71 LS5 distributor pointing #2 or #1 ?
Thread Starter
Burning Brakes
Joined: Jun 1999
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From: Chandler AZ
St. Jude Contributor
71 LS5 distributor pointing #2 or #1 ?
Doing a little failure analysis and have a hunch this might not be correct for the corvette (see fig below). Dizzy cable snapped and I think because of the angle of the Dizzy. I set mine up how I thought it came from the factory. Namely dizzy wire from cylinder #1 pointing to cylinder #1.
I am betting in 1971 when the corvette rolled off the line the Dizzy was actually pointing to cylinder #2. This would better line up the tach with the cable out of the fire wall.
Can anyone find the document where this supports my argument? I do have the Factory assembly manual engine and chassis overhaul and Haynes and some other sources but do not see it explicitly show this.
I am betting in 1971 when the corvette rolled off the line the Dizzy was actually pointing to cylinder #2. This would better line up the tach with the cable out of the fire wall.
Can anyone find the document where this supports my argument? I do have the Factory assembly manual engine and chassis overhaul and Haynes and some other sources but do not see it explicitly show this.
Thread Starter
Burning Brakes
Joined: Jun 1999
Posts: 751
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From: Chandler AZ
St. Jude Contributor
Well now crap I just answered my own question! The drawing does clearly show the Dizzy #1 wire pointing to the #2 cylinder for the 71!
LOL I misinterpreted the drawing and when I went to post it it became clear....
"I see said the blind man"
LOL I misinterpreted the drawing and when I went to post it it became clear....
"I see said the blind man"
Tech Contributor
Joined: Aug 1999
Posts: 14,384
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From: At my Bar drinking and wrenching in Lafayette Colorado
Drop me an e-mail request fore my "Distributor Installation" paper. It will show the factory installed orientation, along with the Service Bulletin "corrected" installation to avoid cable breakage.
Lars
V8FastCars@msn.com
Lars
V8FastCars@msn.com
Race Director
Joined: Apr 2011
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From: North of Toronto - Ontario
Lars details the "alternate" install as well as some excellent install tips
There was a service bulletin that moved the distributor around and ended up placing the vac-can behind the shield support and straightened up the cable. Strange part was that it only seemed to apply to the 327 and left the others alone which makes no sense since they all had the same issue
https://www.corvetteforum.com/forums...-corvette.html
M
Team Owner
Joined: Jan 2006
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From: Crossville TN
The distributor can be "clocked" in ANY position, as long as the plug wires are shifted, correspondingly at the same time. Set engine to TDC (compression stroke), position dizzy however you choose, then see where the rotor is pointing. Install #1 plug wire at that position, then install other wires in proper rotation from that. When you start the engine, do final adjust for timing, as needed.
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
Both diagrams shown above are correct. The one on the left is HEI. On HEI distributors, the distributor is installed "square" in the engine compartment (the square coil on top of the cap is square in the compartment) and the #1 plug wire is the forward, driver's side location in the distributor cap. For points-type distributors and TI, the #1 wire goes in the forward passenger side location in the cap (with the vacuum advance control unit oriented as shown in my paper). To straighten out the tach cable, the distributor is simply rotated 45 degrees clockwise so that the vacuum advance points directly out the right side of the engine, and the plug wires are simply moved over one position so #1 is still in the forward, passenger side location.
Lars
Lars
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From: Austin Texas
Corvette of the Year Winner 2017
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what you are failing to see is the orientation direction of the Gear Drive, and the vacuum advance port, to minimize the tach cable bend, and fit all the corvette dist. shielding. you will need to clock your dist. almost a 1/4 turn further than normal Chevrolet setup,
you will want you vacuum advance port, pointing squarely to the passenger side of the car, behind the shielding bracket. good luck
you will want you vacuum advance port, pointing squarely to the passenger side of the car, behind the shielding bracket. good luck
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Pro
Joined: May 2011
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From: Karlsruhe (Germany)
I just wonder if the lower gear of the distributor also allows to be set in 1/8 turn steps.
What is clear is, that the housing can be set in any orientation and the plugs too.
But it must start at #1 where the rotor is at tdc. But no matter where #1 is on the cap.
Question is, if the angle of the rotor gear is different, no 1/8 turn steps, this would result in
different angles of the housing to match #1 and rotor.
Very special question, I know.
But this could be used to fine tune where the tach cable and vaccum canister come out
in case 1/8 turn steps are not sufficient.
What is clear is, that the housing can be set in any orientation and the plugs too.
But it must start at #1 where the rotor is at tdc. But no matter where #1 is on the cap.
Question is, if the angle of the rotor gear is different, no 1/8 turn steps, this would result in
different angles of the housing to match #1 and rotor.
Very special question, I know.
But this could be used to fine tune where the tach cable and vaccum canister come out
in case 1/8 turn steps are not sufficient.
Last edited by zuendler; May 19, 2019 at 08:11 PM.
Tech Contributor
Joined: Aug 1999
Posts: 14,384
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From: At my Bar drinking and wrenching in Lafayette Colorado
Be aware that you are opening a thread that has been closed for over 4 years. It's usually best to open a new thread after this amount of time, especially since you're opening an entirely new topic.
The distributor gear has 13 teeth, which means that each 1-tooth rotation of the gear will change the housing clocking by 27.69 degrees. Since the retaining pin hole in the gear is not drilled symmetrical (it's drilled at a "tooth" location on one side, and a "groove" location on the other side), by rotating the gear 180 degrees, you can achieve clocking changes in the housing orientation down to 13.84 degrees. This is occasionally required on some of the C2 small block high performance cars with the tall aluminum intake manifold in order to achieve correct timing without the distributor vacuum advance hitting the intake manifold rear runner or the distributor shielding. I've never seen this to be a problem on any C3, since the "alternate" distributor installation outlined in my paper should be used. This does not require any fine adjustment positioning of the distributor body clocking - there is plenty of adjustment in the stock service bulletin position, so it's not an issue.
Lars
The distributor gear has 13 teeth, which means that each 1-tooth rotation of the gear will change the housing clocking by 27.69 degrees. Since the retaining pin hole in the gear is not drilled symmetrical (it's drilled at a "tooth" location on one side, and a "groove" location on the other side), by rotating the gear 180 degrees, you can achieve clocking changes in the housing orientation down to 13.84 degrees. This is occasionally required on some of the C2 small block high performance cars with the tall aluminum intake manifold in order to achieve correct timing without the distributor vacuum advance hitting the intake manifold rear runner or the distributor shielding. I've never seen this to be a problem on any C3, since the "alternate" distributor installation outlined in my paper should be used. This does not require any fine adjustment positioning of the distributor body clocking - there is plenty of adjustment in the stock service bulletin position, so it's not an issue.
Lars
Pro
Joined: May 2011
Posts: 722
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From: Karlsruhe (Germany)
Hi, well I don´t like people who don´t use the search before they open a topic for every thing that comes in their mind.
I knew it´s from 2015, but the same issue.
Thx Lars, a precise answer from you as usual
Do have an idea why they rotated the plug wiring as well in that service bulletin?
They could have keept the plug position by just rotating the housing clockwise 45° and
the plugs counterclockwise to compensate that.
With the other setting they also had to remove the rotor and put it back in 2 teeth advanced (resulting in 55.4°).
A reason could also have been that they found that 55.4° are even better than only 45°. Who knows...
I knew it´s from 2015, but the same issue.
Thx Lars, a precise answer from you as usual
Do have an idea why they rotated the plug wiring as well in that service bulletin?
They could have keept the plug position by just rotating the housing clockwise 45° and
the plugs counterclockwise to compensate that.
With the other setting they also had to remove the rotor and put it back in 2 teeth advanced (resulting in 55.4°).
A reason could also have been that they found that 55.4° are even better than only 45°. Who knows...
Tech Contributor
Joined: Aug 1999
Posts: 14,384
Likes: 6,408
From: At my Bar drinking and wrenching in Lafayette Colorado
Hi, well I don´t like people who don´t use the search before they open a topic for every thing that comes in their mind.
I knew it´s from 2015, but the same issue.
Thx Lars, a precise answer from you as usual
Do have an idea why they rotated the plug wiring as well in that service bulletin?
They could have keept the plug position by just rotating the housing clockwise 45° and
the plugs counterclockwise to compensate that.
With the other setting they also had to remove the rotor and put it back in 2 teeth advanced (resulting in 55.4°).
A reason could also have been that they found that 55.4° are even better than only 45°. Who knows...
I knew it´s from 2015, but the same issue.
Thx Lars, a precise answer from you as usual
Do have an idea why they rotated the plug wiring as well in that service bulletin?
They could have keept the plug position by just rotating the housing clockwise 45° and
the plugs counterclockwise to compensate that.
With the other setting they also had to remove the rotor and put it back in 2 teeth advanced (resulting in 55.4°).
A reason could also have been that they found that 55.4° are even better than only 45°. Who knows...
Lars
Last edited by lars; May 20, 2019 at 11:04 AM.
