[1968GTO421]

This is fascinating info to consider. Joe, are you having Paul replace the distributor with something else, or is Paul rebuilding the existing "dud" for you? Thanks.

[Formulajones]

Originally Posted by TedRamAirII

Although it would not have made sense at the time, to even check the distributor, a shop with a ignition scope would have surely seen a irregular ignition pattern. I can tell you, I dont think anybody would have put a knock and ignition issue together! I'm sure Paul will get it shipped back ASAP and you can get RIPPIN'

Actually I suggested it very early on in this thread. I've had sounds just like this that were distributor related, timing related, vacuum advance related, or any one of those scenarios. But when I mentioned it, there weren't any other comments mentioned afterwards other than Highway said he would look closer at that deal. Then nothing mentioned as they went on to other things and swore it was the windage tray.

I would tend to think that looking at the pics Paul posted and the severe wear, especially up on the reluctor wheel and magnet, that if the timing was checked as I suggested, someone would have seen something erratic going on that might have warranted some further inspection.

We talked about this last weekend when I was down there. I knew all along it was going to be something simple and was no fault of Paul at all.

Excellent detective work Paul, as usual.

[dataway]

Hey ... my sound file analysis was vindicated I knew it was something camshaft driven since it was very clearly half engine speed. But ... a distributor bushing would not have been my guess. I mean how often do you see that happen.

[JSPONT]

Originally Posted by dataway

Hey ... my sound file analysis was vindicated I knew it was something camshaft driven since it was very clearly half engine speed. But ... a distributor bushing would not have been my guess. I mean how often do you see that happen.

Yes sir, good call!!

[Va68goat]

1968GTO421,

I'm going to be guided by what Paul suggests. I think we want to confirm that this isn't some "knock off MSD" distributor. I would hate to have to buy another one but I'm so deep into thismotor that I think I would have to. Paul is going to check out the distributor and give his best assessment and I'll go from there. I trust him 100%.

Formulajones,
We checked the distributor but only for play up and down. It never came to anyone to check for lateral play. Believe me, I wish we would have.

dataway,
Your file analysis was a huge help. I think a lot of guys were stumped with this one. Thank you again for taking the time to do that. I really do appreciate that!

[Va68goat]

Formulajones,

The timing was checked at least 4 times during this process. Of course I have no clue how to time it but but nothing was mentioned that was erratic. I sure learned a lot with this experience!

[grivera]

Joe - If you determine it's an authentic MSD dizzy, I think a new bushing may be best course of action - imagine if you bought a new dizzy and it has the same crap bearing.

Paul - how do the main/rod bearings look? Did any metal from the dizzy bearing make it to them?

[gtospieg]

glad to see the mystery solved...been following this for a looong time

[mgarblik]

Originally Posted by gtofreek

I'll take pics of the rest of the engine tomorrow. Yesterday I was tired afterwards[it was past 5PM]and covered in oil during disassembly to take any pics. Good news is crank and everything else looks great. Piston skirts don't look like they've even been run except for a couple very light scratches that are barely even noticeable. Piston pins are free and smooth moving. I still need to disassemble piston pins so I can clean and re-lube before reassembly. I might still have that MSD box at work. I have one I keep instruction for timing curves and extra parts in. I wrote Joe's name on his box when it came to me, so I'll know if the one at work was his or not. If so, I'll look at the origin code in the UPC code to see if it originated from China. Maybe that will shed some light on this. I have used at least a dozen of these distributors in other Pontiac builds and have never had an issue with one. We have used countless MSD distributors on many other brand builds also without any issues what-so-ever. So I was shocked to see this in such a short amount of time. It just sucks that Joe has been without the use of his car for a year because of this. Who would have ever guessed this was the cause. I think the reason why it sounded like it was coming from the torque converter area was because the noise coming from the distributor cap was hitting the firewall and traveling down the tranny tunnel and coming out around the tranny. Very deceiving. It was also loud under the hood and everywhere else too, so sound really travels with these deals. Just glad it didn't cause any other damage to the engine.

I am glad you found an issue with a true witness mark on the part to verify. Just to clarify above, you mention the noise traveled to the firewall and down to the transmission/torque converter area. You don't mean there is anyway the distributor was contacting the firewall in any way at all do you? That could explain the whole situation. The worn bushing, only hearing it in the car and not on the dyno, the whole thing? Plenty of clearance in the rear around the distributor with the engine installed under all throttle conditions? Again, glad you have a handle on the issue, lots to be learned here.

[gtofreek]

Hey Mike, what I meant was the noise was traveling down the tranny tunnel. Nothing hitting the firewall physically.

[mgarblik]

I was pretty sure that's what you meant. Wishful thinking I guess. That would have explained allot. Are you going to run it before shipping it back? If you have to buy time, I just bet this group following this thread and the way you have handled it would help pay for the time. Let us know.

[STEELCITYFIREBIRD]

....I’d want nothing to do with that dizzy myself.

I’ve seen high mileage units worn heavy in one spot on the lower bushing like that. With the run time you have, I’d eliminate the possibility of a problem housing.

Any interference dist cap to rotor?

( I spent some time this weekend swapping out dizzy gears and locking out advance on two MSD pro billets, SBC, now I’m going to go back and scrutinize them both a little more before installing, both are used but one has VERY little time on it. It Had to go back to MSD, rotor phasing was off, enough to cause cross firing, with mechanical advance functional )

[Dragncar]

Get a PMD iron distributor all set up with a 6AL, good set of points and you won't have to worry about any ignition issues. Big fan of it.

[Cardo]

^^^ +2 I had my last car set up like that. It works well. No issues what so ever.

[STEELCITYFIREBIRD]

If you go with a CD box....get one with a rev limiter!
A quick search produce this image as the first hit;
https://www.bing.com/images/search?v...x=0&ajaxhist=0

[HWYSTR455]

Yeah, I'm thinking if the lower bushing is wobbed out, the top one is too. With the shaft at an angle, I would assume it would wear the opposite side of the upper bushing.

I'm in the same boat, you could replace that lower bushing, get it together, only to find something else wrong with it. Go thru that one, fix it, eGay it, and use a new one.

Maybe the gear was too large in diameter or something? The base circle?

.

[Sun Tuned]

I tried to call you Paul this morning, might've been a tad early. Sitting at the tire shop getting a new set of shoes on my old dually and reading this...

No idea what's going on with that msd thing but I saw the exact same thing twomonths ago on a distributor a guy brought me here in Memphis.

Pontiac that had several other issues than the distributor due to a less than capable machine shop.

Build went 150 miles on a brand new msd pro billet from summit...
bottom bushing looks just like yours. His wasn't knocking yet like yours but bottom bushing looks exactly like yours. They obviously have issues whit where these bushings are sourced. Old o e he had wobbled in the distributor machine...
I thought it had a bent shaft. Runout checks on that proved inconclusive. Certainly not enough to cause that much wobble.

Still have shaft and housing if you need one to look at. Something is going on.

[STEELCITYFIREBIRD]

The Pro Billets I set up this weekend had a bearing at the top. I put gear lube in the hole in the housing before I install them.HTH

[Sun Tuned]

Top is a ball bearing. Or should be in that model.

[STEELCITYFIREBIRD]

Yeah I'm thinking if it has a bushing it may be one of the imposters that are/were going around.