Tach Adapter-90 Degree
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Re: Tach Adapter-90 Degree (ettev)
If the distributer is set in the car correctly you will not need the adapter. If the dist. has to be turned that much for timing purposes pull it out and reset it in one tooth over to get the proper alignment.
Le Mans Master
Joined: Mar 1999
Posts: 6,744
Likes: 1
From: delmont pa
Cruise-In I Veteran
Cruise-In II Veteran
Re: Tach Adapter-90 Degree (paul67)
check to make sure the "dimple" on the drive gear is pointing the same direction as the rotor tip,if not drive out the pin and rotate the gear 180 degrees. ecklers catalog lists the 90 degree adapter. :chevy
Tech Contributor
Joined: Aug 1999
Posts: 14,376
Likes: 6,375
From: At my Bar drinking and wrenching in Lafayette Colorado
Re: Tach Adapter-90 Degree (paul67)
Paul -
On a C3, the tach drive cable will be in a sharp 90-degree bind up against the firewall if the distributor is installed in the usual Chevy position (with the vacuum advance control unit pointing to about the 7 o'clock position as viewed from the front of the car). For this reason, Chevy issued a Service Bulletin in 1969 that allowed the dealers to re-orient the C3 distributors so that the vacuum can points to about the 10 o'clock position (details on this contained in my paper, "How to Install Your Distributor"). This re-positioning straightens out the cable to the point that there is no longer a need for a 90-degree adapter.
Problem with using the adapter is that the cross gear in the distributor is very sensitive to additional torque loading, and the adapter adds torque requirements to the tach drive system. When the torque on the tach drive system increases, the cross gear is pushed harder into the side thrust surface of the distributor housing, resulting in significant wear of this surface with subsequent cross gear seizure and failure.
On a C3, the tach drive cable will be in a sharp 90-degree bind up against the firewall if the distributor is installed in the usual Chevy position (with the vacuum advance control unit pointing to about the 7 o'clock position as viewed from the front of the car). For this reason, Chevy issued a Service Bulletin in 1969 that allowed the dealers to re-orient the C3 distributors so that the vacuum can points to about the 10 o'clock position (details on this contained in my paper, "How to Install Your Distributor"). This re-positioning straightens out the cable to the point that there is no longer a need for a 90-degree adapter.
Problem with using the adapter is that the cross gear in the distributor is very sensitive to additional torque loading, and the adapter adds torque requirements to the tach drive system. When the torque on the tach drive system increases, the cross gear is pushed harder into the side thrust surface of the distributor housing, resulting in significant wear of this surface with subsequent cross gear seizure and failure.
Thread Starter
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 98
From: Ontario
Re: Tach Adapter-90 Degree (lars)
I have your kit and tech paper as you know. I will sort this out in April when I get to see my car again. You've seen this pic before but here is the vacuum can in the 7 o'clock position banging up against the intake at 10 degrees. That is a teeth problem that I will remedy with your "walk" procedure. I have now acquired a Sears advance light to do the timing job properly. As well I have bought a tach drive distributor on EBay that I will rebuild with the Echlin points and condensor parts I mentioned some time ago. Along with your kit of course. This will be a backup to, or supplant, my Pertronix setup. Another little project on the go!
