1974 E-Type V12

I am trying to figure out what compression this engine has. It should be 8:1 or 9:1, but there is no "-8" or "-9" in the engine number, either on the firewall, the block or the head.

I found all these numbers on the head:
P32257 11 2
C2284 G
M LM25
1B NS E
P16
6 AJ E 692
20F3
N
PBM
P29120D

The block has this engine number
7 S16023 LA

The pistons in the engine are NOT all identical. But on some of the pistons I see a "circle 8" marking and a ".9-." marking. Picture attached.

Submitted by rcmaury@bellso… on Sat, 05/15/2010 - 21:25

Your engine number tells that the compression was when the engine was built. The last two letters tell that it was "L" for low compression or 7.8/1. The "A" means that the pistons are the smaller of the two choices. The "B" being .001" larger. Typical damage from dropped seat(s). Seen a lot worse and not to bad to fix. The compression ratio of your engine is controlled by the piston dish size. If the pistons are not identical, then someone has been into the engine and mismatched pistons. This will need to be fixed for the engine to run properly. Markings do not count, the size of the dish area counts.