-9 High Compression '63 XKE 3.8
 

I have been led to believe that most 3.8 XKEs were -8 models. -8 referring to an 8 to 1 compression ratio. I also have learned there were -7 models, but none were sent to the US. My '63 XKE Series 1, 3.8 is a -9 (9 to 1 Compression). All the numbers match my chassis. Does anyone have any idea how special this might be if special at all?

First I'll disclose that I'm no authority on E-types, but......

My impression is that 9.0 compression was standard specification with the lower ratios being "at request" or for select markets. I think all USA models got the 9.0 engine until the introduction of the Series II.

Cheers
DD

E Type Compression Ratios
 

My 1963 E Type coupe has its original 9:1 compression ratio engine as well. I would be interested if anyone knows how many of these were built.

99.9% of the series 1 e-types sent to the USA were 9:1 compression ratio. The 8:1 engines were mainly sent to countries with lower grade fuel. Therefore 9:1 CR is not special at all.

Actually the only difference between the 9:1 and the 7 or 8:1 compression head is the number stamped into the head, i.e. there the same head RXXXX-7,8 or 9. The compression ratio is mainly controlled by the size of the dome/crown of the pistons. You could have a head that claims to be 9:1 compression ratio but if it was rebuilt with 8:1 compression pistons then the engine is really 8:1. Except when the head is shaves then it would be somewhat higher than 8:1. Some people rebuild their engines with 8:1 CR pistons because of the lower octane that is around today.