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A friend of mine has a Marinepower Chevy 350 that blew a head gasket and ruined the block as it cut a passage between two cylinders. I had the sane thing happen with my Marinepower 350, twice. The engines were mildly built, about 320 HP and had the graphite / steel head gaskets. All three lasted about 3-4 years before this happened. Neither of these boats have gate valves. The engines turn at about 4,400 rpms max. I suspected a carb issue with float levels and or jetting issues and or overly advanced timing. He thinks that it is a water pressure issue. Both boats have open cooling systems and are run on rivers and lakes, no salt. Any thoughts? Below are photos. I ran mine for many hours Because I knew it was toast and needed it for a few bass tournaments, so the cracked pistons are probably happened afterwards and are not useful autopsy data.
 

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All your water passage holes in the head gaskets look to be just fine in the photo's.... That could be junk gaskets, bad tune up, poor fuel, etc.... The tune up could have been off from the start and just over time the gasket was taking a beating and one day it finally has had enough and comes apart.
 

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ahhhh, the ol fire notch. I've done that before. My situation was a result of the combination of running wide open on low fuel, clogged filter and hard turns. Basically leaned it out. I don't theink water had anything to do with the fire notching in your case. The water passages aren't anywhere near that area. The gasket was lost as a result of heat. The notching is a result of heat exchange between the two cylinders once the gasket was gone.
 

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I've redone a few 5.7's with those type headgaskets that did the same thing in the same place, but luckily none had notched the block or head. Oh, I've had a few of these motors come in with same issue but customers admitted overheating.I checked for deck/head flatness, installed felpro marine headgaskets, arp head bolts, and then tuned the boats on the water. Quazillion hrs later they are still running fine.

Cheap parts and probable out of tune engine and wallah. Burn......
 

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Rivernut, besides like CFM said, cheap dollar basement gasket that was never intended to use on a boat, you have other major problem that led to this. Look at the same spot between the other cylinder, on the block pic, not the gasket pic.
And that piston DID NOT get like that because of the gasket. It was caused by what blew the gasket. It just happened to blow thru those 2 cylinders, before then other side.

It blew out there first, as opposed to the other side of the bore because that side runs even hottet due to 2 side by side exhaust valves/ports. Not uncommon for a SBC.

But you still suffering from


DETONATION!!!!



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Discussion Starter #6
I installed Felpro MLS head gaskets on my current engine and put a more tunable Marine Demon carb on it and spent a lot of time jetting and plug reading. Total timing is 32, and I always run 93 Octane. At what threshold of RPM's or horsepower do gate valves become necessary?
 

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Complete fix

I've redone a few 5.7's with those type headgaskets that did the same thing in the same place, but luckily none had notched the block or head. Oh, I've had a few of these motors come in with same issue but customers admitted overheating.I checked for deck/head flatness, installed felpro marine headgaskets, arp head bolts, and then tuned the boats on the water. Quazillion hrs later they are still running fine.

Cheap parts and probable out of tune engine and wallah. Burn......
These is a reason cheap gaskets are cheap. Take the above statement to heart, spend the extra money and do a complete fix. I have seen far too many repeat failures because someone refused to admit the fasteners were worn out. Heat destroys flat surfaces, but it also destroys fasteners. Never re use head bolts that have been stressed by excessive heat.... AND NEVER over torque for that "extra clamping force"......
Ray

PS I have a freshly bored 350 4 bolt block for sale......
 

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.......... and put a more tunable Marine Demon carb on it and spent a lot of time jetting and plug reading.
Ahhh. I'm guessing from that statement those marine power engines are the one's that come complete with intake manifold, and Holley 600 that has rear metering plates (no replaceable sec jets) vs metering blocks.

Think I've heard others talk about many hrs of tuning these engine/carb combo's. Going off of memory so maybe wrong.
 
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