Stripped Distributor Gear - Need a Machine Shop

AgShelby · #1 (**permalink**) 10-22-2006, 03:00 PM

Yesterday I was approaching a red light at low speed and downshifted to 1st. The car backfired and then wouldn't start. It would fire intermittently - so I suspected that it was an ignition problem. I pulled off the distributor cap momentarily, and saw that the rotor was turning.

Today I began troubleshooting and checked out the entire ignition system. It all checked good and I was getting good spark from the ignition module, but nothing to the plugs. I pulled the cap again and noticed that the distributor was turning intermittently. I then pulled the distributor and found that about half the teeth were missing from the gear. I suspect that the failure was with an incompatibility between the cam and distributor, or the gear drive timing system failed.

Anyway, I need to go into the engine and diagnose, clean out the metal and repair. This is beyond the detail that I want to get into - so need a good machine shop in the area.

Any suggestions?

joe garland · #2 (**permalink**) 10-22-2006, 03:56 PM

Give me a call.

"Uncle Joe" 512-281-4170

jetenginedoctor · #3 (**permalink**) 10-28-2006, 08:42 PM

I suggest you have a read within this thread:

http://forums.corner-carvers.com/sho...stributor+gear

This is the thread that I mentioned today at the get-together that should be helpful in fixing (and hopefully preventing a recurrence) of your distributor gear failure.

BK

Bob Taulbee · #4 (**permalink**) 11-01-2006, 04:52 PM

AgShelby

Check out the oil pump. I had onethat locked up and took out the distributer gear. I understand that high volume oil pumps and heavy weight oil can can take out the distributer gears, when the engine is cold. My2 cents

MadDog · #5 (**permalink**) 11-01-2006, 05:24 PM

Bob is correct. Remember that the cam drives the distributor that drives the oil pump. So if anything stops the pump or tries to slow it down it is supose to shear off the shear pin that holds the gear on the dist shaft but I have seen it break the gear and sometimes the gear on the cam before the shear pin.
I would recomend checking the oil pump and the cam gear.
MadDog

jetenginedoctor · #6 (**permalink**) 11-01-2006, 11:34 PM

The bottom of the drive gear was clearly grinding against the "landing" on the inside of the block above the oil pump. It's a case of the drive gear being installed too low on the distributor drive shaft, in this case the mistake was made by MSD (big suprise.) He just needs to install a new gear at the correct gear engagement depth.

BK

jetenginedoctor · #7 (**permalink**) 11-08-2006, 07:17 PM

So. . . .

. . . . how did this story end???

BK

AgShelby · #8 (**permalink**) 11-08-2006, 07:51 PM

The distributor is back at MSD for a new bronze gear. Hopefully I will have it back and the timing set by next weekend.

jetenginedoctor · #9 (**permalink**) 11-08-2006, 07:57 PM

Did you follow the instructions outlined in the references I provided regarding the correct placement of the gear on the distributor shaft? If you have MSD just put another one on the same way they did the first one, you're going to end up with the same situation all over again.

BK

vettestr · #10 (**permalink**) 11-08-2006, 08:45 PM

Following the guide to measure correct height in a must as mentioned by Jet. See MSD's instructions here http://www.msdignition.com/pdf/gear_...d_frm22770.pdf

Many surfaces often altered during a rebuild affect this distance and even factory +/- to0lorances when stacked up present a problem if not corrected. Big cams or higher V spring presures also cause this to be an important spec. have fun, it is really pretty easy to do so not a big deal.

Lowell W · #11 (**permalink**) 11-09-2006, 05:06 AM

I set up an extra MSD distributor with a steel gear for my car as a backup. Before I removed the original distributor, I set up a dial indicator and measured the distributor shaft play in and out. Can't remember the numbers now, but it was about half the amount I measured with the distributor out of the car. So far, so good. I pressed the new gear to the dimension indicated by MSD, then measured the play in the new distributor, installed it and measured again. Again, I had roughly half the play in the installed distributor.

As has been noted elsewhere, the forces on the gears act to draw the distributor shaft down into the block. The bottom of the cam gear acts as a thrust face for this "pulling down" force.

Can't recall...maybe I posted this somewhere else already...

Well...hope it helps...

Lowell

jetenginedoctor · #12 (**permalink**) 11-09-2006, 08:03 AM

The cam does pull the distributor gear down toward the oil pump, but the thrust load created by the interaction with the cam is not enough to cause the damage done to the gear I saw from Steve's car. What had to cause that was the distributor shaft having signifigant axial load stress grinding the distributor gear against the landing inside the block, or otherwise clearances itself. Unfortunately for Steve, it appears that the heat generated between the bottom of the distributor gear and the gear landing surface within the block was enough to at least momentarily seize the gear and shred teeth off of the softer distributor gear. The only way this can happen is if the distributor drive gear was installed too "low" on the distributor drive shaft. Don't make the mistake of assuming that just because it comes from MSD that way, that it's correct.

YMMV

BK

AgShelby · #13 (**permalink**) 11-22-2006, 09:14 PM

and the weather is perfect !

Bob In Ct · #14 (**permalink**) 11-23-2006, 05:55 AM

I have to agree with those above regarding gear wear and oil. I know of more than one Cobra owner who insists on using 20W-50 oil, not running a thermostat and not covering their oil cooler on colder days. The result of this is a lot of stress on the distributor gears and poor cooling and lubrication of the engine.

When it's on the street it should be treated like a street engine. Riding around on a 45 degree day with the coolant at 140 degrees and the oil at 120 degrees (before the cooler) cannot be healthy for the engine.

My $0.02 worth.

Bob