Engine Tuning

I finally got the engine tuned up and running right. It has been about 25 years since I have built an engine, so all that experience is basically lost and needed to be re-learned. I had a book back then, but I have Google now, which is both good and bad. In the end, I learned some things and made it through.

The hodge-podge of parts for the front end of the motor continue to cause issues. With a lack of timing marker, I learned I could set the timing and carb with a vacuum meter. Well, I have one of those, so I tried it out. Basically, I set the idle for max vacuum per the Edelbrock directions that came with the carb, then I did the same with the distributor. Unfortunately, I didn’t know at that point that the distributor should be set 1-2 inches of vacuum off max, so my timing was pretty far off. It would start and idle, but it would miss a lot at higher RPMS.

Without a timing marker, the Top Dead Center mark on my harmonic balancer was showing something right of 12 o’clock. I didn’t put it all together until later, but with a 74 engine and timing chain cover, the timing marks on my 69 balancer are going to be wrong for where I need to put the TDC mark. With the later style water pump outlet on the driver side, I cant have a 2 o’clock timing marker since I can’t see it.

To solve this, I dug up the variable timing marker I picked up from Summit a few months ago. I ended up taking the center pulleys off again to get it installed. These are all things I should have done before the engine was in the car. Live and learn.

Summit adjustable timing marker

With a new timing marker, I needed to set TDC according to that mark. I used a piston stop to find clockwise and counter clockwise piston max up position on #1. From there, I split the difference and call that TDC. I had to take the pulley off so I could measure the ballancer’s diameter and use the right timing marker tape for re-zeroing the timing marks on the ballancer. The kit I got from Amazon had 4-5 different length tapes for various diameter balancers and I had to pick the right one.

New timing marks set. TDC is calculated via pistop stops

Once I got it all marked and re-assembled, I fired it up and got ready to figure out just what I had going on. On first check, I was running around 30 degrees before top dead center. I understand the target with the Pertronix ignition should be 10-12. That would explain the stumbling at higher RPM.

I found that when I dialed it back, idle dropped, and vacuum started dropping too. I thought I might have an issue as I heard a ticking from the back passenger side of the engine. Listening closer, I found an exhaust leak. The exhaust shop didn’t tighten down the pipe to the manifold. Before figuring out it was exhaust, I thought it was head related possibly, sending me on the wrong direction from dialing back the timing.

After some research, I learned I should be about 2 inches off max vacuum, which is what it dropped to when I dialed it back to 12 BTDC. I reset the idle and tweaked the throttle connecting rod which was binding a little. I took it for a test drive and everything went smooth. More power, no stumbling.

It was a learning experience, but that’s what this project is. I like that I can be self reliant to tune the car in the future, and keeping it running in top shape. I was starting to think I should take it to a speed shop to solve it, but knowing how it all works makes me feel much better about maintaining it.

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