Post-Rebuild Performance Problems 3.6L C4 - FINALLY SOLVED!!!

[sms1305]

Though I'm somewhat embarrassed, I wanted to share with you - especially those who followed my broken head stud drama & have helped me out - that after rebuild the C4 is finally running the way I always knew it could - great!! [Post-rebuild woes documented at Performance Problems after rebuild - 3.6L C4 ]

It's taken a very long time since I installed the engine because of relocation, work & other issues, but it's finally done. Here are some of my findings, in the hope that others might benefit from my problems & mistakes. In the end the simple things will get you...

1. Emptied and cleaned fuel tank & lines/filter. I was surprised that there was no more moisture anywhere.

2. Checked & rechecked all vacuum lines. All good.

3. Double checked all sensors & connections. Everything looked good.

4. Compression was excellent.

5. Had distributor rebuilt/tested & replaced belt.

At this point, still no improvement...

However, while recently checking compression I discovered the O2 sensor connector behind the blower was disconnected. After reconnecting there was substantial improvement in drivability and enabled me to drive the car without the major hesitation, loss of power or bucking. However, that's when the new problem revealed itself - hot start problems. Found the main ground cable at starter disconnected [self-inflicted after rebuild] but in contact with the starter. (Thanks, Superman & Bill Wagner.) After connecting the ground cable properly - it runs great. Could it be easier?

The most puzzling thing was that the rough operation didn't start until I had been driving for about 30 minutes, and only after filling it with gas. At the time, it seemed to clearly be fuel related, at least to me. I now speculate that the O2 connector was connected but not made tight and then bumped loose after leaving the gas station, after which the car started to act up. No O2 signal coupled with a poor ground connection worsened the situation.

It's amazing. I was just about ready to throw in the towel and take it to a shop, when it all came to together. Now I can finally enjoy all that work (and money) invested.

Anyone have advice on a run-in schedule? I've been keeping it under varying load & speeds. I changed the oil (petroleum) at 50 miles post-rebuild and intend to go synthetic at about 500. How many miles until I check the valve clearance again?

Sport grind on cams, 5 angle valve grind, ARP studs for heads & rods, secondary muffler bypass - it's good to be back better than before! Better late than never.

p.s. Still looking for where that second little spool-looking piece goes. Hmmm...