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James Lamb · 03-09-2019, 03:03 PM

RyanAK,

Another thought RE fuel economy from your original post. After 3 Diesel engines, 2 6.2 NA and one 6.5 w/Holset turbo and none of the engines giving back reliability in proportion to the time and care and $$$ I put into them, I had enough. A friend who owns an engine shop and I built a 350 with rv cam, throttle body heads, low compression so I could run 87 octane, and rebuilt quadrajet.

I got 13 mpg, and I drive easy.

Long story short, thought I had a rod knocking, which turned out to be the transmission pump (agh!) we tore the 350 down only to discover nothing wrong with the engine. But, one thing I noticed with the 350 is on hilly terrain the 700r4 seemed like it had a hard time deciding whether to stay in overdrive or not. The 6.2 was terrible in that way - always shifting in and out at every rise. I decided = not enough torque. Plus, I primarily use the truck for 4wd purposes, so took the exact same block, heads, intake, carb, everything from the 350, dropped in a new 383 rotating assembly for less than $1000.

The truck now gets 15 mpg. Did not even adjust the carb, just bolted it back on.

I attribute this mainly to the fact that it now takes a seriously steep hill to knock it out of overdrive. There's so much torque it just doesn't notice.If I'm not heavy on the peddle as I accelerate through gears it shifts into overdrive, and locks up at 45 mph, and will cruise there all day. Mind you, I have the torque curve shifted towards low-medium range as I rarely am on the interstate, so 70 mph it might well suck gas like there's no tomorrow. But with the 700r4, 3.42 diff, and my 2" oversize tires at 55 mph in overdrive the engine turns over 1440 rpm.

But if you ended up with a truck with a 350 and have the right driving situation I highly recommend a 383 build. I would think if you wanted highway cruising leaving out the rv cam would be a good engine choice. And cheap. And you can always get aftermarket injection if you feel strongly anti-carb.

03-09-2019, 03:03 PM	#9
James Lamb Registered User Join Date: Mar 2019 Location: Knoxville AL Posts: 74	Re: Daily Driving a Square Suburban RyanAK, Another thought RE fuel economy from your original post. After 3 Diesel engines, 2 6.2 NA and one 6.5 w/Holset turbo and none of the engines giving back reliability in proportion to the time and care and $$$ I put into them, I had enough. A friend who owns an engine shop and I built a 350 with rv cam, throttle body heads, low compression so I could run 87 octane, and rebuilt quadrajet. I got 13 mpg, and I drive easy. Long story short, thought I had a rod knocking, which turned out to be the transmission pump (agh!) we tore the 350 down only to discover nothing wrong with the engine. But, one thing I noticed with the 350 is on hilly terrain the 700r4 seemed like it had a hard time deciding whether to stay in overdrive or not. The 6.2 was terrible in that way - always shifting in and out at every rise. I decided = not enough torque. Plus, I primarily use the truck for 4wd purposes, so took the exact same block, heads, intake, carb, everything from the 350, dropped in a new 383 rotating assembly for less than $1000. The truck now gets 15 mpg. Did not even adjust the carb, just bolted it back on. I attribute this mainly to the fact that it now takes a seriously steep hill to knock it out of overdrive. There's so much torque it just doesn't notice.If I'm not heavy on the peddle as I accelerate through gears it shifts into overdrive, and locks up at 45 mph, and will cruise there all day. Mind you, I have the torque curve shifted towards low-medium range as I rarely am on the interstate, so 70 mph it might well suck gas like there's no tomorrow. But with the 700r4, 3.42 diff, and my 2" oversize tires at 55 mph in overdrive the engine turns over 1440 rpm. But if you ended up with a truck with a 350 and have the right driving situation I highly recommend a 383 build. I would think if you wanted highway cruising leaving out the rv cam would be a good engine choice. And cheap. And you can always get aftermarket injection if you feel strongly anti-carb.