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Discussion Starter · #1 ·
There is something screwy going on with my timing. I dropped in a new HEI distributor for my 455. Carb settings are known good based on how it ran with old points dizzy. So I got it dropped in the water and got it fired initially pretty much straight up timing. I readjusted and got 8 degrees advance, but only got 20 degrees when revved up (over 3k) with the 2 orig springs. It 'looks' like the mech advance slot has more travel in it but it wont give it up. So I changed springs to see if the springs were too stiff possibly. One orig and one light spring. Now I have ~12 degrees initial and 25 on the top end. So went to 2 light springs and got 25 degrees on initial! I didnt bother revving it. So I went back to 2 original and now the timing is like 18 degrees initial where it should be back to 8.. Something screwy is going on here. The dizzy body didnt rotate, I checked that twice. Something must be floating or binding up? Everything on the mech advance plate seems to be ok.

So since it was running reasonable, I backed it out and started idling toward the open lake. Not more than 50 yards out it started stumbling, wouldnt idle, had to blip it constantly to keep it running. Then basically died and wouldnt restart. It didnt turn over hard, had gas, didnt check spark. Im thinking the timing changed and killed it?

For you guys who have locked out timing, do you have hard starting problems or drivability problems at low RPM? I am thinking of just locking it out to take the easy way out on this.
 

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Generally the springs are used to change the "rate" of advance. The lighter springs, the faster the advance comes in.

The amount of mechanical advance is usually achieved by some sort of positive stop to limit travel. Changing the amount of advance usually requires changing bushings on the stop pin.

If this distributor has or had a vacuum advance unit, and you are not using it, the breaker plate must be locked down so it cannot move.

Would help if you identified what brand distributor you are using.

From the numbers you have given, you have approx 12* of mechanical advance. When you put in the lightest springs, they were so weak that all the advance came in right off the bat.
 

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So have you checked you're total advance yet?? I'm running a hei locked out at 40* and I'm not bucking the starter as much as I would be at 16*...... If your timing is moving..and you have a vac advance, make sure it's physically locked out. Not just plugged off.
 

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Discussion Starter · #6 ·
40 degrees? wow, that seems like a lot. biggest numbers I have seen are more like 36 degrees.

I found my problem i think, the vac canister itself wasnt tight so it could shift around. PLus it was on its weakest setting, even though I didnt have it plumbed in to a vac line. So I tightened it down and ajusted it to the highest vac setting to keep it in place. If there is a way to lock it down (vac advance), it wasnt obvious to me.

I reset everything straight up and it started up and purred. I will re time it in the water so I dont burn up the pump any more than it already is.

Even though I dont think i have a problem with it, how does one check the phase between the pickup (HEI) and the rotor/cap relationship? My arc marks are right in the center of each post, so I think I am good there. But it does make good sense to get everything set perfectly, so when the advance kicks in there is a good amount of post/cap overlap? The tip of my rotor is pretty wide (1/4 inch?) and the cap posts are even wider (3/8 maybe) so it seems like I have plenty of room on that.
 

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Did you figure out how to change the amount of mechanical advance?

Probably don't have to worry about the rotor phasing.

You should check if there is a lockout plate available that replaces the vacuum advance can. Couple companies used to sell them but I haven't seen one advertised in years.
 
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