Factory tach accuracy - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jasons · 06-15-2010, 04:53 PM

My factory tach has read fast at higher RPM's since it was installed 4 or 5 years ago.
It has always read about 2500 PRM when another known good tach read 2100 RPM at highway speed. Now it reads over 3000 RPM at the same speed. \
I have an HEI distributer, I know that GM cars from the mid 70's to mid 80's used a tach filter with HEI distributers. Could not using one cause the tach to not read correctly? Or if this is a problem with the tach itself is there some way to correct it?

06-15-2010, 04:53 PM	#1
jasons not enough hours in the day Join Date: Jan 2009 Location: Axtell, NE Posts: 550	Factory tach accuracy My factory tach has read fast at higher RPM's since it was installed 4 or 5 years ago. It has always read about 2500 PRM when another known good tach read 2100 RPM at highway speed. Now it reads over 3000 RPM at the same speed. \ I have an HEI distributer, I know that GM cars from the mid 70's to mid 80's used a tach filter with HEI distributers. Could not using one cause the tach to not read correctly? Or if this is a problem with the tach itself is there some way to correct it?



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