base timing keeps advancing by itself...

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TT5.9mag said:
@Phreakish that would not explain why he has to back up the distributor further than it was previously.
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That depends. I don't think we have an exactly clear picture of what's happening. I would expect to have to back it up 'further' in order to re-obtain the set idle speed until the engine cools down. If it keeps moving, at some point the vacuum canister is going to hit something. It's unclear if that's happened. If it's moving 10-20 degrees each time, then he'd be out of space to turn the distributor after 1-2 times of this happening, but it sounds like it's happened more than that.

I suspect what is happening is the following:
Engine cold, idle timing at 12. Rpm sub 700.
Engine warm, idle timing at 12. Rpm sub 800.
Engine hot, timing now reads 22. Rpm 1600-2200 (hanging).
Engine hot, idle timing at 8. Rpm sub 900.
Engine cold, idle timing 8. Rpm 6-700.
Engine warm, idle timing 8. Rpm sub 800 - diminished performance.
Engine hot, timing now reads 18. Rpm 1200-1600 (hanging, but lower).
Engine warm (from hot to warm while adjusting timing), timing now reads 12. Rpm sub 900.
Engine hot, timing reads 22 again. Rpm 1600-2200.
etc...

During the time it takes to reset the timing lower to get the rpm back to idle, the engine loses enough heat that it would probably idle normal again, but now it has less advance too. The fixation on the timing leads to ignoring other variables. I would get it hot and get it to 'advance' and the high idle. Then manually adjust the idle speed down (write down how much the idle screw is turned) then once back to a normal idle speed, re-check the timing. It should be back to normal - if not, THEN we know it's an issue. Timing and rpm vary together so any two timing values at different RPMs do not correlate to one another.

What we do know is that it's advancing. That rules out anything slipping, since it would result in retarding the timing.
If the distributor was not being adjusted back and forth, the distributor would be getting rotated round-and-round. No mention so far of something like that (having to re-order plug wires on the cap, re-stab the distributor, etc).

So, with the information as presented, and the new info that it goes 'back' (to normal? To something else?) when cold, it's either an electronics issue or my theory as presented above.

I find it tough to fully explain through text alone, so it may not be totally clear what I'm trying to state. It would be pretty easy to see in-person though, and I've experienced it.
 
Sounds like its a electronics glitch .
I cant think of any way that it could advance mechanically . And then retard ??? Nope .... maybe Vacuum can sticking then slowly releasing over time but it sounds like that has been addressed
 
I think engine is tight cold, and or, leaking vacuum when hot. RPM is increasing, mechanical advance increasing with that.
A good way to test is gather timing vs RPM at low end. You should find relationship nearly same vs temperature.
Vacuum advance plugged at carb, open at distributor, or monitor vacuum in line to see it stays constant, near 0 at idle and over temperature.
 
Throw this in.
When warmed up, idle is higher.
Because the mech advance springs are soft or too long and distributor is already in the curve.
So advances at low rpms. And it may also be aggravated by dirty, hanging pivotal movement. & May not pull back.
Seen it, been there. - but din’t have enough money to buy the t-shirt.

Does the total timing move?, is the important thing.
If that moves, - then something below.
Base timing? - idle well?
 
Ok folks, thanks for all the brainpower, just got off the phone with Ray and we have the issue figured out. Weak small spring in the advance mechanism.

What was happening was the spring weakened with time, 7 months of storage, and that it was adding timing at idle and under 1k. around 750 it was adding 2 ish degrees, 850 around 4, 950, 6 and so on so that at a high idle of 1k rpm it was adding almost 10 degrees. Timing was almost all in by 2k (which was causing the detonation). When I mentioned "swapping distributor" earlier I misspoke.. what I did was cannibalize another distributor using the same advance weights and springs... so of course problem followed. Visually, there wasn't really anything to indicate the spring had weakened other then light corrosion over everything.

As the motor heated up, it wanted to idle higher, which would pull in advance, which would make it idle higher, and of course making it impossible to accurately set base timing. It wasn't until I sat with the timing light and observed the advance through the entire rev range that I was able to see what was going on.
 
Glad you finally found it. :thumbsup:
Wasn't that suggested as a cause about 30 posts ago? :poke:
This is certainly an odd (but a good) example of the rule that advance should always start above idle speed... (unless locked-out of course).
 
smokinnjokin said:
Ok folks, thanks for all the brainpower, just got off the phone with Ray and we have the issue figured out. Weak small spring in the advance mechanism.

What was happening was the spring weakened with time, 7 months of storage, and that it was adding timing at idle and under 1k. around 750 it was adding 2 ish degrees, 850 around 4, 950, 6 and so on so that at a high idle of 1k rpm it was adding almost 10 degrees. Timing was almost all in by 2k (which was causing the detonation). When I mentioned "swapping distributor" earlier I misspoke.. what I did was cannibalize another distributor using the same advance weights and springs... so of course problem followed. Visually, there wasn't really anything to indicate the spring had weakened other then light corrosion over everything.

As the motor heated up, it wanted to idle higher, which would pull in advance, which would make it idle higher, and of course making it impossible to accurately set base timing. It wasn't until I sat with the timing light and observed the advance through the entire rev range that I was able to see what was going on.
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That's what I suspected, but it's tough to describe in a brief way..

Glad it's been figured out! Let us know how she runs when it's all dialed in.
 
@Phreakish your explanation was perfectly clear and easy to understand. And it turns out you kinda nailed it. What the op said Very early on must not have been true at all about turning the distributor back further than his marks. As we now know what his issue was.
 
Phreakish said:
That's what I suspected, but it's tough to describe in a brief way..

Glad it's been figured out! Let us know how she runs when it's all dialed in.
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You nailed it, thats exactly what was happening, but at lower rpms (between 650-1050) where no mechanical advance should have been coming in yet.
 
DrCharles said:
Glad you finally found it. :thumbsup:
Wasn't that suggested as a cause about 30 posts ago? :poke:
This is certainly an odd (but a good) example of the rule that advance should always start above idle speed... (unless locked-out of course).
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Yes, post #27, took distributor apart to check but of course hard to verify a weak spring by looking at it.. and I didn't want to start revving motor until I put everything back together and manually turned over the engine with breaker bar while watching rotor to ensure no slop or play in cam timing. Once that was one and I had confidence in the timing gear/chain, I fired it up with the light and got to work checking the curve.
 
Damn, think that's what I said.
Glad you found it.
It's nice to have springs that do not allow advance until above, say 1000 rpm.
That way, everything is static at idle.
mixtures and speed can be set without timing changes.
 
smokinnjokin said:
Ok I just identified a really weird problem that has me scratching my head.

Set base timing to 10 with engine warm, vac advance unplugged. Drove all day, ran great. Checked timing on shutdown with engine fully hot... base timing was now 14. I have a mark on the carb plate with an indicator stick I put on the dizzy, confirmed that the distributor is locked down and didn't move. Engine was idling at higher RPM, corresponded to increased timing so I don't think dampener slipped or anything like that. Bolts are tight.

Reset timing back down to 12 base with vac can unplugged and engine fully hot. Drove again next day.. ran great, but about halfway into the day I noticed detonation rattle around 2000-2400 rpm that should not have been happening... and the car was suddenly idling at 1000 rpm which is way too high. Checked timing again... 22 degrees base timing now. Indicator marks show distributor has not moved. Busted timing back down to 12 btdc and idle returned to normal 750-800.

What the hell is going on with this thing? All my theories don't check out...
1) though maybe dizzy springs are weakened some how and it is bleeding in base timing at idle... but that would not effect the WOT detonation I am getting around 2000-2500 that indicates all in timing is way to much (entire curve has been shifted by 10 degrees!)
2) distributor is locked down TIGHT.
3) Vac can locks distributor trigger (pertronix) into position... but everything looks good in distributor no slop and V-Can is brand new and working properly.

What the hell is going on with this thing... I think all my past issues with detonation are due to this movement... when base timing is actually 12-16 degrees, the car runs fantastic. But when I set it warm.. it moves by 4-8 degrees advanced after an hour or 2 of driving... it has done this twice now. Now I realize there is no issue with my curve, plugs, fuel, any of that... my base timing just keeps increasing on its own somehow.
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The rubber isolation ring in the harmonic balancer has shot craps allowing the outer ring with the timing marks to move. Time for a new balancer.
 
TT5.9mag said:
@Phreakish your explanation was perfectly clear and easy to understand. And it turns out you kinda nailed it. What the op said Very early on must not have been true at all about turning the distributor back further than his marks. As we now know what his issue was.
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I'm sure it was true, the timing probably needed to retard further than the original idle timing to get back to a normal idle speed. If I was fixated on the timing (it's happened before), I can imagine thinking it needed to be that way.
 
Exactly i was not touching the carb at all and trying to restore idle to normal with timing. Had me chasing my tail.
 
Good talk last night. There were a few small things missing form the posts. It was not getting reset further and further when it went forwad it was put back to the starting point then it would go to say 20 really fast. Another thing is the small MP spring got rusted in it from shed storage and its tension is lost. Ran great for a few years. Sending him some springs that will fix it. Mystery solved.
 
Have everything in the distributor clean and lubed, ready to go back together just waiting for the mail.
 
Mail came, installed the new spring this afternoon. Bigger/more coils but felt about the same by my non-calibrated stretching. Put everything together, set base timing at 14 and confirmed total was 36 by about 3000 rpm. New curve seemed just a bit slower, still adding in about 6 degrees at the crank mech by 1000 rpm but still less than previous spring...

Let engine get hot, went for a drive and still got serious rattling around 2k-2500. So I said forget what the timing light says, im just going to dial it back to a good safe setting and work my way up slowly from there. Pulled it back to 8 initial, pulled hard, ran strong no rattles and idled well at 800N, 750ish in gear with no carb adjustments. Currently its 70 degrees out. I will drive it tomorrow, hot day and see if I can get any detonation. If not, I will bump up timing incrementally until I get detonation.

Its possible I am running a bad batch of gas as well that is exacerbating the detonation issue. At this point, I almost don't care what the timing light says it feels very strong even pulled back to 8 initial.

Will keep the group posted as I slowly advance timing to a final setting. If I get a baseline on the hottest day with the crappiest gas, I can pretty much operate with confidence from here on out.
 
Did you ever check to see if the inertia ring on the balancer has slipped?
 
No, don't have time right now to fabricate a piston stop. I'm operating on the assumption that it has. Do they generally slip towards retarding the marks? I.E. making it look like the timing is much more retarded than it actually is?
 
smokinnjokin said:
No, don't have time right now to fabricate a piston stop. I'm operating on the assumption that it has. Do they generally slip towards retarding the marks? I.E. making it look like the timing is much more retarded than it actually is?
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Without standin in front of one, I'm terrible at guessing. So I'm just not sure. It should be fairly easy to see. If the rubber ring is all distorted and twisted looking, then chances are pretty good.
 
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