I'm not sure how many, or if, RWD vehicles came with a 3.6? The 4.3 is much more common, albeit slower in a full size. They kicked butt in an S-10, though.
Engine Swap Advice
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I would go back to a 350. There are things you can do to it to improve its efficiency. A standard 350 with 76cc heads and dished pistons only has a 7.7:1 compression ratio.
Bumping it up with flat top pistons or better heads or both will help with mpg.Different cam, better ign curve etc will all improve it.
Swapping in an LS is a lot of work and still gets v8 mpg.
I would be surprised if you got over 14 mpg regardless of what engine it has..It's a square 5000lb brick
Bumping it up with flat top pistons or better heads or both will help with mpg.Different cam, better ign curve etc will all improve it.
Swapping in an LS is a lot of work and still gets v8 mpg.
I would be surprised if you got over 14 mpg regardless of what engine it has..It's a square 5000lb brick
Short of a 6.2 diesel/700R4 swap-I had a very rusty '85 C1500 Suburban that could eke out almost 25 MPG if it was babied on the highway.
You're speaking a foreign language to a guy who doesn't understand what was meant by 'gear ratio'. He's going to have to get much more familiar with auto mechanics, before tackling this, or find a sympathetic mechanic who can competently do a swap, without it costing an arm and a leg.
OP, you have an old, un-aerodynamic truck, and a drivetrain not conducive to achieving high MPG. Putting in a modern drivetrain as you might have in a Camaro, is not going to mean it can achieve the same fuel economy as when it was in the Camaro. The Camaro is lighter, more aerodynamic, and optimized to be as efficient as possible. It would improve MPG some, but the cost to do so, even if you can do it yourself, would never be recouped due to lower fuel usage.
Op, I'd take what you have to a competent mechanic, to make sure it's running as good as it can, and call that good.
There should be a label somewhere on the truck a little bigger than a credit card that has a bunch of 3 digit codes on it. I think it might be in the glove box on a Square Body (could be on the hood but that might be dodge) Give us the codes (mose especially any that start with "G" for example "G80", "GU4".
If the current 350 runs ok, try putting a sniper and hyper spark on it, some tuning and computer control might do it wonders.
If the current 350 does not run or run well, i (i cant believe am about the say this) would LS swap it. Not only will you get a modern engine but you'll get a modern trans and fuel injection. This is a well documented swap plus you can undo any hackery form the prior swap (or your free labor can).
Putting a modern v6 in there you're probably going to be on a bit of an island...
If the current 350 runs ok, try putting a sniper and hyper spark on it, some tuning and computer control might do it wonders.
If the current 350 does not run or run well, i (i cant believe am about the say this) would LS swap it. Not only will you get a modern engine but you'll get a modern trans and fuel injection. This is a well documented swap plus you can undo any hackery form the prior swap (or your free labor can).
Putting a modern v6 in there you're probably going to be on a bit of an island...
^ A 4.8 would be a good swap since the "real" LS swap guys are snobs about running something bigger. But you don't get the 5.3 lifter issues. It's my understanding the older ones with mechanical throttle bodies are easier swaps, but IDK much else.
A 4.3 is basically an SBC with 2 cylinders removed, a lot of stuff will interchange. The Vortec 5.7/350 is an underrated one too, just change the lower intake gaskets & lose the Dexcool first. 4.3 engines came in a 1500 pickup, they’re not rare at all, my next door neighbor has a C1500 with a 4.3/manual combo.
Go for the 6.0 LS, the mileage isn’t that worse. In my experience the 4.8/5.3 is kind of thirsty & pretty powerless.
OP I think you should spend some time reading. You have something with great potential--but also great potential for spending money in return for little. Learn a bit about engines, rear end ratios and everything between. Lots of good advice here, but there's a lot of basics to learn first before making decisions.
And weigh out the costs first. If ROI is important, I would wager, 18 or 20 mpg is the limit of what you could do before it's just money wasted. This truck will never top that on the highway--it's a barn door with a parachute behind it. Accept the low mpg and you'll be happier. As your mechanical knowledge increases, you can make wise choices (4L60 swap, rear end swap, carb tuning, the list goes on) and make it incrementally better.
Just my opinion.
And weigh out the costs first. If ROI is important, I would wager, 18 or 20 mpg is the limit of what you could do before it's just money wasted. This truck will never top that on the highway--it's a barn door with a parachute behind it. Accept the low mpg and you'll be happier. As your mechanical knowledge increases, you can make wise choices (4L60 swap, rear end swap, carb tuning, the list goes on) and make it incrementally better.
Just my opinion.
I'm well aware of that, I don't consider that a modern V6 and it might not get any better mileage....
Had a G-van with a 4.3 and it didn't do any better than the 5.3 i had later.
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Install a EFI kit
The 2011 aluminum 6.2 from a Camaro SS in my 77 c10 is so much fun and gas mileage is about the same as the original straight six that I ordered with the SM 465 4 speed. The rear axle is a 3:40 which is excellent with the 6 speed auto. I don`t miss the stick except for when my left foot reaches for the clutch at an intersection. Original owner here that has 185,000 behind the wheel.
V6 with 5 speed MT pulled out of a s10/sonoma might be a decent “spend thrift” powertrain here as long as loads are restricted to “in bed” or light trailers only. Fuel injection gains a lot, but you do have to get the ecu and harness. Otherwise a v6, manual, and add on single point fuel injection kit would be a good path.
Anything without a lockup torque converter will suck fuel by today’s standards.
They sell crate ecoboost 2.5’s now!
Anything without a lockup torque converter will suck fuel by today’s standards.
They sell crate ecoboost 2.5’s now!
Would a 6 cyl truck have steeper gears? 3.42,3.73?
The current engine is not running. I understand the lack of aerodynamics and that it is not a 1:1 thing here. The idea is to be as fuel efficient as I can under the circumstances. Understanding that it might not be cost effective I will probably just go with some sort of V8.
I have done tons of reading, I am much farther along than I was before deciding to do this. HAHA so I am getting there.
I do not have much desire to be working on cars though. Once this is completed there will not be any work done down the line other than maintenance. If I could get 18, I would be so happy. If not oh well.It is funny you mention that, one of my first ideas was to take an L92 from an escalade or denali. When I realized how bad the mpg would be I went down the rabbit hole of could I use a smaller engine to get similar results. I even looked into some sort of ev conversion.
I will purchase a junk yard engine and do a complete rebuild. Looks like I will be going with LS power.
Finding a competent mechanic that can work on that truck may be difficult. There are things us old guys know that most newer guys don't. One being a stuck mechanical advance in the distributor. That was very common and often overlooked.
Also total timing.
Another goof I see a lot is 350 heads on a 305. Any performance improvement from the larger valves is off set by the lowered compression etc.
It sounds like you already have a decent running engine but it gets bad mileage? What MPG's are you getting? There may be some easier changes than a full drive train swap to improve things. Things like bad ignition timing advance or a poorly working carb can ruin your fuel economy. The wrong gear ratio in the rear end can really hurt you, too.
Changing to more a highway appropriate rear end gear ratio is much easier project than an engine swap which is a lot more complicated than it sounds on paper.
A smaller engine may get worse mpg as it's working harder than a larger engine.The current engine is not running. I understand the lack of aerodynamics and that it is not a 1:1 thing here. The idea is to be as fuel efficient as I can under the circumstances. Understanding that it might not be cost effective I will probably just go with some sort of V8.
I have done tons of reading, I am much farther along than I was before deciding to do this. HAHA so I am getting there.
It is funny you mention that, one of my first ideas was to take an L92 from an escalade or denali. When I realized how bad the mpg would be I went down the rabbit hole of could I use a smaller engine to get similar results. I even looked into some sort of ev conversion.
I will purchase a junk yard engine and do a complete rebuild. Looks like I will be going with LS power.
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