Tom, I would classify up to .001 as tight on the bearings, .001-.002 as middle of the road and greater than .002 as loose. For pistons, .003 or less, normal to tight greater than .004 -.007 as loose. There are a few choices and all grades still available in the oils that are designed for older engines so I wouldn't build it with the fear that the oil is only available in a 50 grade. How you build it as for as the pistons go is more going to be dictated by the material the piston is made out of and how much expansion it needs. Than, you can go looser depending on how you plan to use the engine. Race engines like a loose clearance. Every day driver, tighter. Nick, Alfano Performance 4849-76 st. Kenosha, WI. 53142 262-308-1302 262-942-8271 after 6pm central and weekends Message: 1 Date: Mon, 14 Apr 2008 08:48:22 -0700 (PDT) From: Tom Jennings <tomj@xxxxxxx> Subject: Re: [Amc-list] Oil Weights To: "AMC/Rambler owners, drivers and fans." <amc-list@xxxxxxxxxxxx> Message-ID: <alpine.DEB.1.00.0804140845550.5522@xxxxxxxxxxxxxx> Content-Type: TEXT/PLAIN; charset=US-ASCII On Sun, 13 Apr 2008, Nick ALFANO wrote: > Cliff, > > It really depends on the clearance you have in your engine. > If you built it a little loose for racing, then stick with the > 50 weight. Nick, could you define "tight" and "loose" here? I'm about to rebuild a six for my Classic, and since ZDDP is gone from the thinner oils, and soon to leave the diesel oils, do you think it's sensible to intentionally make things on the loose side with the hope that "specialty" oils like 15W-50 Mobil1 will continue to exist? _______________________________________________ Amc-list mailing list Amc-list@xxxxxxxxxxxx http://splatter.wps.com/cgi-bin/mailman/listinfo/amc-list