I know there is lots of talent on this sight. Anyone set up to recalibrate a 911 tach?

I am doing a /6 conversion for my customer and this tach reads low, p/n 911.641.301.01. Both Hollywood and Palo Alto are quoting a long turnaround time.

Thanks Brad

http://www.914world.com/bbs2/index.php?showtopic=216719
This is a option


Also, how low is it reading? What are you referencing it to?

You could ask Bob Ashlock if his Tach-adapt would help you.
Tach-adapt also cleans up the tach signal and fixes some issues.

http://ashlocktech.com/

Ashlock.tech tachadapt will suit your situation Brad,contact Bob and chat with him,this unit won't fix a bad tach however .

Mark beat me to it,this unit sorts miss matched or modern ignition setups ,MSD make one but they are known to fail.

I did business with Waldek when he was at North Hollywood. Good guy.https://classicautoclock.wordpress.com/

Hey Brad. Give this guy a call: http://seattlespeedometer.com/ He does great work, reasonably priced, and turnaround (last time I checked) wasn't bad. He repaired a 911E tach I wanted to use because the redline more-closely matched the 2.7 engine I was using and I didn't want to alter the stock -6 tach. Another big plus was he lived only a couple of miles from me at the time. Time-warp shop.

- MR

I always try and match the engine and tach to the same model year. What year engine, what kind of ignition?

I had Corey Shepard fix my 964 tach, and he was very fast. Not sure if he can help, but here's his contact info
Cory Shepherd
Specialty Gauge
9904 Par Dr
Nokesville, Va 20181
703-402-4008

For those recommending a Tach-adapt is simply asinine. It is like adding Sea-Foam to an engine with a dropped valve seat. I'm sure Bob's module does condition the signal but I'm also pretty sure that Brad (being the 914 god that he is) has already got this ignition system well tuned. No module will fix a broken tachometer.

It was stated that the RPM readout was low. These tachometers are pushing 50 years in age, which well exceeds the life of a electrolytic capacitor. After reverse engineering the 911 tachometer and updating some obsolete parts, it is very likely that C4 which is part of the timing circuit of the tachometer has degraded with age and causing the tachometer not to read correctly
Click to view attachment

Maybe I misunderstood, but I though the issue was the conversion from 4-6 cylinders, not a defective tach.

The Tach-adapt is a good plug and play tool to make some of these parts play together. Are you sure you did not go off half cocked here sir?

I think Tim called this correct.

I didn't mean for it to sound as if I'm going off. He's got a 6 cylinder 911 engine and he's got a 6 cylinder 911 tachometer. Why exactly does he need a module to make the two talk to each other?

This is a 911 (6 cylinder) tach and the tach itself is defective. I have decided to send this tach to Tim to convert.
I did learn a lot from the answers to this thread and it is great information that the Tach Adapt is available as well as the contacts for other gauge technicians I was unaware of.

Thank you all! Brad

I’m not well versed in electronics, but can use a VOM and a soldering iron. My knowledge base was building Heathkits back in the day (very satisfying to turn your receiver on and have it work). Are these old capacitors available and replaceable? I imagine the same applies to the old CDI boxes as well.

Tim do you offer this tach service?? I want to convert my 4cyl tach to read my 6cyl engine..

The old heathkit circuit boards are very similar to this era tachometer. Yes,you can obtain replacement parts from Mouser or Digikey type stores. Some components are no longer available, so I have found proven suitable replacement parts and updated the schematic in an attempt to help others resuscitate their own broken tachometers. Values for each component is listed in the above schematic, just keep in mind that this schematic is strictly for 911 tachometers only.

The 914 tachometer has slight variations, and I have not posted a schematic for it yet. An answer for a future question, yes you can take a 914 tachometer, change out a few parts and make it work as a 6 cylinder. I have yet to try this out because I found some other cheap but slick answer with the sunpro conversion. It killed two birds with one stone by eliminating the tach bounce and also having the ability in different cylinder selections, all the while keeping the 914 tachometer looking stock. However, the sunpro cheap tachometers are being phased out and my instructional thread will only work with this sunpro tach.

I'm working on a new project that uses a air core friction less motor and a custom circuit board that fits into our existing tachometer without monkeying around like my instructional thread. It will have very quick response time with zero bounce and a memory recall feature. It would be nice to cycle the igntion key twice and have the tach point to it's highest rpm after your kid has borrowed your car for the night.

Once this is finished, I will post the schematic and code for all to have.

Yes, you are correct! When I originally saw the post I thought I read that he had a 4cyl tach and wanted to calibrate it for a 6.

I think a lot of folks would be surprised to know just how inaccurate their techs are!

Tachadapt can do that ,easy setting as per intsructions,I agree with timothy,my tach wouldn't respond,fitted tachadapt and it worked but really unstable,talked to Bob and he said it was ,PO mentioned he didn't know if it was any good but gave it with the car.
It reads low @ idle and is really unstable unless constant RPM is maintained.