Help: Weird Timing Mark Location

[Miles]

Here’s a problem that has me stumped – any helpful info would be appreciated.

I had a 350ci crate engine put in my ’72 C-10 about a year ago and it has been running really well since. When I went to tune it up recently, I found that the timing was set at about 16 before TDC (manual transmission; I’ve been setting the timing at 8 before for the last 20 years with no problems!).

The distributor had not been messed with as far as I can tell, but I went ahead and had a local mechanic switch me over to electronic ignition. He timed the engine ‘by ear’ and found the timing mark to be around 18 before TDC when done. He told me that he checked to verify that when cylinder #1 is at TDC that the timing mark was at zero.

One thing I thought could be going on (however unlikely) is that the harmonic balance/damper may be defective – perhaps there has been slippage of the bonding elastomer connecting the inner-outer pieces which resulted in a mis-located mark? I thought I would see what other folks thought before removing the harmonic balance to check its alignment this since the part is only a year old and I assume it is OK.

I am a bit out of my league on this, so if there is more info needed, please direct me to what additional info you may need to track this issue down/clarify what’s going on.

Thanks in advance!

Miles