View Full Version : Engine choice

October 6th, 2006, 12:59 AM
Folks I am having a heck of a time trying to figure out which way to go on the engine swap for the YJ.

Have a stock 2.5 now.

Running the NV4500/Atlas with 3.0/5.13`s and 33`s

Typical Michigan wheeling. Maybe a once a year to Silver lake. DI and GG are far more appealing.

Stock 2.5 ? Hot rodded 2.5 ?

4.0 or perhaps a 4.6 stroker ?

Chev 4.3 V6 ? Or perhaps a SBC ?

Not looking to be the fastest one up the hill. Just a good reliable runner with the torque to do the job.

The SBC swaps I`ve seen thus far seemed to a bit of a hack job. Melting plastic overflow and windshield bottles, hard to reach plugs. Perhaps a bit too overpowered for Michigan trails ?

The 4.3 Chevy V6 seems like a good bet. Carries over a lot of SBC parts in a smaller package.

But then the 4.6 stroker makes as much or more power then the 4.3 and almost falls into place.

The stock 2.5 has taken most everywhere I wanted but it really does need a bit more grunt. Perhaps the 5.13`s will take care of that ?

I have available a 2.5 that has been upgraded with a cam, headwork, manifolds etc that seems to run pretty well but I hate to spend the money today and wish I had gone different (read bigger) in the future.

What are you folks running and what would you sugguest ?

October 6th, 2006, 09:51 AM
4.6 Stroker.

October 6th, 2006, 11:06 AM
To be honest, that 2.5L won't last as long with the abuse (literally) needed to get it to "compete" with a larger engine. As the old saying goes, there is no replacement for displacement. So, here goes a list/ wall of text for you and hopefully you'll be able to make a choice based upon my useless input (as well as others).

Pros: Already in place, with all of the mounts/ bellhousing/ wiring/ etc. Already have a "built" 2.5L available. Easy replacement, relatively good power for its size.

Cons: Have to spin the heck out of it to make any useable power. Characteristic 4 cylinder narrow power band, meaning that even if you do manage to spin it fast enough, you have to shift or bounce it off the redline.

4.0L (or 4.6L stroker)
Pros: Came stock in that application, so parts are widely available, both aftermarket and stock. Astonishingly reliable engine that can be beat to hell over and over again, yet still requires little more than regular maintainance. Straight-6 engines are known for their high torque output relative to displacement. It's not uncommon to hear of a 4.6L stroker capable of 300hp/350 torque, which is on par with even modern V8s.

Cons: Strokers are expensive, require additional machining, and require custom parts that often have to be special ordered. Would probably have to go to either a custom fuel injection setup or would need to "adjust" factory harness to fit the 4.6L. More power=more breakage down the line. When you wind up a 4 cylinder, often that is the weak point, so your "bulletproof" driveline will last. If you start throwing bigger bullets at it (more power), you start finding the limits of other parts REAL quickly. Sometimes as quick as the first throttle blip.

Chevy 4.3L
Pros: Shares parts with the small block V8, so parts can be found at ANY store (even meijer or walmart in some cases). Parts are cheap. Another reliable engine. Weak in stock form, but can be made to make impressive numbers on a relatively small budget. "Cool" factor of having a V-configured engine in a YJ. Ultra cheap and easy to find core/ rebuildable engines, often with complete harnesses and injection systems.

Cons: Custom mounts, custom bellhousing, custom harness, custom exhaust system. Luckily, this swap is so common that you can buy off-the-shelf "custom" parts to make it work. V-configured engines don't typically make torque as low in the RPM band as a straight engine, so you'll have to rev higher and plan your parts accordingly.

Chevy Small Block
Pros: Basically the same as the 4.3L. Parts are so common, you can get stuff for cheap/ free. Running parts trucks can be had for little more than a case of beer. Rebuilds cost about $150 (plus machining). Swap parts are cheap and readily available (depending on which engine family you choose. Does not apply to GEN III/ IV/ V engines). "REALLY COOL" factor of having a V8 in a YJ.

Cons: Too much power breaks stuff. Bellhousings are expensive. It's easy to mismatch go-fast parts on a SBC and make a horrible running engine. Other than that, same things as the 4.3L.

Forced induction (not discussed)
Pros: Mucho power. Superchargers can make up for a lack of displacement, as can a turbo system. Often will get the reliability/ driveability of a normal engine when not under boosted power.

Cons: Cost (might as well slap in a small block). Must run premium fuel. Expensive. Extensive fuel system/ ignition system/ wiring mods. Expensive. Increases parasitic drag on the engine (supercharger) or underhood temps (turbo). Expensive. Also…it's expensive.

October 6th, 2006, 11:07 AM
the benefit of a v6 or v8 is that it is shorter than the L6, so you can move it forward in the engine bay and get some rear driveshaft length.

With my 4.0/nv3550/atlas when I was stock wheelbase I ran about a 30" front driveshaft and 15" rear driveshaft. I'd imagine with a 4.3 you could move it closer to the rad and have a better shot at running closer to equal length driveshafts and not have to worry about rear driveshaft angles so much.

October 6th, 2006, 12:48 PM
drop in a fuel injected 4.0 and call it a day. its the easiest swap and it has enough power to get the job done. if you want more power then go with a sbc, i'd recommend the vortec.

October 6th, 2006, 01:37 PM
Unless you are planning on high horsepower stuff, as stated before, the 4.0 is pretty hard to beat. I have a sbc which runs really great and is awesome for wheel cleaning tire spinning and hill climbs like the dunes.

The flip side is that my son in law has a 4.0 that goes 99.9999% the same places as I do. He breaks less, burns half (or less) the gas and never overheats.

October 6th, 2006, 03:20 PM
I have a 88 YJ with a 4.3 vortec, 4l60e 231c trans with sye system in it. i used all the parts from a 93 S10 blazer. its not a power house but it is just fine. as Jim said you can move the engine and trans ahead for longer driveshafts. which i did. 2 inches. with the SYE and the move forward i have a 24" long rear shaft. My YJ had a 2.5 in it when i got it but it didnt last long. I checked into the rebuild and it was cheaper to do the conversion to the 4.3.... if you think about a sbc or a V6 you can buy a complete truck for the transplant as i did. maybe one that has been rear ended or sideswiped. keep all the wiring and parts you need. also i have the stock YJ radiator and i dont have any problems with over heating. i have 33" tires and true-tracs on 4.10 stock axles. they seem to do just fine. I do have a D-44, D60 and 37" tires planned for it in the future. the V6 will most likely stay in. it is nice to not worry about running out or gas. or over powering somthing. i was at GG this year and went everywere my tires would let me go. engine size was not an issue.

Ganz............ :D

October 6th, 2006, 07:16 PM
if you keep the 2.5l you probably will break less parts, its already there and running? the 4.3l v6 is real nice and easy to find, and usually injected. if you had a 4.0l lying around id go that way. other wise ream the piss out of the 2.5l till it grenades, then go 4.3l, just my opinion.

October 6th, 2006, 09:06 PM
Tremendous help my friends.

mitrail400ex, thanks for taking the time to show the pro`s and con`s of each.
And to all who have showed there helpfulness.

Did`nt mention that there is a retubed 8.8 that has been HEAVILY reworked in the rear and a HP D44 in the front. Lockers, girdles, trusses, chromo shafts etc. So power (if kept within reason) should not be an issue.

Based on what has been said here and a bit more research on my part has pretty much narrowed it down to the 4.3 or a SBC.

Talked to Advance Adapters and only a few parts will need to be swapped to retro-fit the Chevy. An extra bonus i had not counted on was moving the powertrain forward thus taking advantage of a longer rear driveshaft.

G&T, a local bone yard, has several flavors of low mileage engines. They come complete with wiring harnesses and sensors. The PCM and accs. are extra but still not a bad deal overall.

Then of course is the late 60`s 350 long block tucked away in the garage. Sure it needs a rebuild and may not run as nice as a FI motor but.........

For now, I will twist the tail of the 2.5 till she lets go. Then at that point there will hopefully be a replacement waiting in the wings.

Wish I could make the Mounds this weekend but a family commitment and prep for a major surgery on Monday prevent having the free time.

To all, the best.

John Edwards