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E type ( XK-E ) 1961 - 1975

-9 High Compression '63 XKE 3.8

Old 08-24-2018, 10:35 PM
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Default -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?

Last edited by GusRiley; 08-24-2018 at 10:38 PM.
Old 08-24-2018, 11:13 PM
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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.


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Old 09-10-2018, 02:30 PM
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Thumbs up 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.
Old 09-10-2018, 08:17 PM
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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.
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Old 09-12-2018, 04:38 PM
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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.

Last edited by Bob_S; 09-12-2018 at 06:47 PM.
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