Boats For Sale:
1989 351W Engine Knock |
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Greg_SA 
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Joined: April-19-2007 Location: South Africa Status: Offline Points: 183 |
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 Posted: October-27-2024 at 11:07am |
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Could the "skew" valve spring shims cause extra wear on the valve guides? When I cleaned the heads, there was some very fine metal "grit" in some old oil "sludge". Not shiny, but magnetic. The thin (new) oil was clean.
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1989 Ski Nautique (SN2001)
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3751 |
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Posted: October-27-2024 at 1:18pm |
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I think I see the issue. The fulcrum in your photo listed several posts back shows the bolt hole in the fulcrum is much larger than the stud. I think this is allowing movement of the the fulcrum while running leaving all the marks on your existing fulcrums. I was wondering why they had those marks, you just don't see those on the top of the fulcrum. Check that out. If they do not fit correctly you will have more problems. Fix that and you should be good to go. Running it like this again will probably show the same result again.
The fulcrum fits snug, they will slip up and down but no side to side movement once on the stud. Look at your new stud size compared to the studs in your head currently. The new stud is larger diameter.  |
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KENO
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Joined: June-06-2004 Location: United States Status: Offline Points: 11127 |
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Posted: October-27-2024 at 7:36pm |
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Here's a picture of a stud like Greg has
It's 3/8 at the bottom where it presses in and the threaded part is 5/16. Greg has already mentioned that. That's what his other 15 are like. You tighten the nut down to the end of the threads and the fulcrum with the 3/8 hole fits on the 3/8 part of the stud....no slop  |
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MrMcD
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Posted: October-28-2024 at 1:01am |
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Well dang, thought we had an easy answer. Still does not explain why his fulcrums show wear on the top side. They look like they have been moving around? Hope he figures it out.
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GottaSki
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Joined: April-21-2005 Location: NE CT Status: Offline Points: 3363 |
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Posted: October-28-2024 at 10:29am |
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If the new stud was pressed back in, i give it 5% staying in.
I concur, geometry has to be checked. in early picture it looked like the valve stem was mushrooming over. aiming 90 degree at mid lift would be best
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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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Greg_SA
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Joined: April-19-2007 Location: South Africa Status: Offline Points: 183 |
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Posted: October-29-2024 at 12:37am |
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Thanks Guys. Does anyone have a guide of how to check the geometry? I saw a video which showed: - Top of the valve stem is colored with a permanent marker - Rocker installed - Turn motor - Check that the wear on the valve stem is in the center? Is that good enough?
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1989 Ski Nautique (SN2001)
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GottaSki
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Posted: October-29-2024 at 9:02am |
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middle is overrated, one wants to minimize the contact width of the sliding action
happens when rocker contacts points are squared up at mid lift
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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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GottaSki
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Posted: October-29-2024 at 9:02am |
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get adjustable pushrod tool and some checking springs
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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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Fl Inboards
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Posted: October-29-2024 at 9:51am |
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this is a rebuilt engine and has run through a machine shop? i would wonder how much surface was milled off if the block was decked and the heads re-surfaced?? |
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Hobby Boats can be expensive when the hobbyist is limited on their own skill and expertise.
1993 Shamrock "fat" 20. 2008 Nautique 196 5.0 |
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MrMcD
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Posted: October-29-2024 at 12:05pm |
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Place machinest blue on the valve tip assemble the rocker arm and rotate the engine. Best case the rocker arm to valve tip contact mark will be very close to center. It will move a little side to side but you do not want contact on one side or the other. Centered is correct. The only adjustment is longer or shorter push rods.
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TRBenj
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Posted: October-29-2024 at 2:04pm |
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Tom is right, checking to make sure that your rocker arm is at 90 degrees when the valve is at half lift is the best way to check geometry. You won’t learn nearly as much by checking the pattern on top of the valve stem.
The springs have a specific height (“installed height”) at which they are supposed to be installed. I’d be confirming that your machinist set them up correctly. I’m not getting the warm and fuzzies based on what you’ve shared. |
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Greg_SA
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Posted: October-29-2024 at 2:49pm |
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Thanks Guys. Unfortunately, I don't have much history on this engine's rebuild. I bought it from a machine shop that fitted my marine hardware. Apparently the shop was involved in the rebuild of the bottom end. The shop told me the head was not rebuilt as it was 100%. The engine was used for about a year by a client (after"rebuild") and the client wanted to swap to a higher performance engine and sold it (to me). This is the same shop that said the timing was 100%, when it had a 302 cam and the timing setup for a 351, and also did not have an eccentric properly installed to drive my mechanical fuel pump, even when I explicitly asked. So I really don't have much faith in anything they say. So, as far as I am concerned, everything about the engine is "unknown". The few days that it ran, it was running great though.
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1989 Ski Nautique (SN2001)
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KENO
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Posted: October-30-2024 at 7:11am |
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Sounds like you could be going down a rabbit hole here
It could be a deep one or a shallow one  Since you have the engine, got through some problems getting it together and knew how it ran before the issue, I'd say using your judgement on what to do is the best thing
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Greg_SA
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Posted: October-30-2024 at 1:58pm |
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I think the engine ran really well. Idled smooth and sounded just like my previous 351w. I think I'm gong to try check that the valve geometry is okay - 90 degrees at mid position of valve. Then fire it up. I'll run it for a day, then remove the valve covers see if anything looks suspicious (metal filings, etc). Might also do an oil change and check the oil, cut open the oil filter and inspect.
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1989 Ski Nautique (SN2001)
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