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: 177 |
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 Topic: 1989 351W Engine KnockPosted: September-14-2024 at 6:44am |
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Hi Guys, Its been a long time, but my engine/boat problems aren't over  My previous thread where I replaced the engine is here: Since fitting the "new/used" engine and getting it running last year, I only used the boat for 3 days and everything was great. Then
a week later (still in December 2023) the boat was running great, but
then while cruising for about 10 minutes at ~2500 rpm I heard a knocking
sound. It was a deep knocking sound, at a rate
of about 2 knocks per second. I slowed the boat down, and it idled
fine, and the knock slowed down to about 1 knock per second. I sounded
like it was coming from the back of the engine (transmission side) but
it is hard to be sure as the cover was closed. I
shut the boat down, but couldn't see anything wrong. I tried to
restart, but it puffed and spluttered and would not start. So I towed
the boat in. I am not sure if the starting problem is directly related
or maybe it was totally heat soaked? I have been so busy this year that I haven't had much time to diagnose. - Plugs look fine - Oil looks good - no metal shavings I have pulled all the plugs, disconnect ignition and raw water pump, and cranked the engine. It turns over smoothly, no noises. I then did a compression test, and all cylinders were around 140 psi, but what was strange is than during the compression test of cylinder 4, it made a puffing sound (almost like a backfire) at the intake area. None of the other cylinders did that. Any suggestions or ideas? Greg |
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1989 Ski Nautique (SN2001)
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KENO
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Posted: September-14-2024 at 7:15pm |
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it's coming from the rear, #4 cylinder is in the rear and it did funny things.
As a starting point, maybe pull the valve cover off and look at the rocker arms and springs for #4 especially the intake because of your description. |
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Fl Inboards
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Posted: September-15-2024 at 3:37am |
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leak down test on number 4. and maybe the rest. i had one do that a number of years ago. turned out exhaust valve stem retainer was not installed correctly and it dropped the valve on top of the piston.
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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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Greg_SA
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Joined: April-19-2007 Location: South Africa Status: Offline Points: 177 |
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Posted: September-21-2024 at 6:25am |
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Managed to remove the valve cover, and this is what I found. No. 4 exhaust rocket bolt has sheared off.  - Is it possible to pull the stud and replace without removing the head? - I believe the studs are press fit? - Could this have caused the knock sound? I would expect a tick not knock? I saw a video of someone that tapped the broken thread on the stud a bit longer and use a nut and washers to extract it. Fitting a new one would probably require a press? Or tap the hole and use a threaded stud to replace? I do have my previous engine's heads as spares, but it is a bit different (newer style with bolt down rocket gear). I assume mixing different heads is a bad idea? These are the spares I have.  |
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1989 Ski Nautique (SN2001)
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KENO
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Posted: September-21-2024 at 1:18pm |
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Like you're thinking, you can do it right in the boat with the head on. Kinda a tough spot to use a die, so if you weld a 1 1/2 inch or so piece of threaded rod you can pull it easier using techniques you probably saw in those videos. I'd go for a threaded stud to replace it. I'd guess that the pushrod randomly banging up, down and all around made plenty of noise
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Greg_SA
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Posted: September-21-2024 at 1:59pm |
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Thanks I'll look into both option to remove the stud. Can I safely pull out the push rod, to check that it is not bent? Can removing the push rod disturb the cam followers below?
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1989 Ski Nautique (SN2001)
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KENO
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Posted: September-21-2024 at 4:22pm |
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You can lift it out and replace it with no problems, it looks a little beat up in the picture and might need replacing anyways.
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Greg_SA
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Posted: October-09-2024 at 12:38pm |
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I am looking for a replacement stud. Mine is 3/8 pressfit with a taper to 5/16 thread for the rocker nut. The hole in the pivot (half sphere) of the rocker is 3/8. I can get a replacement (used) from a friend, but if has a 3/8 thread. |
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1989 Ski Nautique (SN2001)
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MrMcD
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Posted: October-09-2024 at 2:25pm |
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After removing your push rod roll it on a flat piece of glass. watch for gaps as it rolls on the glass. It should be 100% flat on the glass at all times.
The rocker stud is a very common part for machine shops to replace. Any local machine shop should have inventory on the shelf for purchase. Parts stores may be able to order these parts in for you but an Engine Machine Shop that rebuilds heads would have them in stock. On Chevrolets the common fix to making sure a press in stud stays put is to drill it and put a press pin in there so it can't ever pull out. When larger cams are run pull out studs is a problem. The studs are normally a life of the engine part, I would be looking for some issue that added pressure to the stud, sticking valve, coil bind on the spring, bad adjustment of the rocker arm. Something changed the way it is designed to work or it would not break normally. The wear pattern on your rocker arm and fulcrum seems a little odd, any chance the fulcrum/washer was upside down? Curved side up. I am wondering why the top side is showing edge wear, those do not move hardly at all with engine running. Compare it to another fulcrum from another rocker and see what you think. I do not know what year Ford went from adjustable rocker arms to fixed rocker arms. I swapped my older 351W from stock 351W heads to older 289 Hi Po ported and Polished heads which gave higher compression and better performance. I had issues with the push rod length, needed custom push rods to make it work, I broke a rocker arm while figuring things out but that was 35 years ago doing it with less experience.
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KENO
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Posted: October-09-2024 at 7:50pm |
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A 351w as it came from Ford never had adjustable rocker arms.
Your present heads (the earlier heads) had the positive stop stud type rocker arms. You had the press in stud and you turned the nut till it ran out of threads. You didn't adjust it like you would adjust a typical Chevy. Your spare heads (the later ones) are also non adjustable, you just tighten down the fulcrum bolt. You could use shims for "adjustment", but you couldn't adjust in the typical Chevy fashion. I figure that you aren't loaded with machine shops and parts stores in South Africa that deal in old American parts, but there should be nothing preventing you from having an engine with 15 non adjustable rocker arms and 1 that's adjustable. But.....with a 3/8 hole you can't put in a 3/8 threaded stud. There are options for what you could do, like install a helicoil for a 3/8 stud or use a 7/16 stud that's 3/8 on the adjusting end.( or a replacement push in stud) But it would be good to try to figure out what caused the problem to happen if possible.
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MrMcD
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Posted: October-10-2024 at 2:48am |
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Good catch Keno on the 351 never having adjustable rockers and that he is in S Africa where parts are not as readily available. The heads should have a casting number that will allow you to find out where they came from originally, 302 or 289 maybe. Once know it will help find the solutions to make your engine run again.
Are both heads the same on your engine? Maybe you are dealing with a previous repair where the heads were replaced as I did on my 1978 351W.
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KENO
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Posted: October-10-2024 at 11:40am |
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Greg's heads are stock 69 through 77 SBF heads.
Non adjustable, positive stop stud type, in78 they went to the fulcrum bolt type heads like his picture of the 89 heads in his original thread shows. Probably rebuilt by the machine shop, but everything looks stock and even though they resemble heads with adjustable rockers, they're not. |
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Fl Inboards
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Posted: October-10-2024 at 4:28pm |
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Any competent head recondition shop can install a new stud. take em both in and have them checked over and and reconditioned. they will come back pretty and ready to paint and install!!
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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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KENO
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Posted: October-10-2024 at 6:31pm |
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Those places are on every street corner in South Africa.
His reconditioned engine has 3 hours or so on it since it was put together by a machine shop
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Fl Inboards
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Posted: October-11-2024 at 12:29pm |
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https://cylinderexchange.co.za/contact-us/ https://cylinderexchange.co.za/cylinder-head-reconditioning/ |
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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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KENO
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Posted: October-12-2024 at 8:36am |
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Maybe you missed the part about it having come from a machine shop.
All he wants to do is replace one rocker arm stud without tearing things apart. Even us backyard hack "hobbyist" types can handle that with a little skill and expertise
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Fl Inboards
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Posted: October-12-2024 at 2:42pm |
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You must have been that kid growing that got his book bag thrown in the ditch everyday! Your going to comment on every one of my posts?? your annoying for sure, are you the owner of this web site? I see when some one else comments on this site your "ALWAYS" there!! get a life dude your not the only person in the world that has some info to share..
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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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KENO
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Posted: October-12-2024 at 7:58pm |
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Little touchy there?
It's OK for you to pop in every once in a while, throw out some info and disappear I guess. Kinda like in this thread. Then when Jody speaks and something gets added by me, it's time to get upset. Look back in this thread, did I jump right in with something after you recommended a leakdown test? Some of us stick with a thread helping somebody actually get their problem resolved instead of one or two comments and poof, you're gone. Now as far as getting a life, mine's just fine, with some time available to help out here on CCF since I'm semi old and retired and don't mind passing on some of what I might know. Plenty of other things to keep me busy too. |
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Greg_SA
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Posted: October-13-2024 at 7:35am |
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Thanks Guys. I really appreciate everyone's input. Keno has been deeply involved, so has the most background with regards to my engine woes  The pushrod is perfectly straight. I
was hoping to repair the broken stud without removing the heads. I'd
like to use the boat ASAP. To do this, I just need a replacement stud
(stock pressfit or some aftermarket threaded stud, and tap the hole). Is
this a bad idea? I have a mobile stud removal guy that can assist. I
just can't find a new replacement stud. I can only get a set of 16, that
need a thread to be tapped in the head. I am waiting for more information from a local supplier. Maybe the broken stud was over torqued? Or just metal fatigue? Can I test the value to make sure it isn't "stuck"? A friend pulled this stud from his 302. Could I use it? Same 3/8 pressfit shaft but with 3/8 thread for the rocker nut (it seems like a locking nut). Mine has a 5/16 thread, with the taper (positive stop).  I wasn't happy with the shop that I used previously. They didn't even know that the engine had a 302 cam, and insisted that the timing was 100%! |
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1989 Ski Nautique (SN2001)
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KENO
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Posted: October-13-2024 at 3:28pm |
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I don't see why you couldn't use that stud from the 302, it's worth a try to get you going again.
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Greg_SA
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Posted: October-14-2024 at 12:59pm |
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Thanks Keno. I'll give it a try. One thing I noticed is that the "washers" at the bottom of the valve springs don't look stock. 2 have been trimmed to fit? And some of the others don't fit 100% flat. Ever seen this before? Could it be a problem?   |
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1989 Ski Nautique (SN2001)
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MrMcD
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Posted: October-14-2024 at 1:51pm |
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When rebuilding heads shops will re use the valve springs unless the customer steps up and requests new valve springs. When they do this they check the springs to make sure they meet the proper requirements. Maybe the spec says 70 ft pounds at the seat, valve closed and 240 ft pounds with the valve fully open. If a spring comes up short and does not meet spec they add shims under the spring making it stiffer and adding the pounds needed to meet spec. Most times this is perfectly acceptable to repair used heads. If the shims are too thick or a cam is used that adds lift the spring can coil bind, the coils are compressed till they touch which would put lots of stress on the push rod and rocker arm. If the spring coil binds it will leave witness marks where the coils touch. You can look for them.
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Greg_SA
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Posted: October-15-2024 at 1:23am |
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Thanks, I'll have a look.
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1989 Ski Nautique (SN2001)
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Fl Inboards
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Posted: October-15-2024 at 12:55pm |
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Little touchy there?
It's OK for you to pop in every once in a while, throw out some info and disappear I guess. Kinda like in this thread. Then when Jody speaks and something gets added by me, it's time to get upset. "Look back in this thread, did I jump right in with something after you recommended a leakdown test? Some
of us stick with a thread helping somebody actually get their problem
resolved instead of one or two comments and poof, you're gone. Now
as far as getting a life, mine's just fine, with some time available to
help out here on CCF since I'm semi old and retired and don't mind
passing on some of what I might know. Plenty of other things to keep me
busy too." Poof! i am gone! i wonder in a day of talking to nautiqueparts.com as well as dim.com customers you take the time to reference Correctcraftfan.com for information? lets see well you do not!! usually in daily correspondence this site gets referenced and even workable links for information passed on to correct craft customers. I do it , Woody also, so? PooF!!! Gone!!
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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-15-2024 at 3:11pm |
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Jodi, I have seen you help with many subjects many times. I guess I have not witnessed the dis respect you mentioned but I do not read every post listed.
Your help is always welcome and appreciated as far as I know. I agree this engine repair would be very simple in the United States but this poor guy is trying to fix it in South Africa where they do not have access to stuff we consider common. Mark
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