1971 340 Build - Choosing piston rings dilemma

JDMopar said
Glad to help, even though I'm sure you're disappointed to have to hunt more pistons. KB243's are what I have bought for a future 340 build. You could do.... Sorry you have to get new pistons or fool with the crank, but I'm glad it was caught now instead of later.

Yes you saved me considerable angst, if you were close by I'd by you a coupla beers! - Imagine getting to the stage of having one or more fitted in a bore and rotating around the assembly to see them misbehaving in the hole. I will just get new 340 pistons - I don't have the original ones to compare (think I sold them 10 years ago). However it's interesting, I have one of these new KBs here on my desk and I remember a thought flitting through my mind that it looked a bit odd. As I am not greatly experienced and have never built a 360, only 340s and 318s. So I am used to seeing the look of those pistons. That stroked unit of yours you described was a success story. You are lucky to have those competent machinist guys around. The state I live in is one of the largest in the world (by land area) but has a small population and a very small capacity for things like this. The places around that can do it are not many and not cheap either. Just to get a dynomometer run costs over $1500 and it's a big deal. The cost to get a 360 turned down to what you describe with internal balancing etc would cost over $700 and that money could be used for a new one. Plus the knowledge about Mopar engines here is so low, I wouldn't trust anyone to do it!! I picked up some 440 pistons for a friend once, from a machine shop he always used. They had put every rod on each piston the wrong way! My friend was spewing, but they denied it! He had to do them all again himself. No great drama, but that gives an indication of competency. Last time I went in there they were still using old scales and counterweights from 1965 to weight match rods! Couldn't even be bothered to buy some digital scales with +/- 0.1gram accuracy which you could get for under $50.

I would not even consider stroking this engine, and it would even be hard to find a 360 crank these days. Even though we (as in Chrysler Australia) have had quite a few 360s over the years. But they are sought after and drying up quickly. I already have the original really nice forged one for it all machined up and the new bearings etc. Plus as I mentioned before in another reply, 340 engines are quite rare here, we only got one model car with them and only for 2 years. The number of Australian designated 340s would be less than 400 in the whole country. Many have been imported in. They are quite revered and it would be sacrilege to many Mopar guys here - me included - to stroke a 1971 340 with a cast crank.