Advice on Distributor Tach Drive

[twoseater]

Hello - the points in my distributor are shot. The current distributor does not have a tach drive so my mechanical tach is disconnected. It also has a vacuum advance.

I am either going to covert the existing distributor with the pertronix conversion kit($80.00) and forgo the tach a while longer OR replace the distributor with a tach drive model.

I am having trouble finding the correct distributor and would like a recommendation from others.

First, I looked at the MSD but it appears I also need to buy their ignition box, which puts the cost way up there.

Secondly, I looked at Mallory, however, I can't seem to find a tach drive with vacuum advance (looks like they only have mechanical?)

Third, I don't want to convert the tachometer to electronic.

Any distributor advice out there? It is a 327 SB.

Thanks,
Bill

 

[Ron Miller]

I'd hunt a Corvette tach drive distributor, myself. Really doesn't have to be the correct '65 distributor to work, any of the '63 thru about '75 (whenever they went to electric tachometer) will work, may need springs and weights, and vacuum advance changed. Try E-Bay, or posting on the parts forum here.

 

[twoseater]

I also have another option

When I got the car I was also give a Mallory tach drive dual point distributor. Apparently that was the distributor that was swapped out for the current one. The distributor itself looks fine. Part #2664501.

Anyone know if that can be converted to electronic?

 

[JohnZ]

Corvette tach-drive distributors aren't rare - there are plenty of them out there, and I always see plenty of them at the major swap meets; lots of them on eBay too. Don't worry about part numbers - they're all the same from '63-'74 except for the tuning parts (autocam, weights, springs, vac advance can), and you can create any one you want on a Sun machine in fifteen minutes, then order a repro part number/date band for whatever you need if you have it judged.

 

[GTR1999]

Good point John, one thing I'd like to add is the aftermarket gears can be a problem. The black cross gears with brass button on the end were not machine correctly. I don't know if this has been corrected but a few years ago I went through about 3-6 gears and all were bad. Also had some bad main shafts.

You don't need the conversion kit either. Stock point setups work great in a dialed in distributor. Some old devices are still good and offer less failure then some new units.

 

[twoseater]

Thanks Guys - in order to get on the road I picked up a pertronix kit to convert points to electronic. For now I'll stick with the current distributor (no tack drive) and locate a vette distributor (as suggested) later on when I get additional dollars.

I realize that points work perfectly fine, however, given my limited experience with them I'm leaning towards electronic just so I don't have to perform the annual adjustments etc. I figure I can move it over when I get the tach drive if I still want the electronic ignition...

 

[Rollin's65]

twoseater:
You might want to try a new mallory ss/comp for the small block with tach drive. It is a magnetic brakerless distributor. Needs ported vac for the advance to work correctly. I got one from Summit. Seems to work.

 

[JohnZ]

twoseater:
You might want to try a new mallory ss/comp for the small block with tach drive. It is a magnetic brakerless distributor. Needs ported vac for the advance to work correctly. I got one from Summit. Seems to work.

I'd be interested in why it needs ported vacuum to work - do you have anything in writing from Mallory that says that?

 

[Rollin's65]

I'd be interested in why it needs ported vacuum to work - do you have anything in writing from Mallory that says that?

John: Nice to see you jumped right in there.
It definitely is a pain in the donkey to get right but it works. The vac. can on the dist. is a 15* can. Thats 15* of dist. adv. not crank, which is 30*. Set starting advance, with vac. unconnected, at 10*. Starts great but sounds like you have a full race cam in it. Advance the dist. by hand counterclockwire to about 20* to 25* and it idles nice. As you know, its not going to start with 20*+ initial. Hook vac can to manifold source and you get 10* + 30*. Way over advance for idle.
So, if you give it ported advance and about 900 to 950 rpm at idle it will give you 22*. At 3 grand can hooked up with no load I get 55* to 60*.
I'm sure I would be far happier if I just used a good old point dist with the correct can. As you know, you by an electronic part and you own it.
Maybe I make a bad purchase?
John -- Thanks for listening Rollin'65

 

[JohnZ]

I have no idea what their logic is for a vac advance can that provides 30* (crankshaft) advance, and I've never seen a can like that - it's WAY excessive. If your total timing (initial plus centrifugal) is the usual 36* or so, you'd end up with 66* cruising down the road.

The generic settings I always start with (that seldom need to be changed) are 10*-12* initial, 24*-25* centrifugal, all in by 2800-3000, and a vac advance can that provides 15* at no less than 2" Hg. below normal idle vacuum level (so it's fully-deployed against the stop at idle), connected to full manifold vacuum.