Points Gap, Dwell & dist advance
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=2546
Printed Date: November-23-2024 at 6:48am
Topic: Points Gap, Dwell & dist advance
Posted By: Guests
Subject: Points Gap, Dwell & dist advance
Date Posted: October-03-2005 at 12:24am
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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. |
Replies:
Posted By: nuttyskier2002
Date Posted: October-03-2005 at 10:19am
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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) |
Posted By: GottaSki
Date Posted: October-03-2005 at 10:21am
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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 ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: Guests
Date Posted: October-03-2005 at 8:31pm
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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. |
Posted By: Morfoot
Date Posted: October-04-2005 at 7:42am
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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" |
Posted By: Guests
Date Posted: October-04-2005 at 11:00am
| 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. |
Posted By: GottaSki
Date Posted: October-04-2005 at 8:55pm
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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." River Rat to Mole |
Posted By: surroundsound64
Date Posted: October-23-2005 at 12:03am
I second that. ------------- 1981 Ski Nautique 2000 SAN Looking for a 2000-2006 SAN |
Morfoot wrote:Posted By: mackwrench
Date Posted: October-23-2005 at 5:37pm
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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 $$ but your done with that issue. ------------- NO LONGER A MEMBER |
Posted By: '83_2001
Date Posted: October-26-2005 at 6:45pm
| what distributor did you go with and where can i get one. what about the conversion kit? |
Posted By: 79nautique
Date Posted: October-27-2005 at 11:23am
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351W motor reverse rotation will take a Mallory YLU-554-CV or you can use a YL-554-CV I would suggest Summit racing over JEGS but thats because Jegs had it back ordered for months and Summit got to me in a couple of days it runs around $375 or you can spend a little more and get a HEI version. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: mackwrench
Date Posted: October-27-2005 at 12:52pm
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Worth every $$$$ ------------- NO LONGER A MEMBER |