Author Topic: Dwell Tach and timing light  (Read 20508 times)

Offline J.A.F.E.

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Re: Dwell Tach and timing light
« Reply #15 on: January 12, 2019, 09:45:11 AM »
IIRC -- you got a 4cyl reading on the Dwell Tach by doubling the value on the 8cyl scale. -- It's been a while since I've used one of the handheld models though --  :)

Doubling the scale values or halving the reading should work. I think. Been 20 years since I used a tach on anything bigger than a twin.

Exactly double the 8 cylinder reading.
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Online goodfellow

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Re: Dwell Tach and timing light
« Reply #16 on: January 12, 2019, 09:56:11 AM »
Man -- that brings back memories. Just for "kicks and giggles" I took a quick inventory of all the portable tach/dwell units I still have. Surprisingly there are a few.

I still have the first Dwell/Tach I ever bought back in the day. At that time there was a company Rite Autotronics Corp. (aka RAC) that dominated the DIY market with bargain test equipment and battery chargers -- all US made stuff, but definitely for the low end of the market. I still have the old vacuum gauge, compression tester, dwell/tach, and several nice battey chargers from RAC. The cheap RAC non-powered timing light went in the trash decades ago though.

This image is from the net, buy mine is in the same shape -- sitting in a box in the attic somewhere. First dwell/tach I ever owned that was exclusively mine. I usually had to borrow dad's or grandpa's when working on cars myself.





These others are sitting in the garage today --

Old Hawk -- tach/dwell/multimeter



Sun Automotive professional tach/dwell meter



Sears Automotive Engine Analyzer tach/dwell unit (perfect shape)



Stewart Warner handheld tach/dwell unit



Some of you older guys probably also have some of these things stashed away in boxes. The problem these days is trying to explain what these things were used for. Most kids have never seen a distributor -- or if they have, they've probably only  seen electronic distributors. They don't understand the technology associated with older point type systems.




« Last Edit: January 12, 2019, 09:58:50 AM by goodfellow »

Online goodfellow

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Re: Dwell Tach and timing light
« Reply #17 on: January 12, 2019, 10:13:44 AM »
BTW -- some may not know what a non-powered timing light is/was. Modern timing lights were hooked to the battery to provide power to the flash tube for a bright light. Original older professional lights, and later on less expensive lights, used the spark itself to power the light. It was simply hooked in series between the plug wire and the plug. Problem was that in non-high energy (regular) ignitions the light flash was so faint as to be almost invisible. Some professional lights from the early days that used the same technology actually included a hood to drape over the engine to create a "dark room" effect for the flash to become more visible.

Found this on the web. RAC made these cheap lights for their intro tune up kits -- circled in red. Notice the lack of battery hookup clips.



« Last Edit: January 12, 2019, 11:20:51 AM by goodfellow »

Online oldnslo

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Re: Dwell Tach and timing light
« Reply #18 on: January 12, 2019, 11:01:38 AM »
I spy with my little eye....a battery hydrometer and filler bulb. Both of which have seen zero use on my end in a decade. Even in the southwest, I'm not adding fluid to a battery.

Just like the dodo bird, and the oil filler spout for metal oil cans....these things fade away.

I too have that RAC dwell/tach (and higher end units), tho mine is proudly branded JC Penneys and is grey. Ha!

Offline lauver

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Re: Dwell Tach and timing light
« Reply #19 on: January 12, 2019, 01:58:35 PM »
AFAIK -- modern vehicles can't be tested with the old analog devices. You need to connect to a high energy spark to trigger the magnetic pickup -- since coils are now directly connected to the plug, then it would take some Rube Goldberg engineering to get the pickup to trigger off the coil pack. The tach/dwell meter is useless in the same manner -- no distributor to hook up to.

The real old lights without the mag pickup were connected in series with the plug wire to the plug through a spring "T" fitting. If you can find one of those lights, and connect it after the coil and make the connection to the plug, then it might trigger the light.  -- BUT for what purpose?

IIRC -- you got a 4cyl reading on the Dwell Tach by doubling the value on the 8cyl scale. -- It's been a while since I've used one of the handheld models though --  :)

GF-- Thanks for the info, I get it.  I have no tachometer in my 2003 Tacoma... it's the standard cab model with no frills.  So, my option would be to get a scanner, connect up to the ECU port and get live readings (engine running) on the scanner?  What if I wanted to add a tachometer in the vehicle?  Is there a connection on the ECU that I could tap?  Or, is there an unused wire for a tach in the wiring loom under the dash? 
When my wife leaves me, my dog dies, and they repossess my home, I'll still have my tools.

Online goodfellow

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Re: Dwell Tach and timing light
« Reply #20 on: January 12, 2019, 02:21:09 PM »
There are a lot of options for adding a tach to modern vehicles. Usually you have to find a switched power source, a ground, a lighting power source, and then a line to the ignition module, or some high tech units use a pass thru connector on the OBDII port to get the data directly from the computer.

Offline slip knot

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Re: Dwell Tach and timing light
« Reply #21 on: January 12, 2019, 02:28:38 PM »
I use the dwell/tach more than the timing light on these old tractors. get the points right and set the timing by ear. if it rattles under load back it off just a tad. ;D

Offline Uncle Buck

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Re: Dwell Tach and timing light
« Reply #22 on: January 12, 2019, 03:39:24 PM »
AFAIK -- modern vehicles can't be tested with the old analog devices. You need to connect to a high energy spark to trigger the magnetic pickup -- since coils are now directly connected to the plug, then it would take some Rube Goldberg engineering to get the pickup to trigger off the coil pack. The tach/dwell meter is useless in the same manner -- no distributor to hook up to.

The real old lights without the mag pickup were connected in series with the plug wire to the plug through a spring "T" fitting. If you can find one of those lights, and connect it after the coil and make the connection to the plug, then it might trigger the light.  -- BUT for what purpose?

IIRC -- you got a 4cyl reading on the Dwell Tach by doubling the value on the 8cyl scale. -- It's been a while since I've used one of the handheld models though --  :)

That Craftsman light shown does have the magnetic pickup clamp for #1 wire. I use mine for up to 1986 GMC just fine. I cannot speak to newer that that application.
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Offline Uncle Buck

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Re: Dwell Tach and timing light
« Reply #23 on: January 12, 2019, 03:43:23 PM »
BTW -- some may not know what a non-powered timing light is/was. Modern timing lights were hooked to the battery to provide power to the flash tube for a bright light. Original older professional lights, and later on less expensive lights, used the spark itself to power the light. It was simply hooked in series between the plug wire and the plug. Problem was that in non-high energy (regular) ignitions the light flash was so faint as to be almost invisible. Some professional lights from the early days that used the same technology actually included a hood to drape over the engine to create a "dark room" effect for the flash to become more visible.

Found this on the web. RAC made these cheap lights for their intro tune up kits -- circled in red. Notice the lack of battery hookup clips.



I have one or two that look like the one circled that are supposed to be suitable for 6volt applications like early Ford V-8 IE (flathead) I also have several twins to the ones Ray showed floating around the shop myself. Too cold and I am not heading to the shop for pics to share, sorry guys.
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Offline Elroy

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Re: Dwell Tach and timing light
« Reply #24 on: January 12, 2019, 04:11:09 PM »
Last items from last weeks auction, I needed a dwell tachometer and timing light so couldn't turn these down for $5.00.

That was a great deal

At one time that light (with the advance dial adjustment) was quite and expensive item.

They weren't cheap but they were were a fairly good timing light.



The adjustable advance feature is what sold Elroy back in the day





This thread had Elroy digging out the antiques



This decal should date it well





 
« Last Edit: January 12, 2019, 04:12:52 PM by Elroy »

Offline Uncle Buck

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Re: Dwell Tach and timing light
« Reply #25 on: January 12, 2019, 04:17:33 PM »
Were those from back in Elroys "hair" days?  :))
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Online goodfellow

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Re: Dwell Tach and timing light
« Reply #26 on: January 12, 2019, 04:20:41 PM »
For those who weren't around then. "The CAMFather" was Ed Iskenderian -- ISKY Cams. Isky grinds are legendary.

Offline Elroy

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Re: Dwell Tach and timing light
« Reply #27 on: January 12, 2019, 04:22:12 PM »
Were those from back in Elroys "hair" days?  :))

Probably

Prior to the "mag pick-up" , Elroy had a light that required physically tapping into the high tension lead with a spring type adapter.  It sucked as it was tricky and would usually ground out.
Elroy still uses the mag-pick up light on his 85 Mustang.

Offline Uncle Buck

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Re: Dwell Tach and timing light
« Reply #28 on: January 12, 2019, 04:46:34 PM »
I recall pop had a golf T he used to plug to vacuum advance hose when timing and setting dwell back in the day.
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Offline J.A.F.E.

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Re: Dwell Tach and timing light
« Reply #29 on: January 12, 2019, 05:06:19 PM »
I use the dwell/tach more than the timing light on these old tractors. get the points right and set the timing by ear. if it rattles under load back it off just a tad. ;D

At least the early air cooled VW's were timed that way although there was a timing mark on the pulley that used the case split as a pointer. I still time the Spitfire that way as well even though I have at least three timing lights.
People who confuse etymology and entomology bug me in ways I can’t put into words.