Hey all I'm new to montes..especially ones that have had the old
305G motor replaced, mine has a vortec 350/300hp, th350C
373 posi.
I put in a Autometer tach and now have an issue of both tachs working!! The stock tach reads considerably higher rpm , while the Autometer reads concerably lower rpm ( by about a 600-1000 rpms)

I should mention the factory ECM has been removed by the previous owner, car is an 84 SS.

There is also a silver box in the glove compartment that has settings from lean to rich in 5 increments, try as I might I cannot locate where these wires go, although there is no change in fuel if switched between selected increments.

Any help on the tach issue would be appreciated

thanks

 

Ya that is pretty common, go by the Autometer. The factory tachs aren't the most reliable.
Is the vortec motor Fuel injected or N/A?

 

the engine is carbed...I need to know how to unhook the factory tach so
the new autometer tach reads correctly...thanks

 

the autometer is more than likly accurate stock tacks ar not always verry acurate...and the box in the glove box sounds more like a advance and retard box for timing...since it's carbed i don't see

 

how it coukd rich/lean by a dial cuz with mosr carbs that with jets and idler screws

 

The box in the glove box definately says lean .... 3 marks..then rich, not sure if someone has a old B & M superinjection set up in the car at one point or not...anyhow just looking to unhook the stock tach so it doesnt read at all...using a
tach dwell meter it read 200 rpms more than the autometer and almost 750 rpm less than the stock tach which would indicate the stock tach is causing problems as far as the Autometer tach reading correctly

 

Just unhook the stock tach outside on the firewall, inline by the tach filter is a single wire connector coming off the filter.
Can you get a pic of the fuel box?

 

your running an hei distributor right?

 

here is a pic of mine had easy access becuase its out of the car..your may look alittle different i have a

 

aftermarket coil but check the wire that comes off there they may have spliced in it for the aftermarket tach if so remove it and rewire...