Tiiming Chain Replacement

[kchampagne]

Hey all, I am working on my "spare" 305 and putting together a list of parts I need, including the timing chain. The chain is extremely loose. The engine was rebuilt and has approx. 15,000 miles since. Anyone know what causes the chain to loosen on low mileage? Maybe the chain wasn't replaced during rebuild. Also, the camshaft sprocket moves (slides on camshaft about 1/8") Based on my maintenance manual, there isn't a spacer or thrust plate behind the sprocket (boneheads probably left them out). Does anyone have a picture of the thrust plate and camshaft sprocket spacer? Not sure if I can fabricate one up. Better yet, anyone have spares laying around I could buy? I would bet they do sell these anymore.

Thanks much!

[HOTRODJOHN]

I can get you a photo tomorrow when I go to the shop. I just changed my motors chain and 2 sprockets. The only piece behind the lower gear is a large splash washer. How is the key way. I had a regular chain and gear but I changed it over to 2 sprocket type gears and double roller chain. I will get you the picture and the part numbers and post them tomorrow night. It should be posted after 7PM EST because I am on the West coast. John

[kchampagne]

Awesome John! No hurries. It is the camshaft sprocket that moves. My manual indicates a thrust plate and spacer are supposed to be behind it? Mine is the double roller also. Where did you buy your replacement?

Thank you!

[HOTRODJOHN]

I decided to go to the shop and take the picture. You can see that there are not any spacers on there the splash washer (not sure of the technical term) is in front of the gear. I believe I bought the gears from Auto Zone. The part #'s are all Cloyes Chain #C-166, Cam Gear # S310 and Crank Gear # S-311.
Hope this helps. John

5463

[kchampagne]

Thank you John! That is the same setup I have on my crank sprocket, so that is good. Do you know if you had a spacer or washer behind the cam sprocket?

Thanks much!
Ken

[TJ's GMC]

You can get a timing chain kit that comes with the sprockets and gears from O'riellys. Nothing behind the cam gear that I recall. :thumbsup: You will be surprised that a new chain really isn't much tighter.

[HOTRODJOHN]

There are no spacers behind the cam gear. Let us know how you make out. John

[turbobill]

Timing chains (all types) will slacken within a few thousand miles. It's the nature of the beast. I usually advance a cam 2 to 4 degrees to compensate.

[James]

I decided to go to the shop and take the picture. You can see that there are not any spacers on there the splash washer (not sure of the technical term) is in front of the gear. I believe I bought the gears from Auto Zone. The part #'s are all Cloyes Chain #C-166, Cam Gear # S310 and Crank Gear # S-311.
Hope this helps. John

5463

That is an oil slinger on the crankshaft. It help the crankshaft seal keep the oil inside the engine.

[HOTRODJOHN]

KC, there are no spacers behind the Cam gear. John

[kchampagne]

Excellent! Thanks everyone for the great advice! I am getting ready to ramp up my suburban project so I will post some updates on my build page.:thumbsup:

[Clarke]

Curious, I pulled my '62 305D out several years ago to replace all the seals and gaskets and repaint it. I remember checking the chain slack and like TJ I was surprised by the amount of slack, but it was still within toleance with 50K original miles.

However, I dont recall mine having a double chain/gears. Maybe it does and I forgot? If it doesn't do you have to change the cam, or do you simply add a second gear?

[bigblockv6]

There is no need to change the cam, you just have to get the full double roller timing chain and sprocket set.:ok:

[Clarke]

There is no need to change the cam, you just have to get the full double roller timing chain and sprocket set.:ok:

Sounds easy enough... Unless I'm mistaken, I'm under the impression that excessive slack in the timing chain is one of the top gambles in a high mileage BBV6? Or worded differently, one of the first areas requiring attention on a high mileage BBV6?

What's the advantage of having double roller set up compared to single? Less wear/stretch in the chain over time?

[1972RedNeck]

What's the advantage of having double roller set up compared to single? Less wear/stretch in the chain over time?

A double roller chain is 1.7 times stronger than the same size single strand chain...