Checking on Timing set

Meant to say no timing mark variations.
Like you said it's NOT bouncing around.
Some times I get into trouble with 5 and dime words. LoL

 

Ahhh yes. Understood. Yes it is steady. I am just curious to see how much slack is there.

 

Nylon isn't the problem. I went back with a steel set on the new build just because that's what was readily available.

To OP, I agree, if no variations on your timing at constant RPM with vacuum advance disconnected, I wouldn't worry about it. It likely isn't going to snap. You can get an inspection camera in the fuel pump hole or the distributor hole to check out the condition of the cam gear and also see what the distributor gear looks like.

 

Check out this conversation from another forum, kind of funny. Whipper snappers, lol.

Haven't seen any (nylon coated timing gears) since I went to Auto Tech school 12 years ago. The old timers in the engine rebuilding class kept a SBC on a stand to show us whipper snappers what they used to have to deal with.
This was back in Feb of 2015.
Though this was funny. Vet

 

To add to what to knucklebusted suggested, if you can get a camera in there to take a look, check to see if the plastic coating is cracked at the bottom or root of the gear tooth. If it is, I would suggest replacement at some point in the near future.

 

Okay, is there a link to check it out?

 

Yes, good one. We have replaced one of these once with a friends 1968 Riviera. That timing mark was all over the place, we weren't able to set initial. So we had to replace it. The nylon gear still had all its teeth though.

 

Here you go. Just want to tell you, i'am not that fantastic moving links from one site to another. Lol. Vet

https://bobistheoilguy.com/forums/threads/nylon-timing-gears-still-in-use.230556/

 

Thanks! I also remember on this board someone mentioned the nylon set up on the Pontiac engines weren't as good as the Buick's nylon timing set in the 60's

 

When using a timing light on both cylinder 1 & 6 result should be the same right? If there is any difference between these 2 cylinders there is slack in the timing chain?

 

I like that idea...not sure if would work....I would think same...but interesting.....why would it be different?

 

I'm going to need some help here. I've never heard of the ability to time different cylinders. You have a timing degree marks on the timing change cover and most initial timing mark on a Buick is around 10 degrees before top dead center (TDC). At least it's what my 455 is timed at.

Anybody want to help???? VET

 

OK, I'm confused. How can you time different cylinders????

Is he putting the timing gun lead from #1 cylinder onto #6 cylinder? If so, what does that prove? I just don't get it.
If there is slack in the chain and it's a lot, the timing mark will move back and forth between say, 10 degrees and 8 degrees. More or less depending on the amount of slack.
If the slack is very large, it can skip a tooth. Vet

 

Each "next" firing event is 90 degrees after the previous.

So, if #1 fires at 15 degrees BTDC, #8 will fire 90 degrees later. So #8 would fire at 70 degrees on the timing mark index and balancer mark, but you would use a timing tape around the entire balancer to see the firing event for every cylinder, and have to realize the crank would turn twice for all eight cylinders to fire once. (Cam and distributor events are 45 degrees apart and require one revolution for all eight cylinder events)

Easier to understand if #1 fired at 0 TDC, then 8 fires at 90 later and then 90 degrees later for 4, and so on through 3,6,5,7 and 2.

But, if the timing chain slack permitted 4 degrees of movement from TDC for #1 (two degrees before and 2 degrees after) by moving the crank shaft fore and aft and observing the rotor. you would only be at most, 2 degrees off the timing event as the chain would take up the 2 degrees slack, and the 2 degrees on the other side, don't factor in.

You are correct that you are not "timing" different cylinders relative to each other. And all one needs to is check the fore and aft play moving the crank on any one cylinder and observing the rotor, then seeing what the total crank travel is between and divide by two for the total "number of degrees off" (late) you timing event will be.

A couple of degrees is not detrimental, as it is only dealing with the firing, and not the interference. By the time you have enough slack to worry about interference issues, that chain is going to be slapping to beat the band.

 

My original 69 wildcat with 80k. Seems ok via inspection camera.

 

Back to the chain slack.
I don't believe I have ever seen a timing chain too much slack dimension given.
So, how much slack is too much?
1/4 in, 3/8 in ect?

If one is worried about chain slack, why not go with a double chain? Will they fit on a Buick without modification?
My understanding is, the big torque 455's can stretch a timing chain in very little running time. Vet

 

With time the laminated teeth of the chain wear a pattern in the soft nylon teeth on the cam gear and this will create what will seem like an alarming amount of free play , (sorry I don’t have a measure of crankshaft degrees but as you state 7 degrees is probably about right), this is normal with these parts , eventually the nylon segments crack and break away from the cam gear , the chain stops turning the cam ,the still rotating pistons contact the opened valves resulting in a mass of scrap metal . Pull the , check the roll pin on the distributor drive gear, you may need to replace it, they tend lose tension and pieces can break off , and wear the shaft Buy a mini usb borescope and check the nylon cam gear while the dizzy is out. good luck

 

Cylinder 1 & 6 should be exactly the same when you check them with a timing light. Install the wire to cylinder 1 sparkplug wire and check and do the same at cylinder 6. Look, for me too much slack would be if i can't set the timing mark on the balancer at a certain number on the timing tab. If it changes too much i would replace the set. A double roller is possible but you would need to bring the fuel pump a bit forward so the timing chain would not rub against the fuel pump arm. If i would go and replace the set i would get an all steel original design set.

 

Luckily if i am not mistaken a 430 isn't an interference engine. But ofcourse damage to the timing cover isn't what you want to happen.