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73 Dash Replacement Project


KenFirch

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I ordered a reproduction dash from Vintage dashes December 2021, finally received July 2022.  Been psyching myself to do the replacement, since dashes a wiring are not my favorite to work on.  When I purchased the car 8 years ago, it already had a full dash cap installed.  It actually looked okay, but the tach has never worked, and a cap prevents the removal of the gauges from the front, at least for me.  So I really couldn't do a proper repair of the tach.  And I want to fix the clock, which always reads 2:40.  All other gauges work fine.

Here's the new dash:

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Here's the old full dash cap.  Also the glovebox door fits tight and has a string to help pull it open.

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The fun begins....🤔

 

Edited by KenFirch
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I marked all connectors and and worked slowly removing all wires.  Plan was to disconnect the multiple plugs on the right side and leave wiring harness attached to backside of dash.

Removing ducting gives a bit more room to work.

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Luckily the wiring in this car isn't butchered with splices, only the radio connections had to be dealt with.  The two main power feeds (large white and white/red) through the firewall had crimped butt connectors, so I assume the dash has been out before.  I should probably check the heater core too.

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Now I removed the cap from the original dash.  To remove the various knobs:

  • Odometer reset: small set screw at speedo end, and pull knob off, remove cable.
  • Hazard switch: push knob in, twist 1/4 turn counter clockwise.
  • Lighter: 1" socket works to remove nut on back.
  • Panel light knob: pull off, remove 2 screws from back.

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Luckily there wasn't too much adhesive holding the cap on, and it took about an hour of carefully prying it off the dash without cracking it.  I'll probably sell the cap eventually.

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Once the screws that held the dash to the metal were removed, it slid right off.

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9 hours ago, Dave WM said:

test fit the glove box door on the new dash once installed on the frame BEFORE reinstalling the dash. You may need some tweeking to get it to open and close smoothly, much easier with the dash out.

Good idea, thanks for that.

I mounted the dash frame just to get an idea of the bolt in process, without all the weight.  Pretty ugly.

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The edges that will need to be slit and folded around the frame is kind of thick, like 1/16" or more of dense foam on back of the dash.  So for the glove box and center panel opening, I used a blade to thin it more like the original dash, as close to the outside material without cutting through.  It was like filleting fish!  I may have to drive over to Reno to get some adhesive, since California has banned all the good stuff.  Weird that it was left to me to do that cutting, but I can't imagine a thick piece like that being wrapped around the edge and being held in place with contact cement!  Maybe I'm missing something here.

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I screwed the vent panel in place and marked the edge, just so I know the top edge is forward enough to "hook" the top front edge of the dash pad when screwing pad to frame.

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Nice that the new dash has the same molded in place steel rails to screw into.  There's 17 screws, here I've got finish nails sticking out of each hole.  I should have ran a screw through each hole just to get a thread formed instead of waiting while trying to mount to frame.

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I also marked each hole with a marker which helped while positioning the dash over frame.  I worked from the center outward.

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I've got the new dash screwed to the frame.  Glad it wasn't a 50 year old original dash pad, as much as you have to muscle it in place to get the holes aligned.  New one has some flex to it.

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Got the holes drilled/cut for the hazard switch, lighter, dimmer, and odometer reset.

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Next is cutting. trimming, folding the edges, and gluing to frame, around the center and glove box opening.  I assume that is what others do.

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13 minutes ago, Richard McDonel said:

I've been considering the same job on my '71.  So far, your pictures are scaring me away from even thinking of it!

Ha, yeah, I know the feeling!  I've never done a Z dash before, and I'm not trying to pass myself off as an expert.  Just showing what I'm doing and hopefully get a few tips along the way.  👍

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make sure you have the dash installed as deeply onto the frame as you can.IIRC the holes on the metal frame are large enough for some wiggle room. You want that wiggle to be biased as far back (on the frame, forward from the driver posistion that is) as possible. The issue is the door opening, The dash is just big enough, if you have it forward at all you risk the edge of the dash being visible with the door open. It should tuck in behind the opening. This was the way it was on a 280z anyway.

Edited by Dave WM
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Thanks Dave for the suggestions!  👍  That's quite a set of videos you have up there!

I attached the defrost vent panel to check the clearance between it and the dash.  Looks good.  I should paint that panel, but I'm afraid I won't get the right sheen and won't match the dash.

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Did a dry fit into the car to see how it fit, and any clearance issues with the doors, etc.

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I still haven't figured out how this car got so much overspray on the inside, shifter boot, wiring near the harness and relays, even some of the diamond tunnel covering.  It wasn't a color change, and no floor or frame work has been done.  What the heck were they trying to accomplish?  

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Got the center and glove box openings trimmed and ready to glue to the frame.  I tried to generally match how the original dash was trimmed in the openings.

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Borrowed a friends solvent based Weldwood contact cement, hopefully it will hold good.

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I think these small dimples may be suggested cutting lines, I ended up cutting fairly close to them as I was trimming.

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Using stir sticks and clamps to hold overnight.  I've got my 10mm 3/8" socket in the glove box button hole so dash is not getting deformed by the clamp.  I ran out of clamps, so I'll finish the center tomorrow.

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Edited by KenFirch
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Got the edges glued, and test fit the center panel and glove box.  Glove box works fine, not more string to pull it open.  Getting new correct fasteners for the center piece.

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Now onto the gauges.  I took the clock apart, tested the motor, which works.  I might just try to clean it up and lightly oil with the correct stuff.  Wait time on quartz conversion is 14 weeks, so maybe I'll hunt around for one already done.  Might be nice to hear a ticking clock though.

The tach has never worked in this car since I bought it.  Not see sure what year tach it is, it has a 6400 redline.  And I've got an old one, correct dial I believe.  Pictures below.  Looks like the one on the right in missing the loop wire on back.  

Is there a way to bench test these?  Thanks!

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11 hours ago, KenFirch said:

Looks like the one on the right in missing the loop wire on back. 

Not quite sure I understand which tach you have (it appears you have two of them?), but the correct tach for your 73 is the style with the loop on the back. The other style (without the loop) will not work in your car without some other modifications.

This is the correct style for your car:
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On 9/21/2022 at 4:36 AM, SteveJ said:

My friend, Google, found a link that led me to this: http://www.mgb-stuff.org.uk/tachtest.htm

I couldn't get that method to work.  Maybe the newer battery chargers are too smart and figure out there's no battery hooked up to it.

I hooked the 260/280 tach with the single signal feed to my Sunbeam Tiger, which also has a Pertronix.  And it works fine!  It read high at 2000 when the Ford 260 was at 1500, which makes sense.  So, I'm going to move the 7000 redline dial the that newer tach, should be good to go.

Edited by KenFirch
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Yes, you have to fool the charger to get it to start. You can do that by having a jumper to a battery that you pull. However, it sounds like your method worked, so there is that.

Now here's the next question. Has the wiring in your car been modified for the 3 wire tach? The stock wiring in a 240Z is for the 4 wire tach.

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Here's the follow-on question. Did the PO get the resistor installed in the circuit? The design of the tach circuit for the 260Z/280Z 3 wire has a 2.2kOhm 1/2W resistor between the tach and the negative post of the coil.

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On 9/22/2022 at 5:48 PM, SteveJ said:

Here's the follow-on question. Did the PO get the resistor installed in the circuit? The design of the tach circuit for the 260Z/280Z 3 wire has a 2.2kOhm 1/2W resistor between the tach and the negative post of the coil.

Yeah, I doubt a resistor is there.  Looks like the tach is feeding from the Black/White wire going to the coil.  And reading this thread, it looks like the need for a resistor is sometimes not needed, maybe depending on the electronic ignition used, I don't know.  But something is funky with my tach wiring, I still need to work it out.

On my clock, I stripped it down to the mechanical clock mechanism, cleaned it good, lightly oiled pivots with clock oil, no luck. Took apart motor too, cleaned and oiled.  everything looked okay, worked for awhile, then quits.  Beyond my capability.

So, I ordered this electric clock off of Amazon for $40, and finessed it into the housing.  I thought of just painting the orange hands white, but decided to clip the originals and epoxy them to the new clocks hands.  I may still get some Testor's paint and mix up the right off white shade, and paint the hands.  Plus I'll have to mount a small push button (negative ground signal) somewhere hidden under the dash or in glove box to adjust the time.  I'm running it overnight to see if swinging the little extra weight of the hands affects it's accuracy.

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