will a new engine require a new tach and spedo?? and if so...how the heck you do that? i thought the ECM controled it all.... thanks

 

What current engine, and what new engine?

If one can assume from your username that you have a '92, I'm not completely sure but it should still be a "direct" wire from the ignition to the tach, not "controlled" by the ECM (even if the harness goes to and through it).

 

ok,, dont mean to fool anyone with the "92" in my SN....but i have a 84.. its the Lg4 engine,, and a 72 vette 350 engine is being put in it... hope this helps

 

You don't need to change either the tach or speedo. In fact, everything, including carb, intake, distributor, accessories, should bolt right to the 350. You should use the harmonic damper from the 350, not the 305, though. Same goes for front cover.

Exhaust - upgrade it all with headers, y-pipe, cat, cat-back, or else you'll sufficate that poor 350.

 

can you..or someone else try to explain to me how the spedo and tach work... and how they are connected?? also, i will be drag racing this in the summer when its all done, i was thinking about getting a new tach (with shift light) and try to put it in the place of the factory tach...maybe spedo too,, i dont like the "85 mph" look. how hard would this be to do, and is it even worth the time and effort?? like you were saying before,, if it was a 92', then it be a simple cable,,, but its not a 92,, its a 84.. whats the differance?


p.s.....SLP headers and a flowmaster cat back are in the works

 

You can use the same wire currently used by your tach to run an aftermarket unit. Or, run a new wire from the tach terminal on the distributor.

The speedo is a simple cable from the transmission to the unit (first to the governor then the speedo if cruise control). The ECM gets the vehicle speed signal from a sensor on the back of the speedo head, which is pulsed by ... (drum roll here)... the turning of the speedo by the cable!

140 mph units are available new but expensive (>$200). You really have to want to see your speed as you exceed 85 mph if the only time you plan on exceeding 85 mph is on the 1320 (I plan on just letting the thing peg).

 

yeah it be kewl to see your speedo peged at 85, then you get your time slip and $h!t yourself ...would it be a good idea to put the new tach in the stock location???? or a pain in the ***

 

Leave the stock tach alone and put in a shift light.

 

how do you do that? just tap into the wire to the tach?