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63 SB, set up as 340 HP w/ 8" balancer. There are 8 marks on the advance side of the timing tab. Assuming 2 degrees per mark makes 16 degrees at the end of the tab. How does one measure total timing in the range of 36 degrees? My timing light is the simplest type: essentially a strobe. Apparently there are lights with electronic degree measurement and readout. Is this what I need?
Steve, it can still be done with a basic timing light, but it's a whole lot easier just to get an adjustable timing light. There is a good article at corvettefaq.com that has the procedure.
There are at least two fairly simple ways to establish a 34 deg line on your balancer. (three if you count a speed shop timing tape) With the timing mark at zero, make a new mark across your balancer exactly 2.513" (2 1/2") below the current zero line on the outer ring of the balancer. This dim, 2.513", is exactly 36 deg along the surface of an 8" balancer. Run the engine at a sufficient RPM to ensure that the cent advance system is all in and then align your new mark with the ZERO line on the timing tab. That will be 36 deg total which is initial plus cent.
Another method, although probably not as accurate, would be to start with the timing mark at zero, then rotate the engine backwards until the mark aligns with the 10 deg line on the tab. Make a small reference mark on the balancer at zero. Again rotate the engine until your new ref mark lines up with the 10 deg line. After the third mark, (30 deg), roll the engine another 6 deg and make your final mark which will be a 36 degree line.
For 34 deg total, use 2.373, or 2 3/8"
For 36 deg total, use 2.513, or 2 1/2"
For 38 deg total, use 2.652, or slightly over 2 5/8"
For 40 deg total, use 2.792, or slightly less than 2 13/16"
First, buy a "dial-back" light. Mine is from Sears and is made by Acton - bought it on John Hinckley's recommendation when it went on sale (about $50). I now wonder how I survived all these year without one. My old static light was beginning to shock me more than it flashed the bulb, so I was in need of a new one.
The second alternative is to carefully measure your balancer circumference and place a mark on 30 degrees (1/12th circumference) or 36 degrees (1/10th circumference.
Then, for example, with your static timing light, you read the location of the 36 degree mark. If you turn the dist. to place it at "0" on the tab then your total WOT timing is 36 degrees, which is about right. If you want 38 degrees you rotate the dist. to put the 36 degree mark at 2 advance.
Given that the OE centrifugal curve doesn't top out until 4600, you will need to rev the engine over this amount to read total WOT timing unless you have installed lighter centrifugal springs.
Also, the OE vacuum can (201) and its service replacement (163) is NOT a good match for the 327/340's manifold vacuum characterisitics. Given that this was the first year vacuum advance was installed on SHP/FI engines they just didn't get it right. They "fixed" the problem in '64 and used the "236" can in all SHP/FI SBs up through '67. (After '67 they changed due to emission control requirements.)
The 201/163 cans don't provide full vacuum advance until about 16" which is less than typical 12" idle vacuum with the Duntov cam. The "236" can provides the full 16 degrees of vacuum advance at 8". Once I installed a 236 vacuum can in my "63 327/340 about 1966, my idle quality and stability problems went away.
The replacement 236 can is marked "B28" and is available from NAPA (VC1810) and other brands, but under different part numbers. A new Delco "236" can is also likely to be marked "B28" rather than "236-16" as were the originals and early replacements since Delco now just buys the same Dana Controls can rather than making their own.
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