It's time for a transplant

If you’re reading this, you are probably considering swapping a V8 into your Jeep CJ or YJ. I’m lumping the CJ and YJ together because they are so similar. I did my swap in a CJ7, but most of the information will apply to a CJ5 (Post 1976) or a YJ (1987-1996).

My goal in this set of 3 articles is to tell you about my swap and what it was that I learned. Hopefully this article will help you through some of the stuff you normally don’t read about. I can’t promise I’ll cover every problem you might run into, but I will certainly share what I had problems with and what was a surprise to me.

Reasons to swap in a Small Block Chevy (SBC) into your CJ5, CJ7, or YJ.

• POWER. Mild modified inline 6 = 175hp, mold modified V8 = 400hp. Nuff said
• WEIGHT. The Jeep 258 engine weighs approximately the same as a Chevy small block with iron heads. Use aluminum heads, and you are even farther ahead. .
• Weight balance. With the 258 engine, the Jeep is very nose heavy, not a great balance. Because the V8 is a shorter engine, the weight sits farther back into the engine compartment, balancing the weight better. This also gives you the advantage of more clearance to the radiator, depending on your accessory setup.
• Fuel economy? OK, neither the 258 or the V8 are gas sippers, but if you can have double the horsepower for the same (or even slightly better) fuel economy, why not?
• Parts commonality: You can find SBC parts at just about any parts store anywhere in America.

Engine choices:

The specific engine I am talking about here is a mid-60’s to late-90’s SBC, which came in variations from 305 to 427 size blocks. Your focus should be on a 4 bolt main block, which is much stronger and gives a better platform for more power should you choose to up the power even further. The cheapest and best choices are 70’s and 80’s Chevy full size trucks, but LT-1 fuel injected models can be found in old Corvettes and some Camaros and Firebirds. Even police surplus and granny cars are decent choices (Caprice, etc). All of these small blocks should have the same basic block with same threaded holes for engine mounts, heads, and accessories. The beauty is that there are so many parts out there for millions of SBC engines, because they are all basically the same! There is little question that fuel injection is an excellent option due to fuel economy, ability to handle angles when off-road. But don’t overlook carbs. Carburators are cheap, easy to tune, and can produce lots of HP. Carbureted engines are a much easier swap too since there is no electronics, harnesses, or sensors to deal with. I decided to go the carb route, and swap in fuel injection in the future. That made my swap less complicated, and less costly now. Lets look at where you might buy an engine:

• U pull from Junkyard (lowest cost at $200+). Low price, but high risk. Pull all the sensors and accessories if you can
• Already pulled from a Junkyard (around $1000 with FI). Usually there is some guarantee of the engine running, and it’s already pulled. Make SURE that you get all of the sensors, wire harness and computer if it is FI, and get as many accessories as possible.
• Ebay. No kidding. I almost bought one off Ebay. I found an LT-1 with 30,000 miles, fully polished and chromed, with 350HP, for less than $3000. Again, look for a warranty or guarantee of operation of some kind. TONS of machine shops fill empty time by building engines (SBC being the most common by far) and selling them on Ebay.
• Local engine rebuild shop: Price varies on options and horsepower, but most shops usually have a warranty.
• Someone selling their engine out of their vehicle. This is what I did. My friend had a CJ7 with this healthy small block, and he was moving to a big block. I could see it run, check compression, and test drive it.
• New Crate engine: Cost is usually much higher at $3000 plus, but you get a warranted engine, which is usually a complete package that someone has spent some time on to make sure it’s correct. In the case of GM performance parts crate blocks, they have gone through extensive testing for durability, and the components are properly matched. The GM Performance Parts Ramjet350 is a great option in that it puts out 350HP, 350ft-lbs of torque, is VERY easy to wire up (almost as easy as carb), and comes complete. This was my 2 nd choice if this SBC had not become available to me.

In the end, what you decide to get depends on how much HP you want, your budget, and how much work you want to do before you install the engine.

Transmission:

Manual or auto? Use your existing transmission or swap in new? Many good questions. The manual T-4, T-5, and 999 auto transmission will not stand up to V8 power for very long. You should strongly consider swapping in a stronger transmission. Some of the adaptor companies do made adaptors for these transmissions, but don’t do it, you will sorry later. Your first choice would be a transmission that bolts up directly to an SBC. I’m not a manual transmission guy, so you’ll have to research those options. For automatics, a TH350 is a great choice. Kind of like the SBC of transmissions (cheap, strong, parts everywhere). This was my choice. I bought it locally from transmission builder for $450 with some upgrades to handle up to 500HP. You can likely find one in a swap meet for less than $200. If you want to take a chance, you can get one from a junkyard for as little as $40

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TH400 is another option, but it is longer and heaver. If you need overdrive, look into the 700R4 or 4L60E (same tranny, but 700R4 can me mechanically controlled). Be prepared to spend $1000+ for these two transmissions (on the conservative side). Make sure you get the 4wd model of any transmission (2wd does not have the right output or tailshaft typically and have to be swapped out at added cost).

Depending on your transmission or transfer case choices, you may need an adaptor from your transmission to your transfer case. I have a Dana 300, so I needed an adaptor to my TH350. The good thing is that the TH350, and 700R4 both have the same transfer case bolt pattern, so I can switch to 700r4 pretty easily in the future. Advance Adaptors, Novak, JB conversions are a few of the companies I know of who make appropriate adaptors. After first choosing an off-brand (not listed) and having just too many problems with it, I chose JB conversions adaptor. It is TINY (1.5” thick), and includes ability to clock the transfer case. Very good quality.

Drivetrain:

Can your drivetrain handle the new power? If you have unmodified Dana 35 and AMC20, the answer is probably no, but that depends on how beefed up they are, if you have lockers, and how you drive. I swapped in a Dana 44 in the front, and Ford 9inch in the rear because I knew I would be putting in a V8 someday. I still have the stock driveshafts, but we’ll see how that goes if I need to upgrade. I have heard of people with V8’s keeping their stock axles, but in most situations, you’ll end up replacing parts often until you beef up.

Budget:

I could have started the article with this, because this is usually the biggest deciding factor in any swap like this. You have to plan down to every detail to get close. Most articles I have seen about swaps say “come up with an estimate and double it”. That’s not too far off, but I think you really need to plan ahead on AS MANY of the small details as possible. For example, here is my detailed list. You SHOULD make one yourself, and look at catalogs or online for actual prices.

ACTUAL costs:

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