Is my truck possibly under powered?

[Jarvis-69 GMC 1500CK]

Got a old 305 under the hood, sounds great, starts great, but wondering if I could get better fuel efficiency with something slightly larger, like a 350. (is this 305 having to work OT to move this truck is my question essentially.) Apparently it is a "newer" 305, from early late 70's to early 80's. Weren't these engine known to be pretty weak in terms of power?

[davepl]

They're not powerhouses, but only your driving experience can tell you if its underpowered in your truck. I doubt it's any worse than the 6 cyl or 307 it could have had!

If it works for you, that's all that matters. Fuel efficiency doesn't change from one motor to the next, largely, unless one motor is forced to operate in an in efficient RPM range to keep up.

Other than a bit more friction a 402 should use the same gas, more or less, to go down the highway as your 305.

[Jarvis-69 GMC 1500CK]

Might just be because it seems to be geared low, but it screams anything past 55, and at 55 the revs are pretty high as far as I can tell.

And yes this truck according to the tag came with a 307.

I just heard bunch of stuff that the late 70's 305's were pretty well junk.

[truckster]

Originally Posted by Jarvis-69 GMC 1500CK

Might just be because it seems to be geared low, but it screams anything past 55, and at 55 the revs are pretty high as far as I can tell.

And yes this truck according to the tag came with a 307.

I just heard bunch of stuff that the late 70's 305's were pretty well junk.

You need to figure out your gear ratio. That might be a place to start, although going numerically lower in the gears (dropping RPM at freeways speeds) is going to make it a little more of a dog off the line.

As far as the 305, I'd never put one in anything I owned, but if you already have it and it runs, I'd just leave it unless you're unhappy with it. And if you're unhappy with it just because of what someone else thinks, I'd think again about that. Even doing all the work yourself, you're going to be into a crate 350 at least $1200 dollars. You can buy a lot of gas for that much cash.

[Warrens69GMC]

The 305's can use most of the same parts to "hop up" the engine, just like the 350. Ask yourself this-

Can this engine have the stock cam in it?
Does it have the stock manifolds on it?

A simple cam and headers can do wonders for the 305.

For the RPM
what speed do I want to cruise at?
Tire size (O.D.)?
Gear ratio in the rear end?
Do I want to spend the money on an Overdrive transmission?

Can a compromise be made with a taller tire and/or driving a little slower?

[geezer#99]

You want to max the power, put some timing in it!

[trac209]

I've seen lots of 305s that make good power,especially in a street application. Headers and dual exhaust on a nice running 305 will move most trucks around pretty well. My dd has a stock 305 and it pulls very strong to 5000rpm in a 3800 pound car. Get it running well and you'll be fine.

[leftybass209]

The 305 is at least equivalent to the inline 6 these trucks originally came with, and in some cases can have more hp and tq; so from an OEM standpoint it wouldn't be underpowered, just considered base model status.

Always consider the source when people say an engine is junk, or worthless. The 305 was: reliable, adequate, and sufficient for non-performance applications. It wasn't a stoplight warrior, but routinely scored better fuel mileage than larger cube engines.

I would think your truck has a gearing issue for the highway driving.

[Already Gone]

If you post a picture of the spid label and what size rear tires you have we can tell you what rear end gears your truck was built with.