318 replacement cams....

318 with a xe268 will run like crap down low with 10 degrees initial timing.

It needs ~16 minimum and the distributor needs to be altered so your total timing number is in range. The reason it runs poorly up top is because when the engine has the proper initial timing, it likely pings like crazy from too much total timing up top.

It's a multi-piece puzzle to get it right. You can't just drop in a distributor and have it run right out of the box. Unless you get extremely lucky and that almost never happens.

If the timing mark disappears, search hillbilly timing tape to solve that issue.

I bet it's really stinky out the exhaust the way it's timed now.