I have been working on my 1973 Corvette, for about eight weeks now. It’s a 5.7 with 115,000 miles and I have started two threads to get some advice on what I was seeing. The threads on Digital Corvettes were titled:
Timing Chain and Gear?????
and
Cam is 180 degrees opposite of what it should be?
I really do appreciate all the advice I received. I talked to a couple of forum members after I was done and they recommended I post a final thread discussing what I learned.
I have only had the car for about two and a half years, so if the lessons I discuss seem like simple mistakes, I will say up front they are. My thought is this may be helpful for someone with similar experience trying to trouble shoot something similar.
To avoid forcing someone who may not be interested in the entire post, I will begin with how the project ended. After that, for those who are interested, I’ll share some of my big lessons from a huge amount of advice I got on both DC and Grumpy’s Performance forum(s).
In the end, the problem was my distributor. I dropped a new one in this weekend and with a friend’s help we got it up and running. Before I dropped the distributor in I made sure the engine was at TDC, marked the old distributor by the rotor, the groove on the front of the distributor, the vacuum canister and the tach drive, just to make sure I got it right. Dropped the new one in, lined it all up, went to start it, and NOTHING.
I went back to the book just to verify my firing order (one lesson from this project was start trouble shooting with the simple) and realized my #1 wire was at least 1 position clockwise from where it should be. That being said, I have changed the wires too many times (I have headers and pipes) and if I know anything about the car, it is which wire is #1 on the distributor. When I took the cap off, it was also aligned with the rotor.
The next step was to ignore the marks from my old distributor and rotate the new one back to factory setting (#1 somewhere around 6:20(ish) as if you were looking at a clock with 12:00 being the firewall). It started with a rough idle first try and with a little adjustment was idling perfect.
I have not quite figured how to post a picture here, but I can provide of the position of the old distributor verses the new one if anyone would like to see.
I did a little research and the old distributor is an original Delco Remy with the metal band and pink tab described in the Richard Prince, Corvette Restoration Guide. It was built July 26, 1972 (2 G 26). That fits the body build date of October 13, 1972 (C13) to make it numbers matching. Unless someone went out of their way to find / put a numbers matching distributor on a car that, granted, is in excellent shape, very well maintained and has been driven (a lot) but is not non-numbers matching, this has to be the original. I am saving the old for when I redo the car somewhere down the road, but for now I think I fixed the problem.
Now here is some more detail for those who are interested. I learned a lot from this project, but here are my biggest lessons that I will remember next time:
1) Take the time to trouble shoot before you dive in. I bought two books before I even went to pick up the car two and a half years ago: Chilton’s 1963-1982 Repair Manual and the 1973 Chevrolet Service Manual. I have used them some, but not quite as much as I could / should have. A few weeks into the project I came across page 6Y-45 in the Shop Manual, “Engine Will Not Start But Cranks Ok.” Step one spelled it out pretty simple that it was timing.
Here is what I posted earlier:
“It looks like the ignition passes the first test for diagnosing the car not starting. Test #1 is engine cranks and plug wire sparks when held 1/4 inch from the block. The manual says go to the timing (I am reading that as distributor since I have already been into the timing chain) if it passes this test.”
“Step one for the distributor is to turn the rotor and see if it comes back to its original position. The rotor is pretty stiff (read that as slightly) and does not come back. I replaced the springs, but no change. Also, going back to what I found at TDC, the rotor ends up between 2 and 1, closer to 2 than 1.”
In retrospect, I noticed early on the rotor was not aligning properly, but I did not put it together with the location of the cap until the project was complete.
2) Related to my lesson 1, randomly replacing parts is not the way to go. My immediate reaction was to replace the distributor cap, rotor, coil, points, plugs and wires. I replaced the coil wire later on as a Hail Mary. Granted, they were not all that expensive and not bad things to do, but had I trouble shot, I would have known they were not necessary. Step one (and more than a few form members) said / suggested the problem was in my timing.
3) Still related to lesson 1, randomly exploring the engine can be enlightening, but definitely unnecessary. From the beginning, I started chasing a potentially obvious problem, the teeth on my timing gear. In the end, I found the timing chain and gears were (pretty much) brand-new double rollers and definitely not the source of the problem.
That being said, I am glad I found my harmonic balancer was coming apart. The outside was walking off at the rubber seal that connects the two pieces. Not sure how long it would take to come apart, but I am guessing it would not be pretty when it did.
And I did get a chance to paint the water pump, fan, timing cover, oil pan, and pulleys, so not a total loss there.
Looking back, I could have had the car back on the road in a weekend or two had I followed some simple troubleshooting and looked closer at the timing. Here are the hints I can see in hindsight:
1) The location of my #1 plug wire was way off (see my earlier picture on the new versus the old distributor). People have been rotating the distributor for years to make up for it wearing out (I think). Maybe I am wrong and I could have continued to rotate it, but I am pretty satisfied that I replaced it.
2) I had looked at the weights before when I had replaced the springs. Someone had welded a spot on top of each one; I am assuming that was to add weight.
If anyone has insight on why someone would do this I would be interested in hearing. Was he compensating for the distributor wearing out, or increasing performance? To me, it seems like another sign the distributor was wearing out.
3) The rotor had a significant amount of play in it and did not snap back at all. I was amazed at the difference once I set the new on in.
4) Pulling the distributor let me take a close look at the condition of the gear. There is not a huge one, but a decent chunk out of one of the teeth. Some of the pics on the articles GrumpyVette provided were much worse, but it was still worn and probably had been for a while.
5) Pulling the distributor let me get a good idea of just how long the old one had been in there. I know just because it’s old, does not mean it is bad (I have said it in previous posts, but I am 9 months older than my vette) but with the other components being new, it was a decent hint. From the looks of the vacuum cylinder and the top of the distributor it had either not been rebuilt or had been a long time since it had.
In the end, I am glad I took the time to trouble shoot. I learned a good lesson from Grumpy Vette, Mattydale, C5 Dude, Sly vette, and diehrd (and others) about trouble shooting.
Taking the time to get inside the engine (and yes use the shop manual) as opposed to randomly replacing parts taught me a lot with this one. Unfortunately, I started with the randomly replacing parts course of action first. Frustration brought me back to the trouble shooting method.
I put about 60 miles on the car today, most of it highway and the car ran EXCELLENT. I am going to drive it for a week or two and then most likely stop by my local shop, just to verify I have the timing right.
Thanks again…
