1973 Charger Hemi Swap

[jstephen1]

Just inherited my Uncles 1973 Dodge Charger SE, I'm the third owner and it's stayed in the family the whole time. The block on the LA series that came with it was broken so I'm figuring out what to do with it. I've been scouring the internet for information on hemi swaps but it doesn't seem like there's much available for 73's. I'm hoping I can garner some wisdom from some fellow enthusiasts while I get this classic back on the road. I'm not looking to do a full resto and aiming more for a daily driver when I'm not using my modern charger. It's in great condition, minimal rust damage, interior is in good condition, so body work will be minimal. Engine and tranny is already gutted so it's in a prime position to do some work. Looking forward to sharing the journey.

I've been tossing around the idea of throwing a 5.7 hemi in there. I've got two 727's that came with but not sure if they actually work so will probably do a rebuild to avoid future problems. I know they make the converter plates so I can avoid issues there, and I've managed to find some mounts from Bouchillon for the engine assembly. A couple questions:

Does anyone have suggestions on a recommended throttle body and drive by cable conversion kit?
I plan on calling Holley, but does anyone know if their 72 swap pieces work for the 73?
Are there any major issues anyone that has performed this swap have run into that might help me avoid some heartache before I go slinging around a ton of cash?
If the need arises, any recommended vendors for a custom driveshaft?

The goal is to getting it running asap, and taking care of additional things as I go such as A/C and cosmetics. I've seen several issues people have had such as the steering pump needing to be replaced etc.

Thanks in advance for any insight. I promise I've been scouring the forums for days and while I've found generally good information I haven't found much in detail related to the 73s.

 

[Ron_M]

Welcome to FBBO from Connecticut

 

[jstephen1]

Welcome to FBBO from Connecticut

Thanks!

 

[70chall440]

The Holley Terminator X Max system is a drive by wire (DRW) system so you will need a pedal, however they are easy to come by from places like Rock Auto. The one I bought is for a 2015 Jeep Cherokee which was recommended by another member here. You can I believe convert to a drive by cable but do your research.

You can use any small block Mopar trans, many opt for one of the newer transmissions because they want the OD which allows them to run deeper gears for around town and racing fun, however there is nothing wrong with a 3 speed 727 either, just depends on what you want and intend to do with the car.

Holley (as i think you have discovered) makes a lot of the parts you need, however you have to do your research well to keep from spending money needlessly but even with research you are bound to run into an issue or 2.

Swapping in a G3 Hemi is not magic, many have and are doing it. The main things you need to look are;

- Engine: there are a number of choices here, pre 09 5.7, post 09 5.7, 6.1, 6.4 or even the 6.2 Hellcat. If you are going to do this on a limited budget, pre 09 5.7's are the cheapest. Then you need to decide if you want a truck engine or a car engine which really has to do with the intakes and the serpentine systems (both of which can be replaced as needed). Whatever engine you select you are going to need motor mounts (Holley, TTI, Ram Man, Bouchillon, etc.). My advice here is to get mounts that are designed to work with the headers you intend to use. Also you are going to need a new oil pan, again Holley, Kevko, Milodon, etc. I prefer the Holley unit because it is cast aluminum and less prone to bending along the mounting rail and is a bit more durable in terms of damage from scraping or road debris, also it uses the stock gasket. Lastly you need to look at where all of the accessories mount or probably better said what accessories you want to use (power steering and AC specifically). This will/can affect which serpentine system you can or will use.

- Electrical system: your car as it sits was never intended to run modern electronics and modern engines require a much higher level of power than the older cars. In stock form most 70's Mopars ran a 60 amp alternator, however modern vehicles today run 120+ amp alternators. Therefore your wiring needs to meet this increase which usually means a new harness at least. Additionally a G3 Hemi will need a unique engine management system (ECU and harness) which can be obtained from a variety of places to include a rewired stock harness out of a modern Mopar, a Mopar Performance system, Holley Terminator X, etc. Which way you go is dependent upon what you want out of it (other than just work) and your level of expertise and comfort with wiring. The Mopar Performance system is basically plug and play but does not offer a lot of tunability (nor does a rewired stock harness), however other systems like the Holley offer a lot of tunability yet are basically plug and play.

- Fuel system: You are going to have to modify or upgrade/replace the fuel system to feed the G3 Hemi. I am not sure if Tanks Inc. has a new tank that will accept an in tank pump or not but if not then you will need to decide what you want to do here. You can run an external pump or use one of the retrofit systems like Holley offers. You are going to need to replace the lines and add EFI rated filters. There is the issue of return lines, some will argue that when set up in a certain configuration you do not need a return line, my belief is that you should run one as it allows the system to circulate the fuel which helps with cooling the in tank pump plus it takes some of the pressure strain off the system. I am sure there are those that will argue this but since you are replacing the lines anyway, adding a return isn't that much of an issue.

- Transmission: I already addressed this but if you were to go to one of the modern AT transmissions then you will need to control the electrical side and there are harnesses that will do this out there that need to be integrated into the system.

- Driveshaft: There are many sources for these and they come in a variety of materials, sizes, etc. You will need to know what size U joints you want to use and then order a shaft to meet this. You should probably wait until you have the engine and trans installed and then measure the length you need. Do not use any charts or internet suggestions on length, measure YOUR car and set up and then get a shaft that meets this. I would bet that you have a drive line shop in your town that would be happy to make you a drive shaft. The upside here is that you can can actually look a human in the eye and explain what you need and when you have an issue you can go back to that human and have a discussion.

- Exhaust: you will most likely be running headers and there are a lot to choose from (Holley, TTI, etc.) but again, do your research and get headers and motor mounts that work together. The rest of the exhaust is like any other car however you will need O2 bungs because you will need to install an O2 sensor (at least 1) for the G3 to operate. Most new "swap" headers offer O2 bungs already installed and your engine management system will probably come with the O2 sensor.

- Cooling: more than likely you are going to replace the radiator, be mindful of where the inlet and outlets are as the G3 Hemis are a bit different than the old school stuff. Also you will most likely will run electric fan/s and this can be a bit of a pain because there are lots of options and not a lot of information. Personally I like factory systems like those offered on the newer challengers. Understand that electric fans draw a lot of power so you will need relays and a good power system.

As for the difference between 72 and 73 I cannot really address that however I built a 73 Cuda and it was/is pretty much the same as it's predecessors. I know that in the B bodies engine mounts changed so that might be an issue but I am sure someone here knows this (@Nacho-RT74)

This is a swap wroth doing IMO, but it not without it's challenges however it is not all that hard either.

I hope this helps, there is a lot of knowledgeable people here so don't be afraid to ask questions. Start a build thread and post your progress and questions there.

 

[jstephen1]

The Holley Terminator X Max system is a drive by wire (DRW) system so you will need a pedal, however they are easy to come by from places like Rock Auto. The one I bought is for a 2015 Jeep Cherokee which was recommended by another member here. You can I believe convert to a drive by cable but do your research.

You can use any small block Mopar trans, many opt for one of the newer transmissions because they want the OD which allows them to run deeper gears for around town and racing fun, however there is nothing wrong with a 3 speed 727 either, just depends on what you want and intend to do with the car.

Holley (as i think you have discovered) makes a lot of the parts you need, however you have to do your research well to keep from spending money needlessly but even with research you are bound to run into an issue or 2.

Swapping in a G3 Hemi is not magic, many have and are doing it. The main things you need to look are;

- Engine: there are a number of choices here, pre 09 5.7, post 09 5.7, 6.1, 6.4 or even the 6.2 Hellcat. If you are going to do this on a limited budget, pre 09 5.7's are the cheapest. Then you need to decide if you want a truck engine or a car engine which really has to do with the intakes and the serpentine systems (both of which can be replaced as needed). Whatever engine you select you are going to need motor mounts (Holley, TTI, Ram Man, Bouchillon, etc.). My advice here is to get mounts that are designed to work with the headers you intend to use. Also you are going to need a new oil pan, again Holley, Kevko, Milodon, etc. I prefer the Holley unit because it is cast aluminum and less prone to bending along the mounting rail and is a bit more durable in terms of damage from scraping or road debris, also it uses the stock gasket. Lastly you need to look at where all of the accessories mount or probably better said what accessories you want to use (power steering and AC specifically). This will/can affect which serpentine system you can or will use.

- Electrical system: your car as it sits was never intended to run modern electronics and modern engines require a much higher level of power than the older cars. In stock form most 70's Mopars ran a 60 amp alternator, however modern vehicles today run 120+ amp alternators. Therefore your wiring needs to meet this increase which usually means a new harness at least. Additionally a G3 Hemi will need a unique engine management system (ECU and harness) which can be obtained from a variety of places to include a rewired stock harness out of a modern Mopar, a Mopar Performance system, Holley Terminator X, etc. Which way you go is dependent upon what you want out of it (other than just work) and your level of expertise and comfort with wiring. The Mopar Performance system is basically plug and play but does not offer a lot of tunability (nor does a rewired stock harness), however other systems like the Holley offer a lot of tunability yet are basically plug and play.

- Fuel system: You are going to have to modify or upgrade/replace the fuel system to feed the G3 Hemi. I am not sure if Tanks Inc. has a new tank that will accept an in tank pump or not but if not then you will need to decide what you want to do here. You can run an external pump or use one of the retrofit systems like Holley offers. You are going to need to replace the lines and add EFI rated filters. There is the issue of return lines, some will argue that when set up in a certain configuration you do not need a return line, my belief is that you should run one as it allows the system to circulate the fuel which helps with cooling the in tank pump plus it takes some of the pressure strain off the system. I am sure there are those that will argue this but since you are replacing the lines anyway, adding a return isn't that much of an issue.

- Transmission: I already addressed this but if you were to go to one of the modern AT transmissions then you will need to control the electrical side and there are harnesses that will do this out there that need to be integrated into the system.

- Driveshaft: There are many sources for these and they come in a variety of materials, sizes, etc. You will need to know what size U joints you want to use and then order a shaft to meet this. You should probably wait until you have the engine and trans installed and then measure the length you need. Do not use any charts or internet suggestions on length, measure YOUR car and set up and then get a shaft that meets this. I would bet that you have a drive line shop in your town that would be happy to make you a drive shaft. The upside here is that you can can actually look a human in the eye and explain what you need and when you have an issue you can go back to that human and have a discussion.

- Exhaust: you will most likely be running headers and there are a lot to choose from (Holley, TTI, etc.) but again, do your research and get headers and motor mounts that work together. The rest of the exhaust is like any other car however you will need O2 bungs because you will need to install an O2 sensor (at least 1) for the G3 to operate. Most new "swap" headers offer O2 bungs already installed and your engine management system will probably come with the O2 sensor.

- Cooling: more than likely you are going to replace the radiator, be mindful of where the inlet and outlets are as the G3 Hemis are a bit different than the old school stuff. Also you will most likely will run electric fan/s and this can be a bit of a pain because there are lots of options and not a lot of information. Personally I like factory systems like those offered on the newer challengers. Understand that electric fans draw a lot of power so you will need relays and a good power system.

As for the difference between 72 and 73 I cannot really address that however I built a 73 Cuda and it was/is pretty much the same as it's predecessors. I know that in the B bodies engine mounts changed so that might be an issue but I am sure someone here knows this (@Nacho-RT74)

This is a swap wroth doing IMO, but it not without it's challenges however it is not all that hard either.

I hope this helps, there is a lot of knowledgeable people here so don't be afraid to ask questions. Start a build thread and post your progress and questions there.

Lots of great insight, I have check off list on most of what you mentioned was on there so makes me feel a little better. Definitely some other things I hadn't considered though. I appreciate all the information! Look forward to sharing everything!

 

[70chall440]

The main key IMO is to plan it all out before committing to anything. Research each sub component thoroughly and make an informed decision.

 

[Nacho-RT74]

engine mounts as mentioned were changed between 72 and 73.
while up to 72 were like these, two separated pieces and the rubber block between them:

Since 73 they were like these... a single metal bracket and the bushing kind rubber mount.

and with a crossing bolt, accomodates like this onto the K frame provisions