Modifying factory Vega tach for V-8

[hoffbug]

How do you modify the factory Vega tachometer to be accurate when swapping in a V-8?

[doogiediamond]

I sent my tach to Tim McCabe when I needed my stock 4 cyl tach to read for a V6. He can do the same for a V8.
Hes a Wiz!!
Some tachs come with some sort of switch on the back to switch from 4-6-8 cyl engines. But mine needed a little mod work.
Has been working great for years now.

[bugdewde]

Tim McCabe did mine for me. He even calibrated it correctly. Most all 70's GM tachs are inaccurate.

I have a print out of a mag article that describes the procedure by soldering in 2 capacitors but I can't get my scanner to work with my new computer..........

I'm sure someone else here has it, too. But Tim does great work and I'd recommend him and his services.

[peterpan]

i have the artical pics saved but they are to big to post give me your email and i will email them to you


i need to get my tach done
when i get to that point i will contact tim and see if he will do mine
instead of trying to do it myself

[hoffbug]

Thanks Ray.
I sent you a PM with my e-mail address.

[BillB1210]

I recommend Tim McCabe. He did two for me, both work perfectly. I believe he installed some new components to replace some older revisions.

Bill

[peterpan]

you have mail

[spencerforhire]

I would like a copy of the tach mod procedureas well. I have an OLD photocopy from probably the same car magazine from the 70's, but the resolution is so bad I can't see the photos anymore. I have a couple of 75 Monza V8 tach & speedo sets(which fit in the Vega GT cluster) but I want to mod the 4cyl tach so I can have the higher redline! Of course I WILL use the Monza speedo, cause it goes to 120- I think with 3.23's and a T-5 the stock 4cyl speedo will not last long.

[peterpan]

get me your email and i'll send the pics

[TimMcCabe]

The magazine article only covers the 71-73 tach (thin free floating needle, returns to zero with the key off). You have to add a couple of caps in series to get it to read for a V8. It works, but it is not very accurate.

74 and newer Vega tachs (Monza as well) use an air core meter (needle stays at last reading with the key off) and digital circuits. They require a lot more tweaking to read correctly (they are way off right from the factory.. kind of a poor mans rev limiter They can read over 1000 RPM higher then actual engine speed).
I modify the circuit board to make the tach accurate to within about 2% at red line (usually off by less then 50RPM at redline).
I have built a test rig that allows me to check the tach from idle all the way up to redline.

Cheers,

Tim

[hoffbug]

Thanks Tim. Now I just have to get a GT dash !

[1973vegasandiego]

I contacted a seller on ebay that had a tach for sale plus the jpeg for the tach mod, he was nice enough to send it to me and I'm happy to share, hope it helps, wow I don't know if I can get this any smaller