[Robert Scheler (Dadawg)]

I just purchased a 1974 challenger with a 340 engine. The owner said he had it for 6 months. He's selling it because he was under the assumption that it was an all orginal car. Well it wasn't. Apparently the owner before him took out the original 318 and put in a 340 4-speed. QUESTION IS, IS HOW CAN YOU TELL WHAT YEAR A MOTOR WAS MADE? The owner says it's either a 1970 or a 1971. And were the motors from those 2 years also have more horsepower than the 1972 cars through 1974?

[Dave-R (Roppa440)]

First of all Bob I moved your message because it is important to have everything in the right sections so others can find it in the future!

The engine has a cast date on the side of the block. Normally this date is a few weeks before the build date of the car it was first placed in.

You can also check out the VIN stamping on the block which will tell you the model year of the car it was in. Don't pay too much notice of horspower ratings. They changed the way the ratings were made. Very little was done to reduce the power of the engines although the most important thing to a 340 owner that is interested in power is what cylinder heads it is fitted with. You can find that out by removing a valve cover and reading the casting number off the top of one of the runners.

[Douglas Little (Dlittle)]

I just bought 340 engine dissembled. I have 10.5 pistons, steel crank, x head, windage tray, etc. The rods are from a 360. It appears that the pin in the piston of the 340 locked in the piston and floated in the rod. In the 360 the pin floated in the piston and locked in the rod. I trust the man I got the motor from. This is not the first motor I have bought from him and he has a lot of mopar experience. He said that the 360 rods will work on the 340 pistons but I worry that they may not hold up as the pins will want to be stiff in the piston and the are no oil holes in the 340 as on the 360 piston to lub the pin as it floats. Can someone advise me on this. I want to get the motor built but not by starting out with doubts.

[Dave_R (Roppa440)]

That is a tough question. I don't think I even have any reference material that infomation would be in.

I thought they were all a press fit in the rods with a foating piston. I did not even fit my own pistons on my 440. That bit I had done for me so now I am unsure about that! The last piston I fitted was on a 1958 AJS 350!

Anyone else have any idea?

[Douglas Little (Dlittle)]

I am getting old and my mind is sometimes fuzzy, but I think the 318's I have seen have floating rods and I believe the last 340 I worked on had the same. The 360 has floating pistons with no place for a clip at the ends of the pin as does the 318, 340. The man I got the parts from said he has built 340 engines using the 360 rods with no problems. He has built some good motors and has always shot me straight. Anyone can make a mistake every now and then though. I don't want to build a motor that is not right. Too much money and time down the tube. Any help well be greatly appreciated.

[Hans (72challenger)]

Well Douglas, I will try to explain how it is on my 340. Hope my memory serves me right.

Through my rods are the pins (duh..) they could spin free in the rods but they also could spin free in the pistons. An both ends of the pins were some sort of clips (the same clips as the ones at the rear of the torsion bars, but a lot smaller)

Hope this helps you Douglas.

[Douglas Little (Dlittle)]

Thanks Hans and Dave. That is something close to what I remember too. So I can assume that a 360 rod could work in that it would float in the piston even if not in the rod. This is something like the man I got the parts from was telling me. He said I would not need the clips. I still wonder about the absence of the little oil hole where the pin is in the piston. The 340 pistons don't have any. Would this be a problem?

[Douglas Little (Dlittle)]

I will be putting the engine up tomorrow. I hope all goes well. I will let you all know how it turns out. Thanks for the help.