Stock 72 tach - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jhow66 · 06-23-2002, 07:37 PM

Will a stock 72 tach work with a HEI dist.

**68SWB4x4** · 06-23-2002, 08:00 PM

yes, mine does

jhow66 · 06-23-2002, 11:13 PM

Thanks for the reply.
www.geocities.com/jhow66/2-.html

Huck · 06-24-2002, 07:48 AM

YES BUT---the stock tach is made for traditional ignition and HEI puts out more so that the tach will read significantly higher rpm then actual. So as long as you are happy with the tach moving, it's fine but don't rely on the actual numbers being real. Look into the ColoradoK5 board (believe it was Steve Chein) for details of how to modify for accuracy.

CE20934 · 06-24-2002, 09:37 AM

Now, unless I miss my guess, the stock tach counts revs the same way aftermarket ones do: off the coil ground. Coil output has absolutely nothing to do with counting revs. The repeated cycling of power is what triggers an electric tach.

**Downtown** · 06-24-2002, 10:35 AM

There is a hole in the back of the tach for adjusting it. It takes a phillips screwdriver. The hole is usually covered by a sticker.

**StingRay** · 06-24-2002, 11:43 AM

Mine works fine.

Stout72 · 06-24-2002, 11:53 AM

Mine works too, but I suspect it reads a bit on the high side.

my new 72 · 06-24-2002, 02:07 PM

It works on how fast the rotor makes it from #1 contact to #8 contact, not how many volts are put out. If it reads higher it is because of interference because of a frayed wire in the harness or something of that nature, not the HEI distributor.

jhow66 · 06-24-2002, 07:28 PM

Thanks guys for all the replies. One of my friends changed from points to HEI--tach worked before change. Will check out his wiring tomorrow.
www.geocities.com/jhow66/2-.html

06-23-2002, 08:00 PM	#2
68SWB4x4 Strongman Garage Join Date: Apr 2000 Location: Salinas, CA Posts: 10,241	yes, mine does __________________ Kalle 68 GMC Suburban 1500 4x4 SOLD 69 Pontiac Lemans 99 Silverado 4.8 5 speed ECSB [ Facebook Instagram Subscribe on YOUTUBE

06-23-2002, 11:13 PM	#3
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	tach Thanks for the reply. www.geocities.com/jhow66/2-.html __________________ 56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer

06-24-2002, 09:37 AM	#5
CE20934 Senior Member Join Date: Apr 2002 Location: Help! I'm in an office park with its own network of freeways! Posts: 470	Now, unless I miss my guess, the stock tach counts revs the same way aftermarket ones do: off the coil ground. Coil output has absolutely nothing to do with counting revs. The repeated cycling of power is what triggers an electric tach. __________________ '67 C20--427 tall deck/SM420, 4.10 HO52 (Michigan has not been kind to the Old Man) '95 Caprice--355 LT1/T56/3.42 8.5" 10-bolt (daily driver, almost 300k on the chassis) '07 Outback--wife's car. 125k & counting. No head gasket or transmission issues yet. fingers crossed

06-24-2002, 10:35 AM	#6
Downtown Senior Member Join Date: Dec 1999 Location: New Palestine, IN Posts: 471	There is a hole in the back of the tach for adjusting it. It takes a phillips screwdriver. The hole is usually covered by a sticker. __________________ 72 Super Cheyenne Longbed 350 49,000 original miles and My dad ordered it new 66 Chevy Caprice 2 dr 77 Caprice Estate Wagon New Palestine, IN

06-24-2002, 11:43 AM	#7
StingRay Senior Member Join Date: Mar 2000 Location: Saskatoon,SK,Canada Posts: 2,476	Mine works fine. __________________ Saskatoon, Saskatchewan Canada

06-23-2002, 07:37 PM	#1
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	Stock 72 tach Will a stock 72 tach work with a HEI dist. __________________ 56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer

06-24-2002, 07:48 AM	#4
Huck Senior Member Join Date: Jun 2001 Location: Shelbyville, KY Posts: 3,261	YES BUT---the stock tach is made for traditional ignition and HEI puts out more so that the tach will read significantly higher rpm then actual. So as long as you are happy with the tach moving, it's fine but don't rely on the actual numbers being real. Look into the ColoradoK5 board (believe it was Steve Chein) for details of how to modify for accuracy.

06-24-2002, 11:53 AM	#8
Stout72 Not my good side. Join Date: Mar 2002 Location: Fairfield, California Posts: 222	Mine works too, but I suspect it reads a bit on the high side. __________________ 72 Chevy K20 Custom Camper, 350/350, 4" lift, dual shock suspension front & rear. Daily driver and a work in progress. 00 Suburban LT 90 Camaro RS 79 Yamaha XS1100 Special (Ol' Reliable)

06-24-2002, 02:07 PM	#9
my new 72 faster, faster, faster Join Date: Dec 2001 Location: Houston ,Texas ,USA Posts: 1,354	It works on how fast the rotor makes it from #1 contact to #8 contact, not how many volts are put out. If it reads higher it is because of interference because of a frayed wire in the harness or something of that nature, not the HEI distributor. __________________ I'm going to Law School, wanna debate? It's good practice.

06-24-2002, 07:28 PM	#10
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	Tach Thanks guys for all the replies. One of my friends changed from points to HEI--tach worked before change. Will check out his wiring tomorrow. www.geocities.com/jhow66/2-.html __________________ 56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer



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