Advice?

Would it hurt the value of my 71 charger 500 if I replaced the original 318 with a larger engine?

Probably not.

If you had the only perfect original one with less than 1000 miles on the clock and a flock of unusual options, maybe. But if it is a run of the mill car that has had parts replaced and maybe has been repainted etc then no.

Do it right and it will be worth more than a 318 car but not as much as an original big block car. However, do not expect to recoup the cost of the changeover.

Keep in mind you will also have to change the transmission and possibly the rear axle, radiator, and other things.

I'd love to see someone restore a 318 Charger since most of them were built that way. I'm planning on keeping my 318 Challenger conv as a 318 car because no one else is doing them that way. The 318 is a great engine. Your cost will be much less going this way as well. It takes BIG bucks to do a conversion to a big engine right to get the big bucks at a sale and the numbers won't match if that maters to you.

It would increase the value of the Charger to most buyers but not by as much as the cost of changing it. If you want to do it for you then go for it, if you are doing it to resale then don't bother changing it. Even to go to a 360 4barrel engine would require a larger capacity radiator, heavier duty transmission, 8 3/4 rear end instead of the 8 1/4 it probably has, disc brakes if it doesn't already have them, different exhaust manifolds and pipes, along with a whole lot of small pieces to make all the big ones mount to the car and work together. You might get away with a stock 360 2barrel engine as long as the car doesn't have a 7 1/4 rear end under it, and let a buyer do the change the way they want to.

The really nice thing about Chrysler Products is that the data plate on the fender apron, under the hood, details ALL optional equipment in plain, open sight. Decode the VIN is easy to do, too. So how it was built is there for all to see!

Putting a 360 where the 318 currently is can be an incognito upgrade. In 1980, the 360 2bbl used the same type of Carter 2bbl which all 318s usually had, so the orig air cleaner will work. The later upgraded 904-family lockup-converter transmission can probably be used too, without the lockup stuff in it, but with heavier-duty guts. No need for the 727 as it takes more power to run it. Going to the later OD automatics can have some center hump clearance issues, but then the car should already have a 2.94 rear axle ratio which would make any OD transmission "not needed".

The 318 is an extremely durable and tough motor--period. Treat it right and it'll take care of you, just not as quickly as a larger V-8 might.

It IS an acceptable upgrade in the Mopar hobby to install the Mopar Perf electronic ignition kit. If you hide the wires and the control box nicely, all that'll be visible is the extra wire coming out of the distributor.

Take a small plastic wire tie, insert it at the firewall side of the slot in the kickdown rod, and tighten it so it stays in the slot as it contacts the stud on the carb linkage. This will add a small bit more pre-load into the linkage and raise the part-throttle shift points in "D" and make the car feel better and a little more lively. It works well without having to turn any wrenches!

The LA engine upgrade is an easy one, but to go to a B/RB engine, LOTS of things need to be changed. The increase in value might not be worth it, especially as it'll be easily-seen that it didn't come that way . . . even if you might not mention it. Keeping it stock is the best route to go. Now, if you want to add some of the 15x7 Chrysler Rallye wheels (repros like would have been optional on it) and some matching tires, that might be something to consider.

Enjoy!

NTX5467