Cannot install distributor to factory position
After experiencing some drivability problems last week (I suspect caused by a malfunctioning ignition coil) , I decided to tune-up my recently purchased 1963 L-76 Corvette with a Pertronix Ignitor electronic ignition. While doing the tune-up and checking the wires, I noticed they were not in the correct position on the distributor cap. I checked on this forum and read the thread L-76 Engine Performance w/H & W Valve Adj. from Jan. After reading the comments in that thread, I decided to reinstall the distributor in the original factory location. When I had the distributor out, I verified that the dimple on the gear was facing the same direction as the rotor. I spent the better part of two days trying to get the car to run smoothly with the correct timing setting and the #1 spark plug wire in the correct factory position on the distributor cap. I attempted to figure out why it wouldn't run correctly by drilling a viewing hole in a old distributor cap and see if the rotor was aligned properly on the factory location #1 wire location on the cap. I couldn't get the rotor lined up correctly on the original #1 position and finally gave up today and returned the wires to the original jerry rigged non-factory position on the cap (almost 180 degrees oposite of the correct factory position). After reassembly and replacement of the plugs, wires, cap, rotor, resistor and ignition coil, the car runs perfectly in the original (prior to me messing with it) non-factory positioning of #1wire on the distributor cap. I do not like this fact, but think the only way I can further diagnose this problem is by pulling the camshaft and verifying what type of cam it is and then doing further research to find out why it is not identical to the original "Duntov" cam. I suppose I would have to install a cam that is an exact match with the "Duntov" cam to correct this problem. Perhaps I could flip the gear on the distributor 180 degrees to solve this problem? I noticed where Duke Williams wrote in the thread I referenced earlier that some cam vendors don't orient the gear on the cam properly. Has anyone else had this issue with a midyear replacement cams? If so, what cam vendor is selling these incorrect cams so I know what to avoid in the future. This issue, along with several others, has me doubting the quality of the the work that was previously done on my recently purchased Stingray.
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Re: Cannot install distributor to factory position
Randall
Lots of things to check before you pull the cam out. First, on a clock face with you looking from the front of the car where do you think no one plug wire should be? Where is it in the position that the car runs good? What is the timing set at when the car runs good? Are you setting it with the vacumn disconnected? Are you sure no 1 piston was up on compression stroke when you tried to put distributor in proper place? What did the timing read then? Changing the gear will not solve your problem and I doubt that the camshaft is the problem either.
Hope this helps, if not feel free to call or e-mail me, easier to talk then type.
Terry -
Re: Cannot install distributor to factory position
Randell,I ran in to a problem after my L76 rebuild, the vacuum can would rotated only so far and could not set the timing correctly, Duke says the aftermarket cams are not indexed correctly, The fix was to rotate the dist gear 180. this solved my problem.New England chapter member, 63 Convert. 327/340- Chapter/Regional/national Top Flight, 72 coupe- chapter and regional Top Flight.Comment
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Re: Cannot install distributor to factory position
I also had to index the dimple 180 degrees from the rotor tip.Comment
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Re: Cannot install distributor to factory position
Some aftermarket cams appear to have the gear indexed improperly, requiring the dimple to be rotated 180 degrees from the correct OE position, but we usually can't ID them because they are in the engine, someone else rebuilt the engine, and there are no records.
Index the engine at about 10 deg. BTDC #1. Install the wires per the OE indexing, and reinstall the dist. starting with the rotor pointing forward. (Tweak the oil pump drive with a paint mixing stick is necessary to get it to drop in.)
As the gears mesh the rotor tip should end up oriented about 20 degrees right of engine centerline.
Rotate the housing until the points just barely begin to open. The VAC should be about halfway between the coil bracket and manifold interference points, and the cap window should be approximately normal to engine CL. If this is not the case, remove the distributor, reorient the gear 180 degrees and repeat the installation.
DukeComment
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Re: Cannot install distributor to factory position
Believe he said he had a Pertronix conversion in the distributor now so observation of the points opening is out.
Distributors can be rotated around without having to remove them in order to move the oil pump with a tool simply by lfting the distributor up while turning (torquing) the rotor in the direction of rotation. This drags the pump shaft along until gear engagement with the next tooth. We used to call it "walking the distributor".
Been doing this since 1955. Doesn't take much of a special touch.
Stu FoxComment
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Re: Cannot install distributor to factory position
You said it runs fine with the wires and distributor off about 180 degrees from OEM. That sounds like the gear needs to be flipped 180 degrees. I had the same problem. Turns out that someone had previously "rebuilt" the distributor and was not familiar with Corvettes and orienting the dimple on the gear.Comment
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Re: Cannot install distributor to factory position
I've had this problem a couple of times; once it was the distributor gear on wrong. The next two times were slipped harmonic balancers. If you have the harmonic balancer off this guy "www.dalemfg.com" can rebuild them to stock specs.Comment
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Re: Cannot install distributor to factory position
Randall,
Sounds like you are timing the engine with #1 TDC on the exhaust/overlap stroke and not the compression stroke. Pull #1 spark plug and feel for compression while rotating motor and bring it to TDC, at this point #1 is on the compression stroke, install the distributor like Duke suggested.
Also, you may want to check TDC mark on the damper as the ring on the damper may have moved.
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Re: Cannot install distributor to factory position
There is one way and only one way that this could have happened. The engine was timed as Timothy has said, and then the wires on the cap were clocked 180 degrees out of phase to compensate. As you probably know, the wires are clocked 1-8-4-3-6-5-7-2 on the cap, going clockwise. The points access trap door faces directly to the front of the engine.......give or take a few degrees either way. Most importantly, the #2 wire is installed directly above that access door, with the rest clocked per above.
The dimple on the gear in it's factory location will be coincident with the rotor electrode. In most cases there is no need to fiddle with it. Swapping it around will only change clocking by 360/13 = 27.69 degrees either way...........................not 180 degrees as I'm hearing here!Comment
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Re: Cannot install distributor to factory position
On my '67 L79 at least, the gear being installed wrong was enough so that the vacuum can would hit the coil when everything else was installed properly.Comment
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Re: Cannot install distributor to factory position
Randall,
You didn't mention WHY the engine would not run properly. If the distributor could not be rotated sufficiently to time it properly without it hitting something, then the cure is to rotate the gear 180*.
Having said that, there should be the same problem no matter which tower was chosen as #1.
If this is not the issue, then something else is amiss (pun intended), possibly firing order.Comment
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Re: Cannot install distributor to factory position
Randall,Randall,
Sounds like you are timing the engine with #1 TDC on the exhaust/overlap stroke and not the compression stroke. Pull #1 spark plug and feel for compression while rotating motor and bring it to TDC, at this point #1 is on the compression stroke, install the distributor like Duke suggested.
Also, you may want to check TDC mark on the damper as the ring on the damper may have moved.
I agree with Tim and Joe. From your description of the wires being rotated 180 d, it sounds like the engine was timed to the exhaust stroke on #1 and would therefore be 180 d out.
Take a look at the procedure for installing a distributor with the engine disturbed in the service manual.Jerry Fuccillo
1967 327/300 Convertible since 1968Comment
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Re: Cannot install distributor to factory position
I don't think so, Mike!
The cap doesn't know where the rotor is, and the rotor doesn't know where the cap is. As long as the firing rotation is right, then you can clock 'em any way you want to as long as the distributor cap (i.e. VAC) is in the proper position relative to the rotor.
By the way. I happened to be sitting down having lunch and so felt the earthquake that happened about 45 minutes ago. It felt like the ground was making gentle circular motion....kinda like those slow moving mixers that are used for test tubes and beakers in labs. FREAKY!Comment
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Re: Cannot install distributor to factory position
Ahh, I think we're violently agreeing with each other, again.
The OP said it runs fine with the rotor pointed at a 'different' tower and the wires arranged accordingly. Presumably this is the conventional #6 position since he said it was directly across from where #1 should be according to the GM diagrams.
If the OP didn't have an interference problem with the wires on those towers, why would he have one now?
I'm happy to hear the earth moved for you. I guess it's been a while, huh?
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