Morris
while it is true that the 32/36 was designed to work for a 2L engine
That 2 liter engine was to operate on up to 6000 rpm
and btw, the 32/36 flows about 350 cfm
when was the last time your 4.2L visited 3000 rpm?
that engine was designed to operate in the 2500 rpm range
A 2L engine that operates at 5000rpm and a 4L that operates at 2500rpm will
require the same cfm
The 38 DGAS will give better performance at the price of fuel economy
If you are looking for better performance above the 2500 rpm range you will be better served by installing a hotter cam shaft first
Thats the key
or consider re jetting the carb for high speed operation as 350 cfm is plenty of air flow for that engine.
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