Re: [OMC-Boats] Dwell/tach

From: Justin DeSantis <duc1098desmo@...>
Date: Sat, 12 Sep 2009 13:53:13 -0400

Thanks for the info Lee. I think I got it. Except the static pointer.
I figured that's waht it would be, I just used the wrong terminology.
I don't see a static pointer anywhere though. Any hints where it might
be? Going to go try the tach now, thanks for the info.

On Sat, Sep 12, 2009 at 12:03 AM, Lee Shuster (lib1) <lib1@...> wrote:
> NO, you're describing a SECONDARY HV INDUCTIVE pickup designed to sense
> pulse firing off No.1 cylinder. I'm not surprised that's what you are more
> familiar with. These induction pickups are also commonly used on timing
> lights as well.
> NOTE:   I"M Pretty sure that's NOT what you have with the RAC   If it has
> the common red and black alligator clips.
> This RAC tach/dwell PROBABLY hooks up to one of (two) the small threaded
> terminals on the COIL. The coil has THREE CONNECTIONS.
> 1) HV SECONDARY which sends high voltage spark to the center distributor
> terminal.  IGNORE
> 2) + IGN (PRIMARY) Voltage from the ballast resistor (small threaded
> terminal)   IGNORE
> 3) - (PRIMARY) voltage small lead to distributor and lead to tach (Small
> threaded terminal)  HOOK UP THE RED TACH LEAD HERE. Connect the BLACK TACH
> lead to any common ground.
> THERE"S NO Timing "port" like you're used to viewing on motorcycles. Instead
> there will be timing "marks" on the rotating damper which is connected to
> the front crankshaft. There will be a static pointer. Point your timing
> light at the pointer when the engine is running (follow the manual
> instructions to adjust timing). The distributor will mechanically advance
> the timing over 20 degrees as you increase the RPMs up to roughly 2750 to
> 3000 RPM. It's not recommended you alter ign timing, until you checked
> compression, gapped the plugs, checked spark plug HT wire resistance/HV, set
> the points & dwell.
> Have fun. BTW, I researched the Buick V8 faimly a little more. The 300
> shares pretty much everything with the 340 and would be a no-brainer bolt
> in.  The 350 Buick shares very little, I'm not sure exhaust manifolds would
> swap over.
> On Sep 11, 2009, at 8:00 PM, Justin DeSantis wrote:
>> Cool, I'm looking forward to hooking it up and comparing it's accuracy
>> to my other 2 tachs. Hopefully it's correct. You just clipping it on
>> to the outside of the plug wire like a modern tach, or does it require
>> some special hook-up procedure. One more question where is the port to
>> inspect timing? (I ordered a service manual. Not here yet.)
>> On Fri, Sep 11, 2009 at 8:47 PM, Lee Shuster <lks@...> wrote:
>>> I've got one of those old-school RAC's too. Pretty common back in the
>>> sixties.
>>> Simple to hook it:
>>> 1) You connect the Red side to the (-) coil primary (same terminal which
>>> has
>>> the lead to your distributor points.
>>> 2) Then the other side is connected to a good engine ground.
>>> Should have a switch to change from 6 to 8 cyl. (4 cyl used 1/2 the 8 cyl
>>> reading).
>>> On Sep 11, 2009, at 5:45 PM, Justin DeSantis wrote:
>>>> Hey gang. I borrowed a dwell meter and tach combo from a friend. I
>>>> can't for the life of me figure out how to use it as a tach though.
>>>> It's an old RAC dwell/tach. all it has is red and black alligator
>>>> clips. Other tachs I've used just go to the spark plug cable, one
>>>> wire. How does this thing hook up for use as a tach? One lead to the
>>>> spark plug, one to the battery negative? I know how to use it as
>>>> dwell, but not as tach. Anyone use one of these old beasts?
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Received on Saturday, 12 September 2009

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