'95 LT1: Opti Drive Dowel Too Short?

I'm trying to sort out what I have going on. This isn't actually on my RMW, but a '95 Formula M6 car I picked up over the winter. The PO had installed a cheap Opti. He had also installed a non-vented cap and just plugged off the vent that was supposed to go to it. The car was throwing some codes for the ignition and would not run, so I figured I'd start by replacing the junk that I wanted to get rid of no matter what.

I purchased a new Delphi opti. I do not feel confident that I had previously installed the Opti correctly. The car would not start at all, and turned over with difficulty despite having a new battery. It also would give a very small backfire. I took the front of the engine apart today to get to the Opti again, and I still cannot feel confident. I just am not convinced that I am getting that little dowel on the camshaft to go into that one hole on the back of the Opti.

I am doing this with the cover of the Opti off so I can move the rotor easily.

I noticed that there is a hole on the Opti's shaft that corresponds to the rectangular hole on the back of the clover leaf. So, when I am under the car and fitting the Opti, I am observing this hole while I insert the shaft into the cam snout. I know that the shaft is being inserted such that the rectangular hole should end up meeting the dowel on the cam. I do need to finesse the rotor to get the Opti shaft to slide into the cam; it requires a little force, it's not like throwing a hot dog down a hallway or anything like that.
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Once I perform the above operation, the Opti is as seated as well as I can get it. Two things bother me. First, the mounting ears for the Opti do not perfectly touch the block. I have read over and over that an Opti is not seated correctly if there is ANY space between the block and Opti mounts. Also, if I grab the rotor, I can still move it back and forth a bit. Should this be possible? It would seem that if that dowel on the cam really was seated in the rectangular hole on the clover leaf, then there would be no back and forth movement. Am I wrong about this?

Here is my cam dowel, pointing down towards the DS of the car.
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Pics to show all three mounting points below, and a short video clip (please excuse quality) showing the rotor movement.
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If I don't have the video posted correctly, please let me know. I have not posted a video on a forum before.
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you are obsessing,.. tighten up the bolts,. fire it up,..

phantom 309 wrote:

you are obsessing,..  tighten up the bolts,. fire it up,..

I am only obsessing because of what I tried to explain in my second paragraph. I might not have been clear. I already had the opti on and the engine buttoned back up. The car turned over with difficulty and acted like the battery was weak; it's new and fully charged. I would get a small backfire at points during the process. The engine was acting like the timing was off, and it had not been doing this before the opti swap; it had other problems, but not this. I marked the plug wires and put them back in their original locations, so that leads me to believe I had the opti installed incorrectly.

From my experience with the opti, it didn't set down at all when I had the pin misaligned. It was really obvious and no where near a flush mount so I would guess you are lined in ok. I guess you never know for sure, but that's my thought.

Pull the coil wire and fuel pump connector/relay/fuse and crank it- does it crank freely? Then...

Check your spark plug wires - you may have crossed the wires where they connect to the distributor.

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Call me crazy but is your dowel pin short for one?

BigBlackBeaSSt wrote:

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Call me crazy but is your dowel pin short for one?

Is that dowel pin fixed or doese it slide out?Thinking that if its removable that there should be longer and shorter pins available at the GM parts department!

It will move. They press in.

Nick and Flash are both correct: There's only one way to put on the opti.  It either goes on or it doesn't.  However there are camshafts that need to have the dowel pin shortened if used with the non-vented opti system: I think all the aftermarket camshafts come with the longer VENTED opti dowel pin.

The non-vented opti is NOT driven by the dowel pin.  This is the root of your problem.  It's apparent by your pic that the dowel pin is NOT long enough for your VENTED opti.  The only thing the dowel pin does on a non-vented opti is go into a hole on the timing gear IOT align the camshaft correctly.  So if your timing is off it's not because of the camshaft.

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Do you know if the previous owner installed a different camshaft ?    Do you have a stock 95 car with a stock 95 engine/camshsaft ? Either way, the PO either tapped in, ground down or put in a shorter dowel pin.

If you use a vented opti dowel pin on a timing cover designed for the NON vented opti you may encounter issues fitting the timing cover.  There aren't enough details about your setup to allow us to infer this without making assumptions.  If your car is a 95 with a 95 engine, this will NOT be an issue.

Thankfully as the school year is winding down, and because of the long weekend, I had some time today to mess with the car for more than ten minutes.

I tried several more times for good measure to get the new Opti base to seat properly.  No way was it happening.  So, I decided to determine if the cam dowel really was too short.  I took some gray putty and stuffed it into the hole on the back of the distributor that the dowel goes into.  I did this on both the old and new Optis, then fit them.  The old unit does, for whatever reason, sit tighter against the timing cover and therefore better engages the dowel.  However, the putty clearly showed me that in neither case was the dowel penetrating that hole more than a tiny fraction of an inch.

I had read that the dowels are installed really tight, so had little hope for an easy solution.  But, I was able to get a wide pair of vise grips on the dowel and pull/twist (not even that hard; I'd say "moderate" force was applied) and the dowel moved outward.  It now sits clearly above the level of the bolts next to it.

I installed the new Opti and sure as shoot, it sits tight and there is zero play when I grab the rotor and try to turn it.  I have confidence that the car will start when I put it back together, hopefully tomorrow.

This is the new length of the dowel.  Hopefully it's not too far out; I don't believe it is.
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Mark showing how little the dowel was pushing against the putty in the hole on the new distributor.
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Old distributor (sorry for blur).
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It sounds fairly loose if you can pull it out with pliers, so if that is the case it should push in when the opti is tightened. Good to see you found the issue.

2 quick questions
Is there a button on the backside of the camshaft to prevent movement in and out?
Could you pull that dowel out and put a crease in it to stop it from going to far into the cam?