<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by SUN RA KAT:
repost - <FONT size="5">Is there sufficient clearance with the 1.75 rollers or is 1.7 the highest safe ratio?</FONT s>
<HR></BLOCKQUOTE> <FONT size="5">HOPE THIS HELPS</FONT s>
I'm not sure what clearance you are referring to? "Coil bind" or "piston to valve clearance?" Either way, there's no simple answer. Piston to valve would be sufficient with 1.75 ratio rockers. There are too many factors that come in to play with "coil bind" which brings us to another question: What lobe lift, how much gross lift, spring pressures closed & open etc. Coil bind & spring pressures must be checked with these specifications and with 1.75 rockers. Coil bind (the distance between the underside of the valve retainer and top of the valve seal must be within a margin of around .100" of clearance or damage could occur with too much lift). Of course, now you must take into consideration spring pressures, closed pressure & at full lift.
But why 1.75 ratio? The vast majority of Viper tuners (other than Lingenfelter Performance) utilize 1.7 ratios that suffice for almost every application. T&D doesn't stock 1.75 but can build them upon request. The net gain of lift going from 1.6 to 1.7 yeilds .032" additional lift, now, go from 1.7 to 1.75 nets another .016" additional lift. The addition of .016" is a bit negligible when your considering a mild supercharging application.
Regards,
Doug