Quote:
Originally Posted by arcosine
Any performance cam will lower your gas mileage (period). If you are going for economy and not performance then there is no need to port the heads, since economy driving is done at low RPMs and velocities are low. In fact trying to port the exhaust may destroy the anti flow back and scavenging that is inherent in most exhaust port designs. Just keep your old cam and that will save more money than any new cam and porting will make up in mpg.
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I disagree with this. This is also a vehicle specific conversation so some experiences you may have will not hold true for a 4.0 jeep engine.
I do not plan on porting the intake valves. I Will port match those and do probably a mild port on the exhaust valves. If you look at a picture of the cylinder head, you will see how small the exhaust valves are in comparison to the intake valves.
I think many performance cams for the vehicle can increase gas mileage. Many Jeep owners want more low end power for rock crawling, and that low end power will increase fuel economy.