1973 Not Running
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
Pop the steering. Drop the pan. Get all the timing gear teeth out of the pan and oil pump. You ain't working in a garage. YOU are the customer you are shafting by half-assing it. It's not like you need to drive to work tomorrow in it. While you're in there, spend 50 bucks on a new oil pump. Not hi pressure or volume, just new.
Last edited by derekderek; Nov 3, 2017 at 07:06 PM.
Le Mans Master
Joined: Sep 2003
Posts: 8,812
Likes: 2,029
From: eastern NC
Ok so I am a novice at best, but here is an update. No spark at the #1 plug wire. So pulled the distributor to find out that a previous owner pull the points and replaced with Pertronixs ignition. Regardless, cranked it over and distributor intermittently spun. It would spin for a bit then stop while the motor turned over. Before I loosened the hold down I noticed there is a little play in the distributor shaft. Should there be? I pulled entire assembly and gears are tapered, but don't look stripped or broken. So at this point am I correct to assume the timing chain or pulley has broke or sheared? Is there any other thing I should be checking before I rip the front end of this motor down? Am I missing anything? I appreciate any thoughts. Thanks!
Good luck... GUSTO
Last edited by GUSTO14; Nov 3, 2017 at 08:09 PM.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
He cranks starter and sees distributor turn intermittantly. It is absolutely a chain slipping on a timing gear that has shed it's teeth. Let's just hope he hasn't bent any, or all his valves.
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
did they use plastic timing gear teeth on this year engine? YES. they claimed it was to be quieter. I swear it was to generate a valve job-timing chain replace well after warranty expired. 
or was that just a Pontiac thing? Probably not. the exhaust backfire could be the chain slipping.
or was that just a Pontiac thing? Probably not. the exhaust backfire could be the chain slipping.Just me. Good luck.
Steve
Now that I've read the entire post, perhaps it is the distributor's Drive Gear. I've never heard of a Cam Gear failing. Weakest link in the system IS the chain, no?
Steve
Last edited by Cavu2u; Nov 4, 2017 at 09:18 AM.
Pro
Joined: May 2016
Posts: 708
Likes: 150
From: Minnesota
Could be right. Pull the distributor and make sure everything is in order there... while it well could be the timing chain, it is always best to check and eliminate easier stuff first. If the disti doesn't seem right, eliminate it as a possibility first.
Last edited by JoeMinnesota; Nov 4, 2017 at 09:23 AM.
Pro
Joined: May 2016
Posts: 708
Likes: 150
From: Minnesota
Pop the steering. Drop the pan. Get all the timing gear teeth out of the pan and oil pump. You ain't working in a garage. YOU are the customer you are shafting by half-assing it. It's not like you need to drive to work tomorrow in it. While you're in there, spend 50 bucks on a new oil pump. Not hi pressure or volume, just new.
Last edited by JoeMinnesota; Nov 4, 2017 at 09:27 AM.
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Race Director
Joined: Mar 2016
Posts: 14,406
Likes: 8,212
From: Napa Valley California
Remove all spark plugs, and distributor cap, rotate the engine while plugging the number one spark plug hole with your thumb. As the rotor rotates past the location of the number one plug wire position you should feel the cylinder compression pressure against your thumb. This will help to let us know if the timing gears have proper alignment
With the cap off the distributor, turn over the engine, using your cell phone video the rotation of the rotor Stop!!!!
Pull the distributor, photograph the distributor shaft and gear from several angles STOP!!!
Post video and photos to this thread. Let us see what things are doing and inspect distributor gear before you proceed to tear into anything else.
Remove the valve covers photograph from several angles, close up and post the pictures, STOP!!!
With the cap off the distributor, turn over the engine, using your cell phone video the rotation of the rotor Stop!!!!
Pull the distributor, photograph the distributor shaft and gear from several angles STOP!!!
Post video and photos to this thread. Let us see what things are doing and inspect distributor gear before you proceed to tear into anything else.
Remove the valve covers photograph from several angles, close up and post the pictures, STOP!!!
Last edited by OldCarBum; Nov 4, 2017 at 11:01 AM.
Instructor
Joined: Sep 2017
Posts: 169
Likes: 20
From: Westlake Ohio
The right way to check the timing chain is to bring the engine to TDC rotating clockwise ONLY with the dist cap off. Once at etc have someone watch the rotor and turn the engine CCW slowly. As soon as the rotor starts to move stop turning. Look at timing Mark if you rotated engine more that 3 degrees the chain is bad. Good luck and remember KISS. keep it simple silly
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
read this quote. now tell me any way the distributor can turn and stop, turn and stop while the engine is cranking. the nylon teeth stripped off the timing gear and the chain grabs, then slips. he needs a chain and upper gear. and he needs to get the plastic teeth out of his engine.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
I missed a shift in my old GTO in 75 or so. western PA long hill. turned around, rolled down the hill. popped the clutch. engine ran for 1 second, popped thru intake, popped thru exhaust, ran for a second... went thru that cycle 3 or 4 times down that half mile hill. got it home. the plastic teeth were gone from the upper gear. replaced the chain and gear and it had no power. I bent all 16 valves in the process of forcing it to turn while chain was slipping.
Last edited by derekderek; Nov 4, 2017 at 11:32 AM.
Melting Slicks
Joined: Oct 2013
Posts: 2,569
Likes: 126
From: San Diego California
read this quote. now tell me any way the distributor can turn and stop, turn and stop while the engine is cranking. the nylon teeth stripped off the timing gear and the chain grabs, then slips. he needs a chain and upper gear. and he needs to get the plastic teeth out of his engine.
If you need a gear/chain set, I've got one you can have, on me. But I'm afraid that if this really IS the problem, I just pray no damage to the valve train has happened.
Steve
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
I have doubts that it's a chain problem. I'd concentrate on the Ignition system first.
Just me. Good luck.
Steve
Now that I've read the entire post, perhaps it is the distributor's Drive Gear. I've never heard of a Cam Gear failing. Weakest link in the system IS the chain, no?
Steve
Just me. Good luck.
Steve
Now that I've read the entire post, perhaps it is the distributor's Drive Gear. I've never heard of a Cam Gear failing. Weakest link in the system IS the chain, no?
Steve
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
read this quote. now tell me any way the distributor can turn and stop, turn and stop while the engine is cranking. the nylon teeth stripped off the timing gear and the chain grabs, then slips. he needs a chain and upper gear. and he needs to get the plastic teeth out of his engine.
Never heard of a chain slipping. They are either on or broken. If they jump one tooth the exhaust manifold would turn cherry red.
The plastic coated cam sprocket was strictly to quiet down the chain noise. Had nothing to do with how well the chain fit. That was the job of the teeth.
Last edited by HeadsU.P.; Nov 4, 2017 at 10:19 PM.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
No, the teeth were made of plastic. When they stripped off, you had little nub teeth that were under the plastic teeth that could barely catch the chain. And I am pretty sure if the OP saw the distributor jumping up and down he woulda mentioned that. I had about 100k on my 10 year old GTO when the teeth stripped off the gear. They could well last 30 yrs on a Vette that gets very little mileage.