My engine gave up recently, and when I took it apart, it was a bit disturbing to see exactly what caused it. The no. 6 rod bearing seized due to oil starvation, snapped off, broke the cam in half, and left an oil pan full of ground up lifters, push rods, and piston pieces. What caused the oil starvation? I believe it all had to do with using a double-roller timing chain. The design of this chain causes a "cutting edge" on the outside of the chain which contacts the plastic tensioner, and the debris from the ground up tensioner wound up clogging the oil pickup screen (debris also opened the bypass valve in the pickup). I was at the track and it happened at the top of 3rd. gear, when the oil was needed most. My advice: DON'T USE the double roller timing chain! Stick to the stock chain with steel cam sprocket, and you won't end up grinding the tensioner up. Look at these images:
http://www.casperselectronics/com/engine/broken1.jpg
http://www.casperselectronics/com/engine/broken2.jpg
http://www.casperselectronics/com/engine/broken3.jpg
http://www.casperselectronics/com/engine/broken4.jpg
http://www.casperselectronics/com/engine/broken5.jpg
http://www.casperselectronics/com/engine/broken6.jpg
http://www.casperselectronics/com/engine/broken7.jpg
http://www.casperselectronics/com/engine/broken8.jpg
Black connecting rod and bearings..pretty much tells it all!
-John Spina
http://www.casperselectronics.com
http://www.casperselectronics.com/cobra.htm
When I bought my kit which included a comp roller cam and a double roller chain, I was specifically told by the vendor (I think it was Ron) not to use a tensioner with it. Just FYI for your rebuild.
Geoff
Sorry about the wrong link info...here's the correct links:
http://www.casperselectronics.com/engine/broken1.jpg
http://www.casperselectronics.com/engine/broken2.jpg
http://www.casperselectronics.com/engine/broken3.jpg
http://www.casperselectronics.com/engine/broken4.jpg
http://www.casperselectronics.com/engine/broken5.jpg
http://www.casperselectronics.com/engine/broken6.jpg
http://www.casperselectronics.com/engine/broken7.jpg
http://www.casperselectronics.com/engine/broken8.jpg
-John Spina
Sorry about your motor. I agree that the double roller chains are not needed on our cars due to the low rpm pulled. Although, I would think your problem was indeed the tensioner. I currently run a double roller, but will be going with a stock, steel replacement on my new motor, coming soon.
Do not use the chain tensioner with a double roller. Ref. Poston Buick Parts Catolog.
I hear ya, but what about the slack in the chain? If there is no slack then ok, but if there is slack, then what???
Just recently rebuilt my motor your right stay away from the the double roller it's not needed.
On the stock chain there shouldn't be any slack
if there is replace it . The stock chain is good
for 150k normal driving and 100k if racing. I
went with the GM stock pieces.
Frank
Just recently rebuilt my motor your right stay away from the the double roller it's not needed.
On the stock chain there shouldn't be any slack
if there is replace it . The stock chain is good
for 150k normal driving and 100k if racing. I
went with the GM stock pieces.
Frank