The Stovebolt Site Forums The Shop Area Engine Shop timing gears slipped a tooth?????

I have had a continual problem with the timing on my chevy inline 6 250. I have tried all convetional ways to time the engine, so please rafrain from thoes suggestions.

My question is, could it be possible that the timing gears have slipped one tooth off. Not that the tooth broke, but that its just moved one tooth off because the teeth are worn down.

It's in a 1965 chevy c20

thanks for the help

If the teeth were worn that badly, they would shear off entirely. I've seen timing CHAINS get loose enough to jump a tooth, and the engine would still run, but never a gear setup. Have you aligned the dots on the timing gears, or are you just guessing that maybe the cam timing is off?

Here's a quick way to check cam timing without having to remove the timing cover: Remove the valve cover, and watch either the #1 or #6 cylinder valves. Turn the engine clockwise from the front by hand until the exhaust valve is fully open. (Exhaust is the last valve on the end, either cylinder) Then turn the engine in the same direction until the exhaust valve is almost closed, and the intake valve begins to open. (It's the next one in line, front or rear) When the valves are approximately the same amount open, intake and exhaust, the piston in that cylinder should be at the top of its travel. You can use a bright flashlight shined into the spark plug hole, or probe into the cylinder with a piece of soft wire to monitor piston travel. Don't use a stiff piece of metal like a screwdriver, etc. to avoid cylinder head or piston damage. If the valve overlap position comes anywhere other than top dead center, you've got cam timing problems.
Jerry

In tinkering with jalopies for over 50 years, I have never seen one jump a cog. Does it run at all? If it does, just time it by ear and don't worry about where the marks are.

I'm guessing you're having trouble with ignition timing?
Not because I have any inside info but because of the theorem of Occam's Razor which paraphrased, says, the most likely problem is the most likely problem. If you've tried everything else, are you sure the harmonic balancer is OK?
The timing mark should be about 2:00 relative to the keyway. (I think)

regards,
Leon

Question , when your timing with a timing light does the mark keep moving around,goes up and down as your looking at the timing mark?

Or does the engine run bad or not run at all when you have the timing mark lined up?

Is it changing from one time to the next and not in the same place the next time you put a light on it?

What is going on?

Pete

I had a problem with the cam gear slipping a little on the boss.

The teeth were all good , the key way was good , I only found the answer when I compared the timing dot with a new gear markings.

Those are prone to dist. shaft/bush wear on the point type dist. Have you checked that or bent dist shaft?

i have had the roll pin on the dist shaft can "waller" out the dist gear. pretty easy to fix if it's that. good luck.

Is the harmonic balancer true and not wobbly? Chances are the outer ring has slipped, this will through your timing way off.
To check it, pull the #1 plug out and turn the engine till the piston is at the top, then check the the timing marks. The line should be on zero. You may have to do it a few times too get a feel for it, use a small wood dowel rod and hold it on the piston to feel when it stops at the top then starts back down.
A well used 250 should turn over by hand pretty easy with a little muscle.

Joe

yes, the timing mark jumps around - and the engine runs bad.

Do you still have points distributor?

I have an almost new one I will send you, wires and all. Send me a e-mail if you are intersted.

As far as gear jumping, no way! If they did, you would have way more problems then rough running.

Joe

Look for loose bushinghs at the top of the distributor. Are you running points, or an electronic ignition? A wobbly shaft, or a worn distributor cam will change the point dewll angle between cylinders. One degree of dwell change equals 2 degrees of timing change. If you can shake the dizzy shaft and see any wobble at all, that's way too much! Even a HEI can have problems with looseness, just not as dramatic as points.
Jerry

Could be your diss and your cam gear are worn ,take the cap off of your diss and try and turn the rotor back and forth also try side to side and see if theres play in it could be the diss bearing is worn out .

Pete

distributor is tight and also new. when i turn the enigine by hand the rotor button lines up in the same position on a half turn and full turn each time.

could it be a bad coil that's causing this issue. i doubt it but........

i wish i could get this issue figued out, i think my first post on this was close to a year ago.

thanks for the help though