Busrydr

I have a 73 that was upgraded with an OEM AC Delco (from a 75 Vette I believe) HEI distributor. It has been working fine since the install years ago. The distributor does not have the mechanical cabel drive for the tachometer so of course the 73 tach on the dash does not work.

Instead of swapping out the distributor for an HEI that supports cable drive for the tach, what all would be required to upgrade the tachometer to an electronic version and maybe use my old face plate for looks?

Not a number one priority but one of those "While I'm in there I might as well fix that too". When your heading for the poor house due to the " While your at its" what's an extra couple of hundred buck, right?

Thanks

Busrydr

Okay, I should know this by now, but the search button is your friend!

Looks of great info to questions that have already been asked and answered.

So who has a 75 tach that they would not mind parting with? Even not working is fime.

Danny456

I just did the tach conversion a few months ago. I had the same situation where someone had put a HEI unit in so i bought a tach off ebay for $40 from a 1975 vette. The faceplate is exactly the same except the rivets are a little wider on one of them. It was a direct install. You can only tell the diffrence if you look very close at both of them.

Dan

mrvette

Dan is correct, that is what I did some 12 years ago, in fact I swapped my old dist/gears/cables/crap, tach too with a vette shop for the '75-77? tach head....still in the car, working fine....

NO WAY in hell I would ever have a mechanical tach again....

RunningMan373

I have a '73 and recently did the swap to an HEI as well. When you swaped yours over, you did bypass the original black with pink lettering resistance wire right? If you don't that will cause serious lack of performance / voltage drop at dist.

Busrydr

At the time my swap was done, I did not have the foresight to do my own work. Now I'm a little more maticulous about how things are done and you know the old saying "If you want something done right ....."

Performance wise I have no complaints so the wires must be correct. I'll check it out when I go out to remove the control valve.

I'm installing a Hot Rod Air system and it came down to that infamous " While I'm in there" that lead me to think about fixing my non working tach. I'm also cleaning up the engine bay and am tired of looking at the tach cable hanging there on top of the intake. One thing keeps leading to another not to mention the complete poly suspension kit I just ordered, seat covers and foam, carpet, Reflectix lining throught the cab, chrome bumpers, weather striping, power steering components, restored ralley wheels and new rings and caps and I'm sure you all know it doesn't stop here


My biggest problem is finding where to stop and finish what I've started. Logic keeps getting in the way with that old "While I'm in there". How do you turn that thing off?

mrvette

U know when to quit when the 3 graphs intersect.....

money, time, effort, and the final overlay....

desire to DRIVE it....

RunningMan373

For me I set a standard,, Dailly Driver. I am restoring to dailly driver, 'cause that's what I'm gonna do with it. Not doing everything, just what it needs to run good and look right. I ammassed all the parts, then started. You sound like me 8 months ago. I am finally down to 1 small box of misc parts and about 12 hours of work left. It will be fun, and you will learn more then you ever wanted to know about your Corvette in the process, but the reward will be a first class ride that won't ever loose value, unless you drive it everyday to work, some people do. enjoy it, but get it done as quickly as you can. the forum will be a huge help, I suspect,, good luck.

Busrydr

For wiring on the tach upgrade, do I need to install the Tachometer Filter in the set up? I this this lisetd as a part for th 75 and up tachs.

gldnkngt

Probably would not hurt to install it. It may avoid spikes that may damage your tach board. I'm sure GM put them there for a reason.

Raphiki

From what I understand, the filter only filters out radio noise. I did the swap about a year ago - no filter - no problems!

Busrydr

Ther is an OEM barrel type with a wire at each end. Then there is a replacementtypes with two wires at one end and a single wire on teh other. I think what I need is a really good diagram that shows how I shoudl wire this tach and filter up.

I'm going with the old school Custom Autosound radio and plan on hooking up XM. Would hate to not have the best sound possible with that set up.

Anyone got a quick sketch of this wiring for the tach upgrade?

ACECO

Here's a schematic of the tach filter. It's just two resistors and two capacitors. Easy to assemble w/Radio Shack parts.



Here's a pic of one of the ones I've built for several forum members.



Good Luck!

chief487

The owner before me put in the Electronic ign. I bought a 76 tach on ebay. On the back of the tach there is a spot for a plug. Can anyone tell me what wire goes where.

1970 LS5

I see from postings it is recommended not to hook up HEI to Black/with Pink Lettering Resistance wire.

If I use alternative wired connected directly to Fuse Box / Ignition connector, do I need to install an auxilliary resistor to protect HEI electronics?

Pete
1970

'75

Just a 12 ga wire from the ign terminal in the fuse box to the HEI is all that's needed.

kerry74

I recently replaced my points distrubitor and had an HEI put in my 74 (by someone else). After reading this post i looked at my distributor and I have what looks like the original wires hooked up to my HEI. There is one orange colored wire and one wire with a fiber sleeve around it coming from my firewall going to the distributor. I don't see a black wire with pink letters at all. How can I tell if I need to run a new wire? If I run a new wire where should it come from?

RunningMan373

The cloth covered wire should hook up down by the starter, it's a bypass to give the spark extra juice during starting, it's stock. You'll need to trace the orange wire back to it's source, to determine if it's original or a add on. GM changes colors every so often, in '73 the wire was black with tiny pink lettering, stating it's ohms per foot. Trace the orange wire back and let me know where it comes from. Also look at the wire closely for any writing, that's a dead giveaway for a resistance wire. if it's stock, it will come from the main connector below the power booster.

kerry74

I checked the wires and they both went into a stock wire harness and traveled down the firewall toward the transmission on the starter side of motor. Guessing thats my indicator that they are both stock!

msandym

I purchased from star performance , an HEI dist with mechanical tach drive that blew up in 3 days . They wanted to see it , sent me a new one (looked different)and it and my tach have been working fine for 3 years .