Actually, since the VE (volumetric efficiency) goes up with the 4.0L head (even more with the HO head) the compression will go up slightly. Jim Blair, Lynnwood, WA '87 Comanche, '83 Jeep J10, '84 Jeep J10 From: Frank Swygert Subject: Re: [Amc-list] LPG 258 To: amc-list@xxxxxxxxxxxx Message-ID: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Look for different pistons -- you can only go up maybe one full point by shaving the head alone. Compression doesn't go up with the 4.0L head on a 258 -- only 8.7:1 (stock 4.0L). The combustion chamber sizes are the same on the 258 and 4.0L. ------------ Date: Thu, 02 Oct 2008 16:43:26 -0400 From: Brien Tourville LPG runs best with high compression - so - a 4.0 7120 head to a stock '81 258 would require roughly how much shaving to accomplish 11 to 1 compression ? -- Frank Swygert _________________________________________________________________ Get more out of the Web. Learn 10 hidden secrets of Windows Live. http://windowslive.com/connect/post/jamiethomson.spaces.live.com-Blog-cns!550F681DAD532637!5295.entry?ocid=TXT_TAGLM_WL_domore_092008 _______________________________________________ Amc-list mailing list Amc-list@xxxxxxxxxxxx http://splatter.wps.com/cgi-bin/mailman/listinfo/amc-list