my questions concern compression ratios. i just got a copy of a volvo performance tuning instruction manual. it recommended, for a B18B, machining .020" off the surface of the head to increase compression to 10.5:1. if memory serves me correctly, the stock compression should be 9.5:1.

my first question is: if '70 and '71 B20's are 10.5:1, is that because the heads are thinner? or, is it because the connecting rods are longer? and, if i acquired a b20 from this period, could the head be machined to increase the ratio to, say, 11.5:1?

my other question concerns my existing engine (which is not stock). my previous engine threw a rod (due to my cousin, its previous caretaker). i replaced it with another B18, which, i believe, is from an earlier model. it has no mounting holes for an air conditioning comp. and the oil pan that came with it had no hole for the oil temp sender. there were also no holes for the reinforcement piece that bolts to the bottom of the bell housing and the block. the numbers on the side of the block are 4968⎡] 󠁒] and JBG418201. the numbers on the head are 1-418205. where did this thing come from (i know, sweden)? is it from a 122 or 444/544? is it a B18A? is it just an older B18B? is it a B18D?

any answers to these questions will be much appreciated.

thanks,