Tach differences - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**ScottH** · 06-05-2003, 12:19 PM

I recently picked up a dash cluster with an original tach. Can anyone tell me how I can determine if it was from a 6cyl vs an 8cyl?

Any info is appreciated. Thanks!

72MARIO · 06-05-2003, 12:27 PM

I think it say's on the back

bpmcgee · 06-05-2003, 12:35 PM

Scott,

As a complete coincidence I just received my tach-dash in the mail from Prof!

Mario is right. On the back of the tach in blue ink is stamped "8 Cyl."

Brian

Baradium · 06-05-2003, 12:37 PM

And do you see a little switch back there to change from 6-8cyl?

I'd always heard that they were either 6 or 8, no in between or changing, but someone in the parts board said you can in his ad?

bpmcgee · 06-05-2003, 01:15 PM

Baradium,

I imagine that on an aftermarket tach you would be able to switch.

On this factory tach, I'm not sure. There IS a little adjustment hole there, but I'm not sure if that's to trim the level precisely or if it serves some other function.

Brian

71Chev · 06-05-2003, 01:29 PM

The screw in that hole on the back, is how it can be recalibrated for 6 or 8 cyl. The factory 6 tach sticker says 6cyl. I recalibrated a 6 cyl tach for my 350.

**ScottH** · 06-05-2003, 10:02 PM

Thanks everyone for the info. Looks like a have 6 cyl, but want to use it with a 350. Any anyone tell me how to calibrate it for an 8cyl?

If easier I'd be willing to trade mine for an 8 cyl if anyone is interested.

Thanks again.

1969 GMC · 06-06-2003, 03:28 AM

I thought I saw somewhere on here of the number differences on the two different types of tachs...which isn't actually the tach but the lens paint, I know. Something liek the V8 tach goes 1,000 rpm higher than the 6banger...maybe someone else could shed some light on this

71Chev · 06-06-2003, 09:45 AM

The diesel tachs are 4000 rpm.
6 & 8 cyl tachs are all 5000 rpm.

bouncytruck · 06-06-2003, 11:31 AM

I've got a tach dash at home I got from my neighbor. I never knew that there was a 6 cyl & 8 cyl difference. I guess I'll have to check it out when I get home tonight. Is the stamp on the tach itself or on the metal backing?

71Chev · 06-06-2003, 12:27 PM

It is the same tach but is either calibrated for either 6 or 8 cyl. The sticker is on the back of the tach housing covering the hole to the calibration screw.

06-05-2003, 12:19 PM	#1
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,187	Tach differences I recently picked up a dash cluster with an original tach. Can anyone tell me how I can determine if it was from a 6cyl vs an 8cyl? Any info is appreciated. Thanks!

06-05-2003, 12:27 PM	#2
72MARIO Registered User Join Date: Nov 2000 Location: Huntsville Ontario Canada Posts: 4,052	I think it say's on the back __________________ 1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD

06-05-2003, 01:29 PM	#6
71Chev Senior Member Join Date: Dec 2000 Location: Indiana Posts: 3,074	The screw in that hole on the back, is how it can be recalibrated for 6 or 8 cyl. The factory 6 tach sticker says 6cyl. I recalibrated a 6 cyl tach for my 350. __________________ 71 Chevy CST Long Fleet 350/350/3.07 leaf rear.

06-06-2003, 03:28 AM	#8
1969 GMC Registered User Join Date: Feb 2003 Location: The Rubber City Posts: 5,498	I thought I saw somewhere on here of the number differences on the two different types of tachs...which isn't actually the tach but the lens paint, I know. Something liek the V8 tach goes 1,000 rpm higher than the 6banger...maybe someone else could shed some light on this __________________ 1969 GMC K2500 1996 Honda Accord 2007 Kawasaki KLR 650

06-06-2003, 09:45 AM	#9
71Chev Senior Member Join Date: Dec 2000 Location: Indiana Posts: 3,074	The diesel tachs are 4000 rpm. 6 & 8 cyl tachs are all 5000 rpm. __________________ 71 Chevy CST Long Fleet 350/350/3.07 leaf rear.

06-05-2003, 12:35 PM	#3
bpmcgee Registered User Join Date: Mar 2003 Location: Northern Illinois Posts: 2,181	Scott, As a complete coincidence I just received my tach-dash in the mail from Prof! Mario is right. On the back of the tach in blue ink is stamped "8 Cyl." Brian

06-05-2003, 12:37 PM	#4
Baradium Binder Rep Join Date: Jan 2001 Location: Salcha, AK Posts: 1,506	And do you see a little switch back there to change from 6-8cyl? I'd always heard that they were either 6 or 8, no in between or changing, but someone in the parts board said you can in his ad?

06-05-2003, 01:15 PM	#5
bpmcgee Registered User Join Date: Mar 2003 Location: Northern Illinois Posts: 2,181	Baradium, I imagine that on an aftermarket tach you would be able to switch. On this factory tach, I'm not sure. There IS a little adjustment hole there, but I'm not sure if that's to trim the level precisely or if it serves some other function. Brian

06-05-2003, 10:02 PM	#7
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,187	Thanks everyone for the info. Looks like a have 6 cyl, but want to use it with a 350. Any anyone tell me how to calibrate it for an 8cyl? If easier I'd be willing to trade mine for an 8 cyl if anyone is interested. Thanks again.

06-06-2003, 11:31 AM	#10
bouncytruck SKINNY TIRES RULE! Join Date: Sep 2001 Location: Bothell, WA Posts: 11,049	I've got a tach dash at home I got from my neighbor. I never knew that there was a 6 cyl & 8 cyl difference. I guess I'll have to check it out when I get home tonight. Is the stamp on the tach itself or on the metal backing? __________________ bouncytruck 1972 K5 The Hauler 1994 K1500 Suburban The Daily2010 Kia Soul Wife's Ride2014 Fiat 500L

06-06-2003, 12:27 PM	#11
71Chev Senior Member Join Date: Dec 2000 Location: Indiana Posts: 3,074	It is the same tach but is either calibrated for either 6 or 8 cyl. The sticker is on the back of the tach housing covering the hole to the calibration screw. __________________ 71 Chevy CST Long Fleet 350/350/3.07 leaf rear.



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