To swap or not to swap...?

[ErikR]

Worn out AMC 258 i6 / 4.2l with a 5-sp manual. Trying to decide on the crate engine into which I want to dive. I'd love the power of a small block V8 but have no idea of the cost differences to make the switch vs sticking a stock, rebuilt AMC 258 i6 / 4.2l (as everything will match up. Just looking at Summit, and Jeggs, and SJ Engines I'm finding the following crate engines

AMC 258 i6 / 4.2l $1596 - $2172
350 $1899 - ??? for a GenI (I don't think I want to get more complicated with fuel injection/computers of a GenII or III) and would like to stay with my stock 5pd Transmission .

The problem is I have no idea what I'm doing trying to estimate the cost for a modification and swap from there. I fix people for a living and am maxed out with changing oil or bolting on a starter.

I know this is a very broad question to try and answer, but could anyone provide estimates/starting points on how to decide, and what the costs at which I'll be looking for a stock swap vs going up to the V8?

 

[cglax6]

Welcome!

Do yourself a favor and read as much as you can on Novak Conversions Home

There's a lot of good info there...

Short answer is you'll need to find the engine/tranny/xfer case combo that fits your build objective, your wallet, and your jeep. Be aware, adaptors can get expensive, but not typically cost prohibitive. Just depends on your budget.

Do a quick search for SBC swaps here and on the other forums.

I'm in the middle of a SBF swap and there's a lot of homework that needs to be done to plan these things...

Bellhousings, clutch assemblies, transmissions, xfer cases, adaptors, clearance issues, exhaust routing, motor mounts, fuel systems, etc.

Scroll through the build posts and you'll start noticing the things you need to think about and plan before you hit the go button.

I thought I did all my homework on mine before I started, and I forgot about height clearance. Turns out I'll be fine, but if the engine doesn't fit the compartment with the hood shut...no Bueno.

Sorry for not being specific to what you want, but these are things you need to think about before you pull the trigger.

Good luck!

 

[RiverandSand]

Welcome!

I have sbc in my 5, but I bought mine that way, knowing some of the costs involved. However the swap job wasn't the best, so I took it all apart and started over.
IF you are wanting to keep the T-5 stay with the six. It is a light duty car Transmission .

If you really want V8 and aren't a purist, you can't go wrong with a sbc, there are thousands of them around and parts are plentiful, unlike AMC V8s.

Same can be said for Ford lots of them, but some added research is needed mainly because Ford was a bit more complex in their combos.

As cglax6 has said Novak is a great site for swap info and parts to do the swap. My adapters are Novak as well as the motor mounts.

If you are planning to farm out the swap job, contact your local Jeep club to find a reputable shop to do the work.

Good luck

 

[gert]

The stroker 4.0 has great horsepower and torque and it’s a direct bolt in for the AMC 258 i6 / 4.2l I think it would be an easier cheaper swap than doing a Chevy/ford or dodge swap


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[Posi]

Welcome!
IF you are wanting to keep the T-5 stay with the six. It is a light duty car Transmission .

This

 

[mtnwhlr]

Something else is the running gear, if you go to a V8 the model 20 rear isn't going to handle the power and you will need to spend a lot of $ on it our swap to something beefier. I agree with gert on the 4.0 stroker. It's what I would like to do with my '84.

 

[caveman]

The stroker 4.0 has great horsepower and torque and it’s a direct bolt in for the AMC 258 i6 / 4.2l I think it would be an easier cheaper swap than doing a Chevy/ford or dodge swap


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I did the stroker thing and I love it. I went all out with my built. I farmed all the machine work out and assembled it myself. I've got about $3000 in it. It can be done for a lot less.

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[coldair]

I did the stroker thing and I love it. I went all out with my built. I farmed all the machine work out and assembled it myself. I've got about $3000 in it. It can be done for a lot less.

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Did you go with a long rod or short rod when you did your stroker?

 

[hole]

OP, everyone has brought up great points. My suggestion would be keeping it stock(ish). You mentioned your comfort zone working on your rig.The more you modify the harder it can be to work on because you need to keep track of whats what when ordering parts down the road. If your doing the swap you will learn quite a bit and save some money, but if your paying someone to do it it will likely get pricey quick. Paying someone to R&R a AMC 258 i6 / 4.2l for a AMC 258 i6 / 4.2l should be a lot less than a conversion.
What are your plans for your rig? How do you intend to use it? Whats your budget? The answers should guide you towards your final decision. Lots of great/knowledgeable folks here to help you with whatever you choose to do.

 

[caveman]

Did you go with a long rod or short rod when you did your stroker?

I really don't remember. I believe it was the rods from the 4.0.

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[caveman]

Did you go with a long rod or short rod when you did your stroker?

I just looked it up in the build book that I forgot that I had with me. I used the rods from the AMC 258 i6 / 4.2l .

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[cglax6]

IF you are wanting to keep the T-5 stay with the six. It is a light duty car Transmission .

Truth!

Based on what you said your comfort level is with working on your rig, I'd stick with the AMC 258 i6 / 4.2l .

Rebuilding may be a little outside of your comfort zone, but it's not as difficult as you might think. If you don't have an engine stand to work on or the proper tools, the investment will still be less than purchasing a crate engine. You have all the accessories, mounts, sensors, etc that you need. You already have the block and crank...take it to a reputable machine shop for cleaning, inspection, and machining if necessary. Get new bearings, rods, pistons, internals, and button her back up. The down side is that it will take more time, and you won't get a warranty that you'd get with a crate engine...something to think about.

There are a lot of good youtube videos out there, but I always recommend taking a look at Pete's Garage's videos. He has a set of videos for engine rebuilding...albeit for a 351w...but it covers a lot of general info and how to choose all the parts and pieces for any kind of engine build.

If you do a rebuild, no matter what route you take, it's good to keep a log book of what you purchased and where you sourced it. Makes it infinitely easier to fix anything down the road so you can use exact replacements. In fact, do it for anything you fix on your rig...you'll be glad you did. I have a written log book that I keep in a drawer of my toolbox and a spreadsheet on the computer.

I kept a copy of my 351w rebuild I did for my jet boat several years ago and I used most of that info for the build I'm doing right now. Glad I kept it because it saved me a lot of time researching parts again.

Let us know what you decide!

 

[ErikR]

Thank you to everyone for your input! Novak was an amazing resource and a great company with which to do buniness. I found a 350 from a suburban in immaculate shape (per my expert mechanic) and am replacing the Transmission and other drive train parts/harness/headers/etc. through Novak.

What started as a modest update has morphed into a frame off restoration. I have some pictures in the chassis section but will post a full accounting of my restoration in a new build thread. I even have a done time lapse video of much of the work, and will have a time lapse of everything going back together! The next two or three weeks is going to be very exciting!