Boats For Sale:
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Tim D 
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Joined: August-23-2004 Location: United States Status: Offline Points: 2641 |
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 Topic: Distributor CapPosted: August-07-2006 at 5:55pm |
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When you buy a new distributor cap, make sure you inspect it and read the fine print. The new one I got is just like the old one that cracked. It is vented. They are both yellow, the first one I bought years ago was burgandy and it didn't have a vent hole. So I had to plug the hole before installing it because mine needs to be sealed. This what the directions say..
"CAUTION: This distributor cap is available in both a vented and a sealed version, to meet the U.S.C.G. regulations. INSTALLATION OF THE WRONG CAP CAN RESULT IN AN EXPLOSION AND POTENTIAL LOSS OF LIFE OR PROPERTY. To determine which version to use, inspect the bowl of the distributor. If the distributor is vented (look for a 7/8" hole, covered with multiple layers of screening), use the sealed version. Non-vented distributor bowls must have a vented cap." here's a pic of the vent in the cap. Looks like they drilled a hole in it. 
here's a pic of the vent (brass mesh) on the distributor bowl they're refering to. 
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Tim D
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Jim_In_Houston
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Joined: September-06-2004 Location: United States Status: Offline Points: 1120 |
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Posted: August-08-2006 at 7:01am |
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Tim, are you suggesting that the distributor must be vented in one of the locations (but not both)? I think mine is not vented in either.
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Happy owner of a '66 and a '68 Mustang
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Tim D
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Posted: August-08-2006 at 8:56am |
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The cap that was on the boat when I bought it was black and not vented. The first two replacements I bought over the years were burgandy and not vented. The last one that cracked and the new one are both yellow and are vented. Same NAPA part number MA-1 on both colors. I figure since the bowl/body of the distributor is vented the cap doesn't need to be. My distributor has another mesh vent on the opposite side. Your Mustangs don't have vents? Mine is a Mallory YL series.
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Tim D
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john33617
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Posted: August-08-2006 at 10:18am |
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I drill a 1/4 inch hole in the top of the cap , the rotor going around acts like a fan and keeps it dry , glue a screen on top of the hole
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79nautique
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Posted: August-08-2006 at 2:41pm |
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I wouldn't use that style of cap to start with they do not last very long compared to the traditional tower style caps, And I do not suggest drilling holes in them either.
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john33617
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Posted: August-08-2006 at 2:59pm |
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after the engine has run about 10 min , condensation would form in the top of the cap , and the engine would start to miss , and would be hard to start if you shut it off , it would dry out if you ran about 30 min , or if you took the cap off and dried it , after drilling a 1/4 inch hole in the top of the cap between the posts never had the problem again , even in the winter , had the same problem on my FN and a hole in the cap cured it to
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79nautique
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Posted: August-08-2006 at 3:20pm |
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drilling a hole is stupid and defeats the spark/flame arrestor feature of the dist and is a major safty issue.
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Tim D
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Posted: August-08-2006 at 3:45pm |
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As far as I know, the flat top cap is the only kind that will fit my single point (electronic now) Mallory distributor.
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Tim D
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79nautique
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Posted: August-08-2006 at 4:01pm |
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what model is it? seems odd I didn't think they used that style untill later in the 80's or early 90's. might cross reference a mallory 9-29412 cap and see if it works.
with that style of cap and the moldling process it creates a lot of knit lines in the cap that breakdown die-electrically in half the time a traditional style would. |
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john33617
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Posted: August-08-2006 at 4:03pm |
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msdtech108-26-2003, 10:18 PM
An ignition system creates a spark that has to jump from the rotor to the terminal in the cap. As the voltage builds up, the gap from the rotor to the terminal is ionized until the voltage is high enough to jump across. Therefore, ionization within the distributor cap is still present even in modern day high tech distributors. In most applications, the ionized air does not present a problem, but as cylinder pressures are increased this can become an issue. All current MSD Distributors are shipped with a distributor cap that already has a vent hole located in the very top of the cap. The vent hole is shielded to prevent water and other contaminants from entering the cap. The problem with drilling holes in the side of the cap is that it exposes the cap to moisture and other materials that could cause just as big, if not bigger problems then the ionization can. Best way to handle this issue is to try the distributor as is and then evaluate how it is performing before modifying it. |
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79nautique
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Posted: August-08-2006 at 4:37pm |
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dude where do you get your bullsh*t info??? the issue is fuel vapor accumelating inside of the cap then igniting when the spark jumps accross the rotor to a terminal and then the flame exiting the cap and igniting the rest of the fuel vapor in the motor box.
Don't confuse automotive applications with marine applications, the voltage doen't build up then jump the voltage is at full strength when it leaves the coil and will jump to the closes ground source to the rotor tip. Go give your bullsh*t to someone else that has never design ignition systems d*ck head. If you would like to see the stuff I have designed then go to your local Cadilac dealer and check under the hood of any V-8 model. |
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john33617
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Posted: August-08-2006 at 5:09pm |
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my two boats run alot better after drilling the holes , and with the screen glued over the holes to contain any flames I don't see a fire problem , and why would you call somebody you don't know a d*ck head . http://www.cartalk.com/content/columns/Archive/1999/October/06.html
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Tim D
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Posted: August-08-2006 at 5:18pm |
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79, I know it is YL-#####. I'll have to look at it and write the numbers down.
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Tim D
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todicus
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Joined: July-10-2006 Location: Napa, Ca Status: Offline Points: 493 |
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Posted: August-08-2006 at 5:21pm |
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79 nautique is right - minus the slander. Don't go drilling holes in your cap, and don't buy ones that have holes when your boat manufacturer never intended for you to vent your distributor. You will blow the engine cover right off your boat when the fuel vapors ignite INSIDE your dist., then everything else blows as well. OR, just risk it and hope your kids are not on the boat when it explodes.
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john33617
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Posted: August-08-2006 at 9:34pm |
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a marine unit is vented at the bottom of the upper casting area to allow hydrocarbon fumes to evacuate from inside the cap.all hydrocarbon fumes are heavier than air so the literally fall out the bottom.as a distributor turns,engine blow by gases can make their way up the shaft and into the housing.these oil vapors are flammable.thusly the housing is vented to the outside world.
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The Dude
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Joined: October-19-2004 Location: Houston Status: Offline Points: 1334 |
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Posted: August-08-2006 at 10:39pm |
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[QUOTE=79nautique] dude where do you get your bullsh*t info??? QUOTE] uh...the dude didn't write that.
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Mullet Free since 93
95 Sport |
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79nautique
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Posted: August-09-2006 at 9:13am |
guess you don't see to well either and don't understand there is only one cast part on a dist. if you look at the picture above the vent is on the side and not on the bottom leaving plenty of room to accumulate fuel vapors. the dude, I was using the term in general and not refering to you specificly. |
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Hollywood
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Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13515 |
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Posted: August-09-2006 at 10:04am |
I think that's my new signature. |
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jbear
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Joined: January-21-2005 Location: Lake Wales FL. Status: Offline Points: 8193 |
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Posted: August-09-2006 at 9:50pm |
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Man I love it when you guys get 79 goin'.
Now I know where hollywood's new sig came from. john |
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"Loud pipes save lives"
AdamT sez "I'm Canadian and a beaver lover myself"... |
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john33617 wrote: