I’ll explain a little background on this situation so that it is easier to diagnosis my possible issue. First let me again thank all of you that have helped me within the last year while I was tackling a lot of suspension and engine work on my 67 dart. I have learned quite a bit from all of you. Thank you. Well I had upgraded the 383 in the dart with edelbrock performer rpm heads switching from the iron 915’s that were on it. I worked on the car for the last 6 months as much as possible and through some trial and error and a lot of help from everyone I was able to do the head change replace the timing gears and chain, put on an aluminum waterpump, install a geometry kit for the Harland sharps on my edelbrocks. I just couldn’t get it to run right. The valve train was very noisy even after rechecking the adjustments on the rockers. It also ran real rough and I wasn’t able to get the 650 speed demon to idle down @ 800-900rpm like it used to. So I was at a loss, winter was here, the dart was outside and so I brought it to a local restoration shop. They said they would get the car worked out and tune it up sweet. Come to find out first thing they said was that I had 2 plug wires going from the cap to the wrong cylinders. Well running on six instead of eight would do that. That I’m sure was a factor in a rough idle. Simple idiotic beginners mistake by me. Always check the easiest things first I have now learned. They also said that about 3 of the lifters were slow to pump up but still had a little life in them. For reference the lifters were standard mopar performance hydraulic flat tappets about 20 years old. Since the engine was built back then I put about 15,000 miles on the engine. I though ok I’ll replace the lifters when I have my garage finished and a comfortable place to work. I go to test drive the car today they tell me it’s all set and running great. Either they are idiots or never got on the car to the point of even 4000rpm. The carburetor idle was set at 1200-1400. Even with the old mopar performance cam in it that is too high. The cam is 484 lift 284 duration not crazy radical. The old engine with the 915 heads had a ton more power and throttle response then it does now. After driving the car and getting the rpm’s up it started backfiring terrible through the exhaust. I noticed it was backfiring much more on the passengers side. I think the issue is that the lifters were worse then they thought and they still reassembled the engine. Im thinking there is at least 2 partially collapsed lifters on the passenger side and one on the drivers side. Wouldn’t that account for the excessive fuel not being burned and being dumped in the exhaust igniting in the mufflers? Also that would account for the real noisy valve train under the valve covers and the rough idle that can’t be turned down like it used to? It would also kill the engines power/performance. Shouldn’t the Ede head upgrade be noticeable in a power gain? I brought the car back to them and went through all the issues. I told them make it right! I just recently bought Rhoades lifters with the eventual intention of replacing them and told the shop to put the new lifters in and set up everything based on those. Am I thinking correctly on this one?