RE: IML: Overdrive & a Tach
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RE: IML: Overdrive & a Tach



I did something similar to one of my Cadillacs a long time ago. The tach that I used though was a diagnostic tool type. It's an old Snap On I got at a garage sale. Regardless of that, any tach will work when you are trying to find out what the engine is doing temporarily.
I used a long shielded wire, and carefully attached it with tie wraps to the wheel well and firewall on its way inside the car through one of the firewall openings. Then I went on my roadtrip test, and it worked quite well.

Someone was mentioning a high pitch sound, or a high RPM sound. Sometimes if the fan clutch is not dong its job, it will have the fan engaged and will make what seems to sound like high revs. Just a thought there.

Also, this is probably an off the wall tangent, but for some time on some newer cars, the tach is not referencing the ignition anymore. It is looking at the stator signal from the alternator, since it is proportional to the engine RPM's, and there is no high voltage hazard associated with it. I guess I'm bringing this up, because you can do the same reference on the alternator's stator of your golden oldie. All you have to do is keep track of the ratio between the crankshaft pulley and the alternator pulley for equivalence. In most cases, the alternator rotates between 3 and 4 times for every crank rotation.

And for those of you with all the toys, an oscilloscope can do a mighty fine job of not only figuring out the RPM loads, but the power loads your alternator is displacing.

Have fun!


Chris Middlebrook
1962 Custom Southampton

--- On Tue 09/12, Rob McCall < Rob_Mopar@xxxxxxxxxxx > wrote:

From: Rob McCall [mailto: Rob_Mopar@xxxxxxxxxxx]
To: mailing-list@xxxxxxxxxxxxxxxx
Date: Tue, 12 Sep 2006 06:56:38 -0400
Subject: RE: IML: Overdrive & a Tach

Dan,

I don't have a tach installed in my LeBaron at this time, but I am partial
to VDO gauges. I've used a few of their tachs with good luck. They offer
one that matches their Cockpit series of gauges that has it's own housing.
Sorry, I don't have the part number handy. It's under $100 (possibly below
$75) and installation is pretty easy. It comes with a bracket designed to
clamp onto your steering column by using a large hose clamp like on e for a
clothes dryer exhaust hose. I'd recommend putting something under the clamp
to keep it from scratching the column.

Otherwise you can calculate estimated highway RPM by using the tire
diameter, rear gear ratio, and MPH. I have a spreadsheet I setup with the
formulas. If you e-mail me direct I'll send it to you, or if you like send
me your tire size and rear gear ratio and I'll punch those values in for you
and send the results.

Rob McCall
'67 LeBaron

-----Original Message-----
From: mailing-list-owner@xxxxxxxxxxxxxxxx
[mailto:mailing-list-owner@xxxxxxxxxxxxxxxx] On Behalf Of
dansgarage@xxxxxxxxxxxx
Sent: Tuesday, September 12, 2006 2:10 AM
To: mailing-list@xxxxxxxxxxxxxxxx
Subject: RE: IML: Overdrive & a Tach

Hi All....I would like to know just how hard my IMperials are working when
we are moving down the road at 50/60/70/80/etc. Since the RPM's generated by
the 440 in my two '66's would be the same (more or less) on a day to day
basis (depending on how many people I am carrying or how many bodies I have
in the trunk - just kidding!!) I am thinking of putting a temporary Tech
inside to see just what the engine is doing while I am going down the road
or up the hills. Has anyone tried doing this? and if so, what kind of a tach
did you use? Since its only going to be there for a short time I do not want
to spend tons of $$$$ on the tach but I would like to get an reasonably
accurate readout. Its not for racing or anything like that. Even I know that
3-ton vehicles do not make good racers! But my daily-driver SUV has a tach,
my last 3 old dailydrivers had them and I guess I am just used to seeing how
the old engin' is running on a 'whenever' basis...no other reason!
So, if anyone has their 2-cents to add let me know....someone may already
know the RPM's for various highway speeds for my Imperials (1966's with the
standard 440 engine - 1 convertible/1 LeBaron with [I believe] standard
rear's) and if so please email me directly (dansgarage@xxxxxxxxxxxx)
Thanks all!
Dan Melnik






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