1967 L-79 Distributor Assembly Question

[Duke W.]

Re: 1967 L-79 Distributor Assembly Question

If you use a dial back timing light you don't need balancer timing tape.

If you want 12* initial just set the timing light at 12 and rotate the distributor so the balancer notch is at zero on the tab.

Likewise, when testing advance at any RPM use the dial to move the balancer notch to zero and read the number on the dial.

Duke

[Stuart F.]

Re: 1967 L-79 Distributor Assembly Question

Duke;

My application of the timing tape was originally only for use in setting my valves using John's and your instructions, and it worked very well. One side effect of that effort was for me to learn that the end bolt in my balancer was loose as I was barring the engine over with my Torque Wrench.
During my recent distributor "rebuild", I searched through all our local Auto Parts stores for a Dial Back timing light without success. So, I used the next best thing by employing what I already had available.

Stu Fox

[Duke W.]

Re: 1967 L-79 Distributor Assembly Question

I bought my dial-back light from Sears a few years ago, and the same light is sold under the Acton brand - about 50 bucks. You really don't need one with timing tape, but I sometimes read the spark advance map for local chapter members, and since none have ever had timing tape the dial-back light makes it easy to do.

I'm sure a simple Google search will yield a number of choices if you want to buy one.

As far as adjusting the valves, marking the balancer can be done with tire crayon and a straight edge. The 90 degree indexing points don't have to be perfect, but the above method should get it within about five degrees, and I think you're okay if the engine is indexed within +/- 10 degrees of the 0, 90, 180, and 270 degree indexing points.

Duke

[Stuart F.]

Re: 1967 L-79 Distributor Assembly Question

Thanks for the tip. I'll check at Sears next time I'm at the Mall. Hope they stick around for awhile as I've bought a lot of things in the past from them including my tool chest and bench, and my air compressor among other things. They still have a lot more "guy" stuff than most anyone - at least in one place.

Stu Fox

[Stuart F.]

Re: 1967 L-79 Distributor Assembly Question

I guess Kenny has all the information he needs and/or wishes to share, and is probably motoring on down the road in a smooth running Vette.

Stu Fox

[Kenny H.]

Re: 1967 L-79 Distributor Assembly Question

I have the distributor re-assembled and hope to get it installed this weekend. Out of town all this week on business this week, so I haven't been able to work on anything. I'll post the results once I get it back in the car and verify the ignition map based on the re-build.

Stu: Did you get my PM regarding the work I did for the blueprint?

[Stuart F.]

Re: 1967 L-79 Distributor Assembly Question

Ken;

Figured you were away, but had to pull your chain anyway just for fun.

Te PM message I received was the same message that you posted saying you had sent one, so please send your info once again when you get time.

Stu Fox

[John H.]

Re: 1967 L-79 Distributor Assembly Question

Have read that timing mark on 8" balancers are about 2degrees more than actual advance. Will applying a timing tape make degrees read from tape be the actual degrees advance?

Bill -

Not true. The timing index line on the damper's inertia weight is at exactly TDC; the keyway on the crank nose that locates it and the seventh hole in the rear crankshaft flange are both also at TDC (the seventh hole in the rear flange was used to index the crank during manufacture to grind all eight crankpins and the damper keyway in the crank nose). Starting in 1969, in passenger cars with the new "long water pump" accessory drive that placed the alternator on the passenger side, the timing index line was moved 10* counter-clockwise on the inertia weight surface, but that change didn't affect Corvette engines. That's why it's important to have the correct damper AND timing cover.

[Duke W.]

Re: 1967 L-79 Distributor Assembly Question

John - I think the original question referred to the fact that the timing tab is not accurate on 327s with the 8" balancer. It reads abaout 15-20 percent high.

I and others have verified by setting timing using the tab and then applying a dial back light. If you set initial timing on the tab at 12 the dial back will indicate about 10. Try it on your '67 and see if you get the same result.

That's why I prefer setting total WOT on distributors with light springs (VAC signal line disconnected and plugged), by revving it to a few hundred revs above the top of the centrifugal curve, and I then shoot for 38-39, and if it doesn't detonate - good to go.

Back in the day I ran as much as 18 initial, which was actually above the top of the tab, but it was probably only about 15-16 so total WOT advance was 39-40, and my 327/340 did not detonate on typical "premium" leaded gasoline. Of couse back then I also thought that it had 11.25:1 CR. I didn't know about the double head gaskets until I took the engine apart for a refresh in the seventies.

Duke

[Stuart F.]

Re: 1967 L-79 Distributor Assembly Question

I thought we went down this road a few years back, with a group that included Michael Hanson, and it was concluded that we needed to adopt a correction factor where the space between marks was equal to 1.36 degrees instead of 2 degrees. My understanding is that this was at least true for the 63 SHP Engines. I have been using that factor since and it has shown some improvement in low to mid range snap given the same distributor curve setup, I.e. 1.36 x 9 marks = 12.25 degrees initial. Since new, prior to this knowledge, I was only running at about 6 marks or less than 8 degrees initial. Another case in support of a dial back timing light, I'm sure.

Stu Fox

[Duke W.]

Re: 1967 L-79 Distributor Assembly Question

I recall discussions a few years ago, and a conversion factor was calculated. You're still short of the "ideal" 38-39 deg. total WOT advance, so bump it up to 16 on the tab.

A dial back light is a huge improvement over the old fashioned type. The other problem is that on SHP engines it is often difficult to get the engine to idle stably below where the centrifugal starts.

With a dwell, meter, dial back light, and Mity-Vac I can determine the spark advance map in a couple of minutes, and another few to reset the timing , if necessary. It's take more time to set up and take down the equipment than it does to do the work.

Duke

[Stuart F.]

Re: 1967 L-79 Distributor Assembly Question

Duke;

On our way to the Mall today so I will follow up on your Sears tip as a source for a dial back light.

I'm still dealing with the issue of initial timing in that my VAC is tight to the manifold at my calculated 12 initial. Yes, I still have the gear on 180 degrees off on my distributor as it was the only way I could get it to run! I'd like to take another shot at rotating it back (dimple to rotor), but I need another stretch of cooler weather to spend time in my garage. That is no longer likely until this coming fall again. Got a month long trip planned out of the country for June and July so that will get me through most of the summer.

Stu Fox