engine knock

just came from there...
bitter...
First pulled the exhaust manifold complete
found rust on exhaust ports on #2 and #3 cylinder, so I undo de riser, and looks like the gasket was bad and leaked water into those cylinders after shut off. I will test anyway to see if I have a cracked water jacket in the manifold.
Then removed the valve cover and all plugs and turned the engine. Valves close fine.
Removed the Cylinder head...geez, found the problem..blown head gasket between #2 and #3. Strange as compression on 3 was fine.
Little scuff on cylinder 3. Looks like at some point overheated @ wot (didn´t notice it) and voila failure.
I´m taking the head to the machine shop to test for cracks and see the valve and seats on 2 and 3 cylinders.

kapla wrote: now why the knock? the blown gasket? or piston slap?

I was just going to ask that. Curious as to why there would be a knock unless the cylinder was filled with water or something.

Could you put a large breaker bar/ratchet on the crankshaft pulley and give it a couple of turns and see if you see any erratic movement? Just don't loose track of piston timing/location.

Or maybe with the starter? Be sure to disconnect/pinch off fuel going to the fuel pump.

Curious to know what brand head gaskets did you use? Marine?

Did you have the knock after changing the bad plug?

Kap, you just may have caught it in time, dodged a bullet. I hope it's back up and running soon.

Don't put it back together without checking those rods

Granted I have not personally heard the "knock" but other than a valve witness mark or something on the piston to explain it I am leaning toward your water in the cylinder trying to be compressed by the piston pushing water through the head gasket and bending the rod, or head gastet leaking first but either way a bent rod Causing the knock. Or a hot piston sticking could also bend a rod.   Other than the labor pullin it apart there isn much reason not to at least check the rods

unless you want to do it twice...........funny, you always find the time to pull it apart a second time,
make sure that not only they check for cracks but they check it for flatness, check the deck too...not to often does a head gasket go, without a reason, could be as simple as stretched, weak bolts, just cover your bases...I know how some mechanics can be....the famous cliche "it will be fine" which translates too, "on your dime"

making "head"way

no progress yet, yesterday I removed the other manifold to have the surface planed like the other, It came right off, only thing I busted a couple of knuckles in the process...


I was looking at the gaskets I have at home to compare them to the ones I removed from the engine, they are all felpro, but they are different. This in the picture, the one from the intake manifold: the one on top was intalled and the one on the bottom is the one i will use to reassemble. Other than the larger middle hole for the acc? they are quite the same. Is this OK?

well ow you guys some update..

sent the head to the machine shop, and checked fine, had it resurface and cleaned.
also had both manifold planed, all surfaces including the exhaust ports.
finally I did not remove the engine, I turned the engine by hand and compared that all pistons would get to the max heigth, they all did.
last week we put the head with new gasket and put the intake manifold.
Today I went and finished intalling the rest of the things, valve covers, exhaust manifolds, new plugs, etc...
fired right out, and went for a test ride....
relief no engine knock, at all, tried a couple of take off and nothing, look likr the engine is ok. Got to cruise a little hit the 3000rpm mark with no problem.
anyway I need to do some tunning as i have a minimal bog upon take off, then it catches. Need to check timing or do some carb adjustment.
I removed the plugs to check for water intrusion and nothing. Oil is clean, temp is fine.
seems i need to give some more running time as all plugs came clean.

Great!

I'm glad to got it Seb.

now seems like 1 1/2 month sleep, screwed up the battery....
or the timing needs to be set...
on cold starts engine turns over fine, after the test drive when the engine was at running temperature, if I tryed ro restart it would crank slowly, then eventually start, but on a 3rd or or more restart it would crank very slowly. As I didn´t had the tester yestrday I could not see the volts.
Today I went with the tester to take some numbers. Started with no problem, the alternator read around 14-15 volts, with peaks of 16. On the battery it read 12.06 volts...The conections at the battery were little rusty so I disconected and cleaned.
Went for a ride again, 15 minutes. And went back to the marina. T was always between 140 and 160 degrees, probably low due to cold water...
shut the engine, and again it cranks very slowly, it would not even start.
let it cool some minutes and is starts, but on a restart is turns slowly...
So either I have to much advance, or the battery needs some more time to get a full charge? Prior to the engine incident I had no problems...
BTW engine runs smooth.

Gary
winter is cold but not as cold as yours, so I use the boat anyway. I prefer footing on winter cause less boats around, only hassle is the drysuit entry!