What did I break?

The car: 72 Dart, 360 stock with mild cam, 4-speed

OK, drove the car to the muffler shop with open manifolds (trashed the cheapie headers), and they couldn't bend head pipes for it on the driver's side, so I said to leave it be and picked it up. This was a 6 block trip.

But,

I've moved about 40 miles away since I dropped it off, and had no choice but to drive it home. With open manifolds.

So,

I drove it carefully home. I wrapped the torsion bars and speedo cables in aluminum foil to stop some of the heat, I took as many breaks as I could to let it cool down (shut it off at lights, coasted with engine off, etc) and this was 10 miles in the city, 30 on the highway (I never went over 50mph) and I coasted a LOT.

I didn't think this motor ever smoked, but it does now, on the driver's side, one puff per engine cycle. It first puffed smoke on one of my many startups, about 2 miles into the trip, and it was leaving a trail by the time I arrived. The result? Only 100 psi compression on #1, and a very oily sparking plug. #3 had 135 psi, for comparison.



I'm thinking that there was some detonation that damaged a ring land or something, unless someone here has some better advice. I knew it was going to be lean so I was very gentle on the throttle whenever possible.

Any ideas? If it is a piston, I'll just pull it apart and bore it over and get some 9.5:1's, but the money is pretty snug right now...so a piston recommendation wouldn't hurt either. If you want to recommend a piston, toss in the cheapest you've seen them! This car is strictly street driven.

The cam is 400 miles new and so is timing chain and tensioner. I have magnum heads if you'd recommend them with what ever pistons. Cam is Comp XE268H.

Thanks
John