Caution timing rant

[Don W.]

Numerous times over the years people have asked about timing and why the engine won’t run or runs poorly. Common answers are “you’re 180 out” or “you’re a tooth off.”

Those comments or a variation of them seem fairly common. I’d like to know the original source but these two thoughts are probably at least as old as I am.

Neither one hold any water so-to-speak. If the timing is “180 out” then you’re firing the cylinders at TDC on the exhaust/intake portion of the cycle. The engine will not run.

Being a “tooth off” is equally meaningless. There are 13 teeth on the dist gear. Consequently each tooth equals aprox. 27.7 degrees of timing. That far off in either direction will cause all kinds of problems. Starter kickback, backfire, or just plain no-start, but regardless it’s very unlikely the motor will run or if it does it will be running extremely poor and require some throttle to keep it going.

I recently installed my dist a “tooth off.” It wouldn’t even begin to run until I rotated the dist counterclockwise a bunch. In effect compensating for the “tooth off” install and bringing the timing to a point where it would start. IE rotating, or advancing, the dist 27 degrees to “compensate” for the “tooth-off” install.

So it really doesn’t matter where you install the dist. Or where someone else installed it. With the engine on TDC COMPRESSION, obviously the most important step, drop in the dist or look where the rotor actually points. That is now #1. It’s as simple as that. Then, in our case, going clockwise, insert the plug wires in order: 6,5,4,3,2. As long as all, including module, wires will reach without stress then NOTHING ELSE matters. Not the position of the gear on the shaft or anything. Of course physical limitations like wires reaching, personal preference, (“this thing is going in like original if it kills me.”) or if on an older vehicle with vac advance the vac advance unit may dictate dist placement witch -will- have an effect on the resulting rotor position and wire order.

The one exception that I know of is certain air cooled VWs retarded the spark ONLY on #3 which required the dist to be installed correctly to provide for that.


Although a :rant: hopefully this will serve to clear-up the kind of questions that occasionally come up when we have no-start, backfire, type ign questions.

 

[Damian]

Re: Caution timing rant

Being a tooth off could be a problem if you don't turn the distributor enough. Being 180 off, which happened to me, can be a pain if you are seeing spark and no start. I've had someone crank the engine over and used a timing light to see if 1, I'm even getting spark and 2, to see if it's even close.

 

[Don W.]

Re: Caution timing rant

I always appreciate Dave's comments and stories. Years ago working in a gas station a friend came in, borrowed the shop for a bit and swapped all the plug wires. Randomly. Then wondered why it wouldn't run. That's what the distributor is for he said. :rotf: That was my first experience at starting from scratch.

I intentionally chose not to go into the detail of lining up the oil pump drive. Figured my rant was long enough as it was. But when done as Dave suggests or just lining up the reluctor points will get you dang close. Another hint is to do a final check of timing after tightening down the dist hold-down. Often that will change timing a small, but in our case important, amount.

Although not spark ignited when I went to diesel engine school one entire semester was spent taking a motor apart and reassembling it AND it had to run when we finished. Dave will enjoy knowing they were mostly old 6-71's.

 

[Z SKI]

Re: Caution timing rant

Never a dumb shit in my eyes DaveP..

As for the distributor install that Dave did... In the best Darth Vader/James Earl Jones voice: "Impressive, Most Impressive."

Thanks again for the help Dave!!

 

[randy merritt]

Re: Caution timing rant

I always appreciate Dave's comments and stories. Years ago working in a gas station a friend came in, borrowed the shop for a bit and swapped all the plug wires. Randomly. Then wondered why it wouldn't run. That's what the distributor is for he said. :rotf: That was my first experience at starting from scratch.

I intentionally chose not to go into the detail of lining up the oil pump drive. Figured my rant was long enough as it was. But when done as Dave suggests or just lining up the reluctor points will get you dang close. Another hint is to do a final check of timing after tightening down the dist hold-down. Often that will change timing a small, but in our case important, amount.

Although not spark ignited when I went to diesel engine school one entire semester was spent taking a motor apart and reassembling it AND it had to run when we finished. Dave will enjoy knowing they were mostly old 6-71's.

I took the shaft out of my old distributor and ground down the teeth on the dist gear just so I could use it to line up my oil pump drive. I works much easier than a long screwdriver, plus you can tell the oil pump shaft alignment from the position of the old dist shaft.

 

[Quickstop [UK]]

Re: Caution timing rant

I just align the distributor with #1 based on TDC and if the oil shaft doesn't engage, I turn the crank using a wrench until the oil distributor settles into it properly. Then I check TDC and the position of the rotor compared to where it was just in case I am out a tooth but it seems to work. No need to mess around with the screwdrivers.

 

[Quickstop [UK]]

Re: Caution timing rant

You have to crawl onto the engine in truck and peer down that hole. I hate that.

I find it easier to turn the crank. I have no issue with that. Whatever suits you.