Randy 71

TACH is jumping around and bouncing. Does this mean its time to replace that 90 degree fitting on the distributor or something else?

Randy

Randy 71

UPDATE.................TACH died this morning. I assume the cable is probably the problem. Is it attached to the distrubtor?

markdtn

Most likely the cable or the distributor gear. Remove the cable at the distributor. If the cable seems ok, then you can start the engine and see if the little gear is turning. Repair as needed. If it is in the distributor be careful, I understand that the main shaft can be damaged if that gear strips/breaks.

page62

Yes. The tachs in Vettes with points-based ignition are mechanical.

Gordonm

Most likely it is the cable. The gear in the dist is another weak spot. Rotate the cable at the dist with your finger. You should see the tach move if the cable is bad. If not replace the cable. The 90 degree fitting on the dist. is not needed. Just remove the dist and rest it in the proper position while restting the rotor. Not a big deal at all. I don't like the 90 degree fittings it is just one more link in the system. Good luck and hope it is just the cable.

Sigforty

You probably just need grease the cable. I know mid america sells a cable fitting that allows you to do this.

maxpanic

the fact that it was jumping & bouncing kinda tells you it's a gear that's hitting & skipping. The gear on the dist shaft is hardened so most likely it's the softer one in the 90 degree box.

Randy 71

Question, does the distributor need to be removed to work on the fitting or remove the cable? Does the point where the cable screws into the side of the distributor need to stay plug? In other words if I take the cable is out will oil leak out when the engine is running?

Randy

Gordonm

No. You can run it without the cable attached. You will need to remove the dist. if the gears in the dist. are broken. If it is just the cable you will be fine leaving the dist in.

maxpanic

No, you can leave the dist in place to work on it. Unscrew the fitting from the dist & look at the gear in the fitting. If it's chewed up or "dished" it's probably the culprit. I think the gear itself will just slide out of the fitting. Take the gear out & put the fitting back in without the gear if you need to run the car. Have ya looked at this thing yet? Mine quit once and it was simply loose, just needed tightening.

Gordonm

Usually if the gear is chewed up the shaft itself is in bad shape. I say usually but not always. Yes you can check it in the car but it is much easier out of the car. It is no big deal to remove the dist. Just make a drawing of where everything is pointed and reinstall it the same way. You will need to retime it but it should fire right up.

verskel

:iagree: ....and DISCONNECT it - Now !.......I didn't do this and the darn thing got wound up (it started working wildly the next day) and POP my darn needle in the tach broke off ! :mad :cuss :mad

You'll never forgive yourself for not having the foresight to grease the cable once this happens. +Plus it'll save you lots of time, grief, and money. For now, UNPLUG the darn thing before something breaks........until you can locate the problem. :yesnod:

GTR1999

Couple of thoughts Randy. It may be just the cable but I would remove the distributor if you can. It wouldn't hurt to disassemble it for inspection.The gear bushing will unscrew with a stiff putty knife. You want to look at the teeth of the side gear and the gear machined into the main shaft for damage. If one is bad the other mostly likely is too. I've rebuilt a couple of these over the past few months and found the replacement parts leave a lot to be desired. If your dist needs a main shaft and gear it will run you about $100 but the blackcross gear sold by many places is not a good fit-at least the 3 gears I bought from 2 places weren't. You can do a search for all the info on my past exerience or let me know and I'll go over it with you.
Good luck,
Gary

Randy 71

Some good info from all. I will look at it tonight. When removing the distributor, is there any special tips I need to know. I have never removed a distributor before. I assume you need to mark the shaft with the block so it will go back in pretty close as before? When I loosen the adjuster nut will the distributor lift straight out? One more, when re-installing will it drop back in or is there a trick to it?

maxpanic

Yeah, there are a few tricks to R&R the dist. It's no big deal if you've done a few but ... 2 big things - getting it back in the same position and getting the shaft onto the oil pump drive. You need to mark where the rotor is pointing as well as the dist itself. The shaft is going to turn a little bit as you pull it up out of the engine - pay attention to this and mark where the rotor is pointing after you pull the dist up an inch. This is where it needs to be pointing when you start putting it back in. The shaft will again turn as you drop it in and the drive gears engage... should end up on the same tooth. Sorry but I disagree with pulling the distributor before you know what the problem is, especially if you've never done it. You might be making unnecessary work for yourself.

Randy 71

I will eyeball it first. I will remove the cable and go from there.

zzyzx

I have the same problem, and am pretty sure its my drive gear. Does anyone know about the replacement that Corvette Central sells? It is $75 and has needle bearings. They claim that it will solve the problem for good.

"These needle bearing cross gears will eliminate all the problems associated with the cross gear design. The problem is metal to metal contact between the cross gear and brass coupling. Cross gears have no undercuts and run through bronze and needle bearings. This eliminates coupling wear and provides a cross gear which will virtually last forever".

GTR1999

I believe tha is the gear that High Tech Innovations makes,they're in FL and you can buy direct. I hav eone of their bearing cross gears in a spare distributor I built. It's sitting on the shelf next to a couple more I rebuilt this year so I haven't used it yet.
ph# 800-777-1818

Gary

Randy 71

Gary, Maxpanic, Gordonm,

Just got finished pulling the fitting out. Here is what I found.

Cable is fine, turned it by hand TACH works OK.

Gear in the main distributor shaft has metal shavings on the gear and in the hole and tips of the teath look very shinny like their striped (hard to tell from the angle I am looking at). No broken teath.

Gear in the fitting appears to be slightly worn, but not bad to the naked eye. Other than that the fitting work ok from the cable end. No broken teath.

Can I drive with the fitting gear removed and the brass bushing put back in the hole then plug it with the cable?

Is there a chance that I can cause damage to the engine? I am concerned about the very small particals of shaving I could not get out?

What's next for repairs...........


Randy


[Modified by Randy 71, 11:14 PM 3/23/2004]


[Modified by Randy 71, 11:29 PM 3/23/2004]

GTR1999

Yes you can drive the car witout the gear in it,just won't have a working distributor. To dis-assemble it you have to drive out the roll pin in the end gear. Before you do look at the rotor location and see if its lining up with the spotface on the end gear. Is that clear? If not let me know. The end gear should slid off with any shims that were there. Remove the rotor,points,condensor, weights,springs, side gear, and small c clip in the point plate. The main shaft should slid out now,but sometimes the end of the shaft is bugged up from the lower bushing.The bushing is 660 bronze. With everything apart it should be clear where your problem is; main shaft gear,cross gear,and bushing hole wear. also look into the housing where the cross gear goes to see if it's worn or still smooth. A lot of the dist have a plastic button there to guard against wear. Check the play in the lower bushing and anything over.002 should be addressed.
You might also go to http://www.corvettefaq.com I think Lars has his dist rebuild paper there which will reall help you. This might sound like a lot of work but its not really.
Gary