Jump to content

'67 430 Timing Chain Question


PWB
 Share

Recommended Posts

Original cam gears had over molded nylon teeth. The plastic  degrades with time and miles, stress crack, and eventually break off in pieces and end up in the oil pan. This generally doesn't cause a short term problem other than lost performance and efficiency so often most people wouldn't even know if the teeth fell off or not. There are many variables that affect longevity of the teeth. I've taken engines apart that had most of the teeth gone and others that were still intact and this includes engines taken apart 30 years ago and more recently. When the teeth break off it causes slop in the timing chain. You can tell if you have slop by removing the distributor cap, put a socket on the crank, rotate engine one direction a short distance then rotate the opposite direction and watch the rotor for movement at time of changing directions. It should move immediately when you change directions. If the engine rotates but no rotor movement you have slop in the chain.

Attached is a pic of a Buick cam gear. Its not for a 430 but shows the same design with plastic coated teeth. The plastic was used to reduce chain noise.

 

 

 

 

s-l1600.jpg

Link to comment
Share on other sites

                           Jason, seeing that picture makes me get angry all over again.....the plastic timing gear teeth was the dumbest

thing ever put on a car ever.  If I had been president of GM I would have fired the engineer that even suggested such an idiot

part to be installed on their cars. These timing gear setups would always jump time when you shut the engine off, as the engine would

suddenly stop and the chain would keep on going. On two  separate occasions in my repair shop back in the 70's, I pulled a car in

to the bay for minor service like an oil change, then it wouldn't ever start back up because the chain jumped. Of course, then I had to

call the customer and try to explain to him that I had to do a timing chain job on his car when he brought it in for an oil change.  Both times the customers didn't know anything about cars and refused to believe that I was not at fault. After it happened to me the second time, I was actually afraid to shut off a 60's GM car to work on it. I actually started warning the customers when they brought the car in that this could happen and I was not responsible and would not eat the repair.  Also, I defy anybody to hear a timing chain without

using a stethescope.....pure hogwash!  If anybody out there can hear a timing chain on a running engine

with the naked ear, call the CIA.....your services are needed for their spy network.

 

Edited by Seafoam65 (see edit history)
Link to comment
Share on other sites

I had similar  concerns over the nylon gear in my 63 Riviera having experienced a failure on a 64 Skylark with 300cu in .

 

Have just replaced the set in the 63 with 401 with Mellings timing gear all steel and Sealed Power crank gear and chain.  All fitted snugly and without any problems.

 

Just waiting on a new cover to arrive to complete the job. Will now have peace of mind and reliability, on a daily driver. 

Just my two bobs worth.

 

interesting to read Seafoams comment about switching them off, never to re-start.

 

My experience was after driving about 5500 miles in the Buick Skylark in 1990 over 4 weeks while in the US and Canada, and dropping it off to the shipper in Phileadelphia all ok. When I went to start it in Australia to take it home, it failed to start.

 

Hours and hours of of lost time, trailer to get it home, a new starter motor, heaps of frustration about why it would not go after being so reliable. Found that an aluminium rocker arm had broken and the nylon covering the timing gear teeth had disintegrated.

 

My thoughts until today  have been that the shipper had revved it out when cold when putting it in the container, however after reading this thread, see that it was probably Lady Luck that kept it going until it failed due to fatigue.

image.jpeg

Link to comment
Share on other sites

I appreciate the method of assessing the amount of chain 'slop' by observing distributor rotor movement while turning the crank, but I believe that by the time an observable amount of lash can be seen the cam gear must have already shed some of it's nylon cladding.  So, if it's already that bad you'd better have the parts ordered and a day set aside to install the new timing set.  As JZRIV pointed out, there's no reliable rule-of thumb as to when failure may occur.  Back in the day, the 'rule' was best to think about changing it anytime after 60K miles.  Even back then some engines would go twice that long with no issue.  Now, 50 years later even a low-mile original engine should be serviced, in my opinion.

Link to comment
Share on other sites

Oh my! :o

 

Didn't mean to rile anyone up. Its all great info. Thank you gentlemen for the years of experience. To this end, it does us all well.

I'm going to have a gears and chain on standby.

Now...who makes the best? :huh:

 

Much appreciated  - 

 

 

 

Link to comment
Share on other sites

Cloyes is a quality piece.  http://www.summitracing.com/search/brand/cloyes-gear/part-type/timing-chain-and-gear-sets/make/buick/engine-size/7-0l-430/engine-family/buick-v8?N=400043%2B4294899544

 

Clevite and Sealed Power offer stock link-belt style replacements.  All of these use steel (no nylon) cam sprockets.

Edited by EmTee (see edit history)
  • Thanks 1
Link to comment
Share on other sites

  • 4 years later...
On 4/15/2016 at 12:04 PM, Seafoam65 said:

                           Jason, seeing that picture makes me get angry all over again.....the plastic timing gear teeth was the dumbest

thing ever put on a car ever.  If I had been president of GM I would have fired the engineer that even suggested such an idiot

part to be installed on their cars. These timing gear setups would always jump time when you shut the engine off, as the engine would

suddenly stop and the chain would keep on going. On two  separate occasions in my repair shop back in the 70's, I pulled a car in

to the bay for minor service like an oil change, then it wouldn't ever start back up because the chain jumped. Of course, then I had to

call the customer and try to explain to him that I had to do a timing chain job on his car when he brought it in for an oil change.  Both times the customers didn't know anything about cars and refused to believe that I was not at fault. After it happened to me the second time, I was actually afraid to shut off a 60's GM car to work on it. I actually started warning the customers when they brought the car in that this could happen and I was not responsible and would not eat the repair.  Also, I defy anybody to hear a timing chain without

using a stethescope.....pure hogwash!  If anybody out there can hear a timing chain on a running engine

with the naked ear, call the CIA.....your services are needed for their spy network.

 


Well I’m guessing it’s happened to me.

All of the sudden my car is having a terrible time trying to start.

I swapped the gasoline, fuel hoses and carb. Borescoped the fuel tank and not a spec of dirt.

All the electrics seem ok. Replaced  

coil, points and alternator anyway.
I get good spark and plenty fuel pressure.

The motor turns with no clankity weird noises when I disconnect coil. Spark plugs look new.

I never ever loosened the distributor and assume it never was. Vacuum advance works fine.

I could only guess the chain has jumped?

 

ugh 😩 

 

Link to comment
Share on other sites

1 hour ago, kegart said:

You can bring the timing mark on the balancer to the 0 degrees then take distributor cap off and look to see if the rotor is pointing to #1.

 

Kevin 

Oh ok

You mean pull the whole distributor?

That may be easier than pulling all the plugs, manually cranking and trying to find 1TDC. I don’t have a second mechanic to help.

I have a good borescope. What do I look for exactly inside?


Thanks

 

Edited by PWB (see edit history)
Link to comment
Share on other sites

On 7/23/2020 at 11:24 AM, PWB said:

ou mean pull the whole distributor?

 

No, just remove the cap and look at which terminal on the cap the distributor is pointing at.  It should be #1 or #6, if the #1 cylinder isn't at TDC.  If that's the case, turn the crank one more revolution and check the rotor position again.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...