engine timing`
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=42251
Printed Date: April-27-2024 at 2:27am
Topic: engine timing`
Posted By: shierh
Subject: engine timing`
Date Posted: December-26-2017 at 3:57pm
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Because I wasn't sure of ignition timing I have been running at base 8 Degrees. However it looks like the prestolite electronic distributor is recommended to be run at 10 base. Engine is rebuilt stock 351w. Right now im getting 4200 with the stock type prop, which I changed from 13x13 down to 12x13. Question is, what can I expect to gain by going to 10 on base timing? will I gain the missing 200 rpms? |
Replies:
Posted By: 8122pbrainard
Date Posted: December-26-2017 at 4:08pm
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Steve, Remind me on what model boat you have. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: shierh
Date Posted: December-26-2017 at 4:14pm
| 2001 Hull |
Posted By: MourningWood
Date Posted: December-26-2017 at 4:17pm
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Idle timing is a good reference, but more important is full advance at recommended rpm. Use a good timing light to adjust timing to full advance at 2500 rpm. If the idle timing is then within a couple degrees of spec, you should be ok. ------------- 1994 Ski Nautique "Riot" 1964 Dunphy X-55 "One 'N Dun" 'I measured twice, cut three times, and it's still too short!" |
Posted By: 8122pbrainard
Date Posted: December-26-2017 at 4:20pm
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Steve, You said you dropped down to a 12x13 prop. Is that dia. x pitch or pitch by dia.? Ether way, with a 4200 red line and that prop, I feel somethings not right with the engine. You should be getting more RPM's than the 4200. Did you check the RPM's with a shop tach? Why did you change the prop? What did the rebuild entail? ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: shierh
Date Posted: December-26-2017 at 4:54pm
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Issue has been that for some reason the boat is going too fast for stated RPM. at 3000 it was doing 34 instead of 30 which I believe is what they always run. Therefore I took an inch of pitch out. It went from 38 to 3900 to 4200. My timing light with advance isn't working now for some reason, gotta get a new one. Have not checked full advance yet due to the light issue. Fact is that the distributor is the only think that I didn't have to fix or at least didn't think it needed anything. Engine is stock rebuild, 30 over, Cam and crank were good. Heads were replaced but Not GT40 so they are essentially stock. I did check the tach with a shop tach and it seemed good a year ago. However I do need to check it again and ck speed with GPS again. Didn't write down anything a year ago so going from memory. |
Posted By: KENO
Date Posted: December-27-2017 at 10:51am
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Sounds to me like you don't know what your issue really is, like whether it's an indication problem. or something physical. Since you're wondering about your Prestolite distributor, I'd pull the plate with the module off so you can get a look at the advance weights and springs. They should move freely and both springs should be in good shape. The small short spring will have tension while at rest and the bigger heavier one has no tension at rest. The big one has an oval shape on one end. It just goes along for the ride until about 2500 rpm,s, then it start to limit advance. A marine Prestolite doesn't achieve full advance till about 4000. rpm if everything is correct with the stock original springs and weights. That means if set your timing for full advance of say 34 degrees at 2500 rpm like somebody a few posts back said, when you get to 4000 rpm's you'll be at 40 plus degrees and be damaging your new engine and you won't be happy.  SO............inspect the distributor weights and springs. If it's from the 80's it's time to inspect them anyways, it may be pretty rusty and ugly. Springs should look like the first picture below  It shouldn't resemble the next picture with springs that are a mess and not original in the case of the big one.  You might also find a broken spring which would totally screw up your advance curve. Is this a Prestolite with a Prestolite module in it or some other aftermarket module? Lots to digest, but make sure the distributor is in good working order and then do everything with a timing light to avoid unwanted problems. |
Posted By: shierh
Date Posted: December-27-2017 at 12:09pm
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I did inspect when rebuilt engine. it all looked good, Thus far it appears to be only engine component not needing replacement- so far. Im puzzled as to y the boat seems to be going faster than it should with the 13x13 and low rpm. That's y I re pitched. Question remains, if I turn up the base timing to 10 then can I expect to gain RPM |
Posted By: KENO
Date Posted: December-27-2017 at 12:48pm
| Yes |
Posted By: Duane in Indy
Date Posted: December-27-2017 at 12:56pm
You don't have to have an advance light. Just mark damper accurately for the TOTAL advance like KENO has said. Initial advance will tell you next to nothing. Too much total will harm your engine. Generally engines like more timing, to a point. Then they start destroying parts rapidly. You have too many "unknowns" at this time: Total timing, RPM, Speed. Nail those down and then you will have some data to work with. JMO FWIW ------------- Keep it as original as YOU want it 1978 Mustang (modified) |
shierh wrote:Posted By: Duane in Indy
Date Posted: December-27-2017 at 1:10pm
Let me add the following for clarification: Total timing - Initial timing = Distributor condition Make sense?? ------------- Keep it as original as YOU want it 1978 Mustang (modified) |
Posted By: KENO
Date Posted: December-27-2017 at 1:23pm
| I think he wanted a one word answer |
Posted By: Duane in Indy
Date Posted: December-27-2017 at 1:26pm
Oh OK how about "Detonation" ??? ------------- Keep it as original as YOU want it 1978 Mustang (modified) |
Posted By: shierh
Date Posted: December-27-2017 at 1:59pm
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Ordered new timing light. Will mess with it next time I put it in the water. This resto project took longer than it should have, largely due to a non participating boat partner. finally got him to sell me his share so I will have it finished soon. Basically all it needed was upholstery and some things like running lights, horn, second bilge pump, etc etc. I found upholstery guy in Orange City FL that seems good and was very reasonable. He is slated to take driver seat and engine box this week or next week and cover them with my design. I have to make a spotter seat yet and will also get that done. |
Posted By: shierh
Date Posted: February-01-2018 at 4:49pm
| I finally adjusted timing from 8 to 10. Gained 200 rpms. Didn't check max advance since I was by myself. Getting almost 4400 and boat speed is 44. or was it 46, well ill ck that again next time. |
Posted By: KENO
Date Posted: February-01-2018 at 10:07pm
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With your Prestolite distributor I'd check advance at full throttle since they don't achieve max advance till around 4000 plus rpm if the original weights and springs are in good working condition. Can always check it in neutral at the dock at 4000-4500 rpm too since the flyweights aren't smart enough to know if the engine is under load or revving up in neutral You won't be bouncing around and having the wind trying to rip the open engine box right out of the boat either
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Posted By: shierh
Date Posted: February-05-2018 at 1:50pm
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Ill pull cap and re check it. Was good when engine was built. Soon as I get alternator back on will run it again. For some reason the new single wire alternator quit charging. So been running on battery only. couldn't remove the cap to zap it so I got a new one with external excitation. |