jkmhb

Well, I thought maybe my harmonic balancer had slipped, but now I wonder. My '65 has the early finned style harmonic balancer (8" dia.), but has the timing cover that uses the bolt-on tab. Could this be the source of a mismatch? Were the earlier and later 8" balancers marked at TDC differently?

Thanks....


[Modified by jkmhb, 4:51 PM 2/3/2004]


[Modified by jkmhb, 4:51 PM 2/3/2004]

Nicky71

Yes, but I am not sure that is your problem. Pre-69 dampers have the timing mark 2 degrees before the keyway centerline, while 1969-up dampers have it 10 degress before the centerline. I am not up on the configuration of original balancers as to which had the fins on the hub and which didn't--Perhaps JohnZ can enlighten us on this.

Once you have ascertained the correct timing tab and balancer configuration, if you are still unable to time the car it is probably that the distributor gear is installed backwards (180 deg out of phase). The dimple on the gear should be aligned with the rotor when installed correctly. The gear has (I think) 13 teeth. If it is installed out of phase, it will be impossible to be able to adjust the distributor body enough to obtain the correct timing.

muncieman

Hmmmm, what about replacement gears or bronze gears that have no dimple?????????

:bs :bs :bs :bs :bs :bs :bs

SWCDuke

If you have the correct balancer for '65, you also have to have the correct timing cover with the welded on timng tab to achieve accurate timing readings.

The later bolt on timing tabs are off. I'm not sure of the exact amount, but it is signficant.

Duke

Nicky71

I don't see why you feel the need to flame me--I'm not claiming to be the resident expert on distributor gears.

The OEM dist gear had a dimple on it. I have never seen one that did not. If there is no dimple or mark of some sort, how can one easily determine if the gear is on correctly?

As for bronze distributor gears, I really don't understand what your point is. There are always aftermarket parts that differ in design and appearance from OEM parts.

Maybe you can educate us?


[Modified by Nicky71, 11:08 PM 2/3/2004]

muncieman

I bought a Sun machine to do these distributors some years ago. I had heard the rumor that the dimple had to go a certain way. After looking hard at this I discovered several things. The hole in the shaft and the gear is dead center. There is no reference in any thing I've read about the gear going on a certain way. So, I set up a unit for a 60 I had, a later tach drive unit, put it in the car, worked just fine. Took it back out, reversed the gear, re-installed it and it worked just fine.

After market replacement gears have not dimple nor do the bronze gears made for the steel billet roller cams.

I think if GM was phasing the gear to the shaft they would have offset the pin so it would only fit on one way.

JohnZ

I have the original Delco-Remy distributor drawings, and they are VERY specific about the gear being installed with the dimple in line with the rotor segment, and how the mid-point of one gear tooth relates to the roll-pin hole in the gear and in the mainshaft. I also have many original camshaft drawings, and they are also VERY specific about the location of the mid-point of a drive gear tooth relative to the indexing dowel hole. These things were designed as a system - if they're not assembled per the drawing specs, chances are you won't have enough available distributor rotation to set timing with a vacuum advance distributor and have clearance to the #6 and #8 manifold runners on the inboard side and to the spark plug wire/coil support bracket on the outboard side. If the drive gear is on backwards, the distributor housing will be out of design rotational position by half a tooth, or 13 degrees.

The timing index line on the balancer (and the corresponding "0" mark on the welded timing tab) were moved 8 degrees counter-clockwise on long-water pump passenger car applications starting in 1969 (Corvette didn't change until several years later); if you have a "finned" balancer, it's previous to that change, and should have the index line directly aligned radially with the key slot in the hub, and the correct corresponding timing cover has the timing tab welded on. All the bolt-on timing tabs I'm familiar with are for post-1969 applications. :thumbs:

jkmhb

JohnZ - thank you very much for your information on both of my posts. It looks like I have a mismatch between balancer and tab - that would explain a lot. Now I either need to put another mark on my balancer, change the timing cover (which I don't really want to do), or always try to account for the thing being 8 degrees off when I do the timing.

Allcoupedup

jkmhb,
I'm in the same boat - switching from the 6" balancer to the 8". I thought about moving the tab 2" outward (radially) but don't want to butcher an original part and don't have the patience to do it right.

There's an original on EBAY right now:
<A HREF="http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2458383906" TARGET="_blank"> http://cgi.ebay.com/ebaymotors/ws/eB...tem=2458383906</A>
I bid $55 and didn't hit the reserve. Bid away!

I'm sure it's not going to be cheap. You can buy replacements for about $10 and the tab for $5. I think I'll take a new cover and cut up a new tab and have it spot welded in the right location.

Brian


[Modified by Allcoupedup, 12:35 PM 2/4/2004]

JohnZ

Just pull your plugs and use a piston stop tool to find true TDC, and put a new index line on your balancer aligned with the "0" mark on the timing tab with the balancer at the true TDC position, and you won't have to change the timing cover or "do the math" when setting your timing. :thumbs: