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Points Gap, Dwell & dist advance
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Aussie Ken View Drop Down
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    Posted: October-03-2005 at 12:24am
2nd issue - I am replacing the points & condensor in my 1980Sn 351. I can set the gap using feller gauges OK, but have no access to a dwell meter. Will it be close enough with the points gapped @ .018 or do I need to find a dwell meter & adjust according to the readings?
Also at what RPM should the mech advance start to come on at? And when should it max out? My mech advance has not been working at all (dodgy PO). I work for a spring manufacturer, so I will be replacing springs until perfect.
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nuttyskier2002 View Drop Down
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Points: 669 		Post Options Post Options   Thanks (0) Thanks(0)   Quote nuttyskier2002 Quote  Post ReplyReply Direct Link To This Post Posted: October-03-2005 at 10:19am
Dwell is the time that the points stay closed measured in degrees of crankshaft rotation. It's important to get the dwell as close to spec as possible to ensure the coil reaches saturation. Normally if you set the point gap to spec, the dwell will be very close. However, if the distributor cam (part of the shaft that the points ride on) is worn, then you can't really rely on gap setting. So a dwell meter is your best friend here.

As far as mechanical advance goes - timing should stay at or close to base timing up to about 1800 RPM. From then it advances rather quickly to about 2500 to 2600 RPM. Then the remainder will come in from then to about 3100 to 3200 RPM. Total advance at 3200 RPM will be about 34-36 degrees BTDC. There are 2 springs as well as 2 weights in the mechanical advance mechanism. One spring is lighter and is engaged with the weights all of the time. The other is a stronger spring and doesn't engage until later in the advance curve. This is the reason that the timing advances quickly at first and then slows down after 2500 RPM.

Hope this helps!
95 Malibu Echelon w/Mercruiser 350 Magnum Skier

Former boats:
88 Ski Centurion Tru Trac II
59 Chris Craft Capri (woody)
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GottaSki View Drop Down
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I find these numbers on a 351 net strong performance.

10 BTDC at 700
21 at 1500
30 at 2000
34 at 2600
37 at 3100
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Aussie Ken View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Aussie Ken Quote  Post ReplyReply Direct Link To This Post Posted: October-03-2005 at 8:31pm
Thanks for the replies. To be safe I'll try & track down a dwell meter as I don't know how much the dizzy cam has worn.

Gottaski - your advance curve seems really quick to me. Have you experienced any pinging with that curve?? I'll try & set it up to that initially and see how it goes.
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Morfoot View Drop Down
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Points: 5320 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Morfoot Quote  Post ReplyReply Direct Link To This Post Posted: October-04-2005 at 7:42am
Ken,
Have you considered going with an electronic conversion kit to avoid this problem? I did mine this year for about 70 USD and it was the best thing I ever did.. Just a thought...
"Morfoot; He can ski. He can wakeboard.He can cook chicken.He can create his own self-named beverage, & can also apparently fly. A man of many talents."72 Mustang "Kermit",88 SN Miss Scarlett, 99 SN "Sherman"
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79nautique View Drop Down
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a conversion kit will have no effect on the advance curve for the mechanical advance. You are better off replacing the whole distributor with a new one.
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GottaSki View Drop Down
Grand Poobah
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Points: 3363 		Post Options Post Options   Thanks (0) Thanks(0)   Quote GottaSki Quote  Post ReplyReply Direct Link To This Post Posted: October-04-2005 at 8:55pm
I understand, but nope, no pinging. I wouldn't go further of course. It runs sweet.
"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."

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surroundsound64 View Drop Down
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Points: 151 		Post Options Post Options   Thanks (0) Thanks(0)   Quote surroundsound64 Quote  Post ReplyReply Direct Link To This Post Posted: October-23-2005 at 12:03am
Originally posted by Morfoot Morfoot wrote:

Ken,
Have you considered going with an electronic conversion kit to avoid this problem? I did mine this year for about 70 USD and it was the best thing I ever did.. Just a thought...

I second that.
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mackwrench View Drop Down
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Go with 79's advice here, a "conversion" kit only gets you out of the work of replacing those points all the time! The full electrontic Dist will have the correct advance you need. I have done both, I can tell you the electrontic dist. will perform better, it's a few more $$ but your done with that issue.
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'83_2001 View Drop Down
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Points: 12 		Post Options Post Options   Thanks (0) Thanks(0)   Quote '83_2001 Quote  Post ReplyReply Direct Link To This Post Posted: October-26-2005 at 6:45pm
what distributor did you go with and where can i get one. what about the conversion kit?
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79nautique View Drop Down
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Points: 7872 		Post Options Post Options   Thanks (0) Thanks(0)   Quote 79nautique Quote  Post ReplyReply Direct Link To This Post Posted: October-27-2005 at 11:23am
351W motor reverse rotation will take a Mallory YLU-554-CV or you can use a YL-554-CV I would suggest Summit racing over JEGS but thats because Jegs had it back ordered for months and Summit got to me in a couple of days it runs around $375 or you can spend a little more and get a HEI version.
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mackwrench View Drop Down
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Worth every $$$$
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