Distributor gear, I think I know

[David Van Weele]

I think I know what has been the problem. When you rotate the gear on the shaft you have to reinsert the shaft 180 degrees from where you removed it. I rechecked the gear today found it ok with the correct dimple orientation. Reinstalled the Dist. and it would not fire the engine. I rotated the wires in the cap 180 degrees and what do you know it fired instantly. I believe that if you rotated the gear on the shaft you must reinstall the dist. with the shaft rotated 180 degrees from where it was when removed from the engine. Is my thinking correct or is my brain fried?

Thanks, Dave

[Duke W.]

I don't know about your logic, but...

there are an odd number of teeth on the dist. gear, so installing the gear "backwards, throughs it off half a tooth. Because the vacuum can limits the amount of rotational freedom the dist. housing has, not all possible installation positions will allow you to get the initial timing dialed into the correct spec.

There are a seemingly infinite number of ways to install the dist. and arrange the wires and make the engine run, but only ONE way that I know of to get the initial timing in at the correct spec - the way they installed it at Flint.

Duke

[Patrick T.]

Re: I don't know about your logic, but...

Assuming you have #1 cylinder mark on the harmonic balancer on about 10 degrees BTDC on the timing tab, if you replace the distributor back in with the rotor cap on, I don't see how you could install it 180 degrees out. The rotor cap will tell you if it's pointing to the #1 cylinder.

This is the way I've always done it, and never had a problem. If I need to move the distributor back or forth 1 or 2 teeth to clear the ignition shielding, I just move the oil pump screw accordingly, and reinstall. Patrick

[Mike Schardt]

Re: I don't know about your logic, but...

I agree with Patrick. You can move the oil pump shaft to seat the distributor and have rotor point to #1 wire in the cap. I've not heard of aligning up the dimple on the gear. What is the procedure for dedermining where the dimple is aligned?

[David Van Weele]

Dist Gear

The way I came up with the rotation of the wires, all of which I have labeled and the #1 terminal labeled, is when it did not even fire I rotated the engine over with a wrench to the correct timing mark that I have used for many years and pulled the cap the rotor was 180 degrees from the #1 position. Is not the distributor tuning at one half of engine speed? When I moved the gear 180 degrees I kept the shaft in the same position and rotated the gear, I should have rotated the shaft and held the gear in position then when reinstalling the dist. I should have lined the rotor up with #1 more or less. By not rotating the shaft it was firing on the exhaust stroke, Is this logical. I do not want to do it again. By the way when I put the dist in with the gear in the correct orientation I have plenty of room to adjust the timing not like I had before event though ever thing is out 180 Degrees. Back to school for me. My wife and I are going out for bagels but see you all later today I hope.

What flavor coffee do you like?

Dave

[Duke W.]

Re: I don't know about your logic, but...

GM installed the gear with the dimple pointing the same direction as the rotor. I don't think my '63 shop manual says anything about this in the distributor section. Many years ago when I first disassembled the dist., I couldn't get the timing right due to interference of the vacuum advance with the manifold. I finally figured out the dimple/rotor tip relationship, reinstalled the dist. and was able to time it. The gear can go on either way - dimple pointing the same direction as the rotor tip or 180 out, but because the gear has an odd number of teeth, the only way to know to get the timing dialed in is to have the dimple properly indexed and the wires in the correct position on the cap. That's why the gear has the dimple. If the gear had an even number of teeth it wouldn't make any difference which way the gear was installed.

If you can get the timing right the dimple is probably indexed correctly, but the only way to verify it is to pull the dist. and inspect it.

Duke

[David Van Weele]

Re: I don't know but it worked

I rotated the shaft in the distributor and realigned the oil pump shaft the it fires on the first turn of the key. It has not started this easy for the last 25 years. Thanks for every ones help. I still have the problem of not being able to have the engine less that 1100 RPM but that has been the case since new. I guess now is the time to play with my new FI Manometer.

http://www.z06vett.com

[Duke W.]

Re: I don't know but it worked

I think the FIs always were more problematic on idling than the carbureted engines with the same cam. For a continous flow system you have to compromise between nozzle size and pressure. Higher pressure and a smaller nozzle would help with a lower idle speed, but would increase system cost.

No, I'm not an FI expert, but I was just reading an article about this in the Fall 1987 Corvette Restorer. It was a reprint of a Road Test of a '57 Fuelie from some defunct magazine, and they discussed this issue.

Back when I first owned my car I was acquaited with a guy who owned a '63 red SWC like mine, but with FI, and he always had to idle it about 1100-1200. Even then it surged and the idle speed varied quite a bit. By contract I could get my SHP to idle steadily at about 1000 with just a bit of lope from the Duntov cam. I could idle it as low as about 900 with a bit more lope, but any attempt to idle it lower than that would really reduce idle quality.

If you still have the OEM vacuum can, Dave, I would replace it with the late '64, '65 FI vacuum can which has all the vacuum advance in at about 8". The production '63 SHP and FI can did not have all the advance in until about 15.5", which is less than idle vacuum. Once I "upgraded" to the 8" can I could idle at 800 to 900 with significantly improved quality.

Duke