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Unusual Main bearing thrust wear

'These are Russ's Racetec pistons with a 9.4CR ......'

Thanks for the pic. I am wondering on the 9.4 CR. I think that is what mine is setup for. I had Russ set mine up for pump gas and a CI head, he ported. I think your has an Eddelbrock aluminum head. I would have expected a higher CR. I'll have to order one of the Summit piston ring compressors. I hear the solid type reduce the chance of the rings scoring the cylinder bores.
 
I don't know what a CI head is, but I'm running a CCH 0331 head that was done by Russ. I run 87 gas every fill-up with zero pinging.
 
Russ and I are in constant contact on this so he following closely. The only possible clue at this time is the Rollmaster lower gear.
 
No idea if this would contribute to the end play issue or not but...

Did you install an aftermarket harmonic balancer? On my '00, I found that the hub of a Dayco balancer was a little shorter than then hub of the OEM one. I think the Dayco was really designed for use with earlier 4.0s that had an oil slinger in between the timing gear and the balancer. If that's the case, maybe your gear walked forward a bit and allowed the chain to contact the cover.

I sent the Dayco back and ordered an OEM balancer.
 
I do have a oil slinger on my 2000 and I'm running a Performance Products harmonic balancer. I have yet to start assembling things and check the alignments on the way.
 
Today is the big day as all I have to do is fill it up with oil and hit the pre-oil switch to see what got accomplished. I still need to find a way to check the flex-plate run-out but it will get checked.
 
Russ e-mailed me last night saying he thought the lower timing gear did not press on to the crank all the way. My thought was that since the gear was a slip-fit so that's not likely. This morning I woke up thinking he might be on to something. I almost broke my puller getting the HB off so I bored it out before re-installation leaving me thinking that it did not seat fully down on the original build.
 
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