69 Tach drive distributor issue
Thread Starter
Le Mans Master
Joined: Dec 2009
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From: Plano IL
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69 Tach drive distributor issue
I have a 69 that we almost done with about to give back to the owner
New dash, new interior etc.....
The tach is inop -
I disconnected the cable - hooked a drill to it and spun it backwards and the tach went to 1000 rpms
I also confirmed the cable is latched in its "clip" at the back of the dash
I feel the tach is good
- I removed the distributor - and took out the tach drive - figuring the gears were stripped or ???
- When I spin the dist in my hand - the drive spins
- I took it apart anyway - gears are good - grease on them I dont see an issue
- greased them both up - put it together
- Installed the dist and made sure the cable is more inline with out a "S" in it -
- Turned over but didnt start - No tach movement - I would have thought the tach would move while under starter....
- Before I light this back off and try to re time in
- What am I overlooking???? Or should I light it and see if it runs
- I also moved my spark plug wires back one hole in order for the tach cable to be more inline - before it had an S in it and was against the firewall
- Engine is a 427 435 4 sp
Thanks
Chris
New dash, new interior etc.....
The tach is inop -
I disconnected the cable - hooked a drill to it and spun it backwards and the tach went to 1000 rpms
I also confirmed the cable is latched in its "clip" at the back of the dash
I feel the tach is good
- I removed the distributor - and took out the tach drive - figuring the gears were stripped or ???
- When I spin the dist in my hand - the drive spins
- I took it apart anyway - gears are good - grease on them I dont see an issue
- greased them both up - put it together
- Installed the dist and made sure the cable is more inline with out a "S" in it -
- Turned over but didnt start - No tach movement - I would have thought the tach would move while under starter....
- Before I light this back off and try to re time in
- What am I overlooking???? Or should I light it and see if it runs
- I also moved my spark plug wires back one hole in order for the tach cable to be more inline - before it had an S in it and was against the firewall
- Engine is a 427 435 4 sp
Thanks
Chris
Melting Slicks
Joined: Apr 2019
Posts: 2,514
Likes: 1,166
From: Northern Wisconsin
Did you connect your drill to the cable near the distributor after disconnecting it from distributor, or did you connect your drill directly to the tach behind the dash? I am just asking this dumb question in order to rule out the possibility of a broken cable.
Thread Starter
Le Mans Master
Joined: Dec 2009
Posts: 5,514
Likes: 1,955
From: Plano IL
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I connected the drill to the cable near the dist - yep - I was trying to rule out a broken cable or disconnected cable - I think I did verify I connected it correctly and it works. - That is what I thought too at first.
Thread Starter
Le Mans Master
Joined: Dec 2009
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From: Plano IL
2026 Corvette of the Year Winner - Unmodified
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Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Sometimes ... when the tach gears(shaft & cross) are Effectively stripped and cannot drive thru the cable's friction ... sometimes there'll be a teeny bit of teeth left ... just enough to turn the crossgear's square hole/receiver ... but not enough bite to drive the cable's load/friction ... just enough to fool ya. T shirt
Stick a little ignition screwdriver in the hole and ... see if ya can turn the cross gear ... or ... careful ... try & hang on to it when ya crank it over.
FWIW ... that's a .104" square drive ... it's about .104" from one side to the other ... and about .147" from one corner to the other.
Stick a little ignition screwdriver in the hole and ... see if ya can turn the cross gear ... or ... careful ... try & hang on to it when ya crank it over.
FWIW ... that's a .104" square drive ... it's about .104" from one side to the other ... and about .147" from one corner to the other.
Last edited by jackson; May 28, 2020 at 05:45 PM.
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Thread Starter
Le Mans Master
Joined: Dec 2009
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From: Plano IL
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I pulled the distributor and replaced the gear and bushing assy
I will refire it and retime it
I will refire it and retime it
Safety Car
Joined: Nov 2008
Posts: 3,717
Likes: 551
From: Seattle Washington
If the Cable is new then like every other reproduction part there is a chance that it was made wrong. Is the square end of it that goes into the Distributor the wrong size ? Either to big or small.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
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From: Unreconstructed, South Carolina
Like Big2Bird said ... doubt it.
Because most Mechanical Auto speedo / tach instruments employ a magnet & drag cup ... there is No direct coupling between rotating cable & needle. The magnetic pulsing drag at very low speed is not sufficient to overcome instruments' hairspring.
https://www.howacarworks.com/accesso...a-speedo-works
Because most Mechanical Auto speedo / tach instruments employ a magnet & drag cup ... there is No direct coupling between rotating cable & needle. The magnetic pulsing drag at very low speed is not sufficient to overcome instruments' hairspring.
https://www.howacarworks.com/accesso...a-speedo-works
Burning Brakes
Joined: Oct 2003
Posts: 836
Likes: 26
From: Harrisburg Pa
When I had my tach drive dist. in my 69 I had that problem and fixed it. I done the exact diag. steps you did.
What I found is that when It was spining or just connected. the steel cable would DROP OUT of the square slot and fall
down in the cable housing, just enough for it to not grab. this is a very little drop. I sent back 2 reproduction cables before I just ordered the repair
kit and cut it myself. worked like new till I modified the whole car and went a full electronic F.A.S.T. 2.0 system
Good Luck: Tom
What I found is that when It was spining or just connected. the steel cable would DROP OUT of the square slot and fall
down in the cable housing, just enough for it to not grab. this is a very little drop. I sent back 2 reproduction cables before I just ordered the repair
kit and cut it myself. worked like new till I modified the whole car and went a full electronic F.A.S.T. 2.0 system
Good Luck: Tom
Thread Starter
Le Mans Master
Joined: Dec 2009
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From: Plano IL
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I removed the dist and replaced the tach gear and reinstalled it
I am going to push it out and re time it tonight
Hope that was the fix
We shall see.
I will also check the engagement - hard to tell - cramped quarters
I am going to push it out and re time it tonight
Hope that was the fix
We shall see.
I will also check the engagement - hard to tell - cramped quarters
Last edited by csherman; Jun 4, 2020 at 02:35 PM.
Thread Starter
Le Mans Master
Joined: Dec 2009
Posts: 5,514
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From: Plano IL
2026 Corvette of the Year Winner - Unmodified
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Update
I had the dist in and out 6 plus times
I changed out the tach drive with C Central parts - several times
and no change
Diagnoses - the drive cable inside is too short - it is just too short to slide into the drive
I ordered a longer cable and will install hopefully just replace the drive cable with taking the whole cable out....
I had the dist in and out 6 plus times
I changed out the tach drive with C Central parts - several times
and no change
Diagnoses - the drive cable inside is too short - it is just too short to slide into the drive
I ordered a longer cable and will install hopefully just replace the drive cable with taking the whole cable out....
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
Update
I had the dist in and out 6 plus times
I changed out the tach drive with C Central parts - several times
and no change
Diagnoses - the drive cable inside is too short - it is just too short to slide into the drive
I ordered a longer cable and will install hopefully just replace the drive cable with taking the whole cable out....
I had the dist in and out 6 plus times
I changed out the tach drive with C Central parts - several times
and no change
Diagnoses - the drive cable inside is too short - it is just too short to slide into the drive
I ordered a longer cable and will install hopefully just replace the drive cable with taking the whole cable out....
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,137
Likes: 4,247
From: US-PNW
Not sure if you are referring directly to Corv. Central no longer selling the core, but they are readily available through regular places like Autozone and Summit. Speedo cable core is the same diameter and ends as far as I can see.
Last edited by barkingrats; Jun 8, 2020 at 05:06 PM.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
