Engine Guru's - Need help-Take a look
07-24-2012 | 03:05 PM
#53
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Wow, reading this thread was like a case of Deja' Vu for me - my 462 was also running domed pistons, although mine were forged and had been flycut and had a little bit of the domes shaved off to help with compression. I had a nearly identical ringland failure as you had. I actually might not have known about it if a piece of shrapnel had not taken a small chunk out of an intake valve. This was causing a backfire under heavy load, which led to a compression test and disclosure of the problem. Like you, I briefly flirted with trying to cobble it back together to salvage the season, but a couple of lifters had stopped spinning, and when I pulled the other head I found another piston broken in the exact same spot! Looks like domed pistons have no business in a marine engine.
I ended up building a 489 stroker based on a gen VI block. Still dialing it in. Make sure you have the right distributor gear on there if you are running a roller cam - see my thread. Little details like that can get you.
I ended up building a 489 stroker based on a gen VI block. Still dialing it in. Make sure you have the right distributor gear on there if you are running a roller cam - see my thread. Little details like that can get you.
07-25-2012 | 04:42 PM
#54
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From: westville, NJ
a couple of sets of 781's on ebay. done set near me in s. jersey. guy wants 800 plus 60 ride. little steep. another set in cincinnati guy wants 375 plus 125 ride. 500 makes the done set look better.
07-26-2012 | 09:12 AM
#55
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From: Western Ma.
Batteries on charger now. Maybe tonight she fires. Still finishing up some minor details, like exhaust flappers and such.
Budman,
I saw your thread about the distributor gear wear and now shakey oil pump. Hope it works out. At least if pump is going bad, or vise versa,, you found the problem before things turned real ugly. I do have full roller set up now, and correct gear has been provided from Bob M. when I got the cam. After reading your thread, I stared at my new distributor gear for a long time. LOL
Piclkenjim,
To your point about recirc pump, are you saying that with a circ pump this would tend to keep sand in suspension longer and give it a better chance of getting flushed through?
Budman,
I saw your thread about the distributor gear wear and now shakey oil pump. Hope it works out. At least if pump is going bad, or vise versa,, you found the problem before things turned real ugly. I do have full roller set up now, and correct gear has been provided from Bob M. when I got the cam. After reading your thread, I stared at my new distributor gear for a long time. LOL
Piclkenjim,
To your point about recirc pump, are you saying that with a circ pump this would tend to keep sand in suspension longer and give it a better chance of getting flushed through?
07-26-2012 | 09:37 AM
#56
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From: Bettendorf, Iowa
Rich,
As stated, the root cause of this failure is evident. The event originated as a localized hotspot, in the thinnest part of the crown. The detonation intensified further as the shallow, sharp edged area of the crown increased in temperature. The land area adjacent to the relief continued to lift until contact with the cylinder head was initiated, resulting in the loss of the ring land. The melted aluminum is clear in the photo. It is my understanding that a second piston was experiencing land deformation also but had not yet failed. The lack of heat discoloration outside of the area of the valve relief would indicate that the detonation was low-grade, localized near the sharp valve relief area of the piston crown. At this point the positive that can be taken away from this analysis would be how to move forward in the rebuilding the engine.
You stated your pistons are Speed Pro/TRW part number, L – 2465 – 030. They are a VMS – 75 high silicon piston, very similar in composition to a hypereutectic 4032 alloy, containing about 11% silicon. Hypereutectic pistons are relatively strong; however, in your instance it exemplifies one of the alloys main shortcomings. While the hypereutectic forgings display exceptional thermal stability, they lack the ductility and 2618 alloy. When detonation comes into play, the 2618 forging, a more malleable alternative, has a tendency toward plastic deformation. This can mitigate crack migration, potentially delaying/preventing eventual failure of the piston. A hypereutectic piston has a tendency to fracture immediately upon exceeding these limits. In the Marine environment, where prolonged high stress, high temperature, potential detonation, and sustained wide open throttle operation is routine, the hypereutectic piston is very unforgiving. While it is impossible to determine whether or not a 2618 alloy would've survived this particular event, you can make a case that it may have provided the necessary margin against catastrophic failure. This is a textbook example of why many engine builders specify the 2618 material exclusively for the marine environment.
Bob
As stated, the root cause of this failure is evident. The event originated as a localized hotspot, in the thinnest part of the crown. The detonation intensified further as the shallow, sharp edged area of the crown increased in temperature. The land area adjacent to the relief continued to lift until contact with the cylinder head was initiated, resulting in the loss of the ring land. The melted aluminum is clear in the photo. It is my understanding that a second piston was experiencing land deformation also but had not yet failed. The lack of heat discoloration outside of the area of the valve relief would indicate that the detonation was low-grade, localized near the sharp valve relief area of the piston crown. At this point the positive that can be taken away from this analysis would be how to move forward in the rebuilding the engine.
You stated your pistons are Speed Pro/TRW part number, L – 2465 – 030. They are a VMS – 75 high silicon piston, very similar in composition to a hypereutectic 4032 alloy, containing about 11% silicon. Hypereutectic pistons are relatively strong; however, in your instance it exemplifies one of the alloys main shortcomings. While the hypereutectic forgings display exceptional thermal stability, they lack the ductility and 2618 alloy. When detonation comes into play, the 2618 forging, a more malleable alternative, has a tendency toward plastic deformation. This can mitigate crack migration, potentially delaying/preventing eventual failure of the piston. A hypereutectic piston has a tendency to fracture immediately upon exceeding these limits. In the Marine environment, where prolonged high stress, high temperature, potential detonation, and sustained wide open throttle operation is routine, the hypereutectic piston is very unforgiving. While it is impossible to determine whether or not a 2618 alloy would've survived this particular event, you can make a case that it may have provided the necessary margin against catastrophic failure. This is a textbook example of why many engine builders specify the 2618 material exclusively for the marine environment.
Bob
Then when I go a little bigger. I'm dropping it off at Young Performance! Another reason I've had good luck with this build. Eddie helped me with fixing the main oiling issues with these engines. And setup after getting my rotating assy back.
Get with Bob on pistons, cam, etc. Set it up with the power of OSO and have some fun boating. Just look at your cam card when you set up your firing order. (Bob knows what I'm talking about
)
07-26-2012 | 01:00 PM
#57
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From: OFallon,Mo.
Yep. If your running in sandy areas and parking on beaches regularly. As stated though that's just my 2 cents.
07-30-2012 | 11:43 AM
#58
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From: Western Ma.
Finally got it wet.
Went out yesterday for maiden voyage. Felt like an anxious father with fingers crossed. Had nobody to blame but myself if this one craps the bed. My first "complete" assy, Motor is running great so far. About an hour on motor now..Have some old gas in there mixed with some new, so taking it easy for now, and haven't been above 3K yet except for a couple quick revs in neutral to 4 k or so. Timing is set to 34 degrees for now. Oil pressure at 65 cold, and 50 hot cruising at 3K. Down at idle below 1K, pressure never drops below 25 hot, then climbs back to 30 or so.. Seeing about 210 on oil temp when cruising for an extended period, and back down to about 160 at idle. Water pressure at 25psi when cruising.
Fuel presssure steady at 6-7psi.
So..... I'm anxious to change oil and filter to have a look, but perhaps too soon? Want to get all the assy fluids and whatever out ASAP. Running 20-50 dino oil now. Plan on going back to mobil 1 15-50, but maybe after 10 hours or so? What do you all think? This is full roller set up.
Also, opinions on how long before I start moving up the rpm band.
Thanks guys.
Also thanks to Bob M. at Marine Kinetics, for his advice, and his patience listening to my many questions and answering every one of them as I went along with my home build. His service extends well beyond any purchases made.
Fuel presssure steady at 6-7psi.
So..... I'm anxious to change oil and filter to have a look, but perhaps too soon? Want to get all the assy fluids and whatever out ASAP. Running 20-50 dino oil now. Plan on going back to mobil 1 15-50, but maybe after 10 hours or so? What do you all think? This is full roller set up.
Also, opinions on how long before I start moving up the rpm band.
Thanks guys.
Also thanks to Bob M. at Marine Kinetics, for his advice, and his patience listening to my many questions and answering every one of them as I went along with my home build. His service extends well beyond any purchases made.
07-30-2012 | 12:39 PM
#60
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You could probably change the filter now and cut it open, but I doubt if you would see much beyond the usual initial start-up debris - a few stray metal flakes from initial machining, maybe some lint from shop towels, etc. This would tell you if something catastrophic was about to happen, but personally I would not feel bad letting it get a few more hours on it first. I waited until I had about 10 hours on my engine before I let it sing much above 4K, but others on here are more adventurous.
FWIW, my engine builder recommends a full season (50+ hours) before switching to synthetic, but as stated before, you will hear differing opinions on this. You might get Bob's or Eddie's recommendation on what oil to run.
I'm curious to know what oil pump you went with and what your bearing clearances are. You oil pressure numbers sound good for 20W-50, but with the same weight oil mine were considerably higher - more like 65 - 70 cold idle, and 60+ warm. I ordered a Mellings 10778c pump to replace the one that has apparently failed on my engine.
FWIW, my engine builder recommends a full season (50+ hours) before switching to synthetic, but as stated before, you will hear differing opinions on this. You might get Bob's or Eddie's recommendation on what oil to run.
I'm curious to know what oil pump you went with and what your bearing clearances are. You oil pressure numbers sound good for 20W-50, but with the same weight oil mine were considerably higher - more like 65 - 70 cold idle, and 60+ warm. I ordered a Mellings 10778c pump to replace the one that has apparently failed on my engine.
