base timing keeps advancing by itself...

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smokinnjokin

smokinnjokin

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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.
 
So when you actually set the timing back down to your previous base timing, are your original marks now no longer lined up? Like you have to keep backing the distributor down to get back to 10 degrees? Or is your v can adding timing once the engine warms up? Or is the v can binding the advance plate? Just throwing out some thoughts.
 
The springs and/or the weights are binding/sticking in the dist. Is the cap on tight. Is the rotor on tight. Try this, take the cap off and turn the rotor back and forth. Turn the rotor anti clockwise first. Did it move any? Turning to the right it should move a fair amount. Kim
 
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Correct.. I have to move the distributor clockwise past the original marks to get it back down to 12 btdc. The spot I had marked as 10btdc cold was now corresponding to 22.

You might have something with vcan binding the advance plate. I don't see any indicators in the distributor that this is happening, moves freely through range of travel, but thats the only thing that makes sense so I will try to run it down.
 
smokinnjokin said:
Correct.. I have to move the distributor clockwise past the original marks to get it back down to 12 btdc. The spot I had marked as 10btdc cold was now corresponding to 22.

You might have something with vcan binding the advance plate. I don't see any indicators in the distributor that this is happening, moves freely through range of travel, but thats the only thing that makes sense so I will try to run it down.
Click to expand...
Set the timing and drive it around for a while with the vacuum advance disconnected. Just make sure when you set the timing the advance plate is sitting at its zero (rest) position
 
Few things,imo possible.

A. Distributor advance sticking, or vac can is still operational
B. The dampener/balancer ring has spun loose.
C. The gear on the intermediate shaft has spun loose allowing the shaft that turns the distributor change phase with the cam shaft/crank degrees. They are pressed on, performance versions are pressed AND pinned .
 
20 question time...

What car
What year
what engine
what modifications
What distributer (OEM / aftermarket)
Points or electronic
if electronic what box


PHOTOS PHOTOS PHOTOS
 
Dana67Dart said:
20 question time...

What car
What year
what engine
what modifications
What distributer (OEM / aftermarket)
Points or electronic
if electronic what box


PHOTOS PHOTOS PHOTOS
Click to expand...
Only things that matter in that list is engine and distributor type electric vs points.
 
Just Spitballing... but it sounds like the Bronze Bushing under the Distributor Drive Gear is getting Scrubbed down.
Can You Pull the Distrib and the Gear and See if the Bronze is Shiny and Worn?
 
distributor is a factory single point with a gen1 pertronix (points removed, magnetic trigger) that was recently rebuilt by ray (halifaxhops).
Specs IIRC are around 12/24 total all in by 2500 rpm. I guess I will tear it apart and take a look.
 
MOPAROFFICIAL said:
Only things that matter in that list is engine and distributor type electric vs points.
Click to expand...
everything matters when people are hundreds of miles away and trying to diagnose a problem blind and buy second hand touch.

I bet most of us could do a few simple tests on site and have a solution in minutes but doing it this way, more info is ALWAYS better and really easy to get.
 
Did Ray install the Protronix?

Are the mounting screws too long?
Are your indicator marks so firmly attached to the dist that there is no way they can move?
have you verified that TDC is still TDC on the balancer?
 
Dana67Dart said:
I bet most of us could do a few simple tests on site and have a solution in minutes but doing it this way, more info is ALWAYS better and really easy to get.
Click to expand...
I appreciate your optimism..
Here's the specs.
'67 satellite 727 auto. 323 rearend gears.
Recently rebuilt low comp (dished pistons) smog motor. headers, comp xe262 camp, performer RPM intake, edelbrock 1403 carburetor. Runs very well when timing behaves.

Intermediate shaft is new, and distributor has a shaft collar to keep from bouncing. Had a serious issue with erratic (varying by almost 5degrees) timing at idle until I installed the shaft collar.

I have been chasing detonation issues last few weeks that I thought were due to a too-fast distributor curve that was putting way to much timing in from 2000-2500. In reality, now I realize every time I set base timing it would advance past that by 5-8 degrees. Best I can tell, with an actual 12-14 degrees base timing the car runs fantastic on 87E10. It only starts rattling from 2000-2500 under heavy load when base timing is up to like 18-20 degrees.
 
First thing is to verify the balancer ring has not slipped. It would be nice to know what engine as well. I have seen slants shear the distributor gear pin and it would run fine for a while then suddenly slip. Drove me nuts the first time I saw that because the ends of the pins were still in the gear so it visually looked fine.
I guess the same could happen to an intermediate shaft, although I cant say I have ever seen it happen.
 
I assume you've been re-attaching the vacuum advance hose after you set the timing? If so, you may have a carb problem where you're getting vacuum advance at idle. Either the idle screw is adjusted in a bit too much, or you may have an internal leak. Disconnecting the vacuum advance, does the timing go back to normal?
 
Vacuum advance is disconnected when I set timing, reconnected after. No it does not affect the timing. Unplugging it, plugging it, plugging the disconnected hose to the carb, no effect on base timing at idle. Have to physically twist the distributor.

And to answer all the questions as to balancer slipping... the idle speed does not lie. The way the carb is tuned, I can almost immediately guess within a few degrees where base timing is sitting by the hot idle. 10 degrees idles at around 750 neutral 650 in gear. 12 degrees around 800... 16 degrees around 950ish.. 22 degrees about 1050. The base timing is absolutely, beyond a shadow of a doubt moving around. Balancer is tight and is giving no indicators that it has slipped in any way.
 
Yup, a slipped balancer wouldn't effect the idle speed. Sounds to me like the point plate may be moving around. Any play in it or the Pertronix pieces? The only other thing I can think of would be the end play on the camshaft is way off, or, it's thrust surface and/or plate is badly worn or missing. What does the timing look like with the light? Is it steady and smooth when it's advancing, and returns the same way?
 
cudamark said:
Yup, a slipped balancer wouldn't effect the idle speed. Sounds to me like the point plate may be moving around. Any play in it or the Pertronix pieces? The only other thing I can think of would be the end play on the camshaft is way off, or, it's thrust surface and/or plate is badly worn or missing. What does the timing look like with the light? Is it steady and smooth when it's advancing, and returns the same way?
Click to expand...

Just tore into the distributor, point plate seems securely fixed by vac-can. When vac is applied, it moves smoothly, snaps back when released. There is some minor corrosion on the weights, but everything seems to be good.. roll pin is intact and not sheared, I just don't understand what is going on here. Im going to put a little grease in the advance slots.. but there is not anything that looks out of order in the distributor.

Timing with the light is a little erratic.. bounces back and forth maybe 2degrees at idle, mark seems to steady at higher speeds. Bounced way more (like 5 degrees) before I installed the shaft collar on the distributor. Still, very minor movement of a few degrees.

The camshaft was installed (and whole engine built) by 3rd party supposedly reputable machine shop. I guess cracking into the motor to check end play, camshaft, timing chain etc will be the absolute last thing to check.

This is a real pain in the ***. The car runs so well when the timing cooperates.
 
I think I found the issue. One of the pins that the advance weight pivots on is very loose. Currently cannibalizing the distributor and assembling another from spare parts. We will see what happens.
 
Hopefully the distributor takes care of it. I had a similar issue with the 318 in my Dart, timing would change every time I shut down/started up. Would run great when the timing was set right, couldn’t shut it down though. Eventually pulled it apart, turned out the last guy replaced the timing gear on the cam without the key installed, timing gear was slipping on the cam.
 
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