What's to know? Your question is so general that it's hard to give you an answer.

About the only down side to 340s is if you start to build them to very high horsepower ratings. They don't have enough head bolts, and you must use special bolts, "O ring" the cylinders for better gasket seal, and do some modifications to the oil system.

For the averag guy, building to 350-400HP this should be be an issue.

If you go searching for parts, like, say, you blow up a trans, you want to be a little careful. 360 engines are "externally balanced" and if you have a 4 speed, that means the flywheel is balanced different between the two engines. If you have an auto, either the flex plate, or the converter is balanced different for the 360.

I ran a 340 for several years in my '70 RR---I put it there, Chrysler didn't--and it was a great combo.

I don't remember if '69s came with aluminum single point or dual point ignition. If you have a stock Chrysler (aluminum) distributor, either get a cast iron dual point, an aftermarket like Accell, or better yet, electronic.

Your '69 should have come with a "square bore" Carter AVS/AFB. These are great carbs. You can buy aftermarket replacements, I believe through Edlebrock.

Don't be too darn quick to chop this all up and build it or customize it. Stock 340 cars have gone up tremendously in value the last few years. When you add up the vast quantity of Mopar muscle cars, there just weren't many 340s built.

 

pretty much all hp engines during this time were under rated mainly for insurance reasons

 

It may have less hp because of use and age though so i would think 275 would be accurate. my fifth ave was originally rated at 140 hp and 265 tq. when i put it on a dyno at a friends garage it had 125 hp and 255 tq. i changed the oil, plugs, wires, and ran a can of fuel treatment through it and with premium it was getting 134 again with 80000 miles. suprisingly the tq was 270 after this. since then ive put on headers, a performance igniton, removed the ac, and air pump and am waiting for him to fix his dyno.

 

dont forget though, that is the old rating

 

Yeah. Insurance companies didnt like anything with 300hp + rated engines. They still dont.

 

not all 340's were internally ballanced sum were externally balanced. (72's)