The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - How to connect a tach to HEI distributor?

ray_mcavoy · 03-26-2011, 08:35 PM

Hi kikkegek,

What type of carburetor is on your truck?

The reason I ask is because GM used some carbs with a computer-controlled mixture solenoid setup in the 80's. Mostly found on cars but I've heard some trucks got them too (California emissions mostly I think).

Anyway, many of those computer-controlled carburetor setups have a wire connected to the HEI tach terminal to send a tach reference signal to the computer. If that's the case, you'll need to keep that wire hooked up, but I don't see any problem tapping into it to hook up your new tach.

03-26-2011, 08:35 PM	#7
ray_mcavoy Registered User Join Date: Nov 2009 Location: Sherman, ME Posts: 2,379	Re: How to connect a tach to HEI distributor? Hi kikkegek, What type of carburetor is on your truck? The reason I ask is because GM used some carbs with a computer-controlled mixture solenoid setup in the 80's. Mostly found on cars but I've heard some trucks got them too (California emissions mostly I think). Anyway, many of those computer-controlled carburetor setups have a wire connected to the HEI tach terminal to send a tach reference signal to the computer. If that's the case, you'll need to keep that wire hooked up, but I don't see any problem tapping into it to hook up your new tach.