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6.5 NA Mileage

Thought I would update this old thread rather than start a new one. Finally got around to installing the Vin J intake from the 93 today. Had to drill and tap the holes for the FFM as they just blank. Removed the vacuum pump as it was starting to squeal a bit. Also swapped on the FSD remote mount PMD from Little D as well. Now all she needs is a tune for the SES light! Other than an alternator and tensioner she has been trouble free since I bought her. Seems to have settled into a solid 20-20.5 every tank. Still need to replace the air dam. It has also gotten a little quicker... seems like regular driving has loosened her up. Still no speed demon but she has gotten sideways on a damp road.:D
 
I am really pleased at getting 20 or so mpg consistently. It does make me wonder if GM missed a golden opportunity with the 6.5. They got hung up on making it a towing powerhouse to compete with Ferd and Dodge and eventually had to abandon the platform. They should have kept the NA motor and marketed like it as a commuter/ parts/ supplies runner truck, not as a towing beat. Same sorta principle as the v6. One of these motors with tweaks to the software, pump, and maybe internals I could see the power maybe hitting 200 with torque in the mid three hundreds. With a six speed trans say 3.23 rear end gears and possibly cylinder deactivation I could see a "modern" NA 6.5 hitting 25+ on the highway. Anyway it has been a solid truck so far and very pleasant to drive just a shame they stopped making a NA motor.
 
Mine is still in the 17-20 range on a B20 . soon as the weather warms up we're going to B99, the 10% decrease in mileage is worth it when I'm only spending 1.50 a gallon for fuel
 
This makes me want a na 6.2l w/ 3.42s or something. Maybe even buy another like my 82, use mine for parts.

Sent from my XT1050 using Tapatalk
 
Chevypoor, Stan's headers still sells headers for the 6.2, which of course will fit the 6.5 na as well. Headers with a good dual exhaust setup provide a strong suction pulse that helps evacuate the combustion chamber, and helps jumpstart the intake flow. I don't know how much they would really help in your case, but they can't hurt. Well except for the $600 cost..
 
scottm said:
Chevypoor, Stan's headers still sells headers for the 6.2, which of course will fit the 6.5 na as well. Headers with a good dual exhaust setup provide a strong suction pulse that helps evacuate the combustion chamber, and helps jumpstart the intake flow. I don't know how much they would really help in your case, but they can't hurt. Well except for the $600 cost..
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I have seen those headers. The price is steep but they are a high quality piece and they probably do not sell too many 6.2 headers. They also sell just the flanges if somebody wanted to fabricate a set of better flowing turbo manifolds from a weld up header kit. After driving the NA motor around you can see how little a turbo is needed at cruise and lower speeds when empty, lightly loaded, or not pulling. She runs 75-80 smooth as silk and seems to love the 1900-2400 range. 80 is a bit over 2400. I do not think the 4l60E is a good trans for this motor... 1st gear is way to short and this sucker has too much low speed torque. I think it would run better with a 4l80E. The only thing it would miss would be the 5% less OD.
 
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