exhaust popping so I adjusted my fuel mixture on my 1406 carb and got it to stop but now I'm trying to see where is my timing at and if it is correct. I need some help.

I got an inductive timing light and my initial timing at idle is 6 degrees advanced. (That's if each mark is 2 degrees and the numbers above the 0 mark is advanced and below is retarded).

At this time I have no way to measure total timing because I do not know what exact rpm I am at but when I go up on the throttle and hold it, the mark goes off the timing tab( my timing tab only have 14 degrees each way), so I know it's more than 14. Do I need to go all the way up on the throttle to get total timing?

How do I know what my timing should be fir this 69 caprice original 350, with a few performance mods like intake, petronix igniter, headers, edelbrock carb and that's about it.
 
#2 ·
Early cast iron heads will want 36 degrees initial and centrifugal, all in by 3000 rpm's. The main problem with timing with a light is that you don't know if the harmonic damper inertia ring is valid or not. The ring is bedded in an elastomeric material (like black rubber) and does not have a mechanical couple to the drive hub of the damper. The ring therefore can slip circumferentially in relation to the drive hub and you will have no idea where the timing is. Please refer to this tutorial and nail everything down concerning the marks on the inertia ring in relation to the drive hub and to the position of #1 piston before you do anything else.....
http://www.crankshaftcoalition.com/wiki/Determining_top_dead_center
 
#3 ·
You can't read total timing with the factory set up as the marks do not go high enough. This is best done on a Sun distributor machine if you can find a shop that has one any more. Even if you put a timing tape on the damper this is hard to do because the engine without any load on it can rev to 3000 RPM or more with hardly any throttle so you can't get a accurate measure of the vacuum advance.

For a 1969 engine that is original except for some external mods that is popping from the exhaust I'd start to worry about the timing set (gears and chain) and 45 years of wear. The chain stretches and most often the cam gear has nylon teeth that disintegrate with age. This appows the cam to fall retarded to the crankshaft, the power drops off and you get popping from the exhaust because the combustion event is still occuring when the exhaust valve opens. You find yourself frequently having to readjust the timing because as the cam falls retarded it takes the distributor shaft with it so you find it's neceassry to readjust the distributor body position farily often to compensate for the changing cam posiiton relative to the crankshaft.

A simple test is to wire the centrigugal advance down so it cant function, remove the vacuum advance hose and plug the carb port where it mounted. With the timing light hooked up and operating run the revs up a couple, three thousand then slam the throttle shut. If you see more than a couple, three degrees in variation of the base timing it's time for a new set of gears and chain under the timing cover.

Bogie
 
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