Ok, I have a 91rs that had a 305 tbi that now has a 350 tpi. This is the delema. On the 305 engine wire harness it had a speed buffer that was wired in right by the junction block on the fire wall. Now my new 350 wire harness for a 91 does not have one. In 91 the 350 had the speed buffer built in to the ecm. So now my dash wire harness is looking for a speed buffer that is not there now. Is there any way to get the vss signal to the speedo without changing the dash wire harness. Also if not would it be easier to just change my speedo into cable driven. Please help!

 

The '91 TPI ECM has the speed buffer built in to the ECM & the ECM has a speedo output (4000 pulses per mile) and a cruise control output (2000 pulses per mile) that you will have to connect to the chassis harness where the TBI (external) speed buffer used to connect to.

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Tim

1992 Z28, 305 TPI 5 speed, 12.0 sec @ 114.8 mph

1984 Berlinetta 305 TPI Auto, 13.8 sec @ 99.7 mph

 

so basically I will need to find out which color wire for the speedo is coming out of the ecm and connect it to the speedo wire from the dash harness to the actuall speedo, right?

 

Correct.

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Tim

1992 Z28, 305 TPI 5 speed, 12.0 sec @ 114.8 mph

1984 Berlinetta 305 TPI Auto, 13.8 sec @ 99.7 mph

 

So did you ever figure what wire to hook up I'm have the Same
problem