Best Engine For Economy vs. Grunt

[Inu-Hanyou1776]

Even though I don't have the funds to get started, I have decided anyway to start putting a plan together for the future in case I do ever decide to get myself a K5 and join the fun with everybody.

Now I'm wondering what's the best motor to go with that offers me good power vs. economy. I'm at the moment thinking of a built-up 305 or a 350 small block. I'm thinking 305 first off because my grandma's '91 Caprice Classic has one, and that car's got plenty of power. I'm not looking for an engine that'll allow me to do burnouts by no means. Instead I'm wanting an engine that'll have tons of low-end and when I drive with a light-foot, still maybe get 17-20 mpg (wishful thinking I know). So look at the poll and tell me what my options are.

Tranny will most likely be either an SM465 or 700r4 w/ full manual valvebody, with a 205 twin-stick case.

EDIT - Turbo'd 6.2 is another option I'm seriously considering. Big blocks are out of the question for fuel economy reasons.

 

[k20]

well, my big block gets better mileage than my old 350 did (it had issues), both were FI'd. 17-20 out of a gasser motor aint gonna happen. 6.2 is your only hope of any respectable mileage. A 305 will be anemic in the power department. A tuned 350, might, MIGHT be able to get 14.

Way your talkin, diesel is the only way to go.

 

[Inu-Hanyou1776]

If I go diesel then, I'm definitely going to do a veggie conversion to it and run it off WVO, the concern then would be whether the 700r4 would be able to handle the 6.2's torque. Did GM ever put the 700 behind the 6.2/6.5 ever? If it can't, then the SM465 with the lowest gears I can fit in the 205 along with a 203 doubler would be the thing to do, so I won't have to constantly dance on the clutch. Despite my bias against automatics, my Tellico outing with dontoe has told me that for the trails around here, being able to focus solely on finessing the gas and brake pedals is key to keeping from getting hung up on crap and avoiding body damage.

 

[k20]

yeh Im pretty sure the 700 made an appearance behind the 6.2. I believe it did with the 6.5 too, not sure whether or not it came behind the 6.5 turbo though. Out of curiosity, why dont you go th400? If you talkin a 465 with a doubler, why not a 400 with a doubler? Thatd surely knock the socks off the 700 with no doubler

 

[jekbrown]

stock/mild 454. Doesn't really cost much more than a 350... and mileage is gonna suck with any gas burning K5. My 350-powered K5 gets less than 10 mpg. Doubt it would be much worse with a 454.

j

 

[Inu-Hanyou1776]

I'm considering the TH400 too, but whether I go with a 400 vs. 700 hinges on whether this truck would be my daily transportation or not. If this truck winds up ever having to serve as a DD, I'd need the 700's overdrive for optimum fuel economy (and with my family's luck with vehicles sometimes, I'm counting on that maybe happening). If I know for certain, without any doubts, that I can keep it a mostly trail vehicle that'll only see street use while being driven to Tellico and back, then I'd go with the th400.

 

[Leper]

502 with a dual quad tunnel ram will get you at least 1 mpg and with enough gearing it will be nice on the low end.

 

[Inu-Hanyou1776]

What kind of actual mileage numbers could I expect out of a hot, turbo'd 6.2? 17-20 like I was thinking, or more or less than that?

Back on the transmissions, I just told myself a good reason to go with a 465/203 doubler/205 twin-stick combo: theft protection. Even though it's probably a non-issue here in Murphy, still anybody who might even think of stealing a vehicle ain't gonna be stealing my rig when they look inside and see three shifters sticking out of the floor! Besides, with the 203 doubler, I might just manage to get my gearing low enough to not have to do the "left-leg boogie" constantly while on the trail.

 

[Russell]

I'm getting 18.5 on the highway regularly with my mild 350 in the 89

Overdrive, and tires that are just the perfect size to get my rpms right at my engine's sweet spot on the highway

You can definitely get over 20 mpg with a 6.2 on highway, esspecially if you turbocharge it. But, remember, those engines are not to be compared to a gasoline engine, which is a common mistake that is made.

A 350 will obviously run circles around a 6.2. 6.2 tops out at like 3500 rpm, while a 350 tops out at like 5500. Diesels are designed to make good torque, and go on long hauls, not random trips around town. They like to be run long and hard, not stop and go

There are only two proven methods to get better milage with any type of engine -- First, overdrive, second, a 2x4 under the skinny pedal. Lots of other little things you can do to help, but those two will net the largest returns.

 

[pauly383]

If your short on funds , and have a TBI 305 already , then use it . Spend money on lockers instead .

I can wheel mine , and drive it to work daily , and get decent mileage .

Its not as glamourous as the 383 I want to build up someday , but anyone who has seen it drive , knows my 305 does just fine for such a heavy truck .

 

[Inu-Hanyou1776]

Probably TBI 305 or the diesel. I plan on rarely, if ever, going WOT. I plan going light with the pedal constantly. Pauly383, what's the approximate weight of your rig? Grandma's 305 Caprice I know weighs in at least 4000, probably 4000-4200+ with two people in it.

 

[beater_k20]

building a 305 is a dumb idea. you can get much better performance out of a 350, at a cheaper price (350 hard parts are very commonly cheaper), and the difference in economy wont be noticable.

 

[73k5blazer]

Since I have one (In a C10), I'll throw it out there, how about the 4.3L V6?
A 350 with 2 cylinders missing. I just rebuilt the one in my C10, it's now pulling 220hp and 235ft-lbs torque. And I didn't even do anything special, just '04 vortec heads, 1-up cam and edelbrock manifold and roller rockers.
The best part, the C10 gets 21mpg on the highway, withs it's stock 3sp manual non-overdrive trans. Ok, I have 2.73 gears.
Some people have the 4.3l over 300hp Natually aspirated.
I don't think I'd want the v6 in a 4x4, but I love it in the C10. Just throwing it out there, if you *really* want to hit the 20mpg mark.

 

[pauly383]

Mine weighs over 5500 pounds , and I am poor , so the 305 stays until it dies .

Thats why I said use what you already have .

Engine talk is really pointless if you can't afford it anyway

 

[mudjunkie 82]

Blown 540" Merlin, not real good mileage but the fun factor is worth it!

 

[daleearnhardt01]

Speachless

Wow yet another great and thoughtless post...

Are you seriously saying a valid reason to avoid an auto is theft protection? Give me a break Guess you better make that 465 shifter as short as the t-case shifters so it doesnt look like a tranny shifter and more like a t-case shifter and confuse those theives...

HAHAHA Never going WOT, are you kidding me? Thats the biggest bunch of bull I've ever heard. Aside from the fact that never going WOT will never happen and is quite stupid what about a valid reason why thats dumb. Say you are in an accident situation or some situation that requires WOT; what are you going to do just lightly press the pedal as the other car plows you?

Are you seriously expecting 17-20 mpg out of a 305 in a K5? That motor doesnt get much better mileage than a 350 and you have a weak ass motor.

Dont be stupid just put a 350 in or get a 6.2

K5 Blazer and good gas mileage dont belong in the same sentence...

 

[pauly383]

15 mpg is doable , and proveable below 1500 feet elevation

 

[DieselDan]

You can definitely get over 20 mpg with a 6.2 on highway, esspecially if you turbocharge it. But, remember, those engines are not to be compared to a gasoline engine, which is a common mistake that is made.

A 350 will obviously run circles around a 6.2. 6.2 tops out at like 3500 rpm, while a 350 tops out at like 5500. Diesels are designed to make good torque, and go on long hauls, not random trips around town. They like to be run long and hard, not stop and go

YES, Yes, Kinda, & Not Quite.

I get 20 MPG with my 6.2 (35" tires & 700R). I will whole-heartily agree "diesels are different". I like the 305 to 6.2 / 350 to 6.5 turbo comparison someone made a while back. I've seen plenty of weak (stock) 350's and a few healthy ones too. The 6.2 was designed to be an "economy engine" from the start (as opposed to Duramax, Powersmokes, & Cum-mons). It loves to putt around town and trail. Much more fuel efficient at idle than any gasser. I know 'cause I get NO heat at prolonged idle

How about a 350 (or a stroked 305 ) add some vortec heads, Scoggin TPI manifold, mild cam, small headers, 700R tranny, and see what kind of numbers (HP, Torque, and MPG) you can pull

 

[beater_k20]

How about a 350 (or a stroked 305 ) add some vortec heads, Scoggin TPI manifold, mild cam, small headers, 700R tranny, and see what kind of numbers (HP, Torque, and MPG) you can pull

stroked 305 is an even worse idea than a mildly built 305. you pay 383 price, and get less than 350 performance. the drawback is the bore size, its too small so it shrouds the valves. and no, you cant bore it out to the 4.00" of the 350. ever notice you never see 335" 'stroker' kits? why? because the aftermarket realizes that building a performance mill based on a 305 is pointless.

at any rate, he's just trying to fit in around here. if this were a Toyota Camry website, he'd be talking about building a Camry.

 

[danny7139]

Inline 6 Vortec 4200? Newer 350 Vortec? My vortec 4200 makes more power then the stock k5 350 and does 18 city 24 highway. Just throwing out ideas. Oh look a 350 vortec short block for cheap here, I might just jump on that deal. Or this 4.3L v6 here?