Slop in original timing chain on 78k 430

The configuration of the mounting area seems like your picture. I would guess its original. I'll use the inspection camera more today. Thanks

 

Yep, true!

 

If i am not mistaken the 1967 timing set is slightly different but the nylon looks the same.

 

Looks like teeth have a redish hue. Possibly from the aged nylon?

 

I've never seen a redish hue when we removed an original nylon timing set. Your chain looks really shiny kinda weird if it's the factory chain.

 

I’ve seen them with a pinkish/salmon color, maybe leaning towards tan

 

Gee, I had one of those nylon coated timing gears back in 1972.

I was young and dumb, let a GM parts dealership tell me this was perfect for my 424 HP
327 ci Chevy small block (1964 vintage).
Didn't last no time. Put the timing light on it and the timing mark was jumping all over the place.
Went to the speed shop and got a nice solid steel timing gear and my problems were over.

GM sold this nylon gear saying it will reduce the engine noise, that was BS. Nylon can't stand up for long with a metal chain on top of the nylon plastic coated gear teeth.
Plus, nylon doesn't like oil and engine heat on it either. Vet

 

On a Buick engine they seem to last a long time. There is a member here (i believe telriv Tom T.) who has a nailhead with a 180K and the factory nylon cam sprocket still in it.

 

I bet he didn't shift between 6,500 & 6,700 rpm.
I had built SB Chevy very strong and raced it a lot.
With 11 1/4 compression, Solid lifter cam and an Offenhuser low profile tunnel ram intake manifold. All this tied to a Borg Warner T-10 4-Speed.
I really expect this level punishment did the nylon timing gear in.
Never seen a stock Buick engine come close that level of rpm level and abuse. Vet

 

I also believe Tom T, baby'ed that nailhead all the way to 180K. lol

 

Yes, i am sure it is in a stock condition but still a 180K with that Nylon set is amazing. Must have been a well balanced engine from the factory.

 

I too am amazed.
I have been a machinist for over 40 years. This particular fiberglass has been fortified with fiberglass. This makes the nylon much stronger and will hold-up much better against oil. Pure nylon will suck-up moisture and other fluids.
This type of fiberglass nylon will also cause the timing chain to become shiny because the fiberglass is abrasive to metal and will change color being exposed to oil. VET

 

Okay, i didn't know that. So for stock use it wasn't a bad idea to use the Nylon?

 

I found the Nylon timing gear. Here's the pic.
Check out the color of the nylon gear teeth.
That light green of color is a dead giveaway being fortified with fiberglass into this nylon material.

On a regular engine, this will last a long time.
However, when you install it on a powerful high revving engine, it will not hold up to the high revs and toque that's being put to this timing gear.

My wife's 71 impala had this same nylon gear too, her car was a low powered, low revving 350 engine/2-barrel carburetor.
It never saw hard acceleration. It had over 100K with no timing gear problems.

 

I am amazed that this gear can hulp-up with the stock power and torque in the 430ci i mean these make some serious torque in original condition.

 

It's not like that gear/sprocket sees actual engine torque.

It sees the load of the distributor/oil pump, and the load involved in smacking the valves open--offset somewhat by the spring pressure on other cam lobes as the those valves close.

The faster the valves open, the more load on the timing set. RPM matters more than throttle position, although the two are sorta-kinda related most of the time; and heavy throttle opening would make it harder to open the exhaust valve due to residual cylinder pressure.

 

I believe it has more to do with high rpm's not torque.
Buicks don't rev high and least not stock ones.

I one time ran my SB to 8,000 rpm's by accident. My Navy buddy and I had one to many drinks at the base club.

We got into my car at the parking lot and started reving the engine. I decided to bring up the revs at 3,000 and then I floored it, I had a 8,000 grand tach ant the tech needle hit the 8,000 rpm peg hard.

I never sobered-up so fast in my life. I let the engine idle so I could hear a bent rod banging around, heard nothing, looked at the oil pressure gauge, still good oil pressure. I swiped the sweat of my forehead and never did something stupid like that again. Dumb & young
at 21.

 

Wow, 8,000 rpm that is beyond the red line

 

Checked nylon gear again with inspection camera. Some cracks in nylon but teeth seem ok. For now.

I installed vacuum advance and set it to about 10* maximum. Connected to ported vacuum.

Initial advance is set about 7* and all in at 30* at 2650rpm. I'm going to try to take it out later today.

 

Just my opinion, the last photo of the gear, crack looks really bad. I wouldn't chance it.
I would replace it.
But, it's your engine.

By the way, if the nylon breaks in small pieces, it will migrate throughout the engine and oil pickup and filter. Won't be picking up the pieces with a magnet nor the aluminum sprocket the chain grinds down. VET (Navy)