• Project ‘Big Green’ 1985 Chevy K10: What Should We Do for an Engine Swap? [Poll]

    1985 chevy k10 big green engine swap
    1985 Chevy K10 “Big Green”

    The 1985 Chevy K10 “Big Green” project truck is moving right along. We love the way the truck looks, but the power and sound do not match the mucho appearance. Simply put, Big Green is currently just too quiet and too slow.

    Under the hood is a Chevrolet 305 cu-in V8, which (when new) produced around 165 horsepower and 250 lb-ft of torque. That was almost 32 years ago. “Big Green” was originally sold in Colorado, so the carburetor was jetted for high elevation. We use the truck at over a mile above sea level, where there is 17-25% less air density than at sea level. Needless to say, the truck is not quick.

    The truck spent the last few years as a hunting rig, and the restrictive exhaust system is way too quiet. Other than that, the truck has the SM465 manual transmission that sends the power via the NP205 transfer case to 10-bolt front and rear axles. The truck has a four-inch lift and rides on 35-inch tires.

    The truck really needs fresh power and a healthy rumble. We are looking at the GM Performance Parts crate engines for a possible swap. How much power can the driveline in this truck handle? Do we go for fuel injection or a carbureted motor? What about the transmission options?

    Keep in mind, that we already spent just over $6,000 on the truck, when you consider tax, registration, insurance, and a couple of spare parts. We do not have a giant budget for this project. We cannot throw in a giant brand new motor into this thing and redo the entire driveline.

    There are many questions to answer, and we hope you can start it off by providing your feedback on the engine swap. At this time, Chevrolet has 61 crate engine options, not all of them are “turn key” packages.

    Please add your input in the poll below and in the comments section. Thanks!

    Andre Smirnov
    Andre Smirnov
    Andre Smirnov is an Automotive Enthusiast, Producer, Reviewer, Videographer, Writer, Software Engineer, Husband, Father, and Friend.

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    95 thoughts on “Project ‘Big Green’ 1985 Chevy K10: What Should We Do for an Engine Swap? [Poll]

    1. Stand the world on its head!

      “Drop in” a crate motor 3.5 ecoboost from Ford Racing. The sheer volume of hate will put TFLTrucks at the top of the charts for Internet traffic among automotive websites. Just think of what you’ll be able to charge for advertising spots!

      I’m sorry, but your other choices on the list have been done so many times it’s just boring.

      1. I doubt they will be able to do it(probably beyond the budget for the project) but I like your thinking.

        1. At least at that HP your other weak links in the system might be ok. Get a boost regulator to maintain boost pressure in all atmospheres. Maintain 20psi boost no matter where you are.

          Running up the gauntlet on those 35’s might prove to be a challenge however. It develops nice torque at low rpm throughout the rpm range peaking at 295ft-lbs. Would be a great choice if you want to keep the stock drivetrain otherwise a bit underpowered should you change the drivetrain.

            1. That’s not true. If they are set at 6psi boost without a gauge regulator than you lose the atmospheric pressure as you go up in elevation.

              In Colorado you only get about 12psi atm boost compared to 14.7psi at sea level. You lose 2.7/14.7= 19.3% of your HP from boost alone. With 6psi added boost you lose less HP 2.7/20.7= 13% of your HP. With a gauge regulator you can keep it at 20.7 if that’s what you want no matter what the atm is as it will spin faster to produce more boost in low atmospheres. Not all engines have the regulator for boost.

            2. Yeah, you can only spin a turbo so fast, and its speed is dependent on the pressure ratio, not the actual boost value. At 3:1 pressure ratio at sea level is ~29 PSI of boost, but a 3:1 pressure ratio at 11,000 feet is like 22 psi of boost. You would have to spin the turbo beyond its limits to maintain the same boost.

            3. Barometric pressure and Manifold pressure are two different things. Manifold pressure is tied to Barometric pressure in a naturally aspirated engine. At Wide Open Throttle the map sensor will only see the available barometric pressure, 14.7 at sea level and dropping with altitude. The less dense air cannot support as much fuel and the power drops.

              The same effect occurs with a supercharged engine, less dense air = less power.

              With a turbo, the turbine wheel is free to spin as fast as drag allows it to. Thinner air means the compressor wheel can spin faster with the same amount of exhaust back pressure. The faster spinning compressor wheel effectively forces the same volume of air into the intake regardless of barometric pressure. That’s a big part of why turbo motors dominate at high altitude.

            4. Jay – That applies to superchargers, that are mechanically locked at a particular ratio to engine speed. Turbos can “freewheel” to much higher speeds when necessary. Granted, they are still subject to the laws of physics and they (mainly the bearings) will self destruct at a certain point, but there is usually a substantial amount of cushion in the design.

            5. I would sure like TFL to dyno a 3.5EB F150 in Colorado where they tested the Raptor to see how much power it retains in that altitude.

        2. Andre I think you should go with a Ram interior package with the Ford 2.7EB motor. Give Big Green a double meaning.

        3. If GM is sponsoring, go for the turbo 4! It can’t sound any worse than the Raptor 😀 😀 😀

      2. Well Danny boy you can buy your great 3.5 echoboost , or have ford donate an engine . Last I checked gm was going to donate the engine not u or ford

    2. 350 = cheaper and easier to install
      LS = More power, Lighter, quieter. will require more parts to install into older vehicles.

    3. I agree with Yama… more a question of how much money do you want to spend… I’d either go for a 5.7 or a 6.0 l swap. What’s the budget?

    4. I’d either go with the injected 350 or look at a newer 5.3. They both will be good matches for the power train– not likely to tear something down line apart but will add a boost in power a more modern touch the next buyer might like.

    5. Are you going strictly off the list? Then I’d go 350. know I’m a couple time zones away in Northern Ohio, but Summit Racing has a lot of different SBC engines.

        1. Double oops. The 427 RPO code was LS1? I just know pre gas ration Chevys were better than the current choked down models.

    6. Why not modify the existing 305? I think that would be more interesting than dropping a new crate engine in.

    7. Junkyard 8.1. Most likely can be had for pennies on the dollar when compared to the popular LS series engines everyone wants for a swap. Chevy parts are easy bellhousings the same etc. Plenty of torque and low revving (Most shift at 4800 rpms). They last a long long time. Pick one up with some miles on it, have a local shop recon the injectors, re gasket it all, toss on a new water pump and you are in business for a long long time.

    8. Even a 330HP motor is likely to break driveline components on that old truck if used for off-roading while running 35″ tires.

      Typically buying an old pickup with plans to up the horsepower requires a careful thinking of what other components down the line might break as result.

    9. The 427 is the best drug of choice in the V8 realm. I would supercharge it for sure and see about getting a boost control unit that regulates gauge pressure so you don’t lose HP from atmospheric pressures in Colorado. You will lose a bit on air density but minor if you can regulate the boost pressure.

    10. If the existing 305 is in good shape, just beef it up for some extra HP/TRQ. With the money saved, you could add a selectable lockers in both the front and rear. This assumes off-road capability is a higher priority than HP/TRQ.

    11. as long as your willing and able to
      spend the money for a brand new motor. I would go with the ram jet injected motor. good power, but not enough to kill an old drivetrain (unless you drive like an idiot). it will also give you the low maintenance and reliability of an injected motor. I remember all the tune-ups and “carburetor fiddling” we had to do–I don’t miss it! what’s the worst case scenario, you install the new motor and the truck turns out to be a big money pit. you can remove that “new” motor and put in in your next “GM project car or truck”.

    12. Just freshen the 305 up. Add a few performance goodies.

      It would be funny on the shear volume of hate and coverage across the WWW you would get if you went and got a 3.5 ecoboost and stuck in it. That swap would likely catapult you to the top of the internet truck world with the Hate and Love it would attract.

    13. I love technology. I say a GEN IV or, heck even GEN V (pretty sure they Holley has swap oil pans already, and there are swap engine mounts too) truck engines could be had relatively cheap, again, it all depends on what one considers cheap and/or reasonable. LS3 EROD if you need the C.A.R.B. E.O.#, hands down. Of course with a swap to newer technology, you always have the ancillary equipment that could add up, but it is 2017, it is not 2007 any more with these types of swaps where items are hard to find or little knowledge. Many will indicate a “me too” demeanor on Gen IV etc. swaps, but if you don’t want to mess with carbureted engines, that would be the direction I would go.


    14. Swap in or modify depending on your budget. Yeah, a simple carb’d 350 is boring, but it works. A LS swap is more exotic and will work better in your elevation but will cost more. Maybe a fuel injected edelbrock engine package on a GM goodwrench 350 short block will be a better, simple, reliable choice. Im in the same dilema except have to deal with Calif. emmisions on my 1994 TBI big block 4×4 Suburban.

    15. 69 thru 72 truck block 396 or 402. Plentiful enough, with a tall deck and smaller valves with round (not square) ports. It’s an engine that has tons of smooth usable torque down low. Get a little rpm into it and the mechanical four barrel will rocket you down the road.
      If you’re going with a carb, get one with quick and easy jet swaps.

    16. NP205? Are you sure about this Andre? Every K10 I’ve seen from that era is running an NP208 T-case.
      As far as engine goes, is there anything mechanically wrong with it? If so I can understand the desire to do a swap but if it’s just a little tired I would give the old girl a refresh. Much cheaper unless you’ve got a donor motor already sitting there

    17. A large block Caddy engine would fit in like it grew there, is only slightly larger than a small block chevy, and considerably less weight than a big block chevy.
      Available at a junk yard near you, either the 460 Cu In or the Eldorado 500 C.I, would give you a torque monster that is one of the smoothest V8 engines around. I know of a fj90 series LandCruiser with the 500 and it is a jewel. The owner says he has used it at Moab, and had so much low end grunt that he never had to use low range in his transfer case. The torque curve is flatter than Kansas and peaks at around 3k rpm.
      Besides, think of the cachet of owning a Chevillac truck!
      To put in a small block is really a boring idea while there are still a lot of these engines available. You should be able to do it around $4500.
      Good luck!

    18. I would install a 6.0L LS engine as they are readily available from salvage. You would have to install ECM’s and you would probably have to find a 4l80E transmission, you would also have to put in custom drive shafts, but there a lot of shops out there that could install all the computer components for you. If that’s to costly I would go with a 383 stroker crate motor and a turbo 400 transmission that’s built to handle it. You could call monster transmission and they could probably even sell you a built 700R4.

    19. L92 from a GM truck. Same block and heads as an LS3 but less sought after.

      Either that or a GNX 3.8L Turbo. It would probably bolt right up to the transmission.

      1. The 3.8 wouldn’t bolt right up because its a 60 degree block and a gm small block like the 305 is a 90 degree block this means that the bolt patterns are different.

    20. Keep that great 4 speed stick with the granny low and add an overdrive for the highway. If it were me I’d just get a good 350 Goodwrench carbureted 350, plenty of power and nice and dependable.

    21. my brother bout a new truck in 1978 it was a GMC step side truck with a stock 454. that was a nice motor it had grate pick up and top end but it was bad on fuel.

    22. A turbocharged lsx 454 would be pretty sweet or a turbocharged 6.2 ls I lean more towards the 6.2 though they are killer engines and they can easily make a modest 650 to 700 hp.

    23. Are-you kidding me…..It is now or never anymore calls parts sponsor the engine as to be a Chevrolet Performance’s HT502 crate engine is an affordable alternative with more power and greater durability.Do it ONE time and do it right, this generation is done GO BIG BORE it is last chance to do a “mise a jour”oh sorry put the real thing enought engine bay space YOU HAVE A chance of taking the time to get some sponsors big block, dinausore with dinausore 502 best cheap built up shure power, It is alway there with a 502

    24. If you want more noise just drill some holes in the muffler or remove it. Since you’re replacing the engine anyway and you’re bored why not hook a NOS system to it. You’ll most likely kill Big Green but you’ll have fun doing it. If you want a bit more power and torque and don’t want to break anything go with the Ram jet 350.

    25. I saysay you got 3 opions…an LBZ Duramax, an 8.1 and supercharge it! Or a supercharged 4.3 from a typhoon or cyclone

    26. I say you got 3 options…an LBZ Duramax, an 8.1 and supercharge it! Or a supercharged 4.3 from a typhoon or cyclone

    27. I think the HT502 or the 502HO would be great to put in your truck also both similarly priced to your listed options.

      1. I agree, the 502HO would be great in that truck. It makes 461 HP and almost 560 lb-ft of torque, according to GM’s website. Dosen’t need a computer(unless they plan on fuel injection) and runs on pump gas. A simple reliable pushrod engine with plenty of power.

    28. 2.0L turbo mine has from the factory tune puts out 340lbs of torque plenty for that truck. Should have been an engine option for new colorado.

    29. Gm performance 350 333 hp.for low budget easy swap if you want a more powerful reliable engine go with the ls3 6.2 I have one in a 2010 sierra 1500 4×4 it has lots of power and trouble free

    30. Assuming you are going to leave the other drive line components as is my first thought was a GM Performance high torque 383. If you are going off road fuel injection is a plus so bolt in the Ram Jet 350. This should be compatible with the other accessories and comes with it’s own plug and play ecm. Great engine with plenty of power, I had one in my 1989 2500 Suburban.

    31. high torque iron head 383

      if the truck still has a 3 speed auto, consider a 4 speed with lower 1st gear and overdrive.

    32. There is a reason that LS motors are the most common swaps around. LS motor with a 4L80E will be bullet proof and offer plenty of power.

    33. I like the 6.2 liter that they put in the Denali. Has 420 HP. Put a set of long tube headers and a Corsa exhaust system.

    34. I was an 80s kid that had a special affinity for the 305 that was in my brand new Monte Carlo at the age of 15 so I vote staying close to original and going with a high output 305 crate engine! 😬

    35. My favorite simple formula for one of these is a 383SB with a 90’s TBI- not a ton of power, but its simple, reliable, simple, cheap, simple, and makes lots of torque. Did I mention it is simple.
      Otherwise- go big with a Vortec 8100. Its a little more complicated, but those things are awesome. Keep the Sm465/205 for sure.

    36. 5L Coyote from Ford, that will wake up that little truck. LMAO at the 305ci. That makes a great paper weight.

    37. I’d go for an LQ4, or LQ9 matched to a 4L80. There is so much you can put these engines through, and it doesnt take serious mods to up the power on them. Im excited to see what you end up doing. Good luck!

    38. Like many others, my vote is to rebuild the existing motor, unless GM is donating a new crate motor. Doing a rebuild will give you a series of stories to hook your readers and keep them salivating (old magazine trick).

      Balance and blueprint the motor, extrude-hone the ports, have a good carb wizard fix up the intake side of things with a nice 4bbl unit. Go with small primaries to enhance off-idle throttle response, go with an RV cam for low-end torque (needed with the 35″ tires), small-diameter pipes (intake and exhaust) to keep torque down in the lower rpm band, and give it a smooth growl.

      You may need to beef up the clutch, depending on final power output curve.

      Remember that smaller wheels will give you much better torque to the ground, also, if they are not needed for ground clearance (although appearance will be degraded in most off-roaders’ eyes). Tires are your biggest factor in traction capabilities….match them to your intended use.

      If $ were no object, then yes, go for a turbocharger for full power at elevation, or better yet, a turbo diesel (but may need to upgrade clutch pressure even more). If you chase the high-HP ghost, I would consider a NASCAR-spec 355 crate motor (except I might go with the Mopar version as it has superior valve train geometry).

    39. Hey Frank, those of us that built those paper weight 305s in the 80s might disagree with you. I just think enough is enough when it comes to power for a 30 plus year old truck with a suspension that likely isn’t built to handle this modern day power. Of course this would be a great excuse to totally mod the suspension so I’m all for that! I do agree that the 305 is limited compared to several me of the mentioned engines but done right it can be more than enough, depending on how we define enough.

    40. Keep stock 305. These engines may be boat anchors, but over the years many people have gotten big numbers for a little money. Use a TPI system from the 3rd gen Iroc Camaro. Add a cam, tune, and vortec heads. Will easily make well over 300hp for next to nothing in cost. Friend of mine has done this, worked great!

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