tach cable optimum length?
Thread Starter
Drifting
Joined: Feb 2011
Posts: 1,259
Likes: 18
From: Dixon California
tach cable optimum length?
ANY members who have a Idea of the best length of tach cable?
PLS submit your thoughts.....
my cable is shot and has a definite "s" curve in it(permanent) hard as can be...and I do have the 90* adapter on dizzy... so instead of getting one from Corvette suppliers I thought I would try the local speedometer shop...mine is 24" long ,black outer with the respective nut's on each end....SO what would be a guesstimate of the optimal length of replacement cable? for 67? any members have a guess?.... my experience is most seem too long
PLS submit your thoughts..... my cable is shot and has a definite "s" curve in it(permanent) hard as can be...and I do have the 90* adapter on dizzy... so instead of getting one from Corvette suppliers I thought I would try the local speedometer shop...mine is 24" long ,black outer with the respective nut's on each end....SO what would be a guesstimate of the optimal length of replacement cable? for 67? any members have a guess?.... my experience is most seem too long
Thread Starter
Drifting
Joined: Feb 2011
Posts: 1,259
Likes: 18
From: Dixon California
cable
thanks for your reply...I was just trying to figure out the best length and thought some members may have been there ..done that
the reason for the 90* fitting is ...if you have dizzy shielding the dizzy has to be in a certain position to have the vacuum pod coming out at the correct position there is only some much room to be in the correct position.... and still have the ability to move the dizzy to get (in my case 6* BTDC)...I actually had to move the dizzy back one tooth to get the correct position cuz the vacuum pod hits the vertical upright that supports the shielding
the cable port on the dizzy is just about facing the fire wall and thats where the hard bend comes in on the cable resulting in (cable separating from the crimpted fitting) that is at the end of the cable ... so the stock cable is now 3-4" too long and rides on the back of the manifold/dizzy shielding.....so I did have a custom length made that is
3 1/2" shorter and now the cable doesn't touch anything as it comes through the firewall and bends to the dizzy
the reason for the 90* fitting is ...if you have dizzy shielding the dizzy has to be in a certain position to have the vacuum pod coming out at the correct position there is only some much room to be in the correct position.... and still have the ability to move the dizzy to get (in my case 6* BTDC)...I actually had to move the dizzy back one tooth to get the correct position cuz the vacuum pod hits the vertical upright that supports the shielding
the cable port on the dizzy is just about facing the fire wall and thats where the hard bend comes in on the cable resulting in (cable separating from the crimpted fitting) that is at the end of the cable ... so the stock cable is now 3-4" too long and rides on the back of the manifold/dizzy shielding.....so I did have a custom length made that is
3 1/2" shorter and now the cable doesn't touch anything as it comes through the firewall and bends to the dizzy
Last edited by bluzrocker; Jun 13, 2014 at 01:45 AM.
Pro
Joined: May 2012
Posts: 707
Likes: 45
From: Portland Oregon
Vacuum can hitting coil bracket or riser on intake manifold is a hint that your distributor drive gear is off "1/2 tooth". Search the archives for more info. Remove distributor and rotate drive gear 180*. The dimple on the drive gear should now be pointed at the rotor. Reinstall the distributor and the vacuum can will now line up midway between the coil bracket and intake manifold runner. 13 teeth on the drive gear so 1 tooth equals about 28*. Moving the distributor one tooth moves the vacuum can 28*. Rotating drive gear 180* moves your reference 1/2 tooth or approx 14*
This will now orient the tach drive cable for a more direct route not requiring the 90* adapter.
I recall the correct length for tach cable is 25 1/2"
Assume your plug wires are indexed correctly, ie, #1 wire is on first tower clockwise from distributor window.
Above applies to SBC not sure about BBC
Randy
Last edited by 66RBS; Jun 13, 2014 at 03:47 AM. Reason: added note re indexing
Safety Car
Joined: May 2014
Posts: 3,785
Likes: 656
Bluzrocker,
Vacuum can hitting coil bracket or riser on intake manifold is a hint that your distributor drive gear is off "1/2 tooth". Search the archives for more info. Remove distributor and rotate drive gear 180*. The dimple on the drive gear should now be pointed at the rotor. Reinstall the distributor and the vacuum can will now line up midway between the coil bracket and intake manifold runner. 13 teeth on the drive gear so 1 tooth equals about 28*. Moving the distributor one tooth moves the vacuum can 28*. Rotating drive gear 180* moves your reference 1/2 tooth or approx 14*
This will now orient the tach drive cable for a more direct route not requiring the 90* adapter.
I recall the correct length for tach cable is 25 1/2"
Assume your plug wires are indexed correctly, ie, #1 wire is on first tower clockwise from distributor window.
Above applies to SBC not sure about BBC
Randy
Vacuum can hitting coil bracket or riser on intake manifold is a hint that your distributor drive gear is off "1/2 tooth". Search the archives for more info. Remove distributor and rotate drive gear 180*. The dimple on the drive gear should now be pointed at the rotor. Reinstall the distributor and the vacuum can will now line up midway between the coil bracket and intake manifold runner. 13 teeth on the drive gear so 1 tooth equals about 28*. Moving the distributor one tooth moves the vacuum can 28*. Rotating drive gear 180* moves your reference 1/2 tooth or approx 14*
This will now orient the tach drive cable for a more direct route not requiring the 90* adapter.
I recall the correct length for tach cable is 25 1/2"
Assume your plug wires are indexed correctly, ie, #1 wire is on first tower clockwise from distributor window.
Above applies to SBC not sure about BBC
Randy
Just keep in mind the lower distributor gear dimple lines with the rotor tip BUT on some aftermarket camshafts the gear needs to be turned 180* for the vacuum control to center itself between the coil bracket and intake manifold runner.
There is nothing wrong with the cam, it's just the way it was made.
