I was on my way to an event this morning and suddenly it sounded like the bottom was falling out my engine. I Pulled over and shut it down. I then tried to restart it but it had locked up. To cut a long story short, back at home I've pulled the head after seeing a build up of molten metal on the plug electrode (!) and to my horror I've found no.1 piston has destroyed itself. Any opinions on why? Faulty piston? Lean mixture on no.1 piston?
<TABLE id=HB_Mail_Container height="100%" cellSpacing=0 cellPadding=0 width="100%" border=0 UNSELECTABLE="on"><TBODY><TR height="100%" width="100%" UNSELECTABLE="on"><TD id=HB_Focus_Element vAlign=top width="100%" background="" height=250 UNSELECTABLE="off">I had a airplane eng do something similiar. one of the mags slipped and went advanced, and the eng was detonating. At full power you could not hear it. </TD></TR><TR UNSELECTABLE="on" hb_tag="1"><TD style="FONT-SIZE: 1pt" height=1 UNSELECTABLE="on"> </TD></TR></TBODY></TABLE>
That baby got hot. I used to do that with my turbocharged 270 GMC but only at WOT on the salt. Could preignition do that?
Some addition info. The pistons are 283 SBC. I noticed when I put them in that they were Mexican specials. I'm sure I've read somewhere that they are prone to inferiour quality? The more I look at it, the more it seems to me that the top of piston has broke away and then got smashed to pieces.
It differently got very hot very quickly because it spat a load of water out which is something it never does. If it was pre-ignition or a case of running lean wouldn't the other pistons be affected especially no.2 because of the siamesed port layout?
Color in #2 looks different from 3 & 4 - #1 header pipe appears to be colored different than 2, 3 & 4. May be cause, may be effect. Hard to see in 2D pictures. What's the mark in #1 cylinder at the top in the area where the piston broke? Did the piston stick there?
Could it have been cross firing from another cylinder like from a carbon track somewhere? I think you would have felt it though.
Headers are an even colour, just the angle of the pic. Engine isn't seised, it still turns over fine. It wouldn't turn over at the side of the road because of all the **** from the broken piston jamming it on TDC. Mark in the bore is a m*** of deep scores and melted piston.
No loss of power at all. Went from running fine to a loud knocking sound in seconds. The point at which a large part of the piston broke away?
Probably got a little bit of water leakage into the combustion chamber. When the engine is hot, the water leaking will vaporize and as it does will erode the piston above the top ring. Once some pieces of piston come off....then the peices get hammered by the valves until you end up like your picture. Could have been a head gasket failure, or a cracked head, cylinder wall, etc... When checking heads for cracks, don't forget to remove the valves and make sure it is not cracked above the valve in the "bowl" area. I had one like that and didn't figure it out until after putting it all back together again.
One cylinder sleeve, one piston and make sure your head isn't cracked or leaking at the head gasket...and you're back in business.
On my 270 the first fix was to plasma spray a cermac coating to the piston top. That worked for a while. Then I stepped up for Arias pistons and that worked real well. A better control of fuel distribution would have been the best answer for my motor.
Please go buy a set of good pistons Everything else looks lovely ....... for a FORD Did you buy fuel at Tesco?
John..... Water would have blown all the carbon away ..... Look at the head I don't think it was water
You'll want to check the valves too to make sure they aren't bent or have had garbage run through the seats. I know on these motors that's probably a longshot, but I've had a mud wasp nest that was built in a SBC cylinder slightly bend a valve when rotating the motor to connect the torque converter to the flywheel - and we were just rotating it by hand!
That's been my experience. The piston looks a little like water erosion but usually that takes place over time and when you pull the head you find little or no carbon and some rust. I haven't seen it happen suddenly although that doesn't mean it's impossible.
I'll have to say detonation. It could have been mild for a while, only affecting that one piston. It was finally enought to make it fail.
Sorry....I thought it was an overhead valve engine...guess the 283 SBC pistons threw me. Disregard my statements about checking under the valve in the head for cracks. I'd still suspect water though. Even though the carbon isn't cleaned off from water...my experiences with similar engine damage has been from a very slight leakage of coolant into the combustion chamber. In my case, twice from cracked cylinder walls and once from a cracked head (SBC has coolant p***ages in the head, not sure about flathead). If the engine had been runing for quite a while, the piston temperature was probably high enough for just a little water entering the combustion chamber to result in instant erosion of the piston top. Then the pieces off the pistons get pounded and cause bigger problems. And yes, don't be surprised the valves are bent or seats nicked up.
Yep, think its time for the forged pistons that should have been in it from the start. HAHA, wasn't Tesco Fuel!
it's detonation. s.b.c. pistons are known for collapsing the top ring land under a detonating load. the collapsed part (especially in a cast piston) can then come off and clobber the works. and it typically only harms one cylinder, because it is the leanest of them all- s.b.c.'s like to claim 1 or 8, pontiacs take out 2 or 7. olsdsmobiles like to hurt 6, and so on. once it's back together, take a reeeal good look at your distributor. the problem started there- and don't be surprised if the tops of the rod bearings (all 4) have had the **** kicked out of them.
I finding it hard to believe that detonation is to blame. I'm running very little compression (7:1), 95-100 RON fuel, there's no hot spots in the combustion chambers, the plugs are the correct heat range and the fueling has always been excellent. I've never once heard or felt anything that even remotely resembles detonation both on the road or racing.
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