Slant Six Timing Chain Oiling is important to insure long timing chain life and predictable ignition timing as well as valve timing.
If you had your slant six rebuilt and have developed a rough idle plus loss of power in only a short period of time since the rebuild suggest your checks & diagnosis steps include the ignition timing.
If it’s determined the timing is “jumpy” and shifting unpredictably while maintaining a constant throttle position it’s possible the timing chain has worn considerably in a very short period of time.
The slop in the timing chain could be causing the cam to be not operating smoothly with the crank. Consequently the distributor would be acting the same way and showing up as “jumpy” ignition timing.
Pulling the timing cover to inspect the timing chain for looseness is one way to see if the timing chain is excessively worn. But the second step is to determine why the chain became loose so quickly relative to your expectations.
Take a close look in the crankshaft timing sprocket area and examine if the upper main bearing shell for #1 main bearing has a chamfer.
If it is not chamfered that missing chamfer could be main cause of the timing chain being loose in a short period of time. See the below picture for the blowup showing the needed chamfer in the upper bearing shell.
Your slant six #1 upper bearing shell serves an important function for lubrication of the timing chain.
Unfortunately many slant six rebuilding kits have defective #1 replacement upper bearing shells since they lack the chamfer used to oil timing chains.
Unless your rebuilding shop is aware of this defect or used original new old stock 60’s or 70’s Chrysler main bearing shells this small detail may escape detection during the engine assembly stage.
Correcting the upper bearing shell would require it’s removal after taking off the oil pan & #1 main bearing cap. The upper shell is then removed.
If your slant is in a car that does not allow removal of the pan unless the engine is removed there is an option…..remove the oil gallery plug and install a homemade plug with small diameter pipe directing oil to the chain. Although somewhat labor intensive it beats removing the engine.
If you are having an engine rebuilt it might be adviseable to go over the #1 upper bearing shell chamfer requirement with your engine assembly person. It’s easy to modify the standard shell furnished in the kits if done in a timely fashion.
More information on this engine rebuilding step can be found about 2/3 of the way thru this slant six comprehensive rebuilding article:
Remember Slant Six Timing Chain Oiling is important to insure long timing chain life and predictable ignition timing as well as valve timing.