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Topic Review (Newest First)
01-09-2006 10:11 AM
red65mustang a tach is simply a "spark" counter, the "timer interval" chip on the tach compares the total number of sparks per time interval and puts out an analog signal (0-5V, 4-10ma as ex) to control the pointer movement

you set the dip switches for 4-6-8 cylinders so the chip will divide the total sparks count so that the pointer will show the correct complete firing cycles (per minute on the dial)
01-09-2006 06:12 AM
farna This is the funniest post I've read yet!! Someone had to much beer this weekend...
01-08-2006 06:11 AM
AmericanPackMule
..66

I see you have a Pontiac I-Con.

I use to race a '58 @ Lions & Orange County 20 years ago; out of Precision Speed Shop. ( Stock Class: H/S ) Best e.t.=14.00 Best M.P.H. 99.99.
01-08-2006 05:42 AM
AmericanPackMule
R.p.m. @ Tach.

hell I had to look it up !

American Pack Mule is the one at fault here(just kidding)///////////////\\\\\\\\\\

WHERE DID YOU FIND IT?

MY FAULT? No problem! You arn't too slow!
01-07-2006 02:05 PM
Rob Keller
Quote:
Originally Posted by predator carb guru
Well, I did some research on the subject and I stand corrected............now i feel really dumb..............................

NO!!! absolutly NOt so
this is how we learn
my nick name is "slowride66" for a reason ( i guess)
I sometimes get off slower then the rest soon as I know what in doin' i figure a way to catch up

if you came off like 'A know it all' than i'd probally let you wolly in it for a little while

hell I had to look it up !

American Pack Mule is the one at fault here(just kidding)

we all learned something so ... nothing to feel dumb about

I'm Really Slow in the morning!!!

SR66
01-07-2006 12:02 PM
predator carb guru Well, I did some research on the subject and I stand corrected............now i feel really dumb..............................
01-07-2006 10:22 AM
lowROLLERchevy
Quote:
Originally Posted by AmericanPackMule
But to check Tach. You Drive 60 M.P.H. / Know the Cir. of your rear tires (Dia. divided by 2 = Rad. X 3.14 = Cir.) [ in Inches! ] Divide 63,360 ( inches in a Mile.) by Cir..! X "Rear end Rato." X 1:1 Trans Hi Gear. = R.P.M. of Crank. { If that number is the same as the tach. is showing; Tach is right!
yea i know the long way to do it

i just didnt feel like typing out all the details ... lol
01-07-2006 10:12 AM
fiscus
Quote:
Originally Posted by onovakind67
Technically, the distributor driven tach only indicates what the distributor is doing. I can take the distributor out of my engine and rotate it with a drill and make my tach read but my crank isn't moving.

your distibutor is POSITIVELY driven!!!!
01-07-2006 09:56 AM
onovakind67 Technically, the distributor driven tach only indicates what the distributor is doing. I can take the distributor out of my engine and rotate it with a drill and make my tach read but my crank isn't moving.
01-07-2006 09:56 AM
AmericanPackMule multiply rpm's X gear ratio X final drive ratio X tire size ..... youll get the speed you were driving ... heres an online calculator that will do it for you :
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXX
But to check Tach. You Drive 60 M.P.H. / Know the Cir. of your rear tires (Dia. divided by 2 = Rad. X 3.14 = Cir.) [ in Inches! ] Divide 63,360 ( inches in a Mile.) by Cir..! X "Rear end Rato." X 1:1 Trans Hi Gear. = R.P.M. of Crank. { If that number is the same as the tach. is showing; Tach is right!
01-07-2006 09:17 AM
fiscus The tachometer indicates CRANK rpm. yes it gets its signal from the distributor, which is driven by the cam, which is driven by the crank.
01-07-2006 09:11 AM
onovakind67 A typical tachometer that hooks to the ignition system isn't reading distributor rpm, it's reading pulses per unit of time. A tach set up for 6-cylinder engine will read 33% high if you hook it to an 8-cylinder engine. If your V-8 engine is misfiring and the pulses aren't getting to the tach, the rpm reading will be off. The numbers you read are only printed on the face of the meter, so you can adjust them to represent anything you want.
01-07-2006 09:09 AM
cliff tate
Quote:
Originally Posted by BRONCO_78
I Know I'm Just A New Guy But I'm With Rob Keller It's Crank Rpm.
look at a 1955 to 57 t bird they all had mechanical tacks driven frome the ditributor, i think corvets as well
01-07-2006 09:06 AM
lowROLLERchevy
Quote:
Originally Posted by predator carb guru
*snip*
corection here

your right that most tachs use the ingition signal as the pickup for the tach, but tachs are designed to cut that speed in half to display crank speed

next time your out in you car do this

research and figure out the gear ratio of your car
drive down the road at a steady speed, say 40 mph
right down what gear your in and what the rpms are

multiply rpm's X gear ratio X final drive ratio X tire size ..... youll get the speed you were driving ... heres an online calculator that will do it for you :

http://www.woodyg.com/fairlane/finfo/mph.html

proof that your tach is showing crank speed, because its the crank thats conectd to the transmission
01-07-2006 08:53 AM
Rob Keller



still fingering out how to use a "sreen shot"!



SR66
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