A 340 Tach question....

-
jimharvard

jimharvard

JimHarvard
FABO Gold Member
Joined
Jan 7, 2007
Messages
1,047
Reaction score
689
Location
Pittsburgh, Pennsylvania
Hey all you "electrics" guys in the audience....

my 68 340 4 speed fastback formula s restoration is continuing.... i recently got my hands on an original nos 68 tach. because of the price of nos parts now, i'm a little afraid to actually put this tach in and hook it up. the fish currently has a 71 340 with an electronic ignition/distributor. do you guys know if it is safe to hook up an original 68 tach to an electronic ignition??? the last thing i want to do is fry this pristine museuem piece of a tach. do you think it would be better to save this nos item and buy one of those reproduction new tachs????

and here's the really embarrassing question... exactly how do you hook up a tach to an electronic ignition???

any help/comments would be greatly appreciated..

jim coster, pittsburgh
 
Most tachs have a green a red a black and a white wires, the green go's to the coil - and the red to a switched hot and the black to ground and the white is the tach light which should be hooked up to the headlight switch or on that circuit somewhere.
If hooked up this way it should work on any engine.
 
hi bjr....
thanks for taking the time to reply ... here's a picture of the back of my 68 factory chrysler tach ... there are only two threaded polls ... one with a tab and one without. i'm assuming that the other bolts with nuts are holding part of the inside of the tach.

do you have any ideas on which poll would be red and which would be black?

thanks again..
jim coster, pittsburgh
a formula s lover...

back of 68 factory tach.jpg
 
The factory harness should have a gray wire (with a black tracer ,I think) that goes from one tach terminal to the negative side of the coil. The other connection (blue wire)should go to the fuse box and supply power for the tach and light. The tach housing will ground to the dash. On my 68 the spade connector on the tach goes to a gray wire connected to the negative side of the coil .The terminal without a spade connector on the tach goes to a blue wire with a 90* push-on connector. Yours should do the same. HTH.
 
I put a clock in the center position of my rallye panel. The factory supplied it's power directly from the hot post of the amp gauge. I choose to add a inline fuse dropped down near the column cover and wrote CLOCK on it with a Sharpie. Funny thing though, I always set the neg. battery cable off when I park the car so that clock never shows the correct time. DOH
Anyway... I think if I added a tach I would place a tiny toggle switch down there somewhere to turn the thing off and on as needed. Might double the life of the tach.
 
hey longgone and redfish....
thanks for the intel on the wiring set up ...
i'm just going to buy one of those new repro tachs and put it in using your instructions. several places are carrying them for about $150 then if i fry it then the worst that i can ruminate about is that some chinese electronic geek somewhere is bummed cause i fried his handywork. at least i won't be watching smoke come out of an original 40 year old chrysler nos silver pig metal cast masterpiece...

man... i just keep having conflicts with the fact that i'm trying to rebuild a couple of great 40 year old muscle collector cars with nos scarce and hard to find parts and my desire to drive and properly thrash these vehicles on the weekends. now i'm starting to understand why over the last couple of years when i went to the mopar weekend at carlisle, pa, the guys just idled around the grass in their beautiful restored mopars. i want to get in these cars and drive them the way they were meant to be driven. wow... i guess you have to make a choice between restoring an "authentic" muscle car and just sit and look at it or put one together with "repro" parts and non-original equipment so you can beat it and maybe break it on the weekends.

thanks again..

jim c...
 
The best thing about these old cars is the history behind them and knowledge gained.
Most every fault has been found and adressed by someone. Lets's start a betting pool on how many technical service bulletins will be issued on the new Challenger in its 1st year... 1 ? 12 ? LOL
Sure we build bionic mopars (better stronger faster). Only because they are worthy. How many 1960 thru 1980 imports do we see one the roads ?
 
jimharvard said:
hey longgone and redfish....
thanks for the intel on the wiring set up ...
i'm just going to buy one of those new repro tachs and put it in using your instructions. several places are carrying them for about $150 then if i fry it then the worst that i can ruminate about is that some chinese electronic geek somewhere is bummed cause i fried his handywork. at least i won't be watching smoke come out of an original 40 year old chrysler nos silver pig metal cast masterpiece...

man... i just keep having conflicts with the fact that i'm trying to rebuild a couple of great 40 year old muscle collector cars with nos scarce and hard to find parts and my desire to drive and properly thrash these vehicles on the weekends. now i'm starting to understand why over the last couple of years when i went to the mopar weekend at carlisle, pa, the guys just idled around the grass in their beautiful restored mopars. i want to get in these cars and drive them the way they were meant to be driven. wow... i guess you have to make a choice between restoring an "authentic" muscle car and just sit and look at it or put one together with "repro" parts and non-original equipment so you can beat it and maybe break it on the weekends.

thanks again..

jim c...
Click to expand...

I know a racer out of Chesapeake ,Va. named Ed Miller who back in the day owned 5 of the SS A/A cars at one time or another. He still races but it`s certainly not a SS A/A car, or a Hemi for that matter, nobody can afford to take these cars out and hammer `em they way we used to. Lol!
 
yea... i remember "the good ole days" when gas was cheap and pennicillian would still kill everything (if you know what i mean...:0) )... i've been collecting old cuda literature and posters off of ebay. i now have original dealer sales brochures for 67, 68 and 69 cudas. boy are they funny to look at now with all the long haired babes in their mini skirts and "nancy sinatra" boots... and of course, the barracudas and all the wonderful options. i guess i just have to keep the trips down memory lane in perspective and enjoy the cars in a way that makes sense.

hey thanks again guys for the tach information ....

me and my fiance' and our house full of animals (especially max ... one of our bad chinchilla boys) hope you all have a great thanksgiving...

jim c...

max's first birthday.jpg
 
FWIW, I have one of the original factory tachs and it works with the mopar electronic ignition or off the MSD tach adapter with the MSD I am currently using. The tach is not powered directly from amp gauge junction, it gets it's power from a switched source. Makes sense that the clock come from that source because you want it running all the time but not for the tach.

The only issue I have with the factory tach is the response is slow. It will not tract the rpm rise like the after market tach I am currently using. It will eventually catch up and the two will read the same.

I plan to rebuild it with one of the new circuit boards RTE this winter.
 
hi dave...
funny that you should mention that problem of factory tachs being slow... now that my memory is jogged a bit... my original 68 fastback s (the one in my avatar) had a factory tach in it but it wasn't very good. so i did what most of the street racers were doing in 1970, i bought a big chrome "Sun Super" tach and strapped it to the stearing column with a screw hose clamp. both tachs worked but the factory one was never as responsive as the Sun... i had the second needle on the Sun set right on 6k cause that's where the 340 liked to be power shifted. but i do now remember that the factory tach wasn't any good. it was too small to see also on those dark late nights of street racing.
take care..

jim c...
 
I knew the tach was switched at the key. I was just suggesting a switch for the tach itself.
 
You must log in or register to reply here.
-

Back
Top