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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: lukieg on January 21, 2012, 04:05:28 PM
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When I decided on a 366 I liked the idea of the torque, the sound and i was hoping due to its small bore.. perhaps reasonable fuel mileage, it is in a 86 c10 with a 700r4 and overdrive, 3.08 gears and i drive so slow its crazy.. and im getting 50 km per 15 l of fuel.. this seems horrible.. i think im having some lifter/cam issues.. but with a q-jet, ver mild fresh cam.. minor porting of everything and super mild driving is it possible for 18 mpg average?? or am I totally barking up the wrong tree? Please opinions are welcome.
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i don't know---i would say compression, decent exhaust with headers, and possibly camshaft might get you to 18.
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I don't think you will ever get close to 12mpg on a 366.
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kind of with capt on this, but if you where to change your gears to higher number it might help you out the 700r4 imo mathematically works better with higher gears for take offs then the od kicks in to give you a lower final ratio. but what type of diving do you do, city hwy?
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what makes the 366 so bad?? heavy rotating assembly... oh one of my cam lobes was wiped right out. Im thinking maybe im better off with a 305 swap.. :(
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mix of both highway and town... 3.08 gears... the truck was set up for mileage... I figure i am getting 5 mpg with the holley and literally 10 with a qjet. The difference in mileage and performance is crazy better with an old junk yard qjet over my new holley 600 vs.
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79 C-30 single wheel reg-cab 366 SM465/Ranger overdrive . 4.10 rear with 255-85-16's gets about 12-13 empty and about 8 mpg empty but I drive like a grandpa
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I would think that big block with a small enough cam would have the torque to hum at high speeds with that rear end and trans and return decent mileage. The 305 isn't a bad option, but if you really wanting mileage out of it, I'd find out what you can do to increase the torque of that little beast at the low rpms, like shorty headers and roller tip rockers and up the compression some. Summit says a holley-like carb for not too bad and would probably real nice on that 366.
Are you wanting to rebuild that 366? The 305 swap would take some work.
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my 1980 c30 dually with 235/85r16s on the back idk the gearing just know its low with a th400 gets 9mpg empty but it seems to get better loaded as when i was hauling gravel the other day it took more gas to get their than it did to get back and it was the same driving distance and i was even stopped at the same spots it took me about a 1/8th of a tank to get their and a 1/16th to get back so this really confused me