Timing running at 20* advance...

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dostroupe

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Here's a little background on the car. 1970 Duster, low mileage (73k), untouched, that has sat for years till this summer. I bought the car in June this year it would start and run with gas being poured in the carb. I have gotten it road worthy. It runs and drives really, really good. In order for me to be satisfied with the slant, it will need to be modified. It needed a tune-up as you could guess, so an HEI conversion was sourced. Distributor from @halifaxhops , Standard ignition products throughout, ran by a Bosch relay.

The day I started swapping in the HEI I checked the timing and it showed 0* TDC (like the sticker says on the inner fender) on the old distributor. I set the engine on TDC, marked the rotor position, did the wiring and set the new distributor in on the mark I had made. I know it doesn't matter where you put the rotor, but I'm a little OCD about things. The car would not start, so I pulled the distributor and moved the rotor back a couple of teeth (retard). It would start but not run good. I did that again and it started and ran good. I set the timing then at 5*.

Road test, not good. It idled fine, but would not pull good. I stopped a couple of times and adjusted the timing (advanced) to where it runs way better than it ever has. It will actually boil a tire while turning (and without turning on smooth concrete). It idles great, so good in fact that yesterday my wife was in the shop leaning against it and didn't know it was running.

So, yesterday I decided to see where the timing ended up, 20* BTDC. That's initial, vacuum advance not hooked up. It has a total advance of plus 30*. Doing searches this morning, but can't find a similar situation. I'm going to throw a lot of mods at this thing to make it acceptable to me. Any ideas?
 
I would hit up the guys over on slantsix.org
It's all they do
 
Man almost sounds like a stretched Timing chain, keep me informed if it is something with the dist. Hey @slantsixdan any ideas?
 
This ^^^is what I thought also, but the timing mark doesn't bounce like it would if the chain was stretched. I'm not concerned at all with the distributor, there's only so much that could be wrong with it, you checked it, I checked it, it's good I believe.
 
It can only be so many things in no particular order
1...You made a mistake, firing order, etc

2...Timing marks are somehow incorrect

3...Cam is out of time

4...You changed the distributor? Maybe it's out of "rotor phasing" Google it
 
I don't get the problem; 20 initial and 30 power, both with the Vcan disabled. And it idles dead smooth and has plenty of power.

If anything;
TDC is not TDC,and
there's something wrong with the centrifugal advance system.

If it doesn't detonate just DRIVE it,lol.
 
AJ/FormS said:
I don't get the problem; 20 initial and 30 power, both with the Vcan disabled. And it idles dead smooth and has plenty of power.

If anything;
TDC is not TDC,and
there's something wrong with the centrifugal advance system.

If it doesn't detonate just DRIVE it,lol.
Click to expand...
Usually, best max timing is 30-32* on a slanty, nothing abnormal here. The fact that the initial is higher is simple, the mechanical plate isn't adding much, why and where
that came from is the question. But like the old saying, if it ain't broke!!!>>>>>>> Curious to see what vacuum adds..............
 
That's what I meant;, there's something wrong in the centrifugal; it should be over 30 centrifugal and not just 10. It seems to be malfunctioning.
At 30 it shouldn't be detonating, and if it's not, I might just leave it where it is.
But there is a very real possibility that at some time in the future, the centrifugal starts operating correctly, and them it might have 20 plus 36 =56, and that would not be good at WOT.
It's also possible that the plate is just hanging up at 20 and that if it stops doing that, then the base timing might return to it's proper place, around zero.

So in other words it's probably best to figure out the why of it and fix it as may be required.
 
After much tuning yesterday evening, it is now running at 12* initial. The idle quality isn't as good, but still good (make sense?). I readjusted the carb a couple of times then the timing. With the vacuum advance hooked up, drivability is awesome. So for now if it ain't broke, I'm not fixin'! The motor is coming out anyway for cleaning, gaskets, cam and head shave. I will enjoy it this way for now, Thanks guys!
 
Good to hear, weird though, seriously do the east chain check with the cap off tap the starter till the rotor moves, mark the balancer on the scale, then hand rotate it the other way and see how much play is there.
 
I think you've got a timing-indication issue here. The fact that you could make it run great without ping at 20° initial suggests the actual timing is different to the indicated timing.

Since you had to move the new dist a few teeth off your indexed location to get it to start, I wonder if you might see more realistic indications with the timing light hooked to a different plug wire (which in turn makes me wonder if your plug wire positions were off by one on the new cap vs. the old cap).

A simple indication issue like this is much more likely than violating basic principles about how engines work and still having it run great and not ping. You ought to chase this down and squash the bug so you can accurately dial in your timing, or at least know what you've actually got.

Speaking of distributor caps, read this entire thread. It's long and gets a little dull, but there's a big reward towards the end.
 
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Interesting thread Dan. I sent him the dist, I rebuilt it a while ago but spun it up again to check to make sure it was ok, it did seem to be right on, that phasing concept is a good one, did not realize all of the differences with cap manufacturers, interesting.
 
dostroupe said:
Road test, not good. It idled fine, but would not pull good. I stopped a couple of times and adjusted the timing (advanced) to where it runs way better than it ever has. It will actually boil a tire while turning (and without turning on smooth concrete). It idles great, so good in fact that yesterday my wife was in the shop leaning against it and didn't know it was running.

So, yesterday I decided to see where the timing ended up, 20* BTDC. That's initial, vacuum advance not hooked up. It has a total advance of plus 30*. Doing searches this morning, but can't find a similar situation. I'm going to throw a lot of mods at this thing to make it acceptable to me. Any ideas?
Click to expand...
Ok, before this thread progresses any further, please clarify " It has a total advance of plus 30*". I want to be sure that the timing light was indicating 20* BTDC at idle, and
then indicating 30* BTDC revved up until the mech. advance stops adding, representing 10* of centrifugal advance. If so it should run pretty damn good, and the marks
may be fine, the only issue is as mentioned there should be more centrifugal adv. in a stock /6 dizzy.
At least You've got Her running good for the time being, enjoy for the season & keep Us updated.
 
Killer6 said:
Ok, before this thread progresses any further, please clarify " It has a total advance of plus 30*". I want to be sure that the timing light was indicating 20* BTDC at idle, and
then indicating 30* BTDC revved up until the mech. advance stops adding, representing 10* of centrifugal advance. If so it should run pretty damn good, and the marks
may be fine, the only issue is as mentioned there should be more centrifugal adv. in a stock /6 dizzy.
At least You've got Her running good for the time being, enjoy for the season & keep Us updated.
Click to expand...

I stopped looking for total advance at 30*, it went further. At that time, seeing where initial was and where total was going, I stopped to recheck things. And yes it runs good, really good, better than I thought it would. My timing light is good, in fact I put it on my truck just to check, and it's fine.

I didn't have a lot of time yesterday to check things, but I did take it to the hardware store just to drive it. I did pull the cap and the rotor is pointing at number one. There is some slack in the chain. Maybe I'll have some time this weekend to dig deeper, but I'm kinda feeling that it's good. Like I said, I'm going to do other things to it later, so I'm sure I'll find out what's going on then. But for now I'll drive it.
 
Drive the hell out of it and enjoy it, should be really fun with the future mods.
 
No sweat glad it worked out. Still a strange one though.....
 
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