Distributor drive gear cover

[wwheeler]

I need to replace the gasket on the distributor drive gear cover. I am going to index the distributor body and rotor to the cover before I take it off. There are eight or so hex bolts that have to be removed. Anything else? I hoping nothing will spring out at me when I take the cover off.

What is the large hex head for on the front of the cover?

Thanks,

Wallace

[Naj ✝︎]

Hi, Wallace,

Take the distributor off with the engine at TDC and the two front lobes of the camshaft at 10 to 2 position. The rotor arm should now line up with with the line on the distributor body. After pulling the distributor, note the position of the slot of the distributor drive gear (remember that the slot is off centre !!). You can now remove (first the small spring and then) the drive gear with a good magnet. The bottom part of the gear is bevelled and will turn (CW I think) as it comes out.
The big hex nut on the front of the cover does not need to be removed. Nothing else should fall out when you take the cover off.

Install the drive gear in the same position after changing the gasket and the distributor and rotor should line up again on reinstall.

There are some useful pictures in the distributor section of the wiki.

Naj

[ja17]

Hello Wallace,

Good advice from Naj.  Be sure to note that the slot in top of the gear is slightly offset. The cog on the bottom of the distributor is also. Be sure to install them so the match up.

[Benz Dr.]

I've found that the helical gears have to be positioned perfectly or there will be too much back lash between the two gears when assembled. This will cause the idle speed to be all over the place but generally too high. This will be most noticed when the engine is cold and the oil is still thick. As the engine warms the idle speed can be brought down by blipping the throttle.
This is very similar to a weak return spring condition inside of the distributor. A quick check will show that the distributor is returning properly but there's still extra play that will be taken up if you turn the rotor past what appears to be its rest postion. The rotor should, at all times, return to the same position after releasing it and have no extra play or movement beyond this point. If you have this problem the two gears below the distributor are not meshing properly.
 This is a very similar condition as having too much play in the tach drive gear. That's a very serious problem while this one isn't as serious. Excess play on the tach drives gears could cause complete oil pump drive failure which WILL cause some very serious engine damage.

I haven't figured out how to fix this distributor drive problem yet and I haven't had time to fix it on my car. I'm thinking if I add a washer behind the helical gear it will make the gears engage better. Or maybe my casting is worn out. I have the spring under the drive on the distributor so it's held tightly in place. I do know that there's no end play on the shaft going to IP and oil pump so it's only excess play right at the gears. More annoying than anything else because the engine will idle nicely at 850 but tends to hover around 1,400 unless I make it slow down.

[wwheeler]

Great thoughts and thank you! I am always one to be on the cautious side and don't want to make things worse just to fix a small leak. Thanks for the reminder about the slot being off set as I had forgotten about that. Great design if you know about it, potential disaster if you don't.

[wwheeler]

Cover came off no problem. I put a new gasket on it that was thin and should do the trick . There was nothing on there but blue RTV silicone. No wonder it leaked and weeped. The fact that no gasket was used makes me wonder about the quality of the rest of the engine rebuild by the PO. Hmmmmmm.

[stickandrudderman]

You should examine closely the bush pressed into the inside of that cover that the dizzy drive sits in. I've seen the bush housing excessively worn on the top face a few times. If you're clever and resourceful it can be repaired, but a replacement cover is the easy option.

[wwheeler]

Thanks for the tip! I hadn't thought about that before and don't want to waste my time refinishing it if it is worn.