[OVERULD]

I have a 74 Formula 455 I'm in the process of freshening. See thread in this section.

One of the things I want to do on this car is change the gauge cluster to make it match the car I owned in 1975. That car had the WW8 option "Gauge -CL + TA" which had the small clock set within the tachometer dial face. The car I am freshening came with the W63 option "Rally GA&CL" which just had the large Rally Clock where the tachometer goes.

My question is can I make this change by simply ordering a reproduction Tachometer/Clock gauge like this one:
https://www.yearone.com/Product/1967...65%20(1000-10)

Or this one:
https://www.firebirdcentral.com/1970...p/das-2012.htm

...and then simply swapping the clock with the tachometer - or will it require changing out the entire cluster? Also, will the printed circuit that came in my current car have the correct circuit to run the tachometer or will it require a new circuit?

Last question: What was the Redline for the 74 Formula 455 D-Port cars?

Thanks,
BJ

[77 Canamman]

https://www.yearone.com/Product/1967...m-parts/cd8075



You'll need the 8K tach. It will screw right in your existing cluster. There is a separate tach harness which connects to the fuse box and to the coil. The PC's are the same.

[OVERULD]

Is that tach harness already in the wiring harness and just not used, or do I need to source it?

BJ

[77 Canamman]

Typically, they are not installed on cars without the tach.

[OVERULD]

O.K. Just got off the phone with Firebird Central and they told me that since this car was not born with Rally Gauges, it would require a whole new engine harness, headlight harness and printed circuit to make the tach work. They suggested that I could buy the tach, new printed circuit and tach harness, and make it work (i.e. it will physically accept the mounting of the new tach and the clock will work) but that it would require getting power and a ground to the tach, and then running a wire to the HEI distributor for the tach to work.

The car had an aftermarket tach on the steering column, but a previous owner removed it. I'm pretty sure that the green wire in the photo below was the lead from the distributor to that tach. So, my question is, how should this new tach be wired to make it work properly? I've provided links below to the items they recommended that I buy.

Tachometer
http://www.firebirdcentral.com/Searc...earch=DAS-2012

Printed Circuit
http://www.firebirdcentral.com/Searc...arch=DAS-2311A

Tachometer Harness
https://www.firebirdcentral.com/Sear...earch=WIR-2352

Gauge Lens Kit
https://www.firebirdcentral.com/Sear...earch=DAS-2061

Tach Wire in Engine Compartment


Thanks,
BJ

[77 Canamman]

Just to clarify, your car has the oil, temp, and voltage gauges with the big clock in the left pod? I.E. NO idiot lamps?

[OVERULD]

Correct

Here is a photo of the dash



BJ

[form74]

Converted my 74 formula that had the same dash cluster as your, did it along with the HEI Upgrade, the wires came from a 75 TA I parted, the power wire I have tapped into the Fusebox off the power for T400 if memory serves me right , I can check tommorrow and the Tach hardness was just needed to be run thru the firewall and plugged in at the HEI and the Tach.

From what you posted this looks like that's all you will need Beside the Donor Tach.

Tachometer Harness
https://www.firebirdcentral.com/Sear...earch=WIR-2352

[77 Canamman]

You currently have the Rally gauges without the tach.. You will need the tach harness, and the tach. The tach harness taps into the fuse box for the 12V source. It also connects the HEI with the tach.. The printed circuits are the same as long as you have the factory temp/oil pressure gauges. GM 8911865 '74-'77 F with gauges according to my parts book. You should have the right PC already.

Per Firebird Central:

New correct design dash instrument cluster printed circuit board for your firebird. If your a 78 model be careful this version is only for the first design tachometer assemblies. Which means the needle on your tach is not attached to the round center hub. So the gray needle moves behind the round hub, hub stays still. 74-77 models, no worries this one is for you if you have gauge package. If your not sure dont hesitate to call 1.859.408.2000 for help. *Exact fit for all models with factory Tach, Gauge, & Clock package *1st design style clusters that the needle moves behind the tach hub center *Replaces GM # : 8911865 perfectly

*If your buying an aftermarket tach assembly this is the right board for you

Part Number: DAS-2311A

[OVERULD]

Thanks guys. I'll go with just the tach and the harness.

BJ

[unruhjonny]

I have done this swap on a couple cars - it's super easy;
iirc the clock and tach use a different backing plate, but as mentioned earlier, the printed circuit board is the same one - the clock still gets it's power from the same source....

I have gone old school, then again my conversions were for points cars - I think you need the 12v lead for HEI tachometers but not points - I just ran a 14(?) gaugue wire from the tach feed with a female end to connect to the back of the tach, and either a open fork/prong or open/circle end on the other end to connect to the coil... but I'm confident you'll do a much better job than myself...
(please forgive me for any mis-speaking, it has been about a decade since my last conversion.)

If you need pictures, I can dig out spare clusters (ect) to show you what to expect.

I would actually buy a good used original tach over a repop, but that's just me.

[OVERULD]

Thanks - Pictures would be great if you don't mind.

BJ

[unruhjonny]

ok...
I'll see about getting some up tonight (I'm in mountain standard time)...

[OVERULD]

Started the Tachometer conversion today and have some questions:

Here are a few photos of the back of the gauge cluster, showing the printed circuit number and some other neat labels for reference.







Here is a photo of the back of the cluster showing the clock and an unused circuit connection point. Also, check out the bulbs next to the cluster. Some are clear and some look red to reddish brown, but I think the red ones are actually the ones that are burned out. Do they turn red like that when they go bad?



Here is the back of the cluster after I installed the new tachometer in place of the clock. Note the arrow pointing to that same unused circuit connection point, which now has a stud coming through it that is connected to the new tach. Do I need to put a washer and nut here to make a connection with the circuit? What does it feed?



Here is a photo showing the tach harness connection to the back of the tach.



Here is a photo showing the rest of the tach wiring harness. I am assuming that connection #1 goes through the firewall to the TACH lead on the distributor and connection # 2 goes to the fuse box...correct? Where in the fuse box should I connect it?



Now, here is the confusion factor...Look at the photos of the distributor. It looks like there may already be a brown wire going to the tach connection, and there are some other wires attached at the battery connection. There is also the green wire just loose behind the tach, which I believe was feeding the old steering column mounted aftermarket tach that previous owner had installed. The other end of that wire is loose in the area behind the instrument panel. Is it possible that this car came with points and someone has converted it to HEI and these are some of their wiring shenanigans?

Walk me through what I need to do to make this tach work properly on the first attempt!






And while we are speaking of random wires...what the heck is this connection and where is/what does the little button looking thing that is stuck through the oil dip-stick handle supposed to go/do?



Thanks,
BJ

[njsteve]

That button thing is the superheat switch connector that connects to the superheat switch terminal on the rear of the a/c compressor. The black plastic three wire connector is the a/c compressor fuse. If the superheat switch reads a loss in freon pressure, it grounds out internally and blows that black plastic rectangular fuse before the compressor can blow itself up. That melted hole in the middle of the fuse indicates it is blown. Does the a/c work?

[77 Canamman]

Usually, bad bulbs or ones going bad get dark, not red. I would replace all, and make sure not to touch them with your bare fingers. Fingerprint oil shortens their life. The unused circuit in two spots is your ground for the cluster. The one with the stud is for the tach..



..and the one that accepts a screw is for the cluster lighting. A washer should be used with the nut, and the correct cluster screw for the hole will suffice. Number 1 goes to the tach terminal on the HEI, and number 2 will plug into the fuse box under the dash in the IGN unfused port.




Here is the location on the firewall where the dist. feed wire should exit:





Also, the under the hood tach wire (originally brown in color) should have an inline fuse in it.

[njsteve]

If I recall correctly, HEI didn't begin until 1975. 1974 would be either a points distributor or the (really hard to get parts for and undependable) Unitized distributor - the ancestor of the HEI. Your PHS invoice should indicate whether your car had the optional unitized unit or not.

The unitized distributor took direct 12 volts from the wiring harness, like the later HEI but a points ignition will use the resistor wire system which reduces running volts to 9 volts. It appears that your car was a points ignition car that they added that yellow wire to feed direct 12 volts to the "BAT" terminal on the cap. The green wire hanging near the firewall looks to be a homemade tach wire that is disconnected from the left "TACH" terminal on the cap. By the way, that yellow wire is too small of a gauge to safely power the HEI. Numerous wiring companies sell the proper HEI power feed wire to upgrade properly.

Here is a shot of the 12 volt direct power red lead to the cap on my Gramma's car with HEI. You can see that it is a 10 or 12 gauge wire. The outer connection circled in red is the 12 volt power feed. The photo with the cap removed shows the inner connector which is the distributor to cap connection (circled in yellow). It connects behind the power lead.

The final photo shows the location of the power and tach terminals. Tach is on the left underneath where it says "TACH", "the 12 volt feed is labeled "BAT" on the right.

By the way: DO NOT CONNECT THE TACH WIRE TO THE "BAT" TERMINAL. YOU WILL INSTANTLY FRY YOUR NEW TACH WITH 12 VOLTS!!!

[77 Canamman]

Late 1974 non SD-455 cars were equipped with HEI.

[njsteve]

Don't replace the fuse and reconnect that connector until you refill the A/C system or it will just burn out your new fuse.

Attached is a shot of the rear of the compressor with the superheat terminal that, that black "button" connector should be connected to.

Here's a link to the thermal limiter fuse as it is referred to.

https://www.rockauto.com/en/partsearch/?partnum=tls1


Here's a link to the HEI power lead wire.

https://www.yearone.com/Product/1967...ll#prettyPhoto


.

[77 Canamman]

Versions of the Delco 15-2109 6551258/GM 3909030 thermal limiter: