compression ratio's
- Thread starter MRJLB84D
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Anonymous
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9.1:1 for the HC 250 in the XY.
8.2:1 in the LC 250.
8.2:1 in the LC 250.
Low compression Taxi cab versions were common up until the loss of Standard fuel in the early 1980's. The last
low compression XD 3.3 was 8.2:1
as an XD cast iron head. Those were the days of 97 or 98 octane leaded, and standard leaded fuel of about 87 octane or so. The
last of the iron headed XD's was 9.15:1 for the 4.1.
This had an aggressive advance curve on the lighter XD. Dump a manual XD engine in a heavier XC with an automatic, and it will ping like crazy.
The XD gained a huge bump in compression with the advent of tha alloy head.
It was 9.35:1 on the 4.1.
This continued with basically the same chamber and head until 1984's XF.
The XF ran 9.35:1 in the 4.1 carby
until unleaded fuel became mandatory in Jan 1986. The October 1985 changes gave a large drop to
8.8:1 compression for the 4.1 carby,
and this allowed the lower grade 91 ULP to be used.
The 1983 to 1988 EFI's got an 8.8:1 compression ratio because word was out in 1981 that Australia was going to go unleaded Regular gas in 1986. I suspect Ford were worried about how the expensive Bosch set-up was going to cope. All changes to the 1984 versions were to help emissions, fuel economy and in late 1985, all 4.1 carb Falcons and EFI Falcons ran 8.8:1 compression.
low compression XD 3.3 was 8.2:1
as an XD cast iron head. Those were the days of 97 or 98 octane leaded, and standard leaded fuel of about 87 octane or so. The
last of the iron headed XD's was 9.15:1 for the 4.1.
This had an aggressive advance curve on the lighter XD. Dump a manual XD engine in a heavier XC with an automatic, and it will ping like crazy.
The XD gained a huge bump in compression with the advent of tha alloy head.
It was 9.35:1 on the 4.1.
This continued with basically the same chamber and head until 1984's XF.
The XF ran 9.35:1 in the 4.1 carby
until unleaded fuel became mandatory in Jan 1986. The October 1985 changes gave a large drop to
8.8:1 compression for the 4.1 carby,
and this allowed the lower grade 91 ULP to be used.
The 1983 to 1988 EFI's got an 8.8:1 compression ratio because word was out in 1981 that Australia was going to go unleaded Regular gas in 1986. I suspect Ford were worried about how the expensive Bosch set-up was going to cope. All changes to the 1984 versions were to help emissions, fuel economy and in late 1985, all 4.1 carb Falcons and EFI Falcons ran 8.8:1 compression.
