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Hole in piston

buick430

Regular Contributor
Hey guys I took my boat out for a power trial today and blew a hole in the #2 piston on the port side. Cause is unknown all other on that bank look fine. I was wondering if you guys could recommend an engine shop in the southern california region. I suspect rhis was an ongoing problem as this engine always had a low Compression cylinder (I was hoping it was a rusted valve).

Any input as to my next moves are appreciated.

Will

1,586 hours by the way
 
Hey guys thanks for the replies. The engine ran great otherwise awesome oil pressure and all other cyliners look good and had 120-130 compression. Im leaning toward buying a rebuild it and throwing it together.

The fuel was really old but dilluted 50/50 with new. Other cylinders looked fine, no indications of a lean mix. I dill check the advance on the distributor or take it to a shop.
 
Too,hot of plug burns a hole in the piston.You just don't burn one.I'm sure you have more in line following as well.High Energy Ignition (HEI) distributor's are known for causing this as well.California region,I'm sure money's no object.Open the yellow pages and pick one.More money the better work.You get what you pay for.You'll be better off buying a New Short block in the long run.Less Money,Time & Man hours with a new short block.Plus,you will know what your getting as well a new block.Your engine must be pulled anyway,may as well drop a new short block in it and be done with it.
The money & time your'll be spending rebuilding that block.Cheaper in the long run with a engine warranty.
Let's face it,
What's the condition of the valves now?If you burned a hole in the piston.Just think about the condition the valves must be.Right now we know you'll need a head job done.Did it get so hot to burn a hole in the piston and put a fine hair crack between the valves to crack the head.Maybe,who knows.
I'm sure the engine was ran while the hole was in the piston,causing metal shavings in the oil pan to the main bearings to oil pump screen as well.
Don't bother wasting your time & money rebuilding the block.Just buy a short block.
 
The plugs are what the factory call for. but that was a thought of mine also. Surprisingly the valves look okay. I will poor some solvent down the runners and see if they leak. While money is no object to some in southern California it s to me, Im only an E-4! thanks again. Still looking around will know more tomorrow after I call some places.
 
Hey guys thanks for the replies. The engine ran great otherwise awesome oil pressure and all other cyliners look good and had 120-130 compression. Im leaning toward buying a rebuild it and throwing it together.

The fuel was really old but dilluted 50/50 with new. Other cylinders looked fine, no indications of a lean mix. I dill check the advance on the distributor or take it to a shop.

If the fuel is old and the ethanol has separated out, adding new fuel to it does not do anything. You need to drain the fuel tank and put in fresh gas or you will burn a hole in a piston in your new engine.........Guaranteed.
 
I agree with the suggestions of old degraded fuel, and possible ignition advance issues. Either may cause detonation damage.
The somewhat surprising thing to me is..... that you damaged only one piston.

Ditto having the distributor tested, or better yet, replace it with new, and go with electronic triggering.


.
 
weather it was the old fuel (7 years) or a bad advance curve I still dont understand that it damaged only one piston. I found a great deal locally on a low hours so I am gonna go that route.

Now I need to figure out how to get rid of 70 gallons of fuel!
Test/replace the distributor.
Turn boat in slip then remove and install the engines.

thanks again guys,

will
 
weather it was the old fuel (7 years) or a bad advance curve I still dont understand that it damaged only one piston. I found a great deal locally on a low hours so I am gonna go that route.

Now I need to figure out how to get rid of 70 gallons of fuel!
Test/replace the distributor.
Turn boat in slip then remove and install the engines.

thanks again guys,

will

Ayuh,.... No Doubt it was Bad gas,.... Detonation from lean conditions does that,....

1 side of the carb is probably boogered up worst than the other,..?.
That spark plug was indexed, just the right way,..?.
That cylinder had more, or maybe less carbon build up,..?.

I'd be doin' a Full system clean out, startin' at the tank, goin' to the carb.....

Seven(7) year old gas,..??..?? What were ya Thinkin',..?? did ya do a Smell test,..??
 
weather it was the old fuel (7 years) or a bad advance curve I still dont understand that it damaged only one piston. I found a great deal locally on a low hours so I am gonna go that route.

Now I need to figure out how to get rid of 70 gallons of fuel!
Test/replace the distributor.
Turn boat in slip then remove and install the engines.

thanks again guys,

will
All of Bondo said,

And the fact that there is always one cylinder that runs more lean then the rest. I have removed and replaced at least 5 engines in the last two years that had one burned piston with no damage to the rest. All from bad fuel.
 
Oh and the carbs are fresh rebuilds. Honestly I was being cheap and lazy by trying to run the old gas. It did smell quite bad.
 
Here is a Freshly rebuilt engine from a good builder. I installed the engine and ran it on a remote tank. I advised the boat owner to have his tank pumped out because of the fuel being 2-3 years old. Someone told him to add some fresh gas and all would be fine. So he did. This was the result. This engine did not make the ten hour mark.

You can ask around until you get the opinion that you want to hear.

In the end it will cost you. Just like this boat owner, Warranty Was Void. Just to save 70 gallons of fuel.

Photo223.jpg
 
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+1 on the old fuel, when I bought my boat it had 300 gallons of year old fuel and you could hear the engines ping at high power so I just limited the rpm to about 2000 rpm until I had used it up.

Dan
 
+1 on the old fuel, when I bought my boat it had 300 gallons of year old fuel and you could hear the engines ping at high power so I just limited the rpm to about 2000 rpm until I had used it up.

Dan

Running your engine at 2000 rpms puts more strain on it than running it WOT. The only place old fuel should go is to the recyclers.
 
...."Running your engine at 2000 rpms puts more strain on it than running it WOT"

Only if it's lugging at low speed. Obviously, your car/ truck motor will last longer cruising at 60 mph than flat out at 100!

Jeff
 
...."Running your engine at 2000 rpms puts more strain on it than running it WOT"

Only if it's lugging at low speed. Obviously, your car/ truck motor will last longer cruising at 60 mph than flat out at 100!

Jeff

Most old carbed boats are lugging between 2000 and 2500 RPMs. Under jetted for ethanol fuel.
 
Chris makes a really good point, for all of the OBs I mess with need their idle mixture screws opened a bit to again idle properly.

I had to rejet one of the Edelbrocks on my boat when the plugs came out a bit too white for me (though that's what tends to happen with ethanol). My late buddy's drag car's plugs were stark white after a run on pure methanol. It takes an expert to read such plugs (which is what he was).

Jeff
 
FYI for all the inboard and I/O owners. With ethanol fuel I adjust the prop size so most engines will approach 5000 rpm at wot. Any engine that is spec-ed to run between 4600 and 4800 @ WOT

Yes, a couple of hundred more RPMs at cruise speed but no damage from Ethanol fuel.
 
Here is a Freshly rebuilt engine from a good builder. I installed the engine and ran it on a remote tank. I advised the boat owner to have his tank pumped out because of the fuel being 2-3 years old. Someone told him to add some fresh gas and all would be fine. So he did. This was the result. This engine did not make the ten hour mark.

You can ask around until you get the opinion that you want to hear.

In the end it will cost you. Just like this boat owner, Warranty Was Void. Just to save 70 gallons of fuel.

View attachment 5200
Chris, if I may...... I'll assume that this is a SBC. Part of the problem with detonation is this piston design.
The full dished piston (with the SBC cylinder head chamber design) gives the gasses a place to hide from the flame front, and the results are often detonation when/if the ignition advance is too agressive.
Good fuel/bad fuel, it sometimes makes little difference.

No real point here, other than to point out this poor piston design.


[B said:
tolly_family][/B] +1 on the old fuel, when I bought my boat it had 300 gallons of year old fuel and you could hear the engines ping at high power so I just limited the rpm to about 2000 rpm until I had used it up.
Dan
Running your engine at 2000 rpms puts more strain on it than running it WOT. The only place old fuel should go is to the recyclers.
Dan, I have to agree with Chris on this.............. 2k rpm is not a good rpm to sustain, IMO.
Most of our hulls are not yet on step at/near this rpm range, which means that detonation potential is greater at/near this rpm.
Plus, at this RPM, you're probably burning excessive fuel for the distance traveled.

.
 
Running your engine at 2000 rpms puts more strain on it than running it WOT. The only place old fuel should go is to the recyclers.

I wasn't saying that 2000 rpm was a good cruising speed it was just a safe rpm where the engines wouldn't ping and I could use up the old fuel, that was 10 years ago.

Now that fuel is so expensive I make my long distance cruises at 1700 rpm and 8 knots, this gives me almost 2 mpg compared to 1/2 mpg at 16 knots and 3000 rpm..

Dan
 
Hey guys, Thanks for all the replies. I Have the block out of the boat and sitting at a machine shop. He said the heads/valves are in great shape. They already have hardened exhaust seats and have ben rebuilt recently. Upon disassembly he noted the crown of the #2 piston is irregularly worn (plus the whole). The cam checked fine along with the mains and rods. He could not come up with a good explanation for the damage to this piston alone, other than bad gas, vacuum leak on that port(ruled out with propane before disassembly) or lots of carbon. Either way a Master rebuild kit is on the way.
Hopefully I have it running soon.
thanks again, will
 
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