marcos beltran

I have a sbc 350 and I just tested the slack in my timing chain by manually turning the engine and looking at the rotor. I have between 8 and 10 degrees difference from turning one direction to another. From my understanding anything over 6-7 degrees needs the chain to be replaced. Is that too much? Also that timing chain is new and probably hasnt seen more than maybe 800 miles. The cars a project and is not even seen the streets yet other than testing them on the back country roads. Its a duralast timing chain. Is it possible for these chains to do this that early or be defective?

Vader

Some of that could be the timing chain, and some between the cam and the distributor (and oil pump) drive gears. If the distributor shaft turns a few degrees by hand with the engine off, that lash can be subtracted from the measurement realized when turning the crank back and forth. Remember that the lash in the distributor gears would reflect twice the lash in crank rotation, so include that mathematical step.

AlkyIROC

Chains will always have slack. It's in the nature of the design. The engine will never rotate backwards so the crank is always pulling on one side of the chain which in turn pulls on the cam gear which in turns, rotates the distributor gear. When under load, all these should be tight. It's only when you let off the throttle or at idle when there isn't enough tension to keep the ignition timing 100% accurate.

My race car however does not need the inconsistency from all these interconnected parts. I run a fixed idler timing gear set (not cheap). Once set up, the cam timing will never move. To eliminate distributor gear looseness, I run a crank trigger which keep ignition timing even more accurate. All my distributor does is provides spark to each plug as it spins around. Rotating my distributor only changes the rotor phasing but does not change the timing since that's done at the crank trigger.

Timing chains in street cars are more preferred however roller chain systems are not designed for long life. A factory style link chain is quiet and will last a long time before it needs to be replaced.

Also something as simple as having the block line honed will change which timing chain you need. When a block is line honed, the crankshaft is positioned slightly higher into the block. This means a shorter chain is required.

BOOT77

Did you soak the new chain in oil?

Always soak your new timing chain or any roller part, once running oil can't get into rotating/moving parts Or at least it doesn't have the chance to soak deep into links/rollers. Chains don't stretch, all the small joints wear and become looser. Not soaking a new chain will accelerate wear.