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N/A Chevy 305, to efi engine, which is best?

6K views 26 replies 11 participants last post by  BrockGrimes 
#1 ·
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.
 
#2 ·
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
 
#3 ·
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.
 
#4 ·
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.
 
#5 ·
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.
 
#6 ·
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
 
#9 ·
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.
 
#11 ·
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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#24 ·
There are a ton of hidden cost with the 5.3 swap that you should know about before you start.
Yep. I have buddy who bought an LS1 and auto trans out of a wrecked Camaro for his 55 Chevy car. Pretty good deal for $1500. Well, around $3000 later, he still doesn't have everything to finish the job. He said he'd probably build an old skool 383 if he had a do-over.
 
#12 ·
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.
 
#14 ·
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.
 
#15 ·
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.
 
#16 ·
I have a retired mechanic who attends my church, he say he'll help people with their mechanic work for like $20 an hour, and he usually works for $30 an hour. He would be able to help me with a lot of stuff. I'm a minor so that's why I know next to nothing. I ask a lot of questions, and research a lot, I really appreciate your guy's help.
 
#22 ·
Do you have an idea of your overall budget for the total upgrade? Swapping in and upgrading a traditional SBC 350 or 383 can be done through incremental upgrades, so it might be less painful and easier to manage the cash flow. Swapping in the LS 5.3 is a good alternative, but you have to buy a lot of parts up front and do a lot of work up front before you have a working truck.

The full LS conversion/transplant is very dependent on getting the computer system and wiring installed and working correctly, so getting help from an old-school mechanic might not be that effective. You already said you are not that skilled with wiring yourself, but for this project you really need to start studying and learning. It is not rocket science, but it does require careful labeling, good wire routing, and attention to detail for grounding and making connections. Make sure you have lots of space to lay it all out, and that you don't have to clean up and put it all away mid-stream just to get space for another project. Its really easy to lose track of where you were at if you have to box it all up for some reason.

If I was going to make the LS conversion I would prefer to buy a wrecked vehicle and pull the donor engine and transmission myself, making careful notes and lots of pictures as I went along.

Bruce
 
#23 ·
I have to ask again, will it all be worth the time and money? What kind of mileage would he expect after the swap? Maybe an LS I saw mentioned but if it's a 1999 like he looked at, mine is a 2000 and I get 10 - 12 mpg. I just turned 100,000 the other week (there was a few years I didn't drive it and now I only work part time). Mine is a 350 and it's a lame pig. Time for it's 100,000 mile tune up but it's always run the same.
 
#25 ·
clefspheare

The truck LS engines are nearly all cast iron block and the yards sell good running usable engines with the ECM and engine wiring for in the $1K +/- area. Most Street Rod owners that I know all want the Camaro / Firebird or Corvette engines that are aluminum blocks.

Programming a power or econ tune, $250, including deleting the rear 2 Oxy sensors, speedo cal etc. in many places.

The weakest link for almost all LS engines are the roller Rocker trunions, usually a performance engine requirement - around $150 a kit.

use a 1999 or 2000 GM ECM and up to 2008. The E38 ECM 2005 to 2008 best choice.

If you shy at wiring of and an engine swap, do look for a valued shop. Get Shop customer references of previous LS swaps (installs) that you can speak with,,, preferably in person and view the vehicle !!

Wiring should be neat and orderly. Welding on the exhaust, mount / trans mounts, radiator, fuel lines and tank must be top quality or you'll have issues.


A $2k installed swap is a very good price if this includes of the labor, engine / trans, wiring, in-the-tank fuel pump, ECM re-programming and wiring harness mods which are always removing wiring that is not used in a conversion. Make sure you get this is a shop's written contract. Never pay UP FRONT $$$ to any shop, EVER. And get some sort of written warranty.

It's always better to purchase the entire donor car or truck so one receives all the parts they can from the vehicle, wreaked vehicles preferred. Saves $$$

Here's the engine bay in my '56 210. We made this upgrade conversion in 2007. Last summer I finally replaced the old headers with tuned BBK shorties. I've never had a single repair or failure on the LS1 / Tremic T-56 6 speed to date. Ls engines are fantastic great power and high reliability.

Good luck

Michael...
 

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#26 ·
Just pull out your 305 and install a 355/383.
Done simple and easy. Save a couple thousand not needing to change the fuel, exhaust, mounts, etc.

Respect the truck for what it is.
A work truck.
Squarebodies were not designed to go 90mph or have a 10 second quarter. Throw enough money at it and sure it can do those things. But there are better platforms that will do it better for less.

If you want better driveablity you can always grab a junkyard tbi system off a 5.0/5.7 and "hack" it using megasquirt or other system.

Mileage wise your realistically talking about 3-5 mpg. Anytime I have added power to something my foot tends to get heavier. Even going down in cubic inches with a small turbo in place of a large displacment v8 (454 to 3800) mileage tends to be about the same.

Best way I have found to get better mileage is to have a 30+mpg car and then a 10mpg truck.
 
#27 ·
clefspheare, If your current engine is still good a cheap option would be to stick a throttlebody off a v-6 or 350. Grab one from the junkyard and replace in internals, again cheap. While there grab a ecu they generally have a last 3 of the # on it of something like 747. The harness, and a few sensors, and chip can be bought from Affordable Fuel Injection or Howell. I've done a TBI swap for less than $500.
 
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