might not make river run |
Post Reply | Page 123 4> |
Author | |
lakedog55
Gold Member Joined: November-11-2010 Location: Lake Weir Fl Status: Offline Points: 835 |
Post Options
Thanks(0)
Posted: February-26-2014 at 6:55pm |
did not expect this. boat was running pretty good, changed props and saw a drop off in performance, might not be prop. and ever now and then a slight valve noise
|
|
Lakedog55
|
|
TX Foilhead
Grand Poobah Joined: February-01-2009 Location: Kingsland TX Status: Offline Points: 2076 |
Post Options
Thanks(0)
|
You're in Fl, of course you'll make it you might have your boat with you though.
|
|
Smithfamily
Platinum Member Joined: December-26-2007 Location: Orlando, Fl Status: Offline Points: 1602 |
Post Options
Thanks(0)
|
DITTO! From Lake Weir, you could walk!! |
|
Js
|
|
Smithfamily
Platinum Member Joined: December-26-2007 Location: Orlando, Fl Status: Offline Points: 1602 |
Post Options
Thanks(0)
|
And, if you drag the boat, I will bet you would get a free and accurate diagnosis!!
|
|
Js
|
|
lakedog55
Gold Member Joined: November-11-2010 Location: Lake Weir Fl Status: Offline Points: 835 |
Post Options
Thanks(0)
|
Yeah it ain't far. Could drag the float boat over. But it ain't the same. not sure but I would say that cylinder is done. Already 20 over . Be real lucky if it could be squared or rounded back up and then be running 40 overs?
What's the old saying boat |
|
Lakedog55
|
|
MrMcD
Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3610 |
Post Options
Thanks(0)
|
Is the cylinder rusted? Hard to tell in the picture.
|
|
lakedog55
Gold Member Joined: November-11-2010 Location: Lake Weir Fl Status: Offline Points: 835 |
Post Options
Thanks(0)
|
Rust came after. The missing portion of the piston is what really troubles me.
|
|
Lakedog55
|
|
JoeinNY
Grand Poobah Joined: October-19-2005 Location: United States Status: Offline Points: 5697 |
Post Options
Thanks(0)
|
Changing a prop will do that to you every now and then. In particular if you put on a steeper prop, just conjecture mind you as to the actual cause. Cruddy gas will do the same, but it happens with the prop as well.
More load with the same timing advance can cause detonation, which heats and beats the piston, first cracking, then eventually losing the piece… hopefully through the valve and out he exhaust manifold fairly easily. My last piston chunk actually left cylinder one, did a bit of damage there but made it through the exhaust manifold to cylinder 4 where it did its real damage. If I were you I would expect to pop in a whole new set of pistons, cause if one saw enough abuse to let go the others are likely showing signs of being too hot for too long as well. The question is did you also bend a rod or more due to the chunk of metal being where only air/fuel mixture should be. Plenty of time between now and the sjrr if you had all the pieces ready by then we can put that thing back together at the boat show and be skiing by the second day. |
|
backfoot100
Platinum Member Joined: January-03-2007 Location: United States Status: Offline Points: 1897 |
Post Options
Thanks(0)
|
That sucks Mike.
Looks like the broken jug has a half moon divit in it like a valve head but the pic is small and might be deceiving. It doesn't look like it ran lean. More like something broke. You figure out what yet? |
|
When people run down to the lake to see what's making that noise, you've succeeded.
Eddie |
|
JoeinNY
Grand Poobah Joined: October-19-2005 Location: United States Status: Offline Points: 5697 |
Post Options
Thanks(0)
|
Eddie, I could be wrong but I think that crescent is the factory valve relief in the piston. The carbon buildup is not a good indication that it didn’t run lean or see detonation, what would be pretty telling typically is discoloration or oil gumming on the bottom side of the pistons. Anything amiss on the bottom side in my experience would indicate that they are pretty much all junk. One of my rebuilds was the result of thinking I could reuse pistons that had seen some heat after replacing only the one with an issue. I did get almost another season out of them… before saving the 550 on a new set cost me 2400 bucks in replacement pistons, rods, head welding, valve replacement, balancing, etc etc… |
|
lakedog55
Gold Member Joined: November-11-2010 Location: Lake Weir Fl Status: Offline Points: 835 |
Post Options
Thanks(0)
|
Don't see any damage. Going to try and get a hold of machine shop and go ahead with the bottom end d If the cylinder is not to egged. A little worried with already being 20 over. Joe thanks for the hand. I have all the top end stuff. Really thought the bottom was great. It was supposed to have 300 hrs on it. The timing chain says different more like 2000.
|
|
Lakedog55
|
|
JoeinNY
Grand Poobah Joined: October-19-2005 Location: United States Status: Offline Points: 5697 |
Post Options
Thanks(0)
|
You can bust up a piston pretty quick by being a little aggressive on the tuning, the piston material is softer than the wall so scoring is not usually an issue with this type of failure unless you get a piece of ring jammed in the wrong way. Last time I had mine cleaned up by .005 just to give a fresh hone while it was apart as it was already 30 over. I would start tearing it apart - demo is the easy part and it will tell you what parts you might want to consider sourcing sooner than later.
|
|
lakedog55
Gold Member Joined: November-11-2010 Location: Lake Weir Fl Status: Offline Points: 835 |
Post Options
Thanks(0)
|
Got the block all stripped. Going to have cylinder tested. If all goes well I will get it bored decked, and fluxes. New bearings, pistons, and crank for like 650. No cam or timing set.
|
|
Lakedog55
|
|
lewy2001
Grand Poobah Joined: March-19-2008 Location: NSW Australia Status: Offline Points: 2234 |
Post Options
Thanks(0)
|
A larger picture of the piston would help diagnose possible cause.
Is there signs of erosion or pitting on that piston crown? Have a good look at the the old piston's skirt area for any signs of scuffing and the associated heat buildup. |
|
If you're going through hell, keep going
89 Ski <a href="http://www.correctcraftfan.com/diaries/details.asp?ID=5685" ta |
|
TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21136 |
Post Options
Thanks(0)
|
Be sure to put a new timing set in that thing when it comes time to reassemble. $40 for a quality double roller is money well spent.
|
|
MrMcD
Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3610 |
Post Options
Thanks(0)
|
That piston shows classic detonation failure. If you had that kind of detonation it was pounding pretty hard in the cylinder. The piston was the first fuse to fail, the head gasket would have been next. Marine head gaskets are pretty tough.
The cause could be 1. over advanced timing for the fuel grade. 2. Lean burn in that one cylinder, normally caused by a intake leak. 3. The Ford is susceptible to mis fire from plug wires cross firing. Use quality plug wires and route them carefully to avoid this. Detonation is when your fuel charge is fired off early, the piston is moving up the cylinder and the early explosion of the fuel charge tries to blow that piston back down while 7 other pistons are trying to push it up. Normal cylinder pressure at wide open throttle might hit 600 PSI in this stock engine, with detonation going on the cylinder pressure will jump to 3,500 to 5,500 PSI and the weak link will break. In this case your piston fractured. Your other 7 pistons may be perfect depending on the cause of your detonation. Over advanced timing will heat the cylinder beyond normal and hot spots will start glowing red, these hot spots will start acting like a spark plug and ignite your fuel charge early, sometimes this happens just before the spark plug ignites, in this case once the spark plug ignites it sets off a second explosion, if these two flame fronts collide it forms a spinning flame front that will burn smooth holes right through the piston and sometimes right between cylinders in the block. A lean burn will do the same thing, lean fuel charge burns much hotter than a rich fuel charge and the same parts heat up till you start getting detonation from hot spots igniting the fuel. Lean burn could be unique to one cylinder or common to all cylinders. Look at the underside of the pistons once removed from the block, if oil is burned black to the bottom of the piston head they have been very hot, if it is gold in color they were hot but not for very long. Cross fire of spark plugs should show in the plug wires, look for small halo shaped white circles on the plug wires where they touch in your routing. If you see halo's you had mis fires. Keep us posted on what you determine. Good Luck |
|
lakedog55
Gold Member Joined: November-11-2010 Location: Lake Weir Fl Status: Offline Points: 835 |
Post Options
Thanks(0)
|
Thanks guys, on a good note heads are done. CC came out pretty good. Ended up between 57.4 and 57.6 .now for to stir it up. I am blaming it on ethanol.
|
|
Lakedog55
|
|
TX Foilhead
Grand Poobah Joined: February-01-2009 Location: Kingsland TX Status: Offline Points: 2076 |
Post Options
Thanks(0)
|
OK, need to get up to speed on who's doing what here, I'm guessing this are some GT40p's and they might have been milled down just a bit. Did this happen while you were running it? I'm really curious to find out if it knocked enough to do that why it was noticeable. I know things can go sideways quick at WOT, but most people don't see that in tow boats that often. I would guess the majority of the time is spent between 2500 and 3500 RPM's and I would think that would make a noticeable sound for a while before it got to that point.
Working on a project to be unveiled shortly so the cause of this is very intresting. |
|
lakedog55
Gold Member Joined: November-11-2010 Location: Lake Weir Fl Status: Offline Points: 835 |
Post Options
Thanks(0)
|
Actually I was running stock. Never heard any noise of any kind. Started to notice a little valve tap and changed props. Drop off in performance and a slight rough idle. Other than that ran decent. Few times I footed had a speed problem but I blamed that on driver. I guess I owe my wife an apology.
now that the heads are done I have read that the stock springs on the gt40p head suck. So I am worried about that. |
|
Lakedog55
|
|
TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21136 |
Post Options
Thanks(0)
|
When approaching or exceeding the .500 lift range, a spring upgrade warrants strong consideration. If you're going with the standard Cam Research .460 grind, I wouldn't stress too much with the stock springs.
|
|
lakedog55
Gold Member Joined: November-11-2010 Location: Lake Weir Fl Status: Offline Points: 835 |
Post Options
Thanks(0)
|
Benj,
thanks I was starting to pace around the house. I am for real. I can go to bed now. no takers on the ethanol debate. |
|
Lakedog55
|
|
lakedog55
Gold Member Joined: November-11-2010 Location: Lake Weir Fl Status: Offline Points: 835 |
Post Options
Thanks(0)
|
With .40 pistons what will that do to performance?
Bigger sometimes does not make it better. Seems like it will need a bigger shot of fuel. To get the same explosion pressure. |
|
Lakedog55
|
|
TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21136 |
Post Options
Thanks(0)
|
Ethanol wouldn't have been a factor. E10 is all we've been able to get here in the northeast for quite some time.
|
|
lakedog55
Gold Member Joined: November-11-2010 Location: Lake Weir Fl Status: Offline Points: 835 |
Post Options
Thanks(0)
|
Shoot it doesn't hardly ever see ethanol gas anyway. Little store by lake put in a new pump and carries ethanol free. Just trying to rattle up Some of the frozen bones up north
|
|
Lakedog55
|
|
TX Foilhead
Grand Poobah Joined: February-01-2009 Location: Kingsland TX Status: Offline Points: 2076 |
Post Options
Thanks(0)
|
Octane is octane, what chemicals they use to hit the number doesn't matter. Adding ethanol does tend to make that number drop quicker as the fuel ages, just one of the benifits from burning our food. From what I've seen the corner pistons (1,4,5,8) tend to run leaner than the center ones and I believe 1 and 8 are the leanest with a dual plane intake. The carb shouldn't need much if any tuning, the extra air flowing through it will pull exta fuel with a moderate upgrade. If these motors were pulling all they could out of the carb then you might get the lean condition, but I don't believe that is the case with the standard HCI upgrade.
Are you the only one that foots? I'm not sure my wife would recognize knock and know its bad, she would probably say something sounded different when I got back in the boat. The stock springs are probably fine, I got a set with stock springs and upgraded them, but I did measure them as I was taking things apart and they would have worked although they would have worked they didn't have much left. I got a fairly cheap set from someone named Alex on the Corral site, about $100 with shims and I think they're good to .550 lift. Again, thanks for the info, I really want a 409 but I would prefer not to be forced to do it because something I did burned up the motor. Much better to have it happen when I want to do it. |
|
MrMcD
Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3610 |
Post Options
Thanks(0)
|
Mild detonation will start sounding like pinging or minor fast rattle inside the engine. Major detonation is usually silent but the engine will feel like you let off the gas even though you are still at wide open. The cause of power loss is the early detonation trying to blow the piston back the wrong way causing the massive increase in cylinder pressure that broke your piston and the big loss of horsepower. If you only broke one piston you probably only had detonation in the one cylinder. Let someone familiar with detonation look at your head gaskets, spark plugs and pistons, they will all record signs of detonation if you know what to look at. You might also find fractured top piston rings in the cylinder that detonated. Going to .040 over will not hurt at all but rebuilder pistons are destroked and will be an additional .020 down in the hole. If you buy performance pistons they will be at full deck height. The factory stock PCM marine engine has been tweaked to avoid detonation so you might want to look at your tune up and parts and find out what caused it before starting the new engine.
Many times I have seen a new engine grenade with the exact same symptoms as the original engine only to find the guy had assembled with the same bad plug wires, distributor or plugged injector that caused the first failure. The poor owner is left holding a second failed engine after spending a ton of money on parts. Find the cause then move forward with your new engine. I called on the major engine builders covering the North West for nearly 20 years up till 2004 so my information is dated but most engine failures can be tracked down to a cause. |
|
lakedog55
Gold Member Joined: November-11-2010 Location: Lake Weir Fl Status: Offline Points: 835 |
Post Options
Thanks(0)
|
Mr Mac,
thanks a ton. I did notice a noise that i thought was a valve tapping mid way through the summer. The motor had been rebuilt before i got it. It had also sat for at least 3 years. I did find a piece of ring in pan. motor is appart but i need to do a better inspection on the other pistons. I am not ruling out early detonation. As many times as i played with timing. Motor seemed to be a touch out of balance. Or in other words not quite perfect. My plan was to rebuild top end this winter. New wires, distributor, carb, intake, cam and heads. Now it will get all of those and the bottom as well. The pistons that were in it all had the arrows pointing to the front. Some where I read they were supposed to be indexed to the back. Who knows the re builder could have broke a ring putting it back. once again thanks. I agree that i do not want to do this thing twice. |
|
Lakedog55
|
|
JPASS
Grand Poobah Joined: June-17-2013 Location: Orlando Status: Offline Points: 2283 |
Post Options
Thanks(0)
|
I know they make air/fuel ratio monitors for cars. Do they make anything like that for boats? Seems like it would be a great way to monitor a lean condition before doing any damage.
|
|
'92 Correctcraft Ski Nautique
|
|
TX Foilhead
Grand Poobah Joined: February-01-2009 Location: Kingsland TX Status: Offline Points: 2076 |
Post Options
Thanks(0)
|
They're available, but they're pretty sensitive to water so the best use is to set things up and then take them out. The bad thing is, especially with a carb, the cylinders aren't all equal so the reading is an average.
|
|
lakedog55
Gold Member Joined: November-11-2010 Location: Lake Weir Fl Status: Offline Points: 835 |
Post Options
Thanks(0)
|
should have better pics of pistons soon. but here is one of the redone heads
|
|
Lakedog55
|
|
Post Reply | Page 123 4> |
Tweet
|
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |