Strange timing issue

[Troy P.]

Re: Strange timing issue

Good tip. I did not know the timing mark was aligned with the keyway.

Took a look. Could not see the keyway on the 63 because it has a pulley bolted on in the way. On the 55 the pulley is integral to the damper and they are riveted together (one year only I think). Using a mirror I could not see both mark and keyway at the same time but best I can tell they are either right on or very close.

[Wayne L.]

Re: Strange timing issue

Troy-
All 56's and low horse 57's have the riveted-on pulley.

[Troy P.]

Re: Strange timing issue

There you have it.

[Troy P.]

Re: Strange timing issue

Looking at photos of other 55 Corvettes I see the distributor is installed much farther counter clockwise than mine is. There is a benefit to this as the early (straight) accelerator arm hits the ignition wires and prevents WOT. (Later in 55 they came out with a bent arm, seen in 56 and newer, that avoided the accelerator from hitting the wires.) Rotating the distributor farther counter clockwise would mover the ignition wires farther from the accelerator link and reduce the conflict.

I have found that rotating the distributor counter clockwise with the cam gear engaged increases advance. My timing is already too far advanced, per the timing light. But I need to rotate the distributor in that direction. So it appears the distributor is off a tooth or two, I think???

If I pull the distributor high enough to disengage the cam gear, rotate it counter clockwise and drop the distributor down into the gear will that tend to retard or advance the timing?

This is all quite a pain because the 55 distributor has a chrome shield and is stuffed with shielded wires with ground screws. So its very difficult to removed the distributor cap and check where the rotor is pointed.

How many teeth on the distributor gear? Need to know how much timing will change for each tooth.

[Troy P.]

Re: Strange timing issue



This is what the 55 set up looks like.

[Troy P.]

Re: Strange timing issue

Searched for photos of distributor gears on the web and counted they have 13 teeth. So each tooth changes about 27 degrees.

Using photos of running 55 V8 engines I see my distributor is not clocked enough counter clockwise. Using a protractor I measured that mine needs to rotate about 27 degrees to match those in the photos. Thus I conclude the distributor is off by one tooth.

I will try to turn it without disturbing the alignment with the oil pump shaft. If that works I'll retime the engine and then maybe know if the distributor gear is also on backwards.

[Troy P.]

Re: Strange timing issue

I've got everything apart now. I know I need to rotate the distributor counter clockwise 27 degrees or so but don't know which way to rotate the rotor and distributor shaft. Its off one tooth.

Recall it ran fine with an advance reading or about 30 degrees. If I rotate the distributor housing counter clockwise which direction do I need to rotate the rotor to get the timing back to spec? I need to move it one tooth on the cam gear but which way?

[Duke W.]

Re: Strange timing issue

You need to start from scratch. First, verify that the plug wires are indexed IAW the '63 Corvette Shop Manual. Assuming the dist. gear is to OE spec use the following procedure.

1. Rotate the engine so #1 is at the initial timing point on the dist. I suggest 14 deg. Note that the shaft will rotate CCW about 20 degrees as the gears disengage.

2. Remove the dist. and verify that the dimple in the gear is pointing toward the rotor tip. Correct if necessary.

3. Hold the dist. above the hole with the rotor tip pointing along engine centerline.

4. Rotate the bottom 90 deg forward and note the orientation of the oil pump drive pin.

5. Check that the slot in the pump drive shaft is so oriented. Tweak with a paint mixing stick if required.

6. Lower the dist into the engine. As the gears engage the rotor tip will rotate about 20 deg. CW.

7. If the gears do not engage, tweak the slot in the shaft with the paint mixing stick as required.

8. Once the gears engage and the dist. is seated rotate the housing until the points just begin to open. This is static timing the engine.

9. Start engine and adjust timing as required with a light.10. If the drive gear is to OE spec and the timing is in the correct range the window should be normal to engine centerline and the VAC should be about halfway between the coil bracket and manifold interference points.

If the above procedure, properly executed, does not get the job done properly them I suspect that the dist. gear is not manufactured to OE spec.

Duke

[Mark E.]

Re: Strange timing issue

I've got everything apart now. I know I need to rotate the distributor counter clockwise 27 degrees or so but don't know which way to rotate the rotor and distributor shaft. Its off one tooth.

Recall it ran fine with an advance reading or about 30 degrees. If I rotate the distributor housing counter clockwise which direction do I need to rotate the rotor to get the timing back to spec? I need to move it one tooth on the cam gear but which way?

Troy,

I'm not sure you're getting it. The above addresses how the distributor is oriented relative to the engine/intake, aka clocking position. The housing can be clocked however it makes sense. As this is done, the distributor shaft gear is also repositioned relative to the cam gear to accommodate this clocking and maintain proper timing.

Changing the clocking of the distributor does not cause or help the odd timing issue you describe earlier. As I and others have posted above, this timing issue is likely caused by an improperly located timing tab, slipped balancer, or user error with the timing equipment or method.

[Troy P.]

Re: Strange timing issue

I bought a new distributor cap for testing purposes so I didn't have to deal with the one enclosed in the chrome shielding. I pulled the distributor enough to rotate the shaft one gear and also rotated the body counterclockwise to match the orientation I found in photos of other 55's. Started engine with rotor roughly pointed at number one terminal and timing mark roughly at TDC while rotating the distributor to a place it liked during cranking. Since it runs in this configuration it provides a starting point for further tweaking. Checked oil pressure gauge when engine started and have positive pressure. Is it thus safe to assume the distributor tang is engaged with the oil pump?

Tomorrow I will reinstall the repainted distributor hold down clamp and see what the timing is with the timing light. Stopped to wait for paint on clamp and bolt to dry.

Only thing I did not do is pull the distributor all the way out to examine if the gear was on correctly. There were two more of many shielded wires I would have had to take off to pull it up high enough to see the gear. Got tired of taking it so far apart.