Piston Slap: Is 4.6 Liters of Juice Worth The Squeeze?
Phil writes:
My 1988 4×4 4.0L Jeep Comanche needs a ring job and the 2nd gear synchro is weak in its Peugeot 5-speed gearbox (with replacement no longer available). I figured I might as well stroke it and swap to the later Aisin tranny, but I am having trouble finding a shop with experience in this kind of work on Jeep XJs/MJs in the Dallas area.
The truck is a really nice, very original, 105k survivor, but I am not sure about the value proposition of spending this money.
Sajeev answers:
From what I have researched, you should absolutely do the Aisin gearbox swap and the 4.6-liter stroker in your rebuild. The question of it being worth the money is relative to your need to make a profit after you are done with the Jeep, and the time value of money. I don’t see either being a big concern for you, as the swaps seem readily available. Correct me if I’m wrong, but reading between the lines, the issue is ensuring you get them done with the right parts and by the right people.
I reached out to Hagerty’s own Davin Reckow and Ben Woodworth to discuss their efforts in creating a 4.6-liter Jeep XJ for our Redline Rebuilds video series. The wrap-up video is below.
You should watch the whole video, but the most relevant bits to this Piston Slap question are 64 minutes into it when Davin and Ben share their thoughts about the difficulty of the 4.6-liter stroker rebuild. But since these guys are my co-workers, I figured it’d be wise to ring them up, tell them about Phil’s situation, and get their candid feedback. So let’s start here:
“Yes its worth it, because we noticed the Jeep will now pull hills in 5th gear. It’s crazy, and it’s a very noticeable difference.”
– Davin Reckow
“It has a noticeable increase in the amount of torque when driving, which is sorta the point of doing a stroker. She pulls hard even in 5th gear. And she’s equally at home around town as well as 75mph on the highway.”
– Ben Woodworth
I asked Davin about the details (most of which are in the video above) and he verified that the work to install the stroker kit is “nothing special”, just prep the block as-is: There is no clearancing needed for the crankshaftas you might expect with a small-block Chevy. The AMC 4.2-liter crank has a different snout, but that’s a minor hurdle to overcome. To get 4.6-liters, you must buy the correct formula of AMC 4.2-liter and Chrysler 4.0-liter crank, rod, and pistons, but from there, it’s a bolt-in affair. (This is also documented in the above video.)
Davin also reminded me that there are plenty of stroker kits available online to remove the guesswork, but he insisted that everything in the video was purchased from Rock Auto. (A glance at their inventory suggests some items might be out of stock in July 2024, but part numbers are still given and might be sourced elsewhere.)
But wait, it gets even easier: Davin was going to add a higher flow fuel pump, bigger injectors, and an ECU re-tune, but none of it was needed to support their 4.6-liter swap. He did need to drill a small (1/8th inch) hole in the butterfly of the throttle body, because the new engine produces too much vacuum for smooth throttle inputs from idle.
One thing I’ve learned in my 15+ years of restomodding is that the less you need that diverges from factory engineering, the better off you are for a daily driver and/or a mild restomod. So my brief time with Davin on the phone was good news indeed.
While I am many miles from the Redline Rebuild garage in Traverse City, I am confident in assuming this torque monster 4.6-liter would be ideal for your needs in Dallas. The final question is probably at the heart of your concern: can you trust someone to do this for you?
Probably not. Instead, you must consider yourself a General Contractor, farming out tasks to specific businesses and making sure it all comes together in the end. Davin and crew wholeheartedly recommend Thirlby Automotive’s machine shop, as they made it work for Redline Rebuilds for multiple projects. They might be game to ship you one of these engines if you can’t find a suitable place in the DFW area.
The transmission is another pay-and-ship affair, and make sure you get everything needed before installation. From there a place like RockAuto will have all the ancillary stuff like hoses, clutch, water pumps, and anything else that should be replaced before the motor is installed. (Especially anything made of rubber!)
For me, this is a buy once, cry once type of deal: replace everything you can with high-quality, brand-name parts. If you are a shade-tree mechanic that can get these parts delivered to your home and get it all installed in a few weekends, that’s great! If not, you have another step: Performing a Google Near Me search for a good independent mechanic that specializes in older vehicles.
Google Near Me results will vary, unless you are my neighbor!
Or find a quality shop that at least tolerates them and works them between their usual rotation of newer, more profitable vehicles to repair. If that last sentence doesn’t make sense, going on a few “first dates” with local shops will make it very clear who will and will not be fair and pragmatic with your plan for a stroker motor and a transmission upgrade.
Keep us in the loop on how it goes. And for the Hagerty Community, what advice do you have for Phil and his Comanche?
Have a question you’d like answered on Piston Slap? Send your queries to pistonslap@hagerty.com—give us as much detail as possible so we can help! Keep in mind this is a weekly column, so if you need an expedited answer, please tell me in your email.
***
Check out the Hagerty Media homepage so you don’t miss a single story, or better yet, bookmark it. To get our best stories delivered right to your inbox, subscribe to our newsletters.
I have some solid advice: listen to and heed what Sajeev, Davin, and Ben have provided for you above. It all seems very solid to me. In looking it over and having had previously watched the YouTube video, it makes me wish I still have my 1990 4.0 Cherokee w/ 5-speed so I could tackle this very upgrade project. Although I was always quite satisfied with the 4-liter’s performance, it would be quite tired by now, and as long as I was doing a rebuild….
Now what I want is that little red Commanche pick-up in the picture! I’m like a kid in a toy store, really – I see something that catches my eye and imagination and “Oooo, I want THAT” is my initial reaction. Reality being, I NEED the truck in that picture like another hole in my head (and I just got a new hole up there, thanks to some recent surgery), but – and this is where all car guys and gals will nod in agreement – “want” and “need” seldom intersect in a logical manner when it comes to vehicles.
Yeah I’d take a 4.0L Cherokee or Comanche any say. Greta motor for that truck.
The truest statement ever spoken- OEM is so much better than aftermarket (mostly). Trust me the Chinese wheel bearings from (fill in the blank auto parts store) are not, and I repeat “NOT” just as good as OEM. Not only that but the havoc coming from a failed component is little consolation when it results in a block that has an “unexpected” window due to a failed rod bearing or the fact that those cheap valve springs have let the valve hit the piston and destroyed a motor. 400 crank in a 350 block- a 383 and a cheap and easy way to make it happen for another axiom- “there is no replacement for displacement”. Nice article but personally I would go for a 4.8 LS and a 4L60E and call it quits- $1500 plus or minus (there is always a plus when it comes to modifying cars) and you have a much better deal in the long run. Real cost (assuming a good running wrecked Tahoe or 1500 series with either a 4.8 or 5.3) $5000-$6000 so maybe 2X of the work on the 4.0 to 4.6 but in the long run much more performance and lower maintenance costs.
Can you support the “much more performance and lower maintenance costs” statement with some data?
I find some confusion in reading your opening – “OEM is so much better than aftermarket” and then following up with an encouragement to trash the OEM powertrain in favor of using non-OEM stuff (GM LS materials are not OEM to a Jeep). I’m not dissing your idea, I’m just curious how you support your claims.
You might be able to do just a simple injector swap instead of getting bigger injectors. IIRC, the Chrysler SOHC/DOHC 4 cylinders use a finer spraying version of the 4 liters injectors, and bolt right into place. College mate of mine bought some junk yard injectors, put it into his XJ, and his fuel economy about doubled!
I did that on my Fox Body Cougar, adding 2004 Mustang GT injectors: the pintle at the end of the injector had four holes instead of one and is apparently a way better design, but fuel economy never changed for me. Your mileage will vary on this upgrade.
I built a 4.6 stroker in my 92 XJ I years ago. Was awesome! Torque was great. Mine was running the auto AW4 transmission, 4.5” lift and 265/75R16 KM2 tires. It was strictly a trail rig for me, but I always drove it to wherever I was going. With the stock 3.55 gears I still would get 19ish mpg. After I put in 4.56 gears the mileage dropped to about 16. I put 24 pound per hour injectors and nothing else. Ran great. I put about 20,000 hard miles on it when life changed and I had to quit rock crawling.
It did create a lot of heat though, too many cubes for the tiny XJ radiator. I ended up cutting vents in the hood to help. But over 95 degrees ambient, and it would overheat under any kind of load.
This is all relevant and good info and I’m amending my advice (in a previous comment) to Phil to: “pay attention to what Sajeev, Davin, Ben, AND 1st gen Fbird are saying”. 👍
I see no mention of why more torque is a requirement. In my opinion, “I mightt as well” is never a good reason. The 4.0L makes pretty good torque stock. I debated stroking the 350 in my Nova, very simple and inexpensive, but decided against it since the advantage is torque, and the disadvantage is less fuel economy. Throw in what you don’t know about changes required to support the additional cubes. If speed and pulling trailers and torque is your deal and you have bucket of money to spend, then by all means, go for it. But if you just need something to poke around in, leave it stock.
Dean, I have personally ran a stroked 4.0L Jeep to a 4.6L in an 92 XJ Cherokee. and a stroked Chevy 350 to a 383 in a 69 3/4 ton pickup. The Jeep got better fuel economy across the board. The Chevy got better fuel economy when I drove it normally, or towing. When I hot rodded it, the 383 could burn more fuel than the 350.
Here’s the reason, with the torque, the engine was always at a lower load. It took tiny amounts of throttle to get up to speed and maintain speed. Especially true in the mountains where I live. With the stock engines when you hit a hill you’re giving it much more throttle to maintain speed, and working the engine much harder.
My Jeep was lifted with big tires, so the 4.0 was taxed more than something stock. You might see a small reduction in fuel economy if the Jeep is bone stock.
Thanks for the input. My garage is suggesting tearing into it and seeing if the piston walls need to be bored or if a simple ring replacement will do. If lucky with the cylinder walls, forego the stroker for a more aggressive cam which should result in notably improved performance. If the cylinders need to be bored out, add the stroker kit. Any thoughts?
DUB6, an alternative would be for me to graciously indulge your wish to take on this project! Let’s talk!