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Old 06-13-2019, 04:37 PM
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N/A Chevy 305, to efi engine, which is best?

So I have an '86 k10 longbox, it has the 5.0l v8 305, but it's carbureted. As much as I love the classic manual choke the carb has, 10mpg isn't so appealing. So I want to do an engine swap eventually, I was thinking a 6.0 from the early 00's, but I have sbc mounts and I can't weld, so I might not be able to mount that. But how complicated is it to do a swap? Which engine is most practical? And finally, how do I go about doing the swap? I have a 700r4, and don't want to switch to a 4l60e, or any other tranny.

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Old 06-13-2019, 06:03 PM
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There are motor mount relocators/adapters for the LS engine swap, to allow you to mount to older style frame stands.
There are adapter kits to allow attaching the 700R4/non LS version of the 4L60E to the LS engines. Very simple spacer/adapter.

Holley, Trans-Dapt, Summit Racing are just a few who sell the mounts, Summit for the best deal on the trans adapter.

A Chevy truck forum specifically for the '73-87 Model is probably going to be your best bet for info on the swap, as to whether a different oil pan is necessary, wiring, exhaust fit.

https://www.gmsquarebody.com/
The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board - The 1947 - Present Chevrolet & GMC Truck Message Board Network
73-87chevytrucks.com
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Old 06-13-2019, 06:06 PM
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IDK? My 2000 3500 van with a 350 gets 12mpg on a GOOD day. Same as when it was new. I don't know what you could do to get much more than that. If you don't drive it a LOT, I don't think you will ever get back the money you'll put into it. But I'm not the best one here to say either.
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Old 06-13-2019, 06:57 PM
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The 5.3 truck is the most practical. Truck intake makes good torque and the pan fits. You loose ac generally. But there are ways to relocate it.

I am putting together a 87 k10 with a 02 5.3, sm465 to a divorced 3 speed brownie/np205 setup which will eventually be pushing front 14/60 and rear 14 ff 4.56 on 35" tires.

Cost wise I am $500 into the engine, around $1000 in fuel pump,seals/sensors/mounts, another $600 into relocating the coils, running forward facing turbo headers(na for now).
Still need to make a custom adapter for the brownie to np205, clutch, piliot, flywheel, steel bell, 6" shaft, rear driveshaft, middle front shaft for the belly, then front shaft. So another $2500 or so before even pulling the 10 bolts out for the 14 bolts.


Start building now and minimize the amount of time the truck will be sitting. Even properly planned out it is far from a drop in deal. 3k is about what a proper junkyard ls engine swap will cost all said and done.
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Old 06-13-2019, 09:03 PM
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If you can get that to 15mpg, then you'll be doing a stroke of business NA. Older 4wd's have too much rolling resistance to be efficient and throw in the brick shape and all mileage is in the toilet.

I'm with cerial about a recommendation - the 5.3 is the best choice for an LS platform - power and economy. A 4.8 will be a hog and a 6.0 will guzzle fuel like a drunken sailor.

If you're interested in spending money to get fuel economy, that you'll never see a return on, then grab a 4.8 and put a dinky little turbo on it that will be flow limited to approx 350-400hp, but will make gobs of torque at low rpm's and spool before 2500 rpm's. With a stock cam and tight converter you could easily see over 15 mpg and still have some snap when you lace into it. The dilemma will be that 'boost is addictive' and you will want to go bigger before long - and there will go any fuel economy.
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Old 06-13-2019, 11:42 PM
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I guess you have to decide if your a hot rodder or a computer geek, and where to put your cash in hard parts or virtual reality.

It really boils down to the fact this is a big heavy 4x4 in need of a lot of torque, a 305 like you have is just worked to death to move this, a 350 would be a little better, a 383 is headed in the right direction.

To get more out of an LS motor compared to a classic small block really needs the modern truck it came in, all the pieces of these are designed to work together, an ala-carte build not so much.

Not that I'm opposed to this swap, but my experience with the LS engine in large older trucks just hasn't shown the rewards many people claim to be there.

Bogie
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Old 06-14-2019, 08:18 AM
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Thanks guys I'll look into the 5.3. But to be clear, my stock engine, the 305, puts out 150 horse, and 240 ft lb. of torque, so pretty much anything would be better, but I do have a quick question, how reliable is the 5.3?
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Old 06-14-2019, 08:37 AM
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The "worked to death" term you used bogie is quite true, my temperature gauge is just 2mm from the red line, almost all the time. Which I know is not good, but this truck is my only vehicle right now.
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Old 06-14-2019, 10:42 AM
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Quote:
Originally Posted by clefspheare View Post
Thanks guys I'll look into the 5.3. But to be clear, my stock engine, the 305, puts out 150 horse, and 240 ft lb. of torque, so pretty much anything would be better, but I do have a quick question, how reliable is the 5.3?
Very...guys are buying these junk yard engines, doing little more than opening up the ring gap, adding head studs and new head gaskets, and maybe a mild performance cam if they are feeling frisky....then adding a turbo or two and making 600 HP up to near 1000 HP on the stock short block. Not even touching the bottom end other than to inspect and make sure there isn't some problem there that put it in the junkyard to begin with.

About the only reported failure that is common enough to be mentioned is hydraulic roller lifter failure on engine with high mileage, 160k to 250k mileage area. If you swap them out as soon as you notice noise, it isn't a problem. It's the folks who ignore it and hope it will fix itself that get burnt by it. Even then, it isn't extremely common.
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Old 06-14-2019, 11:20 AM
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Man, I'm sold then. Looks like I'll be stopping by the wrecking yard here soon. Thanks for the help everyone!
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Old 06-14-2019, 12:56 PM
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Transplant a 5.3

There are a ton of hidden cost with the 5.3 swap that you should know about before you start. Motor mounts and the like are a small part but you will also need a fuel pump that delivers the pressure needed (56-58 lbs) and return to tank line or in-tank pump. Then you will need a harness, modify a stock harness or purchase a new one. Then the ECM and programming. Low end at $800 and up depending on where you get the parts. Total swap as mentioned above at $3K is about right depending on how much you do vs farm out. Do your homework. Later (gen IV) engines have VVT and DoD and 2003 and later are all drive by wire. Don't get discouraged, it's a fun trip.
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Old 06-14-2019, 01:49 PM
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I guess I habe another few questions. What year is the simplest to install, as I don't have a whole bunch of wiring experience, and as stated before, I can't weld, but I can drill 2 holes and stick a bolt through them. Also what parts am I looking for, I know I need the engine, but do I need every single computer component that comes with it, or are there kits to bypass that?Does the $3000 budget come from scrap yard parts, or new parts? Last, but definitely not least, if I have all the parts I need, and very little goes wrong about how long would this swap take? I mean I've pulled an engine out of a '78 GMC, but this is more involved.
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Old 06-14-2019, 02:01 PM
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I figure I'm going to try the 1999 lm7 5.3 as even though it doesn't pump out a whole bunch of power, it's probably the easiest to hook up.
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Old 06-14-2019, 02:03 PM
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The best way to improve your mileage is to park the truck and get a $800 kick around car.
It is one of those "hiden" cost that your going to need even if the thing is only down for a week or two. Honestly I would plan a month(working 8 days on the weekend for around 60 hours) even with everything "ready".

Even with everything laid out and planned there will be hiccups. You could have the thing running on a engine stand shifting a manual 4l60 with transfer case attached all out of the truck.

Lets say you have a sm465 to 205 or208 in that k10 currently(which eliminates many swap headaches) you still have the fuel pump, lines, tank(s), exhaust with 2 O2 bungs, diffrent clutch, flywheel, mounts, some minior electrical work for the motor(it wont be pretty but it will run by just splicing in the fuse box using the 2 wire trick after flash your ecm to turn off vats, then you need to give power to the starter lug feeding your main power junction to power the rest of the truck.

With everything in place and the 5.3 running on a stand your still looking at 20-30 hours to get the thing driving around the yard. Doing "clean it up later" things.
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Old 06-14-2019, 02:15 PM
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Well my local Spalding's shop says they have a conversion engine, (1999 5.3) with all the wiring and computer stuff, and they would pull it and test it, computers and all. It would be almost $2000 though. They're in Spokane Washington, is that a good price? It has 125k miles on it.
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