Timing issue (Distributor)

[SilveradoDude]

I have had a timing issue for a while that I recently solved. But something about the distributor is bothering me. After I replaced my valve seals this fall I noticed the timing needed to be reset. While checking the timing I noticed the timing mark was way off. The timing mark was way off to the passenger side. Normally, the advance pot on the distributor is in the 7 to 8 o'clock position (with 12 o'clock pointing to the firewall and 6 o'clock pointing to the radiator). In order to get the timing mark in the correct position of 4 degrees BTDC the advance pot is not in the 10 o'clock position. Does anyone have any idea how this could have happened and any problems that it could cause?

[85gmcguy]

My GUESS would be that your dizzy is off by a tooth,so you have to move it farther to get the marks to come in line. As long as you can get the timing set correctly (and it holds the set) you don't have a problem. If it won't stay set it may be time for a new timing chain set.

[piecesparts]

Did you pull the dizzy to do the valve seals?

[SilveradoDude]

Originally Posted by piecesparts

Did you pull the dizzy to do the valve seals?

No, I didn't touch the distributor. Was it the distributor that jumped a tooth or the timing chain?

[piecesparts]

How many miles on the engine? It could have enough slack to jump a tooth. If you did NOT touch the dizzy and you did the valve seals and set the valves per the manual, you should still be timed. Are you looking at the right timing marks for this engine? If it is a mid 80s truck the timing marks are directly behind the water pump and not on the side of the block. You have to shoot the timing light down the front of the timng chan cover from the front of the intake manifold. Also, did you disconnect the vacuum line from the dizzy when you checked the timing? Just asking for more info.

[James McClure]

Silverado, How did the truck run before you did the seals? Did it ping or lack power? I doubt the engine skipped time. Usually when a small block skips time it skips more than 1 tooth and runs like crap, or won't run at all and bends some valves in the process. Here are a few things to check. Look inside the dist and see that the vac advance unit returns to base timing. Check the weights & springs under the rotor. Also check the ballencer pulley and see if it has shifted on it's hub. Also make sure you have the timing light on #1. Easy mistake to make if you hook in at the cap and not at the plug, been there, done that. Let us know. jim

[SilveradoDude]

Originally Posted by James McClure

Silverado, How did the truck run before you did the seals? Did it ping or lack power? I doubt the engine skipped time. Usually when a small block skips time it skips more than 1 tooth and runs like crap, or won't run at all and bends some valves in the process. Here are a few things to check. Look inside the dist and see that the vac advance unit returns to base timing. Check the weights & springs under the rotor. Also check the ballencer pulley and see if it has shifted on it's hub. Also make sure you have the timing light on #1. Easy mistake to make if you hook in at the cap and not at the plug, been there, done that. Let us know. jim

Yes, timing light is on #1, (disconnected and plugged vacuum to dizzy). The engine is relatively low miles. 85 Silverado, 305, 4bbl, 113K. Yes, it pinged and lacked power before the valve seals (I assumed it was out of time then).
The dizzy is fine (relatively new). A few of the wires coming from the distributor were so dried out they looked like they had been chewed by a dog, so I replaced them.

[James McClure]

OK, you have pretty much eliminated everything except a shifted timing ring on the ballancer pulley. To check this the easiest way is to pull the timing cover and check timing marks on the timing gears. Be aware that when the marks are right togther (crankshaft mark up and cam mark down) it's in the #6 fireing position. Both marks up is #1. At this point you might as well replace the chain and gears, right? Now just hang the damper on, and remembering where the timing tab is, is the mark on the damper close to being in the right place? If your unsure try to slip the cover back on. If the marks are way off the ring has shifted and you'll need a new damper. Keep us updated, jim

[LONGHAIR]

There is no way that the distributor "jumped a tooth". It is however possible to shear the roll pin that holds the gear to the shaft. Generally when this happens....you get nothing, the distributor shaft doesn't turn at all.
The timing chain can indeed jump....but if it did, the crank would get ahead of the cam. This would make the valvetrain and distributor "late" (retarded) not advanced. If the timing mark on the balancer was rotated toward the passenger's side (counter clockwise) it is advanced. Also, to correct it, you rotated the distributor away from the rotor....retarding.
Jumping valve timing can't do this.
It is more likely that the outer ring of the balancer has moved. You really need to determine exact TDC and check the mark on the balancer.
The pinging you had before is further proof that you were too advanced, so there may not be anything wrong with the marks at all. It may have just been wrong before at the 7-8 position.

After I replaced my valve seals this fall I noticed the timing needed to be reset.

How would you "notice" that? Timing is not really a visual thing, unless you count looking at the timing marks when the light is on them.

[LONGHAIR]

OK, you have pretty much eliminated everything except a shifted timing ring on the ballancer pulley. To check this the easiest way is to pull the timing cover and check timing marks on the timing gears.

No need to get that involved. A simple "piston stop" screwed into the number one spark plug hole can determine exact TDC...this will show you where the balancer mark should be. This way, even if it is off, the only thing you have to remove is the lower pulley and the balancer itself.