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Engine swap idea. 85 k5.

leroynumber9

leroynumber9

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I have an 85 k5 with the 350 and quadrajet. Stock this truck came off the line with about 165 hp. I want closer to 300. For the money I need to do this I can find a wrecked 01-04 silverado and swap out the drivetrain. I figure if I do it this way I will have a much more reliable, efficient power plant. And if I get the whole vehicle I should have just about everything I would need.
So what I'm asking is, is there a specific year this would be easier to do with. I want a 4.8, maybe a 5.3. And I would most likely swap out the 700r as well. Should I swap the np208 or would I be able to keep that. Any ideas here are welcome.
I looked for a thread familiar to this without luck.
 
If I were gonna do it, I would find the entire rig, swap engine, tranny, tcase, make a custom tranny mount. Pull wiring harness completely and put it in the blazer.... Idk how you make stock gauges work though...
 
While the newer drivetrains are definitely more efficient, I believe that the Gen 1 SBC and 700r4 can be equally reliable, if not more, if built by the proper individual. A lot of people are quick to knock them, but I've seen properly built setups outlast some of the newer drivetrains by far. Parts are a dime a dozen, and more seasoned mechanics are very familiar with these setups. You are talking about adding a system that has way more electronic components into a truck that wasn't originally intended for them; I believe that you are providing more opportunity for things to go wrong. My opinion is you could build a 300hp+ engine and build a great 700r4 that will be very reliable for half of the cost and half of the headaches.

However, if you just want an updated drivetrain and a challenge I can appreciate that and you should go for it.
 
I am guessing that your 85 has a carb that is not computer controlled or electronic. If that is the case, it wouldn't be too hard to get 300hp with the original block. A carbed 383 can haul ass. I had one in my 79 pickup. Last time around I went all out and upgraded to a 406 (400 30 over) and reused the aluminum heads, intake, and all external engine components, and I had a ton of work done to the heads and intake. Mine should make 420hp 525tq and is smog legal.

If you go with a modern engine, go as big as you can. The old trucks are heavy and less aerodynamic. You can always drive nice with a big engine and get ok mileage, but it sucks to wish you had more cubes to make more power.

The early 700r4's are not as desirable. My uncle owns a trans shop and build race transmissions as well. He said that the 700r4 in my 88 should be new enough to have the better parts. I don't remember all the details. My trans was rebuilt before I bought the blazer, and I haven't had to tear into it yet.

I considered a 5.3 or 6.0 swap for my K5, but I have to deal with smog in SoCal and I didn't want to drag out an engine swap. I dropped in a GM Goodwrench 350. It runs good, but I wish it had more power. Of course it sucks compared to the big mouse in my pickup that pulls hard to 5500 rpm. The tbi gm 350 is done by 3500 rpm, and just makes more noise when you run it faster.

I settled, based on my time and money constraints, and went with one vehicle closer to stock (88 k5 350) and one that has high end everything on it (79 C20 406). My 79 originally had the 350 and qjet that was also rated at 165hp/265tq.

I have heard that the 700r4 will bolt up to a 5.3, possibly with an adapter.

Wish I had more advice for the newer engine, but my experience with them is limited to oil changes on my mom's 2005 pickup.
 
The LS series motors are a GREAT choice and honestly unless you're looking for a $500 diy basic rebuild, I wouldn't go any other way.

Having built my full roller Vortec headed 383 many years ago, you can buy a motor with aluminum heads (sometimes an aluminum block too), heads that flow better all around, with as much or more power AND factory (great) fuel injection for way less than you could ever build an older motor. The MPFI system practically costs what an LS engine with fuel injection does.

Seriously, I probably had $4K into my roller 383, complete machine work on the block, Vortec heads, intake manifold, roller cam, hypereutectic pistons, etc. It works great but that still had a Quadrajet on it, all the work done by me (other than machine work).

If I had to do it again, it would be LS all the way. That price tag doesn't include a fuel injection system. With TBI, you can only make a limited amount of power. For me, it was a $2500 fuel injection system or propane (which I ended up with because it's a trailered vehicle). I went with propane and it's great for a trail only rig, but if you drive on the street it would be a pain.

If you start with a complete LS motor (say, $1000-3000), you need some harness work and that's it. Tons of factory horsepower with easy gains to be made, excellent cylinder heads and multiport fuel injection system that you can get parts for anywhere. Any Chevy trans still bolts to it and they're a cheap adapter from bolting into any older Chevy system.

Honestly I'd trust a good used GM LS motor over a rebuilt older small block any day, the used motor is good, any rebuild is unknown. Even good, new (and or rebuilt) parts fail, I fought that a bunch. Typical LS engine life is 200K+, not something I'd be worried about.
 
38377k5 said:
The LS series motors are a GREAT choice and honestly unless you're looking for a $500 diy basic rebuild, I wouldn't go any other way.
Click to expand...

Where's the "like" button?

+1

The LS motors are an entirely different animal, I doubt you can match the efficiency of the LS with a SBC no matter how much money you spend. Well, at least within reason.
 
This is great. I'm glad there's a decent amount of enthusiasm behind this. I thought I'd get a few more people callin me a jack wagon. Haha. And I'm definitely not knocking the sbc, it's legendary, but i have to believe there have been technological advances over the past 50 years, that's all.


Ok that being said, does anybody know how easily I can hook the 4l60E up to my np208. I ask because if I can buy either a 4wd or a 2wd it'll be a lot easier to find a donor. I want to go with finding a whole rig so that I have the option of taking everything. Hell I'll probably take the a/c too.

And again, if anyone knows which setup will work best. I'm all ears.
 
Also if you guys know of anybody that has done this and threaded it I would love to get some links or some names. Thanks in advance.
 
I dont know how I missed them before but there are a couple 5.3 swaps on here. Lot of good information too.

Seems like most people go with the dirty dingo mounts and an adapter for the 4l60e to fit it to the transfercase. It seems that part is pretty straightforward.

Now I need to find a donor. Also might as well put that steering brace in when I take the engine out.

What exactly is flashing, will I need to do this when I'm done?
 
38377k5 said:
The LS series motors are a GREAT choice and honestly unless you're looking for a $500 diy basic rebuild, I wouldn't go any other way.

Having built my full roller Vortec headed 383 many years ago, you can buy a motor with aluminum heads (sometimes an aluminum block too), heads that flow better all around, with as much or more power AND factory (great) fuel injection for way less than you could ever build an older motor. The MPFI system practically costs what an LS engine with fuel injection does.

Seriously, I probably had $4K into my roller 383, complete machine work on the block, Vortec heads, intake manifold, roller cam, hypereutectic pistons, etc. It works great but that still had a Quadrajet on it, all the work done by me (other than machine work).

If I had to do it again, it would be LS all the way. That price tag doesn't include a fuel injection system. With TBI, you can only make a limited amount of power. For me, it was a $2500 fuel injection system or propane (which I ended up with because it's a trailered vehicle). I went with propane and it's great for a trail only rig, but if you drive on the street it would be a pain.

If you start with a complete LS motor (say, $1000-3000), you need some harness work and that's it. Tons of factory horsepower with easy gains to be made, excellent cylinder heads and multiport fuel injection system that you can get parts for anywhere. Any Chevy trans still bolts to it and they're a cheap adapter from bolting into any older Chevy system.

Honestly I'd trust a good used GM LS motor over a rebuilt older small block any day, the used motor is good, any rebuild is unknown. Even good, new (and or rebuilt) parts fail, I fought that a bunch. Typical LS engine life is 200K+, not something I'd be worried about.
Click to expand...

Almost exactly the same as what this guy said ^^^^
I think I have about $4000 into my 383 with aluminum heads and full roller setup. That doesn't include what what I spent on upgrading the tranny. If I did it again I think the 5.3L would be just to punny for me. Would need to have the 6.0L.
 
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