1963 Distributor gear dimple

[Richard M.]

I'm ready to reinstall the 024 distributor back into a 340 hp engine after resealing a leaky intake manifold and rebuilding the carburetor, etc.

I did some baseline tests before disassembly and checked timing, etc. It's spec is 12*, but I measured apx 14* on my timing light at idle, apx 750rpm. There is no detonation or unusual behavior under load, except for a slight stumble.(I found the accelerator pump screws loose on rebuild so I think that may be solved).

This engine has ported vacuum. I had it idling for about 20 minutes the other day and it ran fine and cool at 180*. The vacuum can was about 1/8" away from the stock intake, and the plug wires were indexed properly. I would like to get the vac can better positioned and also to ease the strain on the tach cable. I also tested the MS 201 15 vac and it was right at spec, starts at 8" and all in at 15".

The dimple on the gear does NOT align with the rotor tip. This engine is very original but I'm unsure if the distributor was ever out. it has a split pin in the gear.

Rotating the gear to line up the dimple to the rotor tip will do exactly what in this situation? Will I make matters worse by rotating the gear?

P3010021.jpgP3010025.jpgP3010026.jpg

at rotor tip, no dimple.
P3010027.jpgP3010028.jpg

away from rotor tip, dimple.
P3010029.jpgP3010030.jpg


Thanks,
Rich

[Mark E.]

Re: 1963 Distributor gear dimple

Rich,

Hopefully the real experts will chime in, but meanwhile:

- Did this car originally have ported or full manifold VAC vacuum? You might start with whatever was original. It varies by type of cam and engine, but most of our engines like 10 - 24 degrees BTC at idle and 38-40 deg. BTC total centrifugal at 2400-3000 RPM (not counting VAC; this is for WOT performance). In high vacuum conditions (cruising) they like 50-54 deg. total advance at 2400-3000 RPM (initial, centrifugal, plus VAC). There are a lot of threads talking about how you can play around with initial timing, max. centrifugal advance, the timing of that advance, and various VAC types to tailor the ignition advance to your car and its usage. For example, your 340HP solid cam may like a lot of initial advance. That can be achieved with aggressive initial static mechanical timing, reducing the distributor's centrifugal advance so total remains < 40 degrees, and using ported vacuum. Or you might try less initial static mechanical timing, greater centrifugal advance (with initial + centrifugal still < 40 degrees), and manifold vacuum for VAC (manifold vacuum will bump your total timing at idle quite a bit). My car, which has a smooth hydraulic cam, likes only about 10-12 deg. BTC at idle, 38 deg. total centrifugal at 2400 RPM and 50 degrees total at cruise (about 2400 RPM). I played with achieving that with manifold and ported VAC sources and discovered it liked ported VAC best. Each car is a bit different, so experiment.

- Definitely re-orient the distributor's driven gear properly so the dimple is lined up with the rotor tip. That will ensure proper phasing with the cam, and shift the distributor housing's orientation on the engine about 1/16 of a turn (everything else equal).

- Make sure #1 plug wire is in the proper cap tower for your year and engine. Look it up in your shop manual; the proper tower actually changed over the years (I think 1968), and is also different for SBC vs BBC so there's no one correct answer. Also check the recent thread on this topic.

- The shop manual will also show the orientation of the distributor housing relative to the engine. Typically the cap's mounting screws are about 11 o'clock and 5 o'clock (with the front of the car at noon) but this may vary a bit by year and engine also.

With the gear properly installed and the correct #1 tower used, your distributor's clocking should be fine.

[Stuart F.]

Re: 1963 Distributor gear dimple

Couple of quick questions to clear up what animal you are dealing with;

1) you mentioned loose pump screws leads one to wonder what carb you're dealing with, I.e. A Holley or a Carter AFB (std).

2) you mentioned a ported vacuum spark advance again one wonders which carb you have. The standard AFB is full manifold vacuum only.

Also, be certain you take into consideration that the 63 SHP timing tab degree marks indicate less than 2 degrees each (believe it is more like 1.3 each).

Stu Fox

[Mark E.]

Re: 1963 Distributor gear dimple

Also, be certain you take into consideration that the 63 SHP timing tab degree marks indicate less than 2 degrees each (believe it is more like 1.3 each).Stu Fox

Well, that was considerate of Chevy.

[Timothy B.]

Re: 1963 Distributor gear dimple

Richard,

Turn the lower gear to align the dimple and try it in the engine. The housing should retard (toward the coil bracket) and that should get the tach cable better aligned.

The carburetor should be 3461 and the V/A is full manifold vacuum. What you are seeing is the #201 control not being pulled until RPM goes up and vacuum gets better. This is not the best suited for the engine but If you want to use the original parts than you will have to live with it. I thing with that 24* distributor you can get away with 14-16* initial timing if you want to try it.

Look inside the distributor and see if the tach gear wore the housing, if so you can install a bronze button to re-align the main shaft and side gear.

Make sure the float level is correct on the AFB because the at rest position of the fuel in the accelerator pump cavity is the level of the fuel in the bowl and that may cause a hesitation.

[Stuart F.]

Re: 1963 Distributor gear dimple

It is not feasible to install a bronze button in the 63 distributor, or such has been my experience, w/o countersinking a space for it in the housing. The plastic or Teflon buttons will not work either. I had drilled the hole in mine for that purpose, but did not have the tooling to do a countersink. I chose instead to tap the hole I drilled and use a set screw with Loctite. I also stuck with the original gear and cross shaft to maintain a match to my original distributor shaft gear as the damage to the shaft was above the lower bearing and the side to side wear was negligable. Hesitation with an AFB is easy to overcome through float level correction (as Tim mentioned), as well as available squirters and jetting. Also, you could realize improvement to idle an low speed performance with a B28 VAC. The tough one though is lean surge like what drove me nuts. I finally cured that by re-sleeving the primary shaft which, though not leaking vacuum, was uncovering the transition slots differently between left and right primary throttle bores. It was that bad.

Stu Fox

[Gene M.]

Re: 1963 Distributor gear dimple

The dimple in the gear can only go on right or wrong there is no turning it. The pin thru the holes secures it in one of two positions. If the dimple does not align up it must NOT be an original GM gear. Or possibly the shaft is aftermarket.

[Edward J.]

Re: 1963 Distributor gear dimple

The dimple in the gear can only go on right or wrong there is no turning it. The pin thru the holes secures it in one of two positions. If the dimple does not align up it must NOT be an original GM gear. Or possibly the shaft is aftermarket.

Gene, I have seen some issues with using a camshaft made by other suppliers and sometimes it requires rotating the dimple 180 to get the timing to work with the limited throw of the dist., I purchased a camshaft from Napa that has the same profile as the 097 Camshaft, and it needed the drive gear to be rotated .

[Richard M.]

Re: 1963 Distributor gear dimple

Thanks for the responses gents. Just got back in......

This is a 64k mile original 340HP engine. Late February car. Seems engine was never apart, except when I removed the intake to fix the oil leak. I saw 2 metal head gaskets on each side looking into the lifter valley when I had the intake off yesterday. Head dates line up to the block/build etc. I'm pretty darn sure this engine has never been apart. However, I'm baffled about the distributor lower gear/dimple arrangement whereas it's not in alignmnent with the rotor tip. The distributor clamp bolt was seized pretty good when I took it off.

The carburetor is a 3461S with it's original tag dated Jan. It appears it was rebuilt once before based on my internal observations. Today when I rebuilt it I set the float level to spec(from my kit data and verified with the 1963 CSM).........7/32". Float drop 23/32". Everything appeared decent inside. As mentioned the accelerator pump nozzle screws were loose so it may have been sucking air and not getting a good squirt.

I will realign the gear dimple to the rotor tip and retry. I believe the distributor was worked on before and someone may not have known about the dimple to rotor tip arrangement. A lot can happen in 53 years.

Before...
P2230025.jpg

Rich

[John D.]

Re: 1963 Distributor gear dimple

Edward Johnson. Tell me about the cam you purchased from NAPA. Was it the Federal Mogul CS113R?
IF not what cam is it? Thanks, John

[Richard M.]

Re: 1963 Distributor gear dimple

Gene, I have seen some issues with using a camshaft made by other suppliers and sometimes it requires rotating the dimple 180 to get the timing to work with the limited throw of the dist., I purchased a camshaft from Napa that has the same profile as the 097 Camshaft, and it needed the drive gear to be rotated .

Edward, When you say "rotating the gear to get timing to work", which end result?.....Dimple to tip, or dimple away from tip?

Edward Johnson. Tell me about the cam you purchased from NAPA. Was it the Federal Mogul CS113R?
IF not what cam is it? Thanks, John

John, FYI, I've used the CS113R from NAPA, actually Sealed Power, on several C1's and is a good replacement. Albeit these were 0891 distributors which are not vacuum advance types. The only issue is that the lash specs are slightly different from the stock 097 cam by the cam card specs.

Rich

[Duke W.]

Re: 1963 Distributor gear dimple

The dimple should be in line with the rotor tip. The OE AFB VAC signal port should be full vacuum, but the OE 201 15 VAC does not pass the Two-Inch Rule because the cam only generates about 12" vacuum at 850-900, but the VAC requires 15" to fully deploy. This will cause idle stability problems.

Replace the VAC with a "B28", which should still be available under the Airtex Brand 4V1053.

You can validate with a good degree of confidence that the heads have never been off it it has two shim type gaskets on each side that should total about .036" thickness that you can measure with a feeler gage at the corners of the head-block interface. Let us know what you find.

The OE centrifugal curve is very lazy- max of 24 deg. @ 4600. Buy a Mr. Gasket 928G spring kit and install the lighter springs, which will bring it all in at likely no more than 3000, which will improve low end torque and fuel ecomony as long as it doesn't detonate, which it likely will not.

Then use a dial back timing light and with the VAC disconnected and the hose plugged with a golf tee rev the engine to a few hundred RPM above where the centrifugal is all in and set it at 38-39. Total idle advance with the VAC connected should be about 30.

Test drive for detonation (load it up at low revs) and if you detect any, back the Total WOT advance down in two degree increments until the detonation ceases.

Duke

[Edward J.]

Re: 1963 Distributor gear dimple

Edward Johnson. Tell me about the cam you purchased from NAPA. Was it the Federal Mogul CS113R?
IF not what cam is it? Thanks, John

,
John, Rich is correct seal power.I have a 3000 mile since install, Run great with the B28 as Duke states. OE vacuum can did exactly as Duke states.

[Richard M.]

Re: 1963 Distributor gear dimple

Update, I completed the engine work and corrected the distributor gear by rotating it to align the dimple to the rotor tip. After cleaning and resealing the valve covers and replacing the fuel filter, which was a fun task in itself as the fittings required some more adjusting, I set the balancer timing mark at the 12* mark on the tab(spec is 10* but I decided to go a bit higher), aligned the rotor tip to the #1 distributor plug wire, and the engine started right up fine. The vac can in now smack dab in the middle between the intake and the coil bracket, just like it was designed to be.

After it normalized I checked timing. Static timing right around 12* with the vac can disabled and line plugged. Then checked vacuum advance when I plugged it back in and saw apx 25* on my dial back light. I brought it up to about 2000 rpm and got around 35*. After a while I brought static back to spec, 10*, and left idle at around 800-850, checked vacuum on my gauge....around 15" after adjusting the carburetor emulsion screws while observingmy vac gauge. Checked timing again with dialback and now at 23*. Tomorrow I'll test drive and check overall operation and feel confident in the results. Thanks for the guidance on the distributor gear dimple issue and other helpful tips.

I checked for oil leaks at the intake, as that was main objective of this entire exercise, and all is tight and leak free. I got a bit sidetracked with the distributor but all is good now.

I did a video after I started it so you can see some of the action.....

https://youtu.be/V2gWR4pyV4w

Rich

[Michael G.]

Re: 1963 Distributor gear dimple

Glad to see you got it leak proof.

Just to clarify some of the stuff about distributors: The gears can go on two ways. If you look at the pics below, you'll notice that in the first pic the the pin is aligned with a gear tooth. In the second pic (the other side of the gear) the pin is halfway between the teeth. Removing the pin and rotating the gear 180 degrees changes the alignment by half a tooth or about 13.8 degrees. When the distributor is inserted, this 13.8 degrees can make the difference between the distributor being rotated too far toward the carb or being properly oriented more toward the passenger side.

IMG_0189.jpgIMG_0190.jpgIMG_0193.jpg

In the third pic, the distributor is shown with the dimple installed opposite the rotor, which is not usually the proper installation position, but may be necessary with some aftermarket cams.