351 Dropped valve Tinkle Tinkle Bang!
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=50142
Printed Date: November-22-2024 at 11:31pm
Topic: 351 Dropped valve Tinkle Tinkle Bang!
Posted By: Ian H
Subject: 351 Dropped valve Tinkle Tinkle Bang!
Date Posted: August-18-2021 at 2:18am
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Has anyone seen this kind of valve failure before? Put a remanufactured long block 351W with roller followers into my newley reconstructed Nautique Sport 1992 and carefully followed the running in instructions.... but after 30hours, I came up to my mooring buoy changed to reverse revved and Tinkle Tinkle Bang! Engine stopped and no more rotation. Peering into cylinder No.6 with and endoscope I
found the problem. Looks like exhaust valve has dropped into the cylinder and
been mashed around. Pictures are not great but since the valve guide is still
round and not damaged it looks like the valve fell all the way out into the cylinder
before getting mashed. Piston is cracked so I cannot imagine the cyclinder is OK, so engine game over.... Was still only running at limited RPM and never got to WOT so I and cant see that I did anyting to cause this. I am now hoping that the guys at MarineEngines4Less are fair and helpful....and will honor the warranty. It would help to know it this is rare or a typical kind of failure. Now looking at Warranty stress and minimum the shipping cost of another unit to Hong Kong and the practical issues of no place to put the boat, lift engine etc etc. Was a fun challenge the first time but now looking a bit miserable. Any insight or experience would be appreciated. Ian
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Replies:
Posted By: KENO
Date Posted: August-18-2021 at 6:42am
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I'd call it rare and think it was due to an assembly issue with the valve spring retainer, or retainer failure. Sounds like a warranty issue to me
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Posted By: GottaSki
Date Posted: August-18-2021 at 8:29am
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Oh rat farts Yes that is unfortunate Did they install the roller rockers? if so you should have some better leverage ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: MrMcD
Date Posted: August-20-2021 at 12:24am
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I could not tell in the photos but if the valve broke off about 1" above the valve that is where the valve face and valve stem are welded. The stem and face are made of different materials since the valve head is exposed to much higher temperatures. If it broke there it is manufacturing defect. If the entire valve came out of the spring and retainers that is very unusual after the first 15 minutes run time. Once they seat on start up they usually stay put. ------------- |
Posted By: Ian H
Date Posted: August-23-2021 at 8:57pm
Thanks for the feedback, its very helpful, I bought the longblock complete but no word yet from MarineEngines4less yet I hope the will be helpful.  |
Posted By: Ian H
Date Posted: August-29-2021 at 8:03am
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I got the go ahead to strip down to find the problem myself not really what I was expecting , it really looks like the valve spring broke and let the collet come of the valve stem dropping the valve in to the cylinder. It turns out to be the inlet valve not the exhaust as I first thought. But the valve spring is broken in four parts! No marking on the valve stem. Done all I can without getting the engine out, but the crank is stuck solid which does not bode well. Here is the carnage Anyone see this kind of thing before?     |
Posted By: KENO
Date Posted: August-29-2021 at 8:34am
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You were right the first time, it's an exhaust valve. It's the smaller of the 2 valves and it's lined up with the exhaust port. I'd say the same as before, It's a warranty issue. You got a defective valve spring. |
Posted By: 63 Skier
Date Posted: August-29-2021 at 9:06am
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Spring was defective, or assembly problem. I agree DEFINITELY a warranty issue. Any engine place should stand behind that given you bought a long block. There isn't anything you could do to cause that. ------------- '63 American Skier - '98 Sport Nautique |
Posted By: Ian H
Date Posted: August-29-2021 at 9:23am
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Thanks I now see the next valve spring is also broken but the valve has not dropped yet. Good I can now see failure starts with the spring failure.  |
Posted By: MrMcD
Date Posted: August-29-2021 at 1:50pm
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Ian, look closely at your valve spring. Unless it is a glare from the camera flash I see what look like witness marks from valve spring coil bind. Coil bind will break valve springs. Also note in the photo above that the rotator is not seated in the valve spring on the right. The spring is off center or maybe that spring is fractured also. We sold millions of Valve springs in my 30 years in the industry. I only saw fractured springs a few times. One memorable one was in a Ford Van with a 351W engine, the driver downshifted at speed with a heavy load going down hill, he said he was trying to save the brakes. The high RPM made the valves float and coil bind and broke several springs. We actually knew the reason for that failure. Other failures were traced to spring defects but your spring broke in multiple places making me thing it was not a spring defect. Coil bind is when the spring is compressed too far making the coils touch each other, add more pressure and kapow, things fracture. So did someone decide to over rev this engine, liked listening to the sound of it at 5,500 RPM? Probably not but it looks like the engine was running in a coil bind situation on more than one cylinder. Your piston is fractured for sure but if the valve did not contact the cylinder wall it might have zero damage. I suspect getting warranty will not be easy. If you have to fix it you could pull the oil pan, remove the one bad piston have a new piston pressed on install new rings and get a quality valve job on both heads done. Use all new valve springs, they are cheap compared to another failure risk. When the valve gets bent over that hard like yours it may have cracked the valve guide so make sure it gets checked fully before rebuilding it. Your picture also shows shims under all the valve springs. That is another standard trick to get old valve springs to meet the minimum standards, slip in a shim it adds a little more valve spring pressure but it also puts you closer to coil bind. The rotators on the valve springs were used mostly on heavy duty engines to help the valve rotate freely as it operates. The thinking is the rotator helps avoid burning a valve in heavy duty use. You could probably have a quality shop hang your new piston and rebuild your heads and with a new gasket set be running again for under $1,000. Mark ------------- |
Posted By: KENO
Date Posted: August-29-2021 at 4:07pm
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Can't forget about this other minor issue
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Ian H wrote:Posted By: MrMcD
Date Posted: August-29-2021 at 7:30pm
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The crank probably magically unstuck as soon as he pulled the head and got the valve parts out of that cylinder. ------------- |
Posted By: KENO
Date Posted: August-30-2021 at 6:13am
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I guess only Ian knows the answer to this, but to me "stuck solid" means it don't wanna turn in either direction. I guess I'd be wondering why there's so much rust in that combustion chamber too
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Posted By: gun-driver
Date Posted: August-30-2021 at 8:08am
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How the heck did that motor get so rusty? How long has it been in the boat ? How many hours are on it since you installed it ? I ask these questions because with the rust it looks like a motor that’s been in a boat since the ‘80s. Also as Keno pointed there’s quit a bit of rust in the combustion chamber and the exhaust port, you may want to take a look at your exhaust for internal cracks. I’m starting to wonder if that hydro locked and that’s what caused the failure. |
Posted By: KENO
Date Posted: August-30-2021 at 8:38am
Now we're getting there
How'd it get so rusty ?.......water How long has it been in the boat.?......not long How many hours? ......30 from first post in this thread. #5 chamber is black and sooty no water there, and look at that shiny white porcelain on the spark plug, no rust stains there #7 chamber is pretty rusty too |
Posted By: Ian H
Date Posted: August-30-2021 at 11:45pm
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Thanks for all the feedback and the insight. I just dont have an overspeed event to trace it back to, I was still in run in mode at 30hrs on the meter. So I am still hunting for the root cause. I will get a much closer look at the valve fractures and spring condition in the next day or so to see what kind of failure the breaks. But the condition of the surface of the spring is pretty poor even just taking photos with my phone.   Boat has now been on the water 3 weeks. I need to rent space to get the boat out of the water and get it there and of course I am super busy with other stuff when the boat goes bang! |
Posted By: gun-driver
Date Posted: August-31-2021 at 1:14am
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I think you need to look at your exhaust manifolds/risers for cracks. I would bet a dozen doughnuts that, that motor got water in the cylinder and hydro locked causing the catastrophic failure of the valve and spring, not an RPM overspeed.
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Posted By: KENO
Date Posted: August-31-2021 at 7:14am
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How about a picture of all of the cylinder head showing the combustion chambers? So.............does the engine turn over with the heads off or is it still stuck solid? G-D you'll pork up eating all those doughnuts
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Posted By: gun-driver
Date Posted: August-31-2021 at 1:07pm
I imagine this theory could be possible but I find it odd that you have rust in two cylinders, not just the one. Let’s hope that it did happen from a material/assembly failure not a bad manifold. |
Posted By: Gary S
Date Posted: August-31-2021 at 9:42pm
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I don't like the pitting on those valve springs - I'm surprised Mark did not have any comments on them. If I didn't know better (and I don't) they look used...... ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: MrMcD
Date Posted: September-09-2021 at 12:47pm
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The shims under the valve springs indicate the shop built the engine with used springs. The shim are used to maintain proper spring pressure with old tired springs. This is common procedure for low price engine rebuilds. Using shims also puts the spring closer to coil bind. ------------- |