70 Chevelle SS: tach into a non-tach dash - Chevelle Tech
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post #1 of 12 (permalink) Old Apr 5th, 07, 12:43 AM Thread Starter
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70 Chevelle SS: tach into a non-tach dash

Is there anyway, short of a new or butchered wiring harness, t oget a "factory (correct repro) tach to work in a non-tach dash for 1970-1972 Chevelles???? Ithe older tachs (no circuit board), I could build my own harness (ign/ground and dist), don't know if that can be done with these...

I can't afford a complete changeover (I have a malibu sweep now), but found a guy with a non-tach "Chevelle" (not Monte carlo) dash for a reasonable price (I think)... I don't care aboutthe small guages (i have aftermarket under the dash), but the factory tach just looks so cool...

I see where OPGI offers "clock-to-tach replacements, but I think that would be on the wrong side compared to "stock"... plus, i don't think they really loo that 'factory'...

Also, will a standard SS (non-tach dash) use the same wiring harness as the Malibu sweep? plug and play?

My harness appears to be great, so I want to avoid splicing or replacing if possible...

Thanks...

Once you go RAT, you never go back...
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post #2 of 12 (permalink) Old Apr 5th, 07, 7:43 AM
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Re: 70 Chevelle SS: tach into a non-tach dash

I have one of these tachs in my 71 SS454; it replaced the blank in my dash (my car didn't have the clock). Other than being on the wrong side, it looks very close to the factory tachs.
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post #3 of 12 (permalink) Old Apr 5th, 07, 8:32 AM
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Re: 70 Chevelle SS: tach into a non-tach dash

You can put it in the stock location, and wire it up manually instead of using the circuit board, yes.

Just don't ask me which wires to hook up where.... There's a TON of info here on manually converting your wiring complete to convert to a tach/guage cluster from an idiot light cluster.

But if you're starting with a sweep speedo cluster, not sure how the complete swap would work. You can certainly wire the tach individually and get it to work, though - just make sure you ground it.

Mark

1970 SS396
Lewis Racing Engines (Wolfplace) 489:
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627 Lb-ft @ 4,000rpm

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post #4 of 12 (permalink) Old Apr 5th, 07, 2:01 PM
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Re: 70 Chevelle SS: tach into a non-tach dash

Sweep dash wire harness can be made to work but you have to find a 12 pin gauge connector and have the wiring diagram for both the sweep and round idiot light underdash harness. Basically you cut all the idiot lights off the sweep harness and patch them into the 12 pin gauge harness.
The tach is easy to wire. It has two terminals on the back, one for tach input, and one for +12v gauge power. Just wire them up from the back of the tach. It gets ground from the metal plate. So the metal plate has to have at least one screw through it to the gauge cluster metal housing.
If you put the tach where it is normall in a tach/gauge cluster then you will have to remove the fuel gauge. Better option is to mount it to the right in place of the clock (they never work anyway).

Steve Strasemeier (70SS 396, Fathom Blue/White Stripes)
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post #5 of 12 (permalink) Old Apr 5th, 07, 2:57 PM Thread Starter
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Re: 70 Chevelle SS: tach into a non-tach dash

Quote:
Originally Posted by Steve S View Post
Sweep dash wire harness can be made to work but you have to find a 12 pin gauge connector and have the wiring diagram for both the sweep and round idiot light underdash harness. Basically you cut all the idiot lights off the sweep harness and patch them into the 12 pin gauge harness.
The tach is easy to wire. It has two terminals on the back, one for tach input, and one for +12v gauge power. Just wire them up from the back of the tach. It gets ground from the metal plate. So the metal plate has to have at least one screw through it to the gauge cluster metal housing.
If you put the tach where it is normall in a tach/gauge cluster then you will have to remove the fuel gauge. Better option is to mount it to the right in place of the clock (they never work anyway).
Thanks...

Will the large gas guage PHYSICALLY bolt in place of the clock? I could then (using the wiring diagrams) transfer the gas guage wires to the other side...

I just figured it would be great to get the tach on the correct side of the speedo... if I could

Are the wiring diagrams in the Assembly Manual (I ordered one, but haven't received it yet, and I know for '66 the wiring diagrams are included)?

Thanks again... Now to try and find the 12-pin connector... Any other cars (like later 73+ Chevelles, trucks, etc) use a similar connector?

Once you go RAT, you never go back...
TC #1366
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post #6 of 12 (permalink) Old Apr 6th, 07, 2:14 PM
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Re: 70 Chevelle SS: tach into a non-tach dash

Will the large gas guage PHYSICALLY bolt in place of the clock? I could then (using the wiring diagrams) transfer the gas guage wires to the other side...
No.

Are the wiring diagrams in the Assembly Manual (I ordered one, but haven't received it yet, and I know for '66 the wiring diagrams are included)?
Yes. but not for the optional gauges, only the idiot light SS gauges.

Thanks again... Now to try and find the 12-pin connector... Any other cars (like later 73+ Chevelles, trucks, etc) use a similar connector?
70's Camaro, Nova, Truck - When you get the connector peel back the harness tape so you can clip it off with about a foot of wire to splice into.

Steve Strasemeier (70SS 396, Fathom Blue/White Stripes)
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post #7 of 12 (permalink) Old Apr 7th, 07, 9:26 AM Thread Starter
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Re: 70 Chevelle SS: tach into a non-tach dash

Where can I get a "wiring diagram" for the optional guages?

Although, I guess I could "map out" the circuit board terminals and figure it out that way...

Bummed about he gas guage


I did have a guy contact me about buying a 71 Monte Idiot light dash WITH harness for $100... But he's about an hour away... get the harness, an extra speedo and an extra gas guage...

Once you go RAT, you never go back...
TC #1366
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post #8 of 12 (permalink) Old Apr 7th, 07, 10:16 AM
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Re: 70 Chevelle SS: tach into a non-tach dash

There used to be a link to a great conversion diagram - but it's no longer active.

I've got them printed out, I'll have to check on it and get back with you. It details exactly which wire/pins do what and how to move them around for the conversion.

Mark

1970 SS396
Lewis Racing Engines (Wolfplace) 489:
634 HP @ 6000rpm
627 Lb-ft @ 4,000rpm

ProSystems SV1
Gear Vendors Overdrive
Moser 12 Bolt
Alumitech Radiator
Pypes Exhaust

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post #9 of 12 (permalink) Old Apr 7th, 07, 4:24 PM
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Re: 70 Chevelle SS: tach into a non-tach dash

Well, here's a quick summary: Moving FROM a round idiot light SS cluster TO a tach/guage SS cluster:

Move Pin 5 (Power) to Pin 7
Move Pin 7 (Fuel) to Pin 11
Move Pin 11 (High Beam) to Pin 5
Move Pin 10 (Oil Pressure) to Pin 6
Move Pin 9 (Temp) to Pin 10
Pin 3 = brown wire, REMOVE and tape out of the way

I believe you also need to change temp sensors, Year One Part# 9520N will work.

Mark

1970 SS396
Lewis Racing Engines (Wolfplace) 489:
634 HP @ 6000rpm
627 Lb-ft @ 4,000rpm

ProSystems SV1
Gear Vendors Overdrive
Moser 12 Bolt
Alumitech Radiator
Pypes Exhaust

Dyno
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post #10 of 12 (permalink) Old Apr 9th, 07, 2:35 PM
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Re: 70 Chevelle SS: tach into a non-tach dash

Link to gauge conversion: http://www.azendrud.com/gauges/.
Notice this states 70-72 but the 72 is not the same as 70/71. 72 has different pin out at bulkhead connector and the tach wire runs through the bulkhead connector vs running through a hole in the firewall for 70/71.

Steve Strasemeier (70SS 396, Fathom Blue/White Stripes)
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post #11 of 12 (permalink) Old Apr 9th, 07, 4:22 PM Thread Starter
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Re: 70 Chevelle SS: tach into a non-tach dash

Thanks guys...

I am thinking about some "custom" wiring... Let me know what you think...

The "printed circuit" board has a break, in the "dash illumination" circut...

IF I can find the appropriate "sockets", I might try wiring my dash without the "printed Circuit" board...

I DID manage to move the gas guage to the other side... It fit in the existing "clock" hole. I did NOT have to trim the housing. I did trim a few of the edges of the gas guage backing so they wouldn't stick out...

Therefore, I can NOT use the Circuit Board for this setup... BUT, I can directly wire the gas guage (two posts, and I can used the old Circuit board to determine which goes to hot and which to ground). I am hoping the Tach can also be wired separately (I have been told it can)...

I see (from looking at my car), that the "Malibu" dash has at least one socket that fits in the dash, AND has 2 wires (Hot and Ground? Looks like a dash light socket)... If I can find similar sockets, I could wire them like an older car (splice into the harness)...

I just need to find more of these sockets... Anyone know if I can get these new anywhere?

Once you go RAT, you never go back...
TC #1366
'70 Chevelle 427 Stroker
'66 Convertible Sold
Dual Quad 396 & Conv Int
'66 SS L78
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post #12 of 12 (permalink) Old Apr 9th, 07, 4:29 PM Thread Starter
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Re: 70 Chevelle SS: tach into a non-tach dash

Quote:
Originally Posted by Steve S View Post
Basically you cut all the idiot lights off the sweep harness and patch them into the 12 pin gauge harness.

So, do the "Malibu idiot light" sockets have the two wires? If so, might be easy to find some extra sockets... I didn't remove the Malibu dash, just the dash pad, and saw the upper-driver's-side socket had the two wires, and twisted into a small circuit baord with several dash lights across the top... Thats the only two-wire pigtail I could see...


Damn. I forgot to take pictures. I am getting ready to move, and so I wrapped the guages up and put them away...

Maybe I'll try to pull them out and take some pictures of the new gas guage location...

Anyone know if the repro dash lense come predrilled for the clock stem? I hope not, because with the gas guage there, I don't need/want the hole...

Thanks again everybody...

Once you go RAT, you never go back...
TC #1366
'70 Chevelle 427 Stroker
'66 Convertible Sold
Dual Quad 396 & Conv Int
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