Car Craft
Click here to find out more!

Swap A New Hemi Into An Old Mopar

Thanks To Growing Aftermarket Support, It Is Easier Than Ever To...

By , Photography by Courtesy Inertia Motorsports, Courtesy TTI, , Courtesy Bouchillon Performance

First off, here's the good news: The block drops right into place. Yes, with a simple pair of adapter plates bolted to the block, a new Hemi engine will go into any old Mopar muscle car. However, the problems start piling up when you begin to add stuff to the block--you know, essential things like an oil pan, headers, a cooling system, wiring, and a transmission. OK, this swap really isn't easy, but Mopar guys are always up for the challenge (pun intended). Anyone with a Summit catalog and a telephone can build a Chevy, and the Ford guys have it pretty easy, too. But die-hard fans of Ma Mopar are more like pioneers of the Wild West. They need to do more of their own engineering because there simply isn't the volume of parts available for their cars. Now, say you want to do something crazy like swap a new engine into your old Dodge or Plymouth, and you're really asking for trouble.

The new Hemi, referred to as the Gen III, has been around since 2003, and as more engines become available at lower prices, more guys are considering this swap. As more people do the swap, more parts become available to make the job easier--and the business of new Hemi swaps is literally exploding. We spoke with several companies that are making parts needed to adapt the newer engines to A- B- and E-Body Mopars with a minimal amount of frustration. Mopar freaks, pay attention. We'll give you the rundown.

Gen III
The new Hemi first appeared in the '03 Dodge 2500 and 3500 fullsize pickups as a replacement for the Magnum 5.9 (360-cid) engine. It displaced 5.7 liters, and even though the figure should be closer to 350 ci, Chrysler literature often lists displacement as 345 cid, for marketing purposes we're guessing, because the horsepower rating is 345 also. Coincidentally, those figures (345/345) are the same as the '57 DeSoto Adventurer, the first domestic mass-produced engine to make 1 hp per cubic inch as the standard (nonoptional) engine.

In 2004, the 5.7 was an option for the midsize Durango pickup and made its first appearance in passenger cars with the '05 Chrysler 300C. In the '05 model year, a bigger-bore 6.1 (372-cid) version was launched in the SRT8 versions of the 300C and Jeep Grand Cherokee and was subsequently rolled out into Chrysler's other models as more SRT8 versions were developed.

To Swap Or Not To Swap?
The new Hemi is a cool engine that is better than previous Chrysler V-8s in nearly every way. It weighs less, is manufactured to tighter tolerances, is more fuel efficient, and has greater output per cubic inch. In fact, the 6.1 Hemi has the highest power-per-cube rating of any Chrysler engine to date. Knowing that, who wouldn't want one of these in his car? Of course, the resto and Concours guys won't, but the dude looking for reliable, tunable, modern performance wrapped in classic sheetmetal will find this option irresistible. JR Bouchillon of Bouchillon performance says he's sold more new Hemi engines than any other engine his company offers. And his is a family-owned, Mopar-specific business with a 40-year history.

So is the new Hemi right for your project? Old-school guys will say no, and we can appreciate that. The new engines lack the fist-to-the-gut impact of a Six Pack 440 or 426 Elephant Hemi. Plus, the new Hemi swap is by no means a drop-in, weekend job, so you're looking at hours (or years) of work or big bucks to send your car to a shop. Even if you do the job yourself, it won't be cheap. Among other things, you'll need a number of custom parts, new adapters and fittings, a revamped fuel system, and all the electronics to run the engine. If you are down with all that, the trade-off will be "a 425hp engine that gets 22 mpg that you can drive every day," according to Jonathan LaPaglia, who was one of the early adopters of the swap, dropping a 6.1 into his '73 Challenger. He speaks with authority, too. He did the swap himself, and he drives his Challenger every day.

Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!
55 comments
Scott W. Marek Sr.
Scott W. Marek Sr.

Love all the cave man comments......you guys can have all the big cams,carbs,4.00+ gears and oh yea.....Only 3-4 speed trans.....I'll take FI,computer control,6 speed trans.....And drive it whenever I want on pump gas....And go just as fast.

Jeremy Yocum
Jeremy Yocum

Great idea. These new hemis are wicked and make great power. More than those big blocks of the past. Save some gas and haul even more ass.

Ray Kyle
Ray Kyle

Want a new hemi, buy a new Challenger. Got a classic MoPar, stay classic. Don't become the Chrysler version of the LS monolith at GM. Bo-ring!

Jim Gillgam
Jim Gillgam

Voo Doo and Doo Doo... Don't touch a classic Mopar with all that tech crap. leave that for the new plastic cars like the new Dart... Cut those up all you want.

Carroll Smith
Carroll Smith

yes, just buy a crate FOUR O EIGHT, DROPS RIGHT IN,GET MORE PAR

Michael A. Charette
Michael A. Charette

I'd rather see this in a classic Charger than some idiot painting it into that godawful General Lee redneck nightmare!

Dave Tooley
Dave Tooley

My Neon has a factory hemi. What's all the fuss about?

J.j. Brooks
J.j. Brooks

I'd sure rather have the new Hemi than an LS any day. I love the old Hemi

Ismael Armenta
Ismael Armenta

You can order a gen 3 426 crate from mopar performance and if you are a puritan there's a carburated option.

Vincent Joseph Valenti
Vincent Joseph Valenti

Wil Arnett,you don't know what your talkin about,a friend of mine is building a gen 3 hemi for his race car 900 horse power baby.

Charlie Guthrie
Charlie Guthrie

Hey, GM guys are doing the same thing with the newer LS engines, in fact GM itself started phasing out all the divisions engines in the 1970s & eventually replaced ALL V8s with Chevy small blocks.

Craig Schray
Craig Schray

For less money, you could have a 500+ cubic inch big block mopar that is very streetable.

Bry Deweerd
Bry Deweerd

Whatever. I enjoy riding in my 71 c15 with a 455 big block 4 bolt main out of a junkyard 73 buick riveara. Home built and only puts 580 hp and 690 trq to the rear wheels.

Marty Smith
Marty Smith

Depends- if the car's numbers don't match, or the mill is shot, go for it! Just don't butcher an original number-matched ride. Same goes for bowtie and blue-oval brethren.

Keith Weigand
Keith Weigand

Im a mopar guy and love the new hemi. Wish they could be bought for the price of an LS. Everyone that is against the new Hemi should a little research. There is a ton of potential in it.

Thomas Cochran
Thomas Cochran

I need an in depth abody swap. Lots of tech please.

John Lyons
John Lyons

Combustion chamber looks close enough to HEMI for me.

John Lyons
John Lyons

How is that not a hemi head engine?

Tony Duran
Tony Duran

Just make sure you keep your hood shut if you settle for a wrecking yard motor.

James Reyell
James Reyell

Nothing beats a real hemi. 426 bad ass motor. No displacemint for. Cubic inches. 426 is real motor.

Will Arnett
Will Arnett

For one thing, that is not a HEMI head engine.

Gary Huddleston
Gary Huddleston

Depends on the build. If your numbers matching then stick to original. If yours is a Frankenstein...go new and add reliability

Elijah Rose
Elijah Rose

older ones are more of a hemi than the new ones will ever be. and thats not just me being biased, compare the combustion chambers...

Bill Antalek
Bill Antalek

You mopar guys are your own worst enemies. Chrysler gave you a modern Hemi and rather than embrace it like the GM guys are the LS, everyone wants to throw it out of the nest.

Adam Hair
Adam Hair

I'd rather have the 392 6.4 liter.

Scott W. Marek Sr.
Scott W. Marek Sr.

It's all mopar...what's the problem...? Every mopar doesn't need it's chalk marks put back on.....geez..

Brian Becker
Brian Becker

The old hemis aren't in production because of emissions and tooling, take a look at top fuel you tool bag...what motor powers the most powerful dragsters in the world? Old school style 500 cube hemis!!

Cal Remington
Cal Remington

those old hemis are not in production for a reason

Will Lozzi
Will Lozzi

Blasphemy to put a semi hemi instead of a real hemi

Frank Cahall
Frank Cahall

Why wate your time with a hemi. Might as well do it right and put an LS engine in it.

Car Craft