Tach Problem!
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Jack
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- 71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
Disconnect the cable from dist ... crank & run motor ... while running, observe dist where cable inserted into dist ... it should be rotating clockwise ... if not, there's a problem inside dist tach drive (crossgear/mainshaft). If dist OK, then get a reversible drill motor ... lightly chuck the cable core into drill motor and spin it IN REVERSE ... observe tach gage ... it should be registering twice speed that drill is turning (if drill spins 800 then tach should show 1600). Tach cable core has a collar near where it connects to back of tach gage... collar keeps core from pulling out (at dist) ... give the core a little tug ... if it comes out then the core is broken and you need a new tach cable. The mech tach gage itself usually don't fail ... it's usually a chewed up crossgear/mainshaft or broken cable.
Hopefully, it's something simple. But, if it turns out the distributor needs an overhaul ... take at look at this before you spend big$ on fixing old dist.
http://www.corvetteactioncenter.com/forums/showthread.php?t=69113
JACK:gap
Hopefully, it's something simple. But, if it turns out the distributor needs an overhaul ... take at look at this before you spend big$ on fixing old dist.
http://www.corvetteactioncenter.com/forums/showthread.php?t=69113
JACK:gap
probably the drive gear and driven gear..if one is bad, the other is usually bad also...replace both if just doing one, to make them both strong........the drive gear is on distributor shaft and driven gear is on the cable...discinnect the cable and look at the end....the driven gear is at the end....if it is ok..lift the distributor out and look at the shaft....(take a digital pic of the position or a sketch,and replace it back in the same position....its a pretty easy fix.....not to expensive..replace the distributor shaft and get a new gear for the cable....mine was the same way and it works great now....however , right after fixing it, it was sticky and sluggish at first, i guess due to the years of not working...but its great now....while i had the distributor out i also put in an electronic ignition kit and got rid of the points..now she fires right up and purrs like a cat....good luck and let us know what happens...chas 
CAPNZ said:
Jack
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- 71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
The tach gear on the mainshaft is integral part of the mainshaft .... the teeth are cut into the mainshaft ... inseparable ... if bad requires whole mainshaft. On the other hand, the tach crossgear is a separately available part. If any of the gears are stripped and tach gage doesn't work ... the tach cable's lube tends to dry out & bind up cable core ... and then the tach gage tends to act erratically ... dry cable can force & find its way into operation ... or break.
JACK:gap
JACK:gap
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CAPNZ
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BINGO! BINGO! BINGO!
Wheeew! I had to pullout the dist.,(I HATE DOING THAT), because there's a brass collar that goes into the distributor that connects to the Tach cable. The darn brass collar was turning @ 1/4" and I couldn't get the knurled Tach cable collar off. So, I had to hold the cable and turn the dist CW until it came out. The gear looked good. I put the gear into the brass collar and put it into the dist. I spun the the shaft and it turned. (Good So Far)
I then checked the inner square cable. I puled on it and it came out. Albeit, @ 10" long. (BROKE) So, I'll get that inside cable. I'm was planning to take the dash out anyway to replace the LH speaker.
Question:
Whom should I buy the inside cable from?
Any special lube?
TIA
"Jeff"
P.S # Matching Dist.
Wheeew! I had to pullout the dist.,(I HATE DOING THAT), because there's a brass collar that goes into the distributor that connects to the Tach cable. The darn brass collar was turning @ 1/4" and I couldn't get the knurled Tach cable collar off. So, I had to hold the cable and turn the dist CW until it came out. The gear looked good. I put the gear into the brass collar and put it into the dist. I spun the the shaft and it turned. (Good So Far)
I then checked the inner square cable. I puled on it and it came out. Albeit, @ 10" long. (BROKE) So, I'll get that inside cable. I'm was planning to take the dash out anyway to replace the LH speaker.
Question:
Whom should I buy the inside cable from?
Any special lube?
TIA
"Jeff"
P.S # Matching Dist.
sorry i cant help on where to get the cable, my best bet would be Mid-America or the like....i would be carefull using lube as it may end up in the gage and mess it up...just a thought...use care when you start into the dash, not to crack the top...i have seen alot of stories about breaking the dash top , getting it out...i had mine out and i guess a 73 is easy , because mine came out with no problem...use a digital camera to take pics as you go if you can...keep all parts in containers...when i disassemble stuff , i have my wife or son to help , writing the details on each bag and then putting them in a box for the reassembly....good luck ...keep us posted...Chas
CAPNZ said:
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Jack
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- 71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
Tip: If you're gonna replace the tach cable ... also do the speedo cable while you're at it ... it's a tight squeeze to get at back of gages ... and you may have to loosen inst cluster for clearance ... maybe not. I lube mine with moly grease ... it has not creeped into gages (and probably won't) ... it's a potentially messy job to slick up the inner cores and then slide them into outer housings ... but worth it ... as you'll never have to repeat. If you've got the cluster out ... may as well change out all those little lite bulbs ... about a dozen or so. Drop the column a bit ... lay a rag on top of column to protect its paint ... then loosen & pull cluster forward.
JACK:gap
JACK:gap
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CAPNZ
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NEED HELP! I've been working on this for 2 days! I can't get the speedo/tach panel out. I got the whole interior pulled ,(just about), including the top dash. How do you get the clip off the back of the tach that holds in the tach cable in? I'm just ruining my MINT interior.
TIA
"Jeff"
TIA
"Jeff"
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M
magoo
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Hi Jeff,
I've replaced several tach cables in my bros 69. I was able to reach under the dash without removing anything. This was not air conditioned. I eventually rotated the plug wires one hole so there wouldn't be a bend in the cable. They also sell 2 types of adapters for the dist end so the cable doesn't bend so much. If there is a hard bend at that dist end, it's amazing how fast those tach cables will go. Also if you're cutting your own cable, being too long is just as bad as too short as this will also stress it at the bends. NAPA stores and other parts houses sell those speedo cable repair kits where you cut it and attach the one end. Maybe you can save some shipping. A little white lube (lithium lube) on the cable will work well.
Mike
I've replaced several tach cables in my bros 69. I was able to reach under the dash without removing anything. This was not air conditioned. I eventually rotated the plug wires one hole so there wouldn't be a bend in the cable. They also sell 2 types of adapters for the dist end so the cable doesn't bend so much. If there is a hard bend at that dist end, it's amazing how fast those tach cables will go. Also if you're cutting your own cable, being too long is just as bad as too short as this will also stress it at the bends. NAPA stores and other parts houses sell those speedo cable repair kits where you cut it and attach the one end. Maybe you can save some shipping. A little white lube (lithium lube) on the cable will work well.
Mike
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M
magoo
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Jeff
I'm not sure what you want to know how works. The big sweeping bend going into the firewall is ok. It's the first tight bend right out of the distributor that gets you. As people turn up the timing for better performance,(which I'm all for) the bend gets tighter. As far as the clip behind the tach, to remove the cable you push the clip in and pull the cable out. When reinstalling just line up the inner (square tip) cable and push the outer cable in. You will usually hear the spring clip click as it snaps in. Both of these operations can be done with one hand. Good luck, hope this helps.
Mike
I'm not sure what you want to know how works. The big sweeping bend going into the firewall is ok. It's the first tight bend right out of the distributor that gets you. As people turn up the timing for better performance,(which I'm all for) the bend gets tighter. As far as the clip behind the tach, to remove the cable you push the clip in and pull the cable out. When reinstalling just line up the inner (square tip) cable and push the outer cable in. You will usually hear the spring clip click as it snaps in. Both of these operations can be done with one hand. Good luck, hope this helps.
Mike
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