Timing gauge for easier dwell adjustment and more

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JLT
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Location: Sacramento CA
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Timing gauge for easier dwell adjustment and more

Post by JLT » Fri Jun 24, 2016 4:16 pm

I could have sworn that I'd posted this before, but couldn't find it. So I'll put it up again.

If you haven't converted to electronic ignition yet, you've probably spent many worthwhile hours adjusting the points. This involves removing the distributor cap and rotor and checking the points gap. If it's wrong, you loosen the screw, move the non-stationary plate just a wee little bit, and tighten the screw. Then you put everything back together, turn the ignition on, start the engine, and hook up a dwell-tach meter. The adjustment will be wrong. You turn off the engine, go to the back, remove the cap and rotor, and try again, loosening the screw and moving the plate another wee bit. Then you put everything back together again (not forgetting the rotor like you did the last time) and start the engine. When you hook up the dwell-tach again, you will find that you have moved the points not one wee bit, but two wee bits. You turn off the engine....

If you've had this experience, you might want to try another way. Print out this handy gauge on a piece of thick paper or card stock:

Image

Laminate it if you want to.

Now attach it to the crankshaft pulley with a button magnet, as shown here:

Image

Connect your voltmeter or timing light or whatever to the #13 terminal on the coil (where you usually clip your timing light or dwell-tach). Turn on the ignition, put the car in neutral, and rotate the engine to the point where the VOM shows 12 volts or the light goes on. Rotate the gauge so that the zero lines up with the crank-case seam. Rotate the engine clockwise until the light goes off or the voltage reads zero. Read the gauge. That's your dwell.

Now you can adjust the dwell simply by adjusting the points, turning the ignition on, and reading the result. There's no need to re-assemble the distributor or start the engine, although you may want to shut off the ignition or disconnect the wire at terminal 15 on the coil while you're actually adjusting the points, to prevent sparky things from happening. I think you'll find that this procedure will reduce your time spent on the job by quite a bit

Note that you don't have to worry about where top dead center is and all that. All you're measuring is the range of the degrees of rotation when the points are on. But once the dwell is right, you can use the gauge to mark out the various points that you'll need for using your strobe, once you've sussed out where top dead center is on your particular beast. (If you've got a stock pulley and a reference book like the Idiot Book or the Bentley, the notches in the pulley should give you an idea where that is.) I put a drop of white paint at the 32 degree mark BTDC, so I can check how the advance is working with my particular combination of carburetor and distributor.
-- JLT
Sacramento CA

Present bus: '71 Dormobile Westie "George"
(sometimes towing a '65 Allstate single-wheel trailer)
Former buses: '61 17-window Deluxe "Pink Bus"
'70 Frankenwestie "Blunder Bus"
'71 Frankenwestie "Thunder Bus"

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asiab3
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Location: San Diego, CA
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Re: Timing gauge for easier dwell adjustment and more

Post by asiab3 » Fri Jun 24, 2016 4:48 pm

Excellent thought process- the only thing missing is the caveat that degree-pulley owners are laughing at folks like you and me that insist on using stock steel pulleys. :P

Schtock Foreverr,
Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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JLT
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Location: Sacramento CA
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Re: Timing gauge for easier dwell adjustment and more

Post by JLT » Sat Jun 25, 2016 11:38 am

asiab3 wrote:Excellent thought process- the only thing missing is the caveat that degree-pulley owners are laughing at folks like you and me that insist on using stock steel pulleys. :P
Yeah, there is that. And I'm sure that there will be people who are into spending fifty bucks or more for the pulley, plus getting the old one off and the new one on, instead of spending a nickel or two on printer paper and ink.

And I should add that you can use the gauge to mark all the salient points on your (stock) pulley wheel and then just toss it away if you want to. (But what's the fun in that?)
-- JLT
Sacramento CA

Present bus: '71 Dormobile Westie "George"
(sometimes towing a '65 Allstate single-wheel trailer)
Former buses: '61 17-window Deluxe "Pink Bus"
'70 Frankenwestie "Blunder Bus"
'71 Frankenwestie "Thunder Bus"

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Ronin10
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Location: Columbia City, Seattle, WA
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Re: Timing gauge for easier dwell adjustment and more

Post by Ronin10 » Sat Jun 25, 2016 12:25 pm

JLT wrote:Yeah, there is that. And I'm sure that there will be people who are into spending fifty bucks or more for the pulley, plus getting the old one off and the new one on, instead of spending a nickel or two on printer paper and ink.
How do you ensure that the center or the paper gauge is concentric with the center of the pulley? Engine tin on a Type 1 seems like it make that hard to assess.
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

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JLT
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Location: Sacramento CA
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Re: Timing gauge for easier dwell adjustment and more

Post by JLT » Sat Jun 25, 2016 2:23 pm

Ronin10 wrote:
How do you ensure that the center or the paper gauge is concentric with the center of the pulley? Engine tin on a Type 1 seems like it make that hard to assess.
Good point. As you can see in the picture, that piece of tin is missing on my engine. In fact, I'm not sure if it ever was on the engine. I guess you could remove it to do the test, make the marks you need to make, and then replace it. Two or three screws ... not a big project, no?
-- JLT
Sacramento CA

Present bus: '71 Dormobile Westie "George"
(sometimes towing a '65 Allstate single-wheel trailer)
Former buses: '61 17-window Deluxe "Pink Bus"
'70 Frankenwestie "Blunder Bus"
'71 Frankenwestie "Thunder Bus"

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Amskeptic
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Re: Timing gauge for easier dwell adjustment and more

Post by Amskeptic » Mon Jun 27, 2016 7:14 am

JLT wrote:
Ronin10 wrote:
How do you ensure that the center or the paper gauge is concentric with the center of the pulley? Engine tin on a Type 1 seems like it make that hard to assess.
Good point. As you can see in the picture, that piece of tin is missing on my engine. In fact, I'm not sure if it ever was on the engine. I guess you could remove it to do the test, make the marks you need to make, and then replace it. Two or three screws ... not a big project, no?
There is an easy parallel to this. 360* distributor rotation = 90* per cylinder/ optimum dwell 45*.

AT THE CRANKSHAFT, this = 720* = 180* per cylinder / optimum dwell ( test light OFF interval) is 90* of crank rotation.
Wherever your test light switches, just count off an E-Z Visualize 90*. If the light is OFF more than 90* the gap is too small.

That said, just adjust the points with a matchbook, like John Muir said. The dwell will follow. The match book easily ignores the tit on worn points, the cardboard cleans the contact faces, and yer on yer way.

Naranja's (possibly oem) points were set on October 4th, dwell is currently 48* with questionable ignition misses and all, but it moves down the road, we're good.
GoodNChillyMinnesotaMorning
BobD - 78 Bus . . . 112,660 miles
Chloe - 70 bus . . . 206,845 miles
Naranja - 77 Westy . . . 116,898 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 91 Lexus LS400 . . . 84,465 miles

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