Distributor rotors
Thread Starter
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From: Central Arkansas
Distributor rotors
I was browsing through a copy of Corvette Magazine at the newstand yesterday and ran across an interesting article concerning distributor rotors and someone (can't recall the name) who sells a high quality rotor since the replacements on the market now are all cheap, poor-quality items. They used a sectioned distributor cap to measure the rotor to cap gap of an older rotor, a current FLAPS rotor and this guys special rotors. Quite a difference in the gap. The FLAPS rotor had over an 1/8 inch gap while the custom rotor had something like .015 inch gap (don't hold me to exact figures). The older one had a gap in between the two. Suppose to make quite a difference in how a car well the car will start and run. Anyone ever looked into this before?
Le Mans Master
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From: Houston Texas
St. Jude Donor '10-'12-'13
I ran across that info a while back. It seemed to have validity. Some folks said they couldn't get revs in the 6-7k range with replacement caps.
Some were even brazing the tip and filing for a better gap.
I will say, I was running the cheapo white cap. No problem revving to the moon. I recently installed the more expensive "correct" dark brown cap. Much better build contruction. But no better in performance.
They both will rev to 7000 rpm.
Some were even brazing the tip and filing for a better gap.
I will say, I was running the cheapo white cap. No problem revving to the moon. I recently installed the more expensive "correct" dark brown cap. Much better build contruction. But no better in performance.
They both will rev to 7000 rpm.
Last edited by MiguelsC2; Aug 1, 2011 at 07:54 PM.
Le Mans Master
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From: Houston Texas
St. Jude Donor '10-'12-'13
The gap thing is correct. But I think it only affect points cars.
Mine is running the Pertronix II. The hotter spark may override the gap issue?
I haven't ever run points in my C2.
Mine is running the Pertronix II. The hotter spark may override the gap issue?
I haven't ever run points in my C2.
Thread Starter
Race Director
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From: Central Arkansas
I'm running a TI distributor with a CD unit to power it in my Vette so I don't think my car is all that sensitive to it either. But I have a 67 GTX that seems to run a little soft off the line and breaks up a little bit at higher rpm despite a newly rebuilt distributor - and I'm wondering if aftermarket Mopar stuff might have the same problems with wide rotor gap.
Tech Contributor
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From: Conroe Texas
For reference, this is 1stTexan's thread containing discussion on the different rotor tip
http://forums.corvetteforum.com/c1-a...and-rotor.html
http://forums.corvetteforum.com/c1-a...and-rotor.html
Team Owner
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From: Greenville, Indiana
I'm running a TI distributor with a CD unit to power it in my Vette so I don't think my car is all that sensitive to it either. But I have a 67 GTX that seems to run a little soft off the line and breaks up a little bit at higher rpm despite a newly rebuilt distributor - and I'm wondering if aftermarket Mopar stuff might have the same problems with wide rotor gap.
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Racer
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From: Covington Louisiana
St. Jude Donor '10
Check out this link. The seller is a member of this forum. He has a very strong reputation in the Corvette community as a seller. I bought one of these, but have not really checked yet to see how it matches up to an original D-409. The contact has the same wider "cone" shape at the end though.
http://cgi.ebay.com/ebaymotors/Corve...Q5fAccessories
http://cgi.ebay.com/ebaymotors/Corve...Q5fAccessories
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Le Mans Master
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From: Puget Sound
So, if I get one of these "special" rotors, will I be able to rev to 7000+ RPM? I have no problem going to 6000+ as it is using the readily available parts from NAPA. I think it's a bunch of marketing B.S.
Jim
Jim
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Actually, no BS.
If the rotor gap is increased (as it did when GM went to the emission rotor), then less spark is available to jump the spark plug gap. As RPMs increases, coil saturation becomes less due to less time, and this lessens available spark output.
So bottom line is that the emission rotor decreases the total available spark output (especially important at higher RPM), with more chance of a misfire at those RPMS.
But it does force the ignition coil to raise to a higher voltage level before jumping the gaps (both rotor and plug), so if the coil has sufficient time to saturate, it will provide a stronger higher voltage spark (at lower RPMs).
Think of it the same way as if you opened up the spark plug gaps. Engine might actually run better at lower to mid RPMs, but would start breaking up at high revs due to a lack of voltage to jump that larger gap.
Plasticman
If the rotor gap is increased (as it did when GM went to the emission rotor), then less spark is available to jump the spark plug gap. As RPMs increases, coil saturation becomes less due to less time, and this lessens available spark output.
So bottom line is that the emission rotor decreases the total available spark output (especially important at higher RPM), with more chance of a misfire at those RPMS.
But it does force the ignition coil to raise to a higher voltage level before jumping the gaps (both rotor and plug), so if the coil has sufficient time to saturate, it will provide a stronger higher voltage spark (at lower RPMs).
Think of it the same way as if you opened up the spark plug gaps. Engine might actually run better at lower to mid RPMs, but would start breaking up at high revs due to a lack of voltage to jump that larger gap.
Plasticman
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From: Covington Louisiana
St. Jude Donor '10
I do not think it is marketing. The story by Bill Clupper came out before these "replicas" hit the market. All that was out there were expensive originals. If you read the article by Bill Clupper it all seems to make some sense. With that said, I have no issue with getting my engine (L72 with TI) to redline, 6500, using the Accel rotor. I was having some issues with fire breaking down at about 4000 RPM under heavy acceleration before that. It would climb higher under slower controlled acceleration. I can not tell you if the coil gets hotter or it starts easier than it would with the D-409 or its replica, but it does seem as though the basic replacement rotor, the one with the "E" on the contact, did not work well for me.
Le Mans Master
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From: Houston Texas
St. Jude Donor '10-'12-'13
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Le Mans Master
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From: Houston Texas
St. Jude Donor '10-'12-'13
Team Owner
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From: Greenville, Indiana
Actually, no BS.
If the rotor gap is increased (as it did when GM went to the emission rotor), then less spark is available to jump the spark plug gap. As RPMs increases, coil saturation becomes less due to less time, and this lessens available spark output.
So bottom line is that the emission rotor decreases the total available spark output (especially important at higher RPM), with more chance of a misfire at those RPMS.
But it does force the ignition coil to raise to a higher voltage level before jumping the gaps (both rotor and plug), so if the coil has sufficient time to saturate, it will provide a stronger higher voltage spark (at lower RPMs).
Think of it the same way as if you opened up the spark plug gaps. Engine might actually run better at lower to mid RPMs, but would start breaking up at high revs due to a lack of voltage to jump that larger gap.
Plasticman
If the rotor gap is increased (as it did when GM went to the emission rotor), then less spark is available to jump the spark plug gap. As RPMs increases, coil saturation becomes less due to less time, and this lessens available spark output.
So bottom line is that the emission rotor decreases the total available spark output (especially important at higher RPM), with more chance of a misfire at those RPMS.
But it does force the ignition coil to raise to a higher voltage level before jumping the gaps (both rotor and plug), so if the coil has sufficient time to saturate, it will provide a stronger higher voltage spark (at lower RPMs).
Think of it the same way as if you opened up the spark plug gaps. Engine might actually run better at lower to mid RPMs, but would start breaking up at high revs due to a lack of voltage to jump that larger gap.
Plasticman
Le Mans Master
Joined: Dec 2007
Posts: 8,000
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From: Puget Sound
Actually, no BS.
If the rotor gap is increased (as it did when GM went to the emission rotor), then less spark is available to jump the spark plug gap. As RPMs increases, coil saturation becomes less due to less time, and this lessens available spark output.
So bottom line is that the emission rotor decreases the total available spark output (especially important at higher RPM), with more chance of a misfire at those RPMS.
But it does force the ignition coil to raise to a higher voltage level before jumping the gaps (both rotor and plug), so if the coil has sufficient time to saturate, it will provide a stronger higher voltage spark (at lower RPMs).
Think of it the same way as if you opened up the spark plug gaps. Engine might actually run better at lower to mid RPMs, but would start breaking up at high revs due to a lack of voltage to jump that larger gap.
Plasticman
If the rotor gap is increased (as it did when GM went to the emission rotor), then less spark is available to jump the spark plug gap. As RPMs increases, coil saturation becomes less due to less time, and this lessens available spark output.
So bottom line is that the emission rotor decreases the total available spark output (especially important at higher RPM), with more chance of a misfire at those RPMS.
But it does force the ignition coil to raise to a higher voltage level before jumping the gaps (both rotor and plug), so if the coil has sufficient time to saturate, it will provide a stronger higher voltage spark (at lower RPMs).
Think of it the same way as if you opened up the spark plug gaps. Engine might actually run better at lower to mid RPMs, but would start breaking up at high revs due to a lack of voltage to jump that larger gap.
Plasticman
Jim
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I'm making the point that a points conversion module (call it whatever you like) does not cause the system to produce a hotter spark. The module is simply an electronic switch installed in place of a mechanical switch (points).
Your post above states "The gap thing is correct. But I think it only affect points cars.
Mine is running the Pertronix II. The hotter spark may override the gap issue?"
Race Director
Joined: Nov 2000
Posts: 10,347
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From: Beverly Hills (Pine Ridge) Florida
What's with the nasty?
I'm making the point that a points conversion module (call it whatever you like) does not cause the system to produce a hotter spark. The module is simply an electronic switch installed in place of a mechanical switch (points).
Your post above states "The gap thing is correct. But I think it only affect points cars.
Mine is running the Pertronix II. The hotter spark may override the gap issue?"
I'm making the point that a points conversion module (call it whatever you like) does not cause the system to produce a hotter spark. The module is simply an electronic switch installed in place of a mechanical switch (points).
Your post above states "The gap thing is correct. But I think it only affect points cars.
Mine is running the Pertronix II. The hotter spark may override the gap issue?"
Also note that points are current limited (limited to the total amount of current they can handle and still live), so the coil and ballast resistor used must match it (not exceed that current limit). But a "good" points conversion should use semiconductors that can handle higher current, and include a new coil that can utilize that higher current, with a resulting higher voltage output.
However, reliability is always a factor, and there have been many "points conversions" that have come and went just for that reason. Higher current and voltage means more heat and potential for insulation breakdown (and failure).
Plasticman
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From: Bowling Green, Kentucky
Actually, if just a "points conversion" module is used with no other changes, a slight decrease in available coil voltage will be seen. This is due to the inherent voltage drop added via the semiconductor switching, whereas "points" have essentially zero resistance. However if the conversion allows full voltage (bypassing the ballast resistor), then a higher coil output should be seen.
Also note that points are current limited (limited to the total amount of current they can handle and still live), so the coil and ballast resistor used must match it (not exceed that current limit). But a "good" points conversion should use semiconductors that can handle higher current, and include a new coil that can utilize that higher current, with a resulting higher voltage output.
However, reliability is always a factor, and there have been many "points conversions" that have come and went just for that reason. Higher current and voltage means more heat and potential for insulation breakdown (and failure).
Plasticman
Also note that points are current limited (limited to the total amount of current they can handle and still live), so the coil and ballast resistor used must match it (not exceed that current limit). But a "good" points conversion should use semiconductors that can handle higher current, and include a new coil that can utilize that higher current, with a resulting higher voltage output.
However, reliability is always a factor, and there have been many "points conversions" that have come and went just for that reason. Higher current and voltage means more heat and potential for insulation breakdown (and failure).
Plasticman
Excellent explanation.
Larry
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From: Bowling Green, Kentucky
Larry