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My nephews 24 ft htm has a 565 gen v 10-1 motor with edelbrock aluminum victor heads , roller cam, dominator , lightning exhausts, and has been running fine for years. All of a sudden at 5800 rpm it starts to miss a little so he brings it back home and we remove the sparkplugs. # 3 cylinder spit out quite a bit of water when the plug was removed. Turned engine over and more water came out of that hole. Did a leakdown and that hole is 18% leakdown. 1 , 5, and 7 are at 4 % leakdown. Removed intake and gasket is solid stuck with NO evidence or leaking around port. No water in oil. Removed head and it has felpro 1075 mls gaskets. No sign of any leakage around combustion chamber. There are signs of some water spots in cylinder from most likely a getting worse situation to the point of misfire. Cant find any sign of a crack in the cylinder, head . A close inspection of the lightning headers , which are 12 years old, shows no signs of water going thru that header tube. What to do next?
 

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My nephews 24 ft htm has a 565 gen v 10-1 motor with edelbrock aluminum victor heads , roller cam, dominator , lightning exhausts, and has been running fine for years. All of a sudden at 5800 rpm it starts to miss a little so he brings it back home and we remove the sparkplugs. # 3 cylinder spit out quite a bit of water when the plug was removed. Turned engine over and more water came out of that hole. Did a leakdown and that hole is 18% leakdown. 1 , 5, and 7 are at 4 % leakdown. Removed intake and gasket is solid stuck with NO evidence or leaking around port. No water in oil. Removed head and it has felpro 1075 mls gaskets. No sign of any leakage around combustion chamber. There are signs of some water spots in cylinder from most likely a getting worse situation to the point of misfire. Cant find any sign of a crack in the cylinder, head . A close inspection of the lightning headers , which are 12 years old, shows no signs of water going thru that header tube. What to do next?
So was the leak in the intake, exhaust or rings?

If you have the head odd, pour some laquer thinner iso-alcohol in the exhaust port of #3 and see if it leaks out of the exhaust valve.



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Discussion Starter #3
So was the leak in the intake, exhaust or rings?

If you have the head odd, pour some laquer thinner iso-alcohol in the exhaust port of #3 and see if it leaks out of the exhaust valve.
cylinder leakage was going past the rings. Intake and exhaust valves seem good. I filled exhaust with brake cleaner about 1/2 inch deep and nothing was leaking around the valve, nor the intake and the same with the rest of the cylinders.
 

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Valve guides go through water. Sometimes they will seep past the guide. Boats will corrode the guide pretty bad because there is no coolant.
Pressure up the cooling system.
Also the exhaust header should be suspect.
 

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12 year old Lighting headers is where I would look first, probably a small leak at weld joint.
 

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I have heard of Gen V blocks leaking around the head studs, bolts with thread sealant may fix it, but u would signs on the head gasket I would think
 

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Discussion Starter #9
I have heard of Gen V blocks leaking around the head studs, bolts with thread sealant may fix it, but u would signs on the head gasket I would think
Keep in mind, the water is not getting in the oil but in the combustion chamber only. The head bolts go into blind holes where there is no water to seep back.
 

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Keep in mind, the water is not getting in the oil but in the combustion chamber only. The head bolts go into blind holes where there is no water to seep back.
I've seen that happen from exhaust and guides both. Pressure test the exhaust and if OK pressure test the head.

Correction I have seen water get in the chamber from pin holes in the exhaust port also.
 

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I have heard of Gen V blocks leaking around the head studs, bolts with thread sealant may fix it, but u would signs on the head gasket I would think
That only happens to flat bottoms. :p
 

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Had a cylinder wall that would only leak under load. Preasure checked the block in the boat with 60psi. No leak. Came back the next morning and a small rust line had formed in the middle of the cyl. wall. Like Magnaflux. I figure the 8-22psi of water during opperation and the piston swingin' on the major thrust face would open it slightly and ingest water. It (the crack) ran somwhat verticle and peeked just below the bottom ring, so it would make a little milkshake. New block for me. Hope this isnt your prob. because it took me weeks to find it.
 

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Discussion Starter #13
I've seen that happen from exhaust and guides both. Pressure test the exhaust and if OK pressure test the head.

Correction I have seen water get in the chamber from pin holes in the exhaust port also.

Info , you were right about the pinholes. The leak is coming from the water jacket seeping through the pores in the exhaust port on 2 cylinders. Heads are edelbrock victor and i was told today that was a big problem with those castings. why after 12 years do the heads decide to start leaking ???? Its a shame as the heads are show polished and look very nice.
 

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Info , you were right about the pinholes. The leak is coming from the water jacket seeping through the pores in the exhaust port on 2 cylinders. Heads are edelbrock victor and i was told today that was a big problem with those castings. why after 12 years do the heads decide to start leaking ???? Its a shame as the heads are show polished and look very nice.
:D Where is the pat myself on the back smilie?
 

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Had a cylinder wall that would only leak under load. Preasure checked the block in the boat with 60psi. No leak. Came back the next morning and a small rust line had formed in the middle of the cyl. wall. Like Magnaflux. I figure the 8-22psi of water during opperation and the piston swingin' on the major thrust face would open it slightly and ingest water. It (the crack) ran somwhat verticle and peeked just below the bottom ring, so it would make a little milkshake. New block for me. Hope this isnt your prob. because it took me weeks to find it.
Damn...i had that same problem..never had any water in the oil, good compression and leakdown..never dropped a cylinder, never had any water in the cylinder either...

All it did was bend intake valves...4 damn times...Hairline crack in upper cylinder....No problem low rpm/load.......load it up and let it rev i guess it would push super hot air into cooling system and the air pocket would get stuck in the top of the head...intake guide got hot and stick the valve....the last time it pulled the guide out of the head...Gary Kincaid put the guide in the last time..all he said was 'it's been hot"..2 days later i find the crack....Yep, replaced the block...and that's all i replaced...it's been happy ever since...

'Weeks to find it' lol
I might not have spent close to a year finding it..if i had any idea what i was looking for...Local machine shop who replaced the guides several times said it was something i was doing..Smart ass me...asked them what the break in procedure is for valve guides.
 
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