Should I make the swap to G3?

racerjoe

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I've been kicking around the idea of swapping to G3 lately, particularly since Holley came out with their parts for the A-Body. I'm looking for input to either talk me into it or out of it.
I'll preface with describing how I use my car. I built the car to drive, and drive it hard. I drive 45 miles one way to my local autocross and don't even need to open a toolbox (normally). I competed (participated) in the Holley Moparty Grand Champion event in 2021 and intend to keep going back. (Autocross, drag race, speed stop). I have AC & PS (Borgenson box) and want to keep both. The car cruises and handles great. I want to keep that way. (I doubt the engine swap would affect either of these)
Current setup is a aluminum headed 408 with solid roller and EFI, TKO500, 3.91 gear, 18X8s up front, 18x10s out back with 200 tread wear tires and stock style suspension.
I have an 06 5.7 from a Charger with, what I was told, 60K miles. I recently pulled a head off it and I believe it has to be something around that mileage. The hatch marks in the cylinders are still there. I'd likely do an eagle head swap along with a rods/piston drop in kit and a larger cam, obviously.
I don't intend to purchase any fancy front runner belt system as I want to use the factory accessory drive. I know I'll need to notch the frame rail for the alternator and likely have to modify the K-member to accept the stock location of the AC compressor.
My dilemma is, Holley's kit uses a 73+ K-member. I have the early K. A local guy who I don't know wants $500 for a 73+ K. Seems high to me. What's the going rate for K-members these days?
I'm also wondering if I should just buy the QA1 K and use TTI mounts. I've seen someone on here modify the TTI mounts that allowed access to the factory oil filter location. I liked that! It would also be nice to know if the Holley headers will work with TTI mounts, particular on the driver side. I like the clearance Holley has at the AC compressor and Borg box. I'd also have to modify the QA1 K to accept my Hotchkiss sway bar.
Sorry for the rambletron... I would love to have the engine on a K, wire harness made, headers on ready to drop in so I can do the swap over a weekend to limit downtime of the car.
Give me your opinion. I want to hear about how much you love or hate your swap, how much of a ***** it was, particular with certain brand parts, and whether or it not it was worth the trouble.

Thanks!
 
You failed to say what year and model car you have and if it has any value numbers matching etc. You also did not say what your expectations are. What will you gain, less weight? More power? Personally if I was swapping to a G3, it would be one of the larger displacement engines, not the 5.7.
As for the k frame, that does seem rip but if these new swaps are the new trend, I would expect it to add value to that year k frame. I would make sure that k frame was pristine for that price, original paint, no rust pitting and no dents in the bottom.
 
I think $300 for a 73 up K is fair. JMO Good luck. There are lesser priced ones . Did you check the classified.
 
Dang, it sounds like you have what you wanted. I get the change it up big too, but if it ain't broke?

I will say, the though of a G3 has crossed my mind too, and I don't even have 100 miles on my 340......
 
What will the g3 do that your 408 won’t? That’s the big question. If you’re happy with the performance of the car now then I can’t imagine the work will be worth it. If you need a bunch more power or are looking to lighten up the car, or make more useable power than the current small block can handle then it’s a no brainer. The g3 imo is worth it if you want 600+ hp capability, fuel mileage, and weight reduction. Just my thoughts.
 
You failed to say what year and model car you have and if it has any value numbers matching etc. You also did not say what your expectations are. What will you gain, less weight? More power? Personally if I was swapping to a G3, it would be one of the larger displacement engines, not the 5.7.
As for the k frame, that does seem rip but if these new swaps are the new trend, I would expect it to add value to that year k frame. I would make sure that k frame was pristine for that price, original paint, no rust pitting and no dents in the bottom.


Don't take this the wrong way, but the whole numbers/value thing doesn't mean anything to me. If it was a hemi car and I wanted to put in an LS in it, I would without hesitation, nor would I care what others think. I'm completely aware of number matching crap but they don't matter to me, nor do they apply to this car. This car doesn't have any value to a "collector".

The car is a 70 Duster as seen in my profile picture.

I already own a 5.7. If I was wanting to spend $10K on the swap, I would without a doubt buy a 6.4. I feel like I could do this swap "relatively" cheap since I already own the engine and efi controller.

Some goals: No oil leaks. No matter what I do, I still seem to have a very small oil drip after putting some miles on it. Also, V-belts are a *****, they don't like to stay on when you turn the engine 7000RPM. I recently purchased some serpentine pulleys for the 408- we'll see how that works. This point may become moot if they work. I'll likely add a centrifugal supercharger soon. This will make leaks on the 408 even worse. Lastly, I think the 5.7 will offer similar if not more power than the 408 (even in NA form) after changing to the eagle heads, rods/pistons, and cam.
 
Honestly, the main thing that talked me into the G3 swap was just having a newer engine with all the tech and design updates that have come along with it. You can typically make good power on a modern engine with little work. Your 408 sounds like a blast and something that has been built up pretty nicely, but in the end it's still "old tech" to some degree. Kind of like you are seeing with the oil leak, it feels like the aftermarket doesn't really improve old designs as much as just keep building them. Modern engine are all o-rings and better tolerances and generally more efficient right out of the box. Efficiency isn't just about using less fuel either, it means getting the most out of what you put in, which means more power for the same fuel input.

In my mind, getting 400 hp out of an old style smallblock is not near as hard nowadays, but starting with a modern engine you're basically just a cam swap and a tune away, plus it won't leak and will also tend to be more drivable throughout the whole rpm range and now just a top end number thing.
 
RJ,
I just put a 6.1 in a 72 Demon. I love it and drive the crap out of it. I will never look back and plan on doing it again in a B body. I have a Cuda with a stroked 440 in it which I race and love but the simple fact for me is that the Gen 3 modern technology is just outstanding! To your point, I pulled out a perfectly good 360 to do the swap. The biggest advice I can give you is do some research. I too chose Holley for the fuel management and would do so again. My opinion, one piece that made the whole thing slick as butter was a HDK front end. He is a FABO guy on here and one of the good ones. I also paired mine to a T60 manual so had to fabricate my own tunnel and tranny cross member. I have a build thread on here but feel free to PM me anytime. I say do it and never look back, let the haters hate!
 
I bump up against this all the time. Part of the problem is I used to have a 2015 Challenger R/T 6M and know how it drove. The 5.7 was a great all around motor, only really needed a cam and exhaust to really shine but even stock it was far better than the carb'ed 360 in my Duster. The motor would happily cruise at 1400-1600 RPM on the highway and pull some good hills without having to down shift, returned 25 or so mpg on the highway and pulled well when I got on it. Really miss that car.

I've often thought that a stock Eagle 5.7 in my Duster (losing 600 +/- pounds) with similar gearing (T56/2.97/0.50 with 3.55 gears due to smaller tires) would be an absolute kick. Add a 6.4 cam and intake and it would be all (I think) I would ever need.

My opinion only, the big differences between an LA and a G3 (stock for stock) is - air, spark and fuel (wait...isn't that the formula for adding HP? :D ). All the G3's have heads that flow substantially more air than an OEM LA head. Even the pre-Eagle heads are at least equal to most of the aftermarket LA heads. Add consistent spark due to coil on plug and crank triggers to an EFI system that can more easily meet the target fuel over a broad range of RPM's and they just seem to run good all around. Now, if all 3 of those were updated on an LA motor (like you have), get's a little harder to say. Sounds like you have most of those advantages whittled away.

For me, I think I have decided to leave the LA 360 in the car and EFI it (some day). It's the numbers matching block and I don't want to store it somewhere and I think it will give me the performance I want (no big goals for me, just fun), and if it doesn't then I will look at changing things then. Bigger step is the T56 swap I am on the edge of pulling the trigger on.
 
Honestly, the main thing that talked me into the G3 swap was just having a newer engine with all the tech and design updates that have come along with it. You can typically make good power on a modern engine with little work. Your 408 sounds like a blast and something that has been built up pretty nicely, but in the end it's still "old tech" to some degree. Kind of like you are seeing with the oil leak, it feels like the aftermarket doesn't really improve old designs as much as just keep building them. Modern engine are all o-rings and better tolerances and generally more efficient right out of the box. Efficiency isn't just about using less fuel either, it means getting the most out of what you put in, which means more power for the same fuel input.

In my mind, getting 400 hp out of an old style smallblock is not near as hard nowadays, but starting with a modern engine you're basically just a cam swap and a tune away, plus it won't leak and will also tend to be more drivable throughout the whole rpm range and now just a top end number thing.


Everything you said is exactly my motivation. I'm guessing my motor is around 500HP, which I may not get with the small 5.7 displacement, but I think the eagle heads and a healthy cam will get me close. I'm not chasing a dyno number, but those eagle heads flow so much at lower lift, I'm sure the smaller displacement will be offset by this increased head flow.
 
Don't take this the wrong way, but the whole numbers/value thing doesn't mean anything to me. If it was a hemi car and I wanted to put in an LS in it, I would without hesitation, nor would I care what others think. I'm completely aware of number matching crap but they don't matter to me, nor do they apply to this car. This car doesn't have any value to a "collector".

The car is a 70 Duster as seen in my profile picture.

I already own a 5.7. If I was wanting to spend $10K on the swap, I would without a doubt buy a 6.4. I feel like I could do this swap "relatively" cheap since I already own the engine and efi controller.

Some goals: No oil leaks. No matter what I do, I still seem to have a very small oil drip after putting some miles on it. Also, V-belts are a *****, they don't like to stay on when you turn the engine 7000RPM. I recently purchased some serpentine pulleys for the 408- we'll see how that works. This point may become moot if they work. I'll likely add a centrifugal supercharger soon. This will make leaks on the 408 even worse. Lastly, I think the 5.7 will offer similar if not more power than the 408 (even in NA form) after changing to the eagle heads, rods/pistons, and cam.
The supercharger changes things drastically. Even at 5-6 psi the 500hp 408 will now be very close to the limits of the block. Trust me it will always be on your mind when you stand on it. If any kind of forced induction is in your future, do the g3 swap and never ever look back.
 
The supercharger changes things drastically. Even at 5-6 psi the 500hp 408 will now be very close to the limits of the block. Trust me it will always be on your mind when you stand on it. If any kind of forced induction is in your future, do the g3 swap and never ever look back.

Good point.

Add that you can buy a positive displacement SC with a built in intercooler for a G3. Nothing like that for the LA. Certainly a centrifugal or turbo will need a front mount IC either way, but a roots style with a built in IC just seems like a much cleaner install.
 
Everything you said is exactly my motivation. I'm guessing my motor is around 500HP, which I may not get with the small 5.7 displacement, but I think the eagle heads and a healthy cam will get me close. I'm not chasing a dyno number, but those eagle heads flow so much at lower lift, I'm sure the smaller displacement will be offset by this increased head flow.

I know you already have a G3, but if I was going to take the time and money to make the swap, it would be for an Eagle G3 only. Gives you the VVT option as well. Maybe you wouldn't use it, in which case it probably wouldn't matter. But I think a 5.7 with the 6.4 cam and intake (plus the required headers) would be close to 450 and would drive so nice. Put an SC on it after that if you want more. Just a thought.
 
I now understand your car as far as collector value. Was just saying. Are you sure you would be able to do a 5.7 swap for under 10k? Your talking after market performance parts heads and the such. Costs add up quickly. Not trying to talk you out of the swap. G3 swaps are cool. Just as long as you achieve your goals with the swap.
 
Who cares about numbers matching anymore. I mean really....just save the block and sell it with the supercharged G3 hemi car. As if the new buyer will ever put that LA back in...no. If a G3 we're to fall into my lap, I'd have a fire sale on all my LA stuff. I'd keep my slant though. I'd just make double sure the 5.7 heads had the valve seats staked in or go for some 6.3+ heads. Witnessed 2 dropped valve seat hemis. Shame.
 
I'd just make double sure the 5.7 heads had the valve seats staked in or go for some 6.3+ heads. Witnessed 2 dropped valve seat hemis. Shame.

My understanding is that is only an issue with the pre-Eagle (09) heads. At least as a common problem, nothing is impossible.
 
The supercharger changes things drastically. Even at 5-6 psi the 500hp 408 will now be very close to the limits of the block. Trust me it will always be on your mind when you stand on it. If any kind of forced induction is in your future, do the g3 swap and never ever look back.

Good point
 
The supercharger changes things drastically. Even at 5-6 psi the 500hp 408 will now be very close to the limits of the block. Trust me it will always be on your mind when you stand on it. If any kind of forced induction is in your future, do the g3 swap and never ever look back.
Hell, if that's all we're worried about, go slant 6. They'll take 30 plus PSI and not even breathe hard. lol
 
I've been kicking around the idea of swapping to G3 lately, particularly since Holley came out with their parts for the A-Body. I'm looking for input to either talk me into it or out of it.
I'll preface with describing how I use my car. I built the car to drive, and drive it hard. I drive 45 miles one way to my local autocross and don't even need to open a toolbox (normally). I competed (participated) in the Holley Moparty Grand Champion event in 2021 and intend to keep going back. (Autocross, drag race, speed stop). I have AC & PS (Borgenson box) and want to keep both. The car cruises and handles great. I want to keep that way. (I doubt the engine swap would affect either of these)
Current setup is a aluminum headed 408 with solid roller and EFI, TKO500, 3.91 gear, 18X8s up front, 18x10s out back with 200 tread wear tires and stock style suspension.
I have an 06 5.7 from a Charger with, what I was told, 60K miles. I recently pulled a head off it and I believe it has to be something around that mileage. The hatch marks in the cylinders are still there. I'd likely do an eagle head swap along with a rods/piston drop in kit and a larger cam, obviously.
I don't intend to purchase any fancy front runner belt system as I want to use the factory accessory drive. I know I'll need to notch the frame rail for the alternator and likely have to modify the K-member to accept the stock location of the AC compressor.
My dilemma is, Holley's kit uses a 73+ K-member. I have the early K. A local guy who I don't know wants $500 for a 73+ K. Seems high to me. What's the going rate for K-members these days?
I'm also wondering if I should just buy the QA1 K and use TTI mounts. I've seen someone on here modify the TTI mounts that allowed access to the factory oil filter location. I liked that! It would also be nice to know if the Holley headers will work with TTI mounts, particular on the driver side. I like the clearance Holley has at the AC compressor and Borg box. I'd also have to modify the QA1 K to accept my Hotchkiss sway bar.
Sorry for the rambletron... I would love to have the engine on a K, wire harness made, headers on ready to drop in so I can do the swap over a weekend to limit downtime of the car.
Give me your opinion. I want to hear about how much you love or hate your swap, how much of a ***** it was, particular with certain brand parts, and whether or it not it was worth the trouble.

Thanks!
It's one of the ugliest engines ever produced so if you don't mind looking at modern lack of marvel POS in your engine bay go for it
 
I had this opportunity for my B-body. A '69 GTX. That's a nice driver quality car. But not even close to numbers matching. Period correct 440 of lightly upgraded performance. 4-speed Dana rear. Car is D32 coded for an automatic. With interior not even close to fender tag. Thus a very decent candidate for performance upgrade.

I had the opportunity to buy a just off the dyno 6.4 non supercharged Gen III at 545 HP. So the choice? Pull a very good running '68 440 engine at 425 HP for $14k. For this engine. I would need to upgrade K-frame. Clutch/bellhousing. Electrical. Fuel system to EFI. Radiator plumbing redesign. And that's just what I can think of off the cuff?

My Answer was "Thanks, but no thanks. I could spend that $14k on aluminum heads and intake upgrades and cam. A833 transmission replacement for ideally a A855 5-speed. And save all the support hassles and costs to accommodate the newer technologies. And blow that Gen III off the road.

The only engine upgrade I would consider? A Gen II hemi. (A real hemi)

Just my opinion of course. And a quick walk around vid of the subject vehicle below.

 
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