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Hand Held Tach?

bobfake

bobfake

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Hi all - I want to verify that the tach in my 68 Super Bee is accurate. Currently shows 3000 RPM at 60 MPH. I have an A833, 3.23 rear with 225/70R14 tires. Calculators show I should be turning more in the 2500 RPM range.

Short of buying another tach and wiring it for the only purpose of validating the current tach, is there a "handheld" device? Like the old dwell meters?

Thanks in advance!!
Bob
 
Do you have maps on a smartphone? It will do GPS mph.
 
Last edited:
bobfake said:
Hi all - I want to verify that the tach in my 68 Super Bee is accurate. Currently shows 3000 RPM at 60 MPH. I have an A833, 3.23 rear with 225/70R14 tires. Calculators show I should be turning more in the 2500 RPM range.

Short of buying another tach and wiring it for the only purpose of validating the current tach, is there a "handheld" device? Like the old dwell meters?

Thanks in advance!!
Bob
Click to expand...
@HALIFAXHOPS sells nice used tach/dwell meters and timing lights with digital tach's.
 
bobfake said:
Jerry…I did that and am getting a new speedo gear. Need to verify the tach.
Click to expand...
Some timing lights have a tachometer. They always say in order to test and calibrate a tachometer is to compare it to a known good one.
 
pnora said:
Some timing lights have a tachometer. They always say in order to test and calibrate a tachometer is to compare it to a known good one.
Click to expand...
Hoppy tests and calibrates every one he sells.
 
bobfake said:
Hi all - I want to verify that the tach in my 68 Super Bee is accurate. Currently shows 3000 RPM at 60 MPH. I have an A833, 3.23 rear with 225/70R14 tires. Calculators show I should be turning more in the 2500 RPM range.

Short of buying another tach and wiring it for the only purpose of validating the current tach, is there a "handheld" device? Like the old dwell meters?

Thanks in advance!!
Bob
Click to expand...
Are you sure that you have the CORRRCT speedometer take-off gear in the transmission?? Your tach may be correct but the MPH may be wrong. Verify the take off gear tooth count or all your calcs will be inaccurate. FSM lists the take off gear tooth count for your application.
BOB RENTON
 
The digital tachs such as on the Innovia timing light or some multi meters are thought by some to be more accurate than the usual analog tachs.
 
For the record, halifaxhops name is Ray. And he is a great asset to the Mopar community.
 
RJRENTON said:
Are you sure that you have the CORRRCT speedometer take-off gear in the transmission?? Your tach may be correct but the MPH may be wrong. Verify the take off gear tooth count or all your calcs will be inaccurate. FSM lists the take off gear tooth count for your application.
BOB RENTON
Click to expand...
Bob…are you referring to the speedo gear? If so, that’s on my list to check as well. Speedo reads gradually more fast the faster I go compared to gps or radar speed limit signs.

IMG_3179.jpeg
 
YES......THE take off gear is located on the transmission tail shaft and is secured with an adapter body and an O ring seal and where the speedometer cable is attached via a Ferrell sleeve. Disconnect cable first then remove the fork adapter holding the gear housing to the tail shaft.....expect lubricant to come out when removing the adapter. The FSM shows the assembly.
BOB RENTON
 
I have tons of different tach dwell meters all over the place in price. Just shoot me a pm with needs.
 
Never tried it on a Mopar tach, but here's a link to my page about re-caling a Mazda tach for a V8. The deadly accurate 1800rpm signal source I use is just an old battery charger. Here's a copy/paste from the webpage.

PREFERRED SIGNAL SOURCE...an inexpensive 12v battery charger can be used as a deadly accurate signal source for the re-cal of your tach. This signal source is so steady and accurate that there is no need to compare the reading with another V-8 calibrated tach. Battery chargers typically use a rectifier bridge to convert the AC power source into DC. This turns the 60 hertz sine wave input into a 120 hertz ripple wave DC output. The ripple wave output is be read as 3600rpm by the stock rotary calibrated RX-7 tach. For a V-6 application, an RX-7 tach should be adjusted to read this signal as 2400rpm. For a V-8 application, adjust your RX-7 tach to read this ripple signal as 1800rpm. Please note that you must use a 12v battery for a power source, and the battery charger as a signal source only. The ground wires for both the battery and the battery charger should be connected to the ground terminal of the tach.

Here's a link to the page...
https://members.tripod.com/~grannys/rx7tachrecal.html

Grant
 
I bought one of these cheap digital tachs years ago. Mainly use it on the diesels, the picture is checking 540 PTO speed. It was less than 10 bucks on eBay. You put a piece of reflective tape on the part you are checking and the red beam shows speed.

100_1711.jpeg
 
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