Unless you swapped the pistons, I would guess you were down most of 2 points of compression in that 360. They were all low-compression engines...I would bet that whoever rebuilt the 340 used higher-compression pistons.About 25 years ago a friend ended up with a 1973,340 Duster with a miss. We pulled the 340 down and found a broken valve stuck in a piston.
The block was already .060 over.
We put a piston it it and new rings on the other 7. Then had a shop do a valve job on the heads.
The 1973,340 was a low compression 340 with smaller valves. But it was still a runner. It was a hand full at a stop light drag race.
A few days later it dropped another valve. Yes we were having fun with the car but we did nothing to cause a valve to break off.
This time it broke a cylinder wall. We had it sleeved then bored to match the other 7.
Had the heads checked and another valve put in.
Ran 3 days and dropped another valve! My friend was at the end of his rope with it and was in a bad spot financially.
I traded him my decent 69 Chevelle for the Duster. He got a dependable car and I got the kool but blown up E55 340 car with the stripes,340 call out,fold down rear seat etc.
I had ANOTHER sleeve and piston put in it. I had the heads redone with all new valves and springs.
It ran 3 weeks and guess what!
I pulled the 340 out and scrapped it. I put a 318 in it for a while,while I was building a 360 for the car.
I built the 360 as a 340 copy. Another set of "J" heads,340 cam,4bbl,340 manifolds etc.
The 360 was a gutless turd! Nothing mechanical wrong just did not run like the 340 did. I played with degreeing the cam,timing,carbs etc
Car was a full 1.5 seconds slower than the 340. The 360 I built in my garage ran for many miles with no mechanical problems.
Something to do with the bore x stroke maybe?
I ended up trading it for a lifted Ramcharger as I preferred 4 wheeling and exploring vs cruising the streets.
I often wonder what happened to that car. Occasionally I do an internet search looking for it. It had some ways I could easily identify it by.
Hindsight 2020 I should have mothballed it until I was old enough to redo the car.
But if it has been repaired and painted I would not recognize it.
Probably because the earlier 340s absolutely ripped. (I recall the NHRA factored one 60HP over the rating.) 1968 (only) 4-speeds got a big cam, and 1970 used the J heads, big carb, and high compression.1973 340 Magnum - 245 bhp Net
1974 360 Magnum - 245 bhp Net
(Same Cam, Heads, Intake & 800 cfm Carb as the 340)
1973 Torino 351C 4V - 246 bhp Net
1974 Camaro Z28 350 L82 - 245 bhp Net
Don't know why people think the 340 Magnum was the only Hi Performance Small Block Mopar. In my experience the 360 Magnum was faster.
That's low compression engine to low compression engine.
You can also get a title from the state of Vermont "out of thin air", all legal and legit. A few years ago, I picked up a Ford Ranger in excellent shape that came out of a storage unit, but had never been in the state of Vermont. I believe the vehicle has to be 15+ years old is the only requirement. You send the state of Vermont the VIN on a form they send you, a little bit of money (IIRC, it was about $200), and the state of Vermont will give you a license plate valid for one year. After that, you take your registration to your local DMV to get a title. I actually took the Vermont license plate to the local fuzz office to make sure it was good. They hadn't heard of this before, but they said my license plate was valid and told me "motor on". While I fully recommend getting your title locally, this was a painless method.A <1995 Maine registration counts as a title elsewhere. This is how companies like Broadway Title (in the ads in the back of Hot Rod magazine) get you papers for barn finds.