swap or not???

yjmudder90

New member
I have a 5.7l 350 from my 99 tahoe that i am rebuilding right now. should i swap out my old 4.2l with ax-15 for the 350 or not??? if so, what all do i need to buy/do to make it work???
 
I did the swap in an '88 YJ, but used a carbed 350 for simplicity. Consider what you will do for a 'puter and wiring harness if you want to keep the FI, otherwise use a good carb that handles inclines well.

You will need a transmission and transfer case that can handle the 5.7L power, and best to find GM parts that will bolt up without costly adapters.

You will need conversion motor mounts, available from Advance Adapters. You will need a larger capacity radiator, I had a radiator shop rebuild mine from 2core to 3 core and moving the lower inlet to the opposite side. Top thermo housing requires a straight forward neck.

I reused the jeep PS pump, mounting to the v8 with an oem bracket from a fullsize GM van, had to cut one mounting ear off the bracket that interfered with the PS reservoir cap.
 

Depends on what you expect out of it when it's finished as well as how you plan to go about performing the swap.

I try to discourage as many people as possible from doing non-AMC V8 engine swaps into inline 6 equipped Jeeps. I've shut many V8s down with the AMC sixes I used to run in my CJs, and I even embarrassed a couple with my 2.5L YJ. The bigger engine has more potential, but if you aren't tapping into that potential, a smaller(yet more efficient) engine can make it look stupid. In my opinion, considering the wonderful torque curve of a healthy inline six, a V8 is a waste unless you plan to make some serious power up top.

I can understand wanting fuel injection, but you can add FI to the six cheaper than doing the swap. I can understand wanting more power, but you can make the six outperform most stock V8s cheaper than you can swap in a stock V8. I can also understand wanting the "coolness" of a V8, but then again, a cammed stroker inline with a split header and dual exhaust is cooler than any factory V8. If you want to make more power than the great inline can put out, stepping up to an AMC V8 is another option that makes more sense to me since you already have a six in there. Now that AMCS have gotten popular with the car crowd, parts are easy to get and making 400hp with an AMC 360 is a no-brainer... So, how much power do you want, and how much do you want to spend?
 
I love V8's! My Jeep has a 304 and it is so much more pleasing to the eye and ear than any straight six would be. My jeep is a factory V8, and I considered putting a Small block chevy into it myself. The Power, parts availability, and resale value will soar (assuming you do it right).

It's not all rosy, however. You can google "swapping a chevy
V8 into a jeep" or something like that and get TONS of info. I did the research, and decided against it for the following reasons:

1. Plan on the Jeep being out of service for at least a month or 2.
2. Plan on paying way more than you expect. This project will nickle and dime you to death. If you go with F/I, it will cost even more.
In short, my research taught me that you better be really handy with tools, have lots of help, a deep wallet, and tons of time on your hands in order to properly pull this off.

One other thing, at $3.00 + a gallon for gas, are you sure it is worth it?

If you do it, post some pics, I would love to see them!

Personally, I wouldn't have a CJ that wasn't a V8, but mine is factory, and it's only a weekend cruiser that I can afford to let sit while I'm working on it, and I don't need it for daily transportation.

Good luck
dave
 
That's how most people feel Dave. I'm the sick SOB that likes to pull up beside you in a similar Jeep, with what sounds like a pack of angry Harley Davidsons under the hood, and proceed to pull you by 3-4 Jeep lengths by the time you hit third. The bigger and lesser built engines are more friendly offroad, have better manners but still produce plenty of low RPM power... there is nothing wrong with a V8, my current CJ is a V8 and I wouldn't have it any other way.

One thing to note though, after dealing with both: You can make a MUCH better trail Jeep with a six than a 304, and it would only get pulled by a slight margin by the 304 on flat ground in a similar Jeep. With the parts available today you can build a stroker inline AMC 6 that would murder the low rpm output of even the gnarliest 304, and the 304s advantage in the higher RPM range is sort of limited in the real world by the fact that the bottom end likes to come apart over 6000 RPM. This is where I messed up with the one in my CJ now... the way it's built, it's a freakin grenade.
 

I would have to agree with Junkpile here...the main goal in off-roading is torque. Its not RPM that gets you over a rock or up the broken hill but pure torque.

RPM is for sand and pure mud where your looking for high wheel speed only.
Another thing here your not looking at is power to weight ratio. V8's are big and heavy, and the transmission needed to take a V8.
Another thing is the axles, The Dana 30 is not meant for V8 power and will grenade on you...its not a question if, but when.
Heck Dana 44's are not really meant for that kind of power either. A stock V8 can produce over 400lbs of torque and you mate that to 44's pushing 33's+ and one good slip to lock situation and your going to be spending an hour or two on the side of a hill gutting an axle.
Theres a balance here. Ask yourself what type of off-roading will I be doing.
Do I need high RPM's or low torque to crawl with.
Most of your off-roading will be done locally so gear your selection to that.
Ifs in sand or deep mud, drop in that 5.7L and throw that mud, but if its a mix maybe look into a 4:1 to go with that 5.7L
But if it is low and slow...torque is the king, low compression with long cylinder strokes will give your the ability to chase cats up tree's. And stroking a straight six and easier than a V8.
 
I'm sick too, I like my 2.5L that's been built a little. This after having a 350 in my old YJ. It's not ALL about displacement.
 
Now that the AMC fans have chimed in, I'll honk the chevy horn for a minute. My Jeep started life equipped with a 304. It later got a fresh 360 that had more power, but was a gas guzzling fool. I spent megabucks converting it over to TBI fuel injection and it was no better on power or fuel but would run on angles. Rocked that motor for a few years and ended up installing a chevy 5.3 from a 2001 truck. I have about $1600 in that engine and it is the best mod I have ever done to the Jeep. My 5.3 is only modified in the ECM and makes around 315hp, is good on gas and probably weighs less than a straight six (aluminum heads, plastic intake). Yes, you can build bigger more powerful engines than the 5.3, but I have never had a more powerful, responsive, quick to spin-up engine. Now that it is in there, if I ever blow it up, I can buy a used 90 day warranty replacement all day for $700.
Back to your 5.7. Are you scrapping the Tahoe or just saying you might like to put another Vortec in your Jeep? If the Tahoe is available for parts, then you can use the engine, wiring harness, ECM and 4L60E transmission together. I'm not sure if your YJ transfer case will bolt up, but a little research will net you the answer. Both used New Process transfer cases I believe, but not sure about the spline count and adapter.
There are companies that make motor mounts if you don't have the fab skills to make them yourself. You will likely also have to modify the cross member and drive shafts due the change in length of your drivetrain. ECM and harnesses can be tuned and modified to your specs by companies such as Affordable Fuel Injection, Wait4MePerformance and others. My harness and computer were done by Wait4MePerformance for $325. It was plug and play easy.
Cooling is another small issue to work around. I used my same original Jeep 3 core radiator with some creative steel tubing work and random radiator hoses. I used a dual 10" electric fan from a Ford Focus and the Taurus fan is another popular swap.
Here's the thing...you can put the chevy in there without destroying your axles, but it's going to require self control. If you think you may want to put larger axles, tires, etc on it in the future, then you may as well do the engine now.
 

RR, what did your 5.3L come out of? We've got one in our TrailBlazer and love it. A fellow club member put one in his CJ and it is a sweet mod. I think he added a performance cam and vette exhaust manifolds and likely a stock 'puter.
 
thanks for all the info guys. both sides have really good points and i guess i have some thinking to do. i have plenty of wrench and fab skills and a vast knowledge of doing 350 swaps ( one in an s-10 and one in a 88 toyota). I guess i just have to think about it and do what i feel would be best.
 
Dude told me my 5.3 was out of a 2001 z-71, but who really knows when you are talking salvage yard motors. The place is a chain called LQK auto parts and they sell the motors for $600 up depending on mileage. Chevy put them in nearly every truck/SUV application and some cars and SSR's have the all aluminum version rated at something like 325 hp stock. LQK had 20 something of the engines in stock at the time and that is why they are so cheap. There is some expense involved just like any engine swap, but once it is in there, I can use and abuse it knowing that $600 and an afternoon will get me another engine. Hardly worth even considering building one these days.
I did do one extra mod that is not entirely necessary but is nice. That was replacing the stock 6 quart pan with a 5 quart from an LS1 Camaro. It cost about $250 but shortened the pan 3-3/4" making it level with the TH400 pan. I worry alot less about damage than I would have with the 6 quart.
The harness, did not come with the engine, but a friend hooked me up with a factory harness. It looked like a bird nest and even had the taillight bulbs still attached. I sent it off with to Wait4MePerformance in Indiana and he modified the harness for $325 and took out all the unnecessary stuff and cut it to length. I also bought a computer from him since I didn't get it from the junkyard. The computer was $100 with programming included. I don't know the particulars of the programming, but told him it was going in a rockcrawler so low end power was desired. He tuned it to make about 315hp (up from 285 stock), took out the electronic transmission controls, speed sensor circuit and Vehicle Anti Theft System. It comes back as a 5 wire hookup and it's ready to fire.
There are some other little tricks to installing the heater and coolant hoses and temperature gauge, but the rest was a breeze..especially if you have a little fab experience for the mounts and such.
I was running an AMC version TH400 with Novak adapter to my Atlas. I acquired a Chevy Th400 housing and had my internals installed with some new packs for good measure. It's been in there for over 2 years now and beat hard with no overheating, no loss of oil pressure or anything. It's tight and makes me grin every time it fires.
Several buddies run LS1 motors which are similar platforms. The 5.3 won't hang in a drag race, but it holds it own on the trails. I can also run all weekend on a 15 gallon fuel cell and still have a few gallons left.
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I'm not really that big of an AMC fan rooster, I just know the potential of these engines. I'm actually a Chevy fan as far as cars go, and they have been churning out the best smallblock V8s since 1955...

The thing is, an engine can be setup a multitude of different ways to perform in different ways. Equip that old weak gas-guzzling smog era AMC 360 with a roller cam and lifters like the 5.3L, high flow manifolds like the 5.3, sophisticated computer management and multiport injection like the 5.3, a decent compression ratio like the 5.3, some modern (aluminum or not) or reworked stock heads like the 5.3, do all of the valvetrain mods that the 5.3 comes with... and you'll make much more power than the 285hp or so that the Gen III 5.3L put out stock. My AMC 5.0L makes as much power as your warmed up 5.3L, and the torque and horsepower curves are probably similar.

I'm not knocking the 5.3L at all though, if you can get them at that price and you did the conversion so cheaply, then you are doing the right thing. But also look at your rig... the OP here is rolling a stock YJ and asking if he should just drop a 350 into it. He isn't even set up to handle the power of a built inline 6 yet. My point in bringing up the AMC V8 swap was to offer an alternative to the more expensive swap at this time. If you just want a V8 in a Jeep, the AMC almost drops in place of the six, and around here a running 360 can often be had for $200 or so.
 
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