The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - CO WTB - NOS or perfect used tach dash circuit board

chipflyer · 01-19-2011, 12:59 AM

When GM went to HEI, the tach filter was necessary to filter out the high frequency noise from the HEI so the tach gives a steadier reading. Our trucks didn't have HEI originally and the old dizzy/coil setup probably worked pretty good way back then. Now everyone adds the tach to their HEI truck but not the filter and then complains about the tach not being accurate. All the GM vehicles that came with HEI (73 and up) had the little tach filter. I wouldn't call the original tach a "piece of junk", but it is just a show piece and has no real use in a daily driver.

Jeff

01-19-2011, 12:59 AM	#13
chipflyer Registered User Join Date: May 2004 Location: Topeka, Ks Posts: 2,293	Re: WTB - NOS or perfect used tach dash circuit board When GM went to HEI, the tach filter was necessary to filter out the high frequency noise from the HEI so the tach gives a steadier reading. Our trucks didn't have HEI originally and the old dizzy/coil setup probably worked pretty good way back then. Now everyone adds the tach to their HEI truck but not the filter and then complains about the tach not being accurate. All the GM vehicles that came with HEI (73 and up) had the little tach filter. I wouldn't call the original tach a "piece of junk", but it is just a show piece and has no real use in a daily driver. Jeff __________________ I'm not a pessimist, I'm just optimistic that bad things are going to happen. 1971 Cheyenne Super K10 - tilt, cruise, air, am/fm, tow hooks, factory buckets! 1986 Jeep J10 pickup, - 5.3L Vortec with 4L60e and NP241.