Engine Swap Advice

Gen 3 LS 4.8/5.3 pan to intake could probably obtain a junkyard pull around $1k if that much. Even could probably U Pull It one cheaper.

P01 PCM, delete VATS and segment swap manual trans. if running a glide, THM350/400/700R4 or run a later model 60e or 80e. DBC if older trans, DBW if newer trans.

I don’t think they cost that much. They only get expensive when you buy fancy swap kits or cam/springs and power adders, etc.

Reliable fuel injections, decent MPG, and dead nuts reliability. I’d go LS.
 
Ok this is now all over the place. I gave what I thought to be pertinent details but it seems to have created more questions than answers. Hopefully this clears up all the confusion. Probably not it will just make more questions. :)

I live on out west but my home is the deep south. I go home about 3 or 4 times a year to check on my dad and help him with anything he needs done. I am generally there about a month or so. He has 5 vehicles at his house that I can drive. Prior to my the passing of my mother my visits we shorter and less often as the two of them were there and I felt less was needed. I know the thought is if he has 5 cars why do I need my own because my dad being my dad. If I drive 20 - 30 miles in the car he is fine. Yet if I drive 75 miles in the car, we have to have the conversation of why I am going so far in his car. He doesn't drive his car that far. Yet he will have just driven 150 miles in a car 2 days prior. To alleviate this issue I decided, I will get a vehicle of my own. His old truck was just sitting in my uncle's yard wasting away. I could have very well bought something new or modern but that is not what I want to do. I want that his old truck.

Level 2 to whats going on here. Where I live, I have a 65 F100 that runs drives and whatnot but the engine was a bit tired. I was talking to my childhood (mechanic instructor) friend about it and he suggested I reach out to the schools as the students and instructors might love to do a rebuild on something that old. I called around most of them said they would love to work on it but they just could not. However, one school said we have a class that we teach engine rebuilding. It is not to be an automotive machinist, it is a class where the students bring in their engine and it is rebuilt in class. Mechanic friend says this is going to cost you far less than paying someone to rebuild your engine AND I will have learned a lot. Well now I am in this class learning to rebuild this 352 FE engine. Talking to the instructor and students about my two trucks (everyone is talking about their projects) they are asking why am I not doing an engine for the C10 as well. After providing all my objections I realize it will be more cost effective to buy a junk yard engine out here and send it home than to buy an engine already done.

As far as my mechanic friend, this is not about the money. We do things for each other all the time that is in the other's wheel house. I built out his wireless network for his 7 acre property that included running ethernet lines to all the buildings. Not a difficult task for someone that knows how but for those that don't it is a **** near impossible. This is what we do for each other on a regular basis. I appreciate everyone being concerned for his work and time but do not worry he will get it back in full. :) His suggestion is to go LS because of the potential it has. Loudest fastest thing in the county is his idea, maybe even the state.

I am not tied to a 6 cylinder I really just do not want to be getting 8 - 10 mpg. If it is more practical to go with a SBC or LS I am down to do that. I just have to figure out which one. Part of my learning is not just the what but the why.

@PontiacHO Do you know which engine might fit the bill?

@02SE He has built tons of engines and swaps. He drives a 442 with an LS. As kids, when I had my head stuck in a computer, he was wrenching on a car. I have no doubt he can do the work. The 350 is a great engine, the one in my truck is not running.

@AdmiralYoda Sounds like a good place to start.

@ripcord No stress, I should have been more clear in what I was saying. That is what I get for hitting post without proofreading.
:)

@redhat The local upull yard sells engines for $500 does not matter which. A few weeks ago, they were $100 as part of a clearance sale. HAHA
 
Gen 3 LS 4.8/5.3 pan to intake could probably obtain a junkyard pull around $1k if that much. Even could probably U Pull It one cheaper.

P01 PCM, delete VATS and segment swap manual trans. if running a glide, THM350/400/700R4 or run a later model 60e or 80e. DBC if older trans, DBW if newer trans.

I don’t think they cost that much. They only get expensive when you buy fancy swap kits or cam/springs and power adders, etc.

Reliable fuel injections, decent MPG, and dead nuts reliability. I’d go LS.

This is all true but can be highly dependent on location too. I'm probably going to spend $1,500 on a complete engine with 150k miles in my area and probably another $500 for the ECM and harness, at least. That is for the garden variety 5.3's. If I want a 6.0 or 6.2 its going to be higher.

The OP is doing this for MPG so an overdrive trans is a must. If he is going down the LS road he'd best avoid a 700r4 since that would require special adapters. So a 4L60e (yuck) or 4L80e/6L80e/8L90e would be more like it so he would need the to make sure the engine ECM and harness is compatible.

At the very least he'd need a new radiator, come up with a new fan shroud if mechanical or an electric fan setup, motor mounts, LS swap headers and exhaust, a trans crossmember and a new driveshaft. In addition to the engine/trans/harness/ECM. That's the bare minimum.
 
One major question, what do you consider terrible mileage? I did a full restoration on my 1970 Chevy C-10 between 2006 to 2009. I purchased a 350/330hp GM Performance HO Turn-Key in 2007 and installed it in the "70. The engine comes complete with everything including a serpentine system. I have never had "gas mileage" less than 18MPG. I don't consider that a bad issue since I built it to drive and that is what it does. Plenty of power when needed but drives like a dream.

It all depends how your 350 was built and used before you bought it. Maybe a "race" and go engine? I'd look into that first if you possibly can. the Chevy 350 can be built to your specs and driving style. And built to save gas too, if that's what you want but MPG is a relative term, it's all about how you drive!!
 
@TPK Yes that is it. 18 MPG sounds wonderful. I want to drive this thing, it just will not be lots. I live several thousand miles away.

@AdmiralYoda My lack of knowledge here may be the issue. I figured when rebuilding an engine that one would just automatically also get new fuel pump, starter, alternator and all that jazz. Similarly in my class, the instructor talks about reusing the valves. My thought is, this thing is torn apart replace nearly everything. In my head all that is already included as a cost. It is an almost 50 year old truck which to me means it will be rewired, new brake and fuel lines. Am I wrong in thinking this way?
 
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What is making the old engine not run? Worn out, low on power and burning oil; and when it last stopped running, no effort was used to make it go further? or did it forcibly eject parts?

Just wondering if it got out of tune, maybe has a bad timing chain, and is trying to push 4.10:1 gears out back, thus getting bad mpg while otherwise being awful to live with. Is it worth doing a compression and leakdown test first? Maybe it can be brought back to life with ease, then trans and rear end addressed (which would have to be addressed with a newer/better motor anyhow).
 
@Cruck aside from drivable MPG's what are your end goals? 400hp in an old square body can be a handful if the rest of the truck isn't 100% up to snuff.

I really think a good rebuild on the old 350 with an overdrive transmission is the way to go.

The heads are tiny and stink on the smog Era v8's. An aftermarket set of aluminum heads would really help. Those engines also had waaaaay to much quench (how far the piston is below the deck height) at TDC.

Horsepower kills mpg. For simplicity I'd rebuild the 350 to 300-350hp with an overdrive transmission like a 700r4. At 60mph you should get 16-17mpg. Maybe a touch more if you are not lifted and have good street tires.
 
@Cruck - I used to drive a ‘77 one ton Chevy with a 454 and a dump body on it at work. It weighed about twice as much, had a bigger engine and lower gears and still got better MPG than your truck.

I suspect that your engine is the issue - it is just plain worn out.

But with a rebuild, good compression, and properly tuned, it will get much more acceptable fuel economy. Throw a set of Performer Heads, a cam and manifold on there if you would like a bit more power - all while keeping the cost of this project far below that of a complex swap.

Pull the 350, go through it. It probably has 4 bolt mains and is worth saving. A re-bore, and all the rest of the machine work, and you’ll be surprised how well it can do.
 
The heads are tiny and stink on the smog Era v8's. An aftermarket set of aluminum heads would really help. Those engines also had waaaaay to much quench (how far the piston is below the deck height) at TDC.
In the OP he says that the motor was swapped late 80's / early 90's. Hard to say what it has. I still think there's a chance it's a 305 or 307--maybe its problem is that it got one of ones that liked to get flat cams.

Otherwise, agree, work with the engine it has. Ok, I can see the allure of building a known good core and swapping that in. If nothing else, it's easier to bolt parts onto an engine while it's on a stand. 350, Vortec heads, mild cam. 8.5:1 compression? 9:1? not sure what will run on RUG vs PUG, but if one can tolerate the cost of PUG, the higher compression should surely help decrease tire life. Back it up with a nice 4L60 / 700R4. If it has a truck 4 speed (with granny) I'd swap it out, maybe a 4 speed manual with 3.42's out back would be tolerable... not sure if OP wants a stick or auto. 3.42's without overdrive sounds like it might be turning a bit fast--but to be honest, if mpg is desired, driving past 55mph won't find it.
 
@AdmiralYoda I just want this to be nice enjoyable ride when I am in it. I want when I get in it starts with not any issues. This idea of electronic fuel injection sounds great. I have to learn more about it let my buddy know what I want. If I leave it up to him, I will have some 500-600 hp monster. HAHA. When you say the rest of the truck is 100% up to snuff, can you elaborate more please.

@Astro14 That engine has not been started in at least 20 years. When I removed it from my uncle's yard the gas tank was missing. It had no plugs or wires. Honestly, there is no telling what he did to it. He breaks and destroys everything. Also, I am on the other side of the country from it. Knowing that I can get ~18 MPG out of it is what I was hoping for. Now I just have to tell me buddy because if I don't I will have this loud beast of truck.

@supton Of course I will drive over 55! :) I am going to drive this truck when at home. I just don't want it swallow 5 gallons just getting to the gas station. I am going to assume RUG - regular and PUG - premium. I would prefer RUG not sure why PUG would be preferred. The truck is automatic. I would like to keep it that way.
 
Premium gas would allow more compression and more power. But regardless of which is preferred, on an engine rebuild, selecting compression is one of the variables to be played with. On a mild engine, maybe not so much, but the pistons have to work with the heads chosen. Chose wrong and you'll have to run PUG.

If the plugs have been out for 20 years (or even just 5), yeah perhaps moisture has gotten in. Not good. Still an unknown, still making assumptions that it's frozen and wore out, but all the more likely.

Not sure what an I6/auto would be pushing for gears out back. Probably still somewhat deep. I want to say the RPO's should be listed on the glovebox door; the rear end ratio should be listed there. Then again, the RPO's would say it has a six cylinder--at this point, who knows what is out back. Before you go working on the engine, perhaps pull the rear diff cover and drain the rear end. If it's full of junk, well it's something else to fix/replace. While open count the teeth (or refill and do the other method). Once you know the rear gears you can decide on transmission. I doubt it has tall gears but it is a good thing to know. Then you can find a 700R4 with a lockup convertor, figure out how to get lockup to work, and use that.
 
@AdmiralYoda I just want this to be nice enjoyable ride when I am in it. I want when I get in it starts with not any issues. This idea of electronic fuel injection sounds great. I have to learn more about it let my buddy know what I want. If I leave it up to him, I will have some 500-600 hp monster. HAHA. When you say the rest of the truck is 100% up to snuff, can you elaborate more please.

@Astro14 That engine has not been started in at least 20 years. When I removed it from my uncle's yard the gas tank was missing. It had no plugs or wires. Honestly, there is no telling what he did to it. He breaks and destroys everything. Also, I am on the other side of the country from it. Knowing that I can get ~18 MPG out of it is what I was hoping for. Now I just have to tell me buddy because if I don't I will have this loud beast of truck.

@supton Of course I will drive over 55! :) I am going to drive this truck when at home. I just don't want it swallow 5 gallons just getting to the gas station. I am going to assume RUG - regular and PUG - premium. I would prefer RUG not sure why PUG would be preferred. The truck is automatic. I would like to keep it that way.
You could always find a small diesel and go that route with better gearing.
 
@AdmiralYoda I just want this to be nice enjoyable ride when I am in it. I want when I get in it starts with not any issues. This idea of electronic fuel injection sounds great. I have to learn more about it let my buddy know what I want. If I leave it up to him, I will have some 500-600 hp monster. HAHA. When you say the rest of the truck is 100% up to snuff, can you elaborate more please.

@Astro14 That engine has not been started in at least 20 years. When I removed it from my uncle's yard the gas tank was missing. It had no plugs or wires. Honestly, there is no telling what he did to it. He breaks and destroys everything. Also, I am on the other side of the country from it. Knowing that I can get ~18 MPG out of it is what I was hoping for. Now I just have to tell me buddy because if I don't I will have this loud beast of truck.

@supton Of course I will drive over 55! :) I am going to drive this truck when at home. I just don't want it swallow 5 gallons just getting to the gas station. I am going to assume RUG - regular and PUG - premium. I would prefer RUG not sure why PUG would be preferred. The truck is automatic. I would like to keep it that way.
"When you say the rest of the truck is 100% up to snuff, can you elaborate more please."

The tires, the brakes, the suspension, the wiring, etc. 20 years outside?? :devilish: :mad::unsure:

Sorry to say, but it appears you and this truck are beyond hope.

I'm afraid to see what pics would reveal.

AdmiralYoda post #56 is the best summary. Much more involved than it appears.
 
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The RPOs would be nice, would answer some questions.

I'm gonna give you some other advice to do with what you will.

Find a square body forum, they wont call your truck "beyond hope" or a "sows ear"...

When i hear someone swapped it in the late 80 or early 90's several things go trough my head, none of them good. not only do you not know what they put in it but you're bound to find at least some hackery to straighten out.

You can go on Holley's website and order just about everything to bolt an LS into this, including fuel injection that will control a GM 4 speed automatic.

Even if you go with classic SBC your gonna want fuel injection and spark control for your purposes.

Everyone is having lifter problems on flat tappets again, id figure a hydraulic roller and good heads into your SBC calculation. An LS already has good heads and a hydraulic roller cam.

Frankly, i'd put a basically bone stock pre AFM 5.3 in it, hook it to a 4speed automatic and motor on.
 
Your 350 with fresh rebuild and 300 horsepower camshaft (-929 cam at 195/202, 112/108, .390"/.410" lift) will be the most economical result with bang for your buck effort that there is. You already have all the accessory brackets, engine mounts, transmission that bolts up, and exhaust system in place. The problem with your poor fuel mileage is mostly associated with the current rear end gear ratio. 6 cylinder trucks have a lower gear ratio (numerically higher) for torque multiplication. Find a rear axle assembly from a factory V8 with automatic truck for a swap and your golden.
 
Find a rear axle assembly from a factory V8 with automatic truck for a swap and your golden.
That will help but if he still has a non-lockup TH350 then I have to wonder if the gains will be great. IMO better to keep a 3.73 rear end and get a 700R4 or 200 4R. Actually, I forget, is the 200 the same length as a TH350? not the 3 speed TH200 but the 4 speed 200-4R. If it's the same length (just different yoke) then the driveshaft might be reusable.

But swapping in a taller rear will help, no doubt about that. Keep existing trans, driveshaft... it's less work, less sourcing parts. Might be easier to just buy new gears than to find a good junkyard rear end? I've never gone to a junkyard, not sure what is out there (I suspect most of our stuff gets crushed in short order and recycled). Setting up a rear end is tricky business but there are shops that will do it--or it can be a good learning experience.
 
Based on what i can find 3.08 is standard for a V8 and 3:42 for a 6 and EITHER could be ordered with a 3.73.

Gotta check RPO codes and axle tags.
 
Yes. 6 cylinder trucks in the late 70s were typically farm or fleet use. The lower gears were usually speced by the ordering dealer.
 
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