Checking on Timing set

Turning the crank/balancer mark to 0 on the timing tab than turn it back and see when the rotor starts to move. What is an acceptable number? I can imagine that some tiny bit free movement is normal.

Thanks.
Robbie

 

Im assuming your checking for timing chain stretch?
As you've said some movement is normal, as the chain is slack on the pass. (right) side and tight on the left (drivers) side.
Is this the OEM timing set up?
If so, I'd replace it as the nylon cam gear is prone to breaking
If its a replacement (iron cam gear) and you get a bit of movement, I'd run it
BUT, since your asking, Im assuming (again) you have a LOT of movement.

 

Yes. To measure slack.
Stock with nylon still in it. Not going to replace the set (yet). Just my question. Thanks.

 

I had a nylon gear when I tore down my 91K 71 350. It was still running fine though the worn out cam was more of my issue and wouldn't rev over 4500. Lifters were badly cupped and lobes had lots of wear. Also, my aluminum rockers had eaten up the shafts.

One of the things that can cause a lot of slop in timing is the distributor gear riding up and down on the cam gear. If it does, you might check end play on the distributor to tighten it up.

Some slop in the chain but the gear was all there.

Worn out cam and lifters.

 

That cam gear looks great still. I have no issue's with timing. When i check the mark with a timing light it is steady and not bouncing around. It's just that i would like to know what is a good number before the rotor starts to move. I read somewhere that 7 degrees is the max acceptable number. That seems like a lot.

 

The side (drivers/left) with tension will always have tension, until you rotate the crank CCW, then the slack will shift to the drivers (left) side
Of all is good, leave it be, OR go ahead and replace it if it makes you uneasy ( I would ) since it’s the OEM Buick set on there.

 

Wow, that nylon timing gear is a ticking time bomb.
Unfortunately, when rebuilding my Chevy 327, one of my friends forgot to tork the timing gear bolts. After awhile I heard this scraping noise on the metal timing chain cover. I removed it and found the timing mark was scraped off. I went to the dealership to get another gear and the guy handed me this nylon coated timing gear.
What the heck is this? Lastest thing out of GM, makes it much quieter.
Well that didn't last 100 miles. At the strip I shifted at 6800 to 7000 rpm's.
Went to a speed shop and bought a steel gear. That's what happened to me with a nylon coated timing gear.
Maybe your Buick 350 never saw that level of rpm's, but that's the first thing that would go if that engine was mine.
Just don't trust nylon being rotated by a metal chain. Vet

 

LOLOL and that’s the EXACT reason for the nylon gear!
BUT, I’ve NEVER heard an iron replacement cam gear with a link chain (like stock) OR a roller chain MAKE NOISE!
BUT I’ve heard chains slapping around BECAUSE of a near stripped NYLON cam gear

 

I agree with you. With all the noise from an engine, especially a supped up engine with tube headers, you get enough noise in the engine compartment you can't hear the timing chain.
I would love to know the reason behind GM's decision to build a nylon coated aluminum timing gear. I mean the real reason! Vet

 

The nylon was primarily for less wear, noise was secondary.

The service life and interval, along with proper oil/filter changes, posed little risk to nylon failure.

But people skipped all that, especially folks buying used cars.

I remember people driving with no coolant other than tap water, driving until the brake linings were gone and it sounded like your car was a running lathe, steering and suspension links worn so that tires had three inches of camber, smoking like a 55 year old bar fly, and more.

The "rhythm" was about a three year and 50 thousand miles ownership before trading/selling to buy a new car.

Poor maintenance revealed the choice for nylon was not bad for the car, but bad for the customer's care of the car.

Vet. Did you replace the crank sprocket and chain at the time the nylon gear was installed? You said, "another gear" not set, so I am curious of 100 mile failure with nylon.

 

An article I just read.
Had pics of nylon missing from the aluminum timing gear.

Think about WHERE all those little pieces of nylon go and what they do, if your clueless...they tend to block or restrict the oil flow into the oil pump pick-up and get ground up and forced into the oil passages by the pump gears.

Another article says, to quiet the chain noise. That's BS, it's another way of making more profit. Find another way of cheaper manufacturing and cheaper materials. Vet

 

Okay, so my question is too complicated?
For the moment i am not looking for opinions or whatever experience with the nylon gear. Just somebody who has experience checking for slack on the oem set. But thanks anyway

 

nylon coated timing gears last 100,000 miles, usually. And yes, Buicks don't need to rev that high.

 

I only changed the nylon coated aluminum timing gear back to a steel gear.
When we built the engine, I only had maybe 200 miles on the engine when the original steel timing gear came lose and scraped off the timing mark. That when the nylon gear got installed.
This engine was newly rebuilt, with only 200 miles on it.
After I replaced the nylon gear with a steel gear, I raced the car at the track and street. I never had another problem for two years. I only had to replace clutches. I did have a push rod eat it's way through the back of a rocker arm. That's because I used the same rocker and that came with the 1964 Corvette 327.
Back in my Navy days, I was a poor boy. Made $64 bucks a month, so I used some of the original parts on the engine, like the rocker arms and generator. Vet

 

I apologize for getting your thread off topic here. I'am very sensitive to nylon timing gears.

For what it's worth, I depend on the timing light to determine if I have too much slake in my timing chain.
This is how I knew I had a problem with my timing chain.
I was getting the timing mark moving back and forth. I knew I had even chain stretch or timing gear tooth ware down.

My 70 GS Buick is my first Buick muscle car and when I was checking some of the mechanical parts after I bought the car, we noticed I had timing chain stretch, so we replaced the chain.
However, I joined this Buick forum shortly afterwards and was told that Buicks are famous for chain stretch.
If the slack is not effecting your timing with your timing gun, it would not bother me. Just my opinion.
Sorry for screwing up your thread. Vet

 

My second reply to your question.
Any time you start moving the rotor back and forth, you have to take into account you have clearance in the cam and distributor gears and the timing gear/chain slack.
Sorry since your engine is moving in one direction, I would go with the timing light, if you have no timing mark isolation, then you should be good to go.
Since you have that part of the engine disassembled, I would replace the timing chain and timing gear. Again my best opinion on this subject. Vet

 

A buddy replaced nylon cam gear timing set with sealed power steel (I offered to sell him a new nylon set) and a few thousand miles later his driver side lifters were noisy due to front cam bearing eaten up. The steel set was quite tight...had to work to get it on cam ledge. I think the nylon would have been more forgiving even if tight....nylon softer than cam bearing. Take it or leave it....just my thoughts. I have 2 low 12 sec cars with stock chain setups. Will likely outlast me at this point....
Like has been said....overheating, using too thin oil and lack of oil changes make for accelerated wear.....

 

Hi Vet, no sorry needed! Somebody might chime in on my quesstion. You're always here with good info.. Thanks

 

Trying/thinking to understand what you meant with "no timing mark isolation"........

 

Might sound weird to a lot of folks here but i think this was actually a great design back in the day. Modern day engines have crappy all steel sets that don't even last half as long as this old Buick design.