1970 Roadrunner - again

Unfortunately it's too hard to read the fender tag in this picture.
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New Vintique wheels.
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As good of a start we had when we bought the car, it did have it's issues. We picked it up from a storage facility that was gated and gave us limited area to drive it around. So although we weren't able to take it on a lengthy test drive we had a few hundred feet to run the car. When first started it was a bit cold blooded. I wasn't too concerned because I knew the Holley wasn't running a choke. I hadn't run a manual transmission in a long time and although I consider myself pretty adept with them, I couldn't tell for sure what was going on with the clutch. It definitely didn't seem to be adjusted correctly.

We were eager to get back home so after completing the transaction we loaded the Roadrunner on our trailer and headed back to Nebraska.

It was late before we got back home. - Too late to play with the car that night. Even though the car was capable of being driven as is, we knew that clutch still needed attention. The prior owner had said that he was aware that it wasn't quite right but assured us that everything was new and it was surely an adjustment issue. The next day was time for us to really try the car out. The 8&3/4 was running a set of 3.55s. Although we were aware of those issues with the clutch, we still hadn't tested the engine much.

We live in a small town of about 2500 people in a rural area. So there are open highways with limited traffic only minutes away. We drove to the nearest gas station first to make certain we wouldn't run out of fuel. I didn't want to assume that the 40-some year old gas gauge was accurate. After finding a secluded area we proceeded to run it through the gears. It was pretty disappointing. Although it didn't seem to run bad, it was sorely lacking power. After a few minutes we returned home.

I popped open the hood to see if there were any tell-tale signs of a problem. Although I couldn't see anything wrong, I almost burnt my arm on one of the hood hinges. The engine temperature gauge hadn't even reached 180' yet. Further inspection revealed that the heat was coming off the exhaust. - A possible sign that we were running awfully lean. Without having any replacement jets on hand we decided to investigate the motor further. When we put a timing light on it we noticed something strange. The initial timing was set at around 16' BTDC at 850 RPM. As RPM increased, the advance kept climbing until it was over 70' advanced and still climbing. We had only gone to around 3200 RPM. As far as how the car seemed to be running, - it was very sluggish on the bottom end. Unless you took it up to over 4000 RPM when you left from a standing start, you couldn't even bark the tires. Over 4 grand and it seemed to develop a decent amount of torque and HP. There were no signs of detonation as the timing advanced. So I was confused. Too much timing could have caused an increase in engine temperature, but it didn't run like there was too much timing. When we felt the firewall behind the engine, - it was still cool and the intake and block were actually cooler than the inner fenderwells of the car. The heat was definitely coming off the exhaust. Adjusting the initial timing back and forth didn't affect the exhaust temp.
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When they rebuilt the engine they installed a COMP cam. We aren't sure which cam because the previous owner never supplied us with the info. When we asked him over the phone about the build, he told us that the block had been milled but he didn't know how much. He couldn't tell us much more.
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I began to wonder if the cam and crank were synchronized correctly. The prior owner had done the assembly and he didn't degree the camshaft. One other theory I had was that there wasn't enough valve lash after the block was milled. The engine was still running stock rocker arms and pushrods. So, I decided to test my theory by shimming the rocker shaft with some brass shim stock. The effect was that we seemed to lose some power and increased the valve train noise. I pulled the shims back out. I put a degree wheel on the front of the motor and used a piston stop to see if the 0' timing mark was accurate on the harmonic balancer. It seemed to be within 1'.
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So I figured that I should focus on what I did find out from my tests. I was certain that we were getting way too much advance and indications were that we were probably running too lean. We have always been big proponents of MSD equipment, so we ordered an MSD Pro-billet distributor and an MSD Digital 6 Plus control box. Then I went ahead and ordered the full set of replacement Holley jets to experiment with.
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When the parts arrived I began to play around with them. After doing multiple jet changes we ended up increasing the sizes by about 8. The exhaust temps normalized. The switch to the MSD equipment seemed to give us a substantial increase in power throughout the entire RPM range. Although not a super powerhouse, the car was beginning to behave respectfully.
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We had a friend of mine test drive the car who was much more experienced with manual transmissions. He made some clutch adjustments which improved things but said that we should check our Z-bar bushings. When we did, we found that they were actually missing. He set us up with some extras he had on hand. Viola! The clutch problems were gone!
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