Noy2014

I just installed the following Mallory HEI Distributor

http://www.jegs.com/i/Mallory/650/85...0002/-1?CT=999

However, I overlooked where the tach cable would now be connected to. Mechanic says I need an electric tach. I don't know what this part is for my '68 BB

Little help please?

Ret.Horsecop13

I bought a DUI distributor with the tach drive installed. Was that an option for your mallory? I'm not sure what to do about the tach without it. I'm sure someone will know! Good Luck!

baxsom

the best thing you can do is sell that one and get a tach drive distributor. look for the dragonfire brand HEI ones. They use GM parts run about 100 bucks. They work directly with your existing tach. the one you have there will require you to either install a tach from a 74-77 or get the adapters and mount a 5" autometer

johnt365

I was in the same boat you were. I chose to have my original tach converted to an electric unit by Roger at www.corvetteclocks.com

You have several options.

gbvette62

74 was still a mechanical tach. 75 was the first year for the electronic tachs.

When Chevrolet switched to the HEI ignition in 75, they eliminated the cable driven tach, and went with an electric one.

Any 75-77 tach will fit in your dash. If you want it to match your other gauges though, you will have to switch the face from your 68 tach, onto the later electric one. Used 75-77 electronic tachs sell for about $100. The printed circuit board in them is about $59 dollars and easy to replace (and a new circuit board is cheap insurance against having to pull the tach out again).

If you don't want to tackle this yourself, Roger, or anyone else that does Corvette gauge restoration, can convert your tach to electric.

Noy2014

The hei distributor with the tach connection was selling for $470 (compared to $150), that's $300+ more than what I bought. Not that I noticed it at the time of purchase, but I don't think that difference could be justified. ...well now, I'll just have to see what the additional parts will run me.

Noy2014

Man this sucks!! I think I need to just pull the distributor, send it back to Amazon and get one with a tach drive! Seems to be the easiest approach!

rugerm44

Might be cheaper in the long run.

Tom73

...or go back to the original and installing an electronic module.

68/70Vette

I have am HEI tach drive distributor in my 69. I don't know who I bought it from since it was many years ago. It was one of the major Corvette vendors though for sure. I bought it in the early 1990's for about $400, which was VERY BIG BUCKS for that day. I'll probably buy one for my 70. They are not so expensive now, it appears. On my 68, I use the HEI tack drive signal to drive the speed controller on my Aeromotive fuel pump speed controller.

kdf1986

I dont think that conversion is as easy or as cheap as it seems. On one hand the mechanical tach drive unit is more expensive than the electric one. On the other hand modifying the mechanical tach to an electronic one also involves extra work and cost.

If you already installed the tach in your car, you may have voided the warranty. Some places may have no returns on electronic, electrical or used parts.

kdf

boltnut

Sell it on eBay and get the right one.....with vac advance as well....much better deal than modifying your dash components and worth the extra expense IMO. The second and maybe best choice is to send your stock hei out to be recurved and upgraded to an electronic module. Often just as effective as a swanky billet distributor if you are not also running other aftermarket ignition devices such as separate coils, ignition boxes, ect.

Mike Ward

That's the best advice. HEI will gain you nothing in performance and possibly set you back some depending on the advance curve.

ElCameeeno

Pertronix Ignitor III in the stock distributor with the matching Pertronix coil. Looks stock and with the multiple spark, runs much better than an HEI. Best upgrade I have done to my car yet.

gcarpenter

Bought my HEI for my 73 from Ecklers and it had the tach drive and vac advance for like great. PN 47935 Corvette HEI Distributor Part# 479 $189.99 Conversion, 1962-1974 35

centralcalvette

I would recommend swapping back to a tach drive, that way it's easier to convert back to original. Mine has a Accel dual point with out TD. I bought and cleaned and painted an original tach drive Dizzy thats going in very soon. I plan on installing an MSD T/D unit later on, but that's way down my list of things to do...

Tom73

Also, isn't the head of the HEI too large to fit under the stock ignition cover?

Mike Ward

Most are.

Paul L

You haven't mentioned the cost of HEI 8-mm spark plug wires. Conversions can be expensive.

Noy2014

Yes, the hei with tach drive are more money, but saw no reason to not go with this one for $80 delivered!

http://cgi.ebay.com/ws/eBayISAPI.dll...m=330509920081

Mallory wires ran me another $75.
Heck no, was I getting into the changing the tachometer to electrical. Too much work.

btw, as it turns out, I was running a stock distributor with an electric module all along, ...which I now yanked out for an hei. So did I gain anything there, ...who knows?!