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Timing advance chart? |
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Connelly3 
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 Topic: Timing advance chart?Posted: September-01-2020 at 10:06pm |
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I was wondering if anyone had a good timing advance chart for a 351 Windsor. I’m having trouble with power at slalom speed in my 1988 ski nautique and I suspect lack of timing advance. I’m only advancing to 24 degrees at 3300 rpm(these are rough numbers my timing light is limited) Any help would be appreciated
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SNobsessed
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Posted: September-02-2020 at 7:37am |
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That is about right for stock. I think it is about 18 degrees advance. You could bump up the initial timing a bit to get a higher final advance.
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Connelly3
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Posted: September-02-2020 at 8:21pm |
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I was able to compare with an identical boat tonight. The other boat was advancing to 28 degrees. Also noticed it was advancing more rapidly. It was at 27 degrees at 3000 rpm. I advanced my initial timing 4 degrees and it helped some but it does not seem as responsive and seems to lack power in comparison. I have already had the internals of the distributor apart multiple times and everything is free and well lubed. This has been such a long ongoing problem that I’m going to order a new dui distributor from skidim and hope it’s money well spent. Thanks for the input Seems like you were right on with 18 degrees of advance.
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GottaSki
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Joined: April-21-2005 Location: NE CT Status: Offline Points: 3327 |
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Posted: September-02-2020 at 9:28pm |
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What is your initial at 650 now?
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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SNobsessed
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Posted: September-02-2020 at 9:35pm |
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You might want to check compression. That would result in low power too. Edit: Before you buy new dizzy, you could test for timing caused power loss by changing initial setting to 10 or even 12 DBTDC. It might be hard to start but it is only a test. You could even set it just before your run so it is already started.
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“Beer is proof that God loves us and wants us to be happy.”
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MrMcD
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Posted: September-03-2020 at 2:17am |
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For comparison purposes we need to know if you are including the Initial timing setting for your totals.
10* at idle plus 18* advance by 3,000 RPM would total 28*. That is a little conservative but not terrible. You could adjust the distributor to bring in your timing sooner or to advance it a little further. Find someone local with a distributor machine and they could dial it in pretty quick for you. Call first, see what they charge, it might be cheaper to buy the DUI. I think a new distributor would allow 24* advance. And most have you fully advanced by 3,000 RPM. I know the older boats did not fully advance till 4,000 or so. I believe modern information has shown the engines run well with the advance in by 3,000 so they make them that way. With 24* built in to the advance you could play with your timing at idle and vary it between 6 and 12 to see where your boat responds the best without having any pinging or detonation issues. An over advanced engine will cause excess heat in your head chambers and while it will run like a screamer for a few moments soon after that parts can break so be conservative and figure out what works safely in your engine. PCM had a very safe timing curve and the engines worked well in this application. I think if you use too much timing at idle in a boat you will lose the torque needed at idle to engage the prop without stalling |
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KENO
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Posted: September-03-2020 at 6:40am |
A little more info would be helpful. Was the boat running right for you and then it started having this issue? Or did you just buy it and it doesn't run right.? What do you mean by "my timing light is limited" For some reason, people think that a Prestolite screw down cap distributor (which is what you would have on an 88) can have 34 degrees total advance at 3000 rpm with the initial advance set at 10 degrees. The numbers SNObsessed is giving you are a good description of a stock Prestolite screw down cap distributor. Initial set at 10 degrees with 18 more degrees mechanical advance to give a total of 28 degrees and it's not fully advanced till about 4000 RPM So........your 24 degrees at 3300 rpm isn't bad for a stock distributor. The earlier(before 1987) clip down cap Prestolites had a different advance limiter plate that had longer slots and allowed more mechanical advance SNObsessed went thru all this and had it modified at a distributor shop. Back to more questions,  Is it sluggish accelerating up to speed? What's your top speed and RPM at top speed ?. Are your secondaries on the carburetor working ? From a distance, through the computer, I think your problem isn't the distributor, but that's just me thinking. As far as your secondaries go, you can only tell if they're working in the water, at speed, Revving the engine in neutral will never make the secondaries open and on your engine they won't fully open on a 600 cfm Holley but I'd check to see if they move at all. . |
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SNobsessed
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Posted: September-03-2020 at 7:42am |
A guy could just lengthen the slots with a dremel for a lot less than the cost of a new DUI.
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“Beer is proof that God loves us and wants us to be happy.”
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GottaSki
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Posted: September-03-2020 at 7:57am |
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Also, If initial is set at too high an rpm, or the small spring is too loose, one can eat up a lot of the span and never get a good final
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
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Connelly3
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Posted: September-03-2020 at 4:42pm |
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Just FYI The new distributor is already in the mail I ordered it right after my last post. Here are some answers. first test on my boat Initial timing set @ 10*@650rpm final advance was 24* @nearly Wot.
Second test on my boat Initial timing set @14*@650rpm final advance was 28* @ nearly wot Test on identical assumed properly running boat. Initial timing set @10*@650 rpm and final advance 28* @ nearly wot. In this boat I noticed the timing was advanced almost completely To 27-28*@ 3000-3200 rpm. My boat only sees its max 14* advance at much higher rpm and with the secondary’s open. As for the back story I bought the boat in 2013 and I’m pretty confident it was running properly for many years. First started having problems last fall with perfect pass not keeping speed with a hard pulling skier. After spending way to much time talking with the people at pp and working on that, I hand drove a skier one day and realized it was the boat and not the pp. I installed the pp and it worked flawlessly for about 2 years. I have replaced the power valve (2.5) and upgraded to the ignitor II electronic ignition and coil. also have tried 2 sets of springs in the distributor and am back to the originals. Best way I can discribe the problem is a little sluggish accelerating and with load there is a dead spot in the throttle between 3200 rpm and the secondary’s opening. It has gotten better since I started working on it but I don t feel it’s 100 % and the pp is still like a yo-yo. |
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KENO
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Posted: September-03-2020 at 6:33pm |
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I guess all that's left to do now is install the new one and update the thread with the results
On second thought, how about posting a picture of the bottom of the housing showing the spark arrestor screens?
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Connelly3
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Posted: September-12-2020 at 9:35am |
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Dropped the new dizzy in last night and went for a ride. Wow what a difference. Feels like a new boat. Initial timing set @ 10* advancing to 31-32* total which according to my engine manual 32* is maximum @ wot. It now advances almost fully to 31* @2200 rpm. I was able to con my brother into a ski ride despite the cold temp and choppy water and my perfect pass Worked flawlessly. It had been borderline working previously with the old dizzy and the Initial timing bumped to 14* but last night it was spot on. Warning to anyone considering the DUI distributor from skidim it is tall and just fits under the engine cover. Actually had to move my cover forward an inch or two to get It to clear and it fits but still just touches the cover on the front corner of the dizzy. In dui’s defense my cover always seemed to sit back to far and had to be pulled forward a bit when closing.
Also the new dui dizzy appeared to have a machined gear compared to a cast gear on the prestolite. Do I need to worry about cam wear? |
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Connelly3
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Posted: September-12-2020 at 9:38am |
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Keno were u looking for a picture of the bottom of the Original prestolite dizzy or the new dui?
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KENO
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Posted: September-12-2020 at 9:51am |
The new one, but I get the feeling it may be a little late for that
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KENO
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Posted: September-12-2020 at 10:00am |
Being an 88 reverse rotation application, it's probably a cast iron gear, because I don't think anybody makes a steel reverse rotation gear for a 351w The steel gears look smoother due to the machining done on them. DUI says it's cast iron I'd probably call DUI and ask about the gear and then ask them where your extra couple degrees of advance went to also. Seems that they advertise 24 degrees of advance plus the initial and everybody lately gets 20 or 21 or 22
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MrMcD
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Posted: September-12-2020 at 12:31pm |
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Timing all in at 2200 seems 600-800rpm early to me, you might ask them about that also but happy for you that the boat is running much better.
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Connelly3 wrote: