How to bore out the engine on a 1973 Dodge Charger?

It will be an uphill battle…. The 413 ci would get you there easier, but you are going to have to put some money into bolt-ons for the 400 ci and some internal parts. You will definitely need performance heads which will be a chunk of money. To bore the engine to achieve the displacement of the 413 you are talking about more money than buying a new crate engine. I am not a big mopar fan…. but you would be best off replacing the cam next followed by a Victor Jr. type of intake manifold. There are several little parts for the pistons that could help but won’t give you the biggest bang for your buck. You will need functional scoops in your hood or a cowl induction hood. (A twin screw super charger would be really sweet but the price is outrageous). Replace your pulleys and harmonic balancers with lighter weight aluminum versions. Get exhaust headers and an “x” or “h” pipe with high flow mufflers (2 or 3 chambers, but the 2 chamber are a lot louder.) Make sure your fuel pump is up to the task of getting the gas there or upgrade the pump. Get a performance thermostat to keep the engine cool for high RPM. You do most of what I am suggesting and you may be able to get that 400 up to around 400 horses which the thing came stock at 255 I believe.

Now comes the reality check…. You will also need a strong enough clutch, transaxle, and rear end to support the horsepower gain. Upgrade your clutch to a racing-type clutch that will allow you to release more ponies into your rear gearing. Posi is a must to do a proper burn-out or go racing anything- no matter how big your engine is. If your rear end can support the horsepower gain then you might consider going with 4:11’s and up the size and width of your rear tires. Unless you plan on rebuilding the car from scratch with high performance parts - Do Not use Slicks with a rear end setup like this. You will tear apart your hard work with a few burnouts.

If it were my project car…. I would pay the initial money to get the 413 ci engine then work on aspirating it better with heads and edelbrock intake parts. Put more money into the suspension then go ape with the rear end. Of course you do need 100 octane gas to make this car run right.