340 Hydraulic lock inspection update...

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moparodbuster

moparodbuster

moparodbuster
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I need some seriously good advice. My 340 12.6:1 pro streeter was running fine for days and days after overheating but after not running for about 5 weeks I went to start it and it ran really rough like it had a fuel issue. When I finally did get it to fire it ran like it was on 5 cylinders and really rough. I thought it might be old fuel or a stuck jet so I tried to clean it out by giving it some revs but it wouldn't idle and eventually died. When I tried to crank it over again it turned over a few times without firing then did not want to turn over at all and I felt a solid resistance in the block when turning the key. I haven't taken the spark plugs out yet but I'm thinking I've got hydraulic lock from a leaking head gasket into the cylinders. Any advice on what to look for what to watch out for and how to identify what size head gasket to get would be helpful all I know from the previous owner is that it's a 30 over 340 from a '71 Cuda with x Heads.
I work away and only home 1 day a week. have to pay a mobile mechanic by the hr to come do it while I'm away so I need to educate myself as much as possible to make sure I'm directing him to do everything right. He's not a mopar guy just a heavy equipment mechanic. So I'm basically paying him to be my hands and eyes.
Soooo... I'm guessing pull plugs, tap starter and look for water coming out of cylinders and see if she turns over, if I see water, mark that cylinder and then pull heads and look at gaskets, cylinder walls and check piston heights for possible bent rods then put straight edge on heads to check for warp... am I right? Am I missing something?
 
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pull the oil drainplug, water will come out first. do a cranking compression test, it will reveal bad head gasket and info on compression. a good head gasket is the felpro 1008 HP
 
If you hit water, you need a complete and thorough engine tear down and analysis. taking some measurements is good and all, but even if they check out ok, you don’t have a baseline, so you need to tear down anyways.
 
I would pull the plugs and turn it over by hand then hit the starter. It will make a mess blowing it out of the plug hole. Then run compression test. Then pull the heads off.
 
furrystump said:
I would pull the plugs and turn it over by hand then hit the starter. It will make a mess blowing it out of the plug hole. Then run compression test. Then pull the heads off.
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Okay that sounds logical. But why compresion test ea cylinder? What is the compression test going to tell me... if there's water, I know it means gasket replacement.
 
Marcohotrod said:
pull the oil drainplug, water will come out first. do a cranking compression test, it will reveal bad head gasket and info on compression. a good head gasket is the felpro 1008 HP
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By 'oil drain plug', I'm assuming you mean the sump plug? If there's no water in the oil, does it mean the water might all be contained in the cylinders?
 
I think a compression test will tell whether there's something wrong with your engine... but not indicate WHAT is wrong. Can be many things... head gasket, bent rods, valves not sealing, rings not sealing (a lot threads here lately :)).
 
You have to be vigilant with a compression test and coolant leakage. You cannot get all the water out due to the angle of the plug. so remaining water will increase the compression, and give you a false reading. A leak down, especially in the case of a coolant leak, would be better
 
Was thinking compression testing would show bent rod, but with heads off you can just use deck bridge and dial indicator.
 
Pull the plugs first, then turn by hand. I have seen an engine hydrolock from fuel so be careful.
 
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67Dart273 said:
You have to be vigilant with a compression test and coolant leakage. You cannot get all the water out due to the angle of the plug. so remaining water will increase the compression, and give you a false reading. A leak down, especially in the case of a coolant leak, would be better
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Okay, so either compression or leak down would be done before pulling heads so should I remove plugs, try to turn over by hand, if it turns over by hand, crank starter to get as much water out as possible then spray air with my compressor into the plug holes to get as much remaining water out then do leak down first then compression test?
 
moparodbuster said:
Okay, so either compression or leak down would be done before pulling heads so should I remove plugs, try to turn over by hand, if it turns over by hand, crank starter to get as much water out as possible then spray air with my compressor into the plug holes to get as much remaining water out then do leak down first then compression test?
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moparodbuster said:
I need some seriously good advice. My 340 12.6:1 pro streeter was running fine for days and days after overheating but after not running for about 5 weeks I went to start it and it ran really rough like it had a fuel issue. When I finally did get it to fire it ran like it was on 5 cylinders and really rough. I thought it might be old fuel or a stuck jet so I tried to clean it out by giving it some revs but it wouldn't idle and eventually died. When I tried to crank it over again it turned over a few times without firing then did not want to turn over at all and I felt a solid resistance in the block when turning the key. I haven't taken the spark plugs out yet but I'm thinking I've got hydraulic lock from a leaking head gasket into the cylinders. Any advice on what to look for what to watch out for and how to identify what size head gasket to get would be helpful all I know from the previous owner is that it's a 30 over 340 from a '71 Cuda with x Heads.
I work away and only home 1 day a week. have to pay a mobile mechanic by the hr to come do it while I'm away so I need to educate myself as much as possible to make sure I'm directing him to do everything right. He's not a mopar guy just a heavy equipment mechanic. So I'm basically paying him to be my hands and eyes.
Soooo... I'm guessing pull plugs, tap starter and look for water coming out of cylinders and see if she turns over, if I see water, mark that cylinder and then pull heads and look at gaskets, cylinder walls and check piston heights for possible bent rods then put straight edge on heads to check for warp... am I right? Am I missing something?
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Sure you ain't got a rats nest in the exhaust plugging it up?
Had it happen. Only found it after replacing everything!!!! Except the exhaust.
 
moparodbuster said:
Okay, so either compression or leak down would be done before pulling heads so should I remove plugs, try to turn over by hand, if it turns over by hand, crank starter to get as much water out as possible then spray air with my compressor into the plug holes to get as much remaining water out then do leak down first then compression test?
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That is a good idea. What I'm saying is the remaining water will raise compression figures erroneously
 
moparodbuster said:
When I tried to crank it over again it turned over a few times without firing then did not want to turn over at all and I felt a solid resistance in the block when turning the key.
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The above does not tell me that you necessarily have water in the cylinders at all. 12+ SCR is a high compression engine. The battery may be down after 5 weeks setting. And the rough running may be due to the charging system having failed and the system voltage being low.

First I'd measure the battery voltage without ever touching the starter. A decently charged and good condition battery should be at 12.6 volts or thereabouts. If OK, then look for water. If battery is low, then charge for 1-2 days, and then try again. Once running, see what the battery voltage is at 1500 RPM.
 
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nm9stheham said:
The above does not tell me that you necessarily have water in the cylinders at all. 12+ SCR is a high compression engine. The battery may be down after 5 weeks setting. And the rough running may be due to the charging system having failed and the system voltage being low.

First I'd measure the battery voltage without ever touching the starter. A decently charged and good condition battery should be at 12.6 volts or thereabouts. If OK, then look for water. If battery is low, then charge for 1-2 days, and then try again. Once running, see what the battery voltage is at 1500 RPM.

I'd pull the plugs and look for signs of water and then crank it over with no plugs installed and look for water. If no signs there, then measure the battery vol
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I thought this too, also measure the voltage AT THE starter and block while cranking. Should be above 10V the higher the better.
 
moparodbuster said:
I need some seriously good advice. My 340 12.6:1 pro streeter was running fine for days and days after overheating but after not running for about 5 weeks I went to start it and it ran really rough like it had a fuel issue. When I finally did get it to fire it ran like it was on 5 cylinders and really rough. I thought it might be old fuel or a stuck jet so I tried to clean it out by giving it some revs but it wouldn't idle and eventually died. When I tried to crank it over again it turned over a few times without firing then did not want to turn over at all and I felt a solid resistance in the block when turning the key. I haven't taken the spark plugs out yet but I'm thinking I've got hydraulic lock from a leaking head gasket into the cylinders. Any advice on what to look for what to watch out for and how to identify what size head gasket to get would be helpful all I know from the previous owner is that it's a 30 over 340 from a '71 Cuda with x Heads.
I work away and only home 1 day a week. have to pay a mobile mechanic by the hr to come do it while I'm away so I need to educate myself as much as possible to make sure I'm directing him to do everything right. He's not a mopar guy just a heavy equipment mechanic. So I'm basically paying him to be my hands and eyes.
Soooo... I'm guessing pull plugs, tap starter and look for water coming out of cylinders and see if she turns over, if I see water, mark that cylinder and then pull heads and look at gaskets, cylinder walls and check piston heights for possible bent rods then put straight edge on heads to check for warp... am I right? Am I missing something?
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UPDATE... Pulled plugs. Water in #7 cylinder. It won't turn by hand. So now onto a stand to pull heads. Wondering whats physically preventing motor from turning now.
192.jpeg
 
Perhaps rust in that cylinder holding the rings to the cylinder wall. Don't try to turn it just in case that is the issue; take it apart piece by piece. Then you can soak that cylinder from top and bottom with penetrating oil before trying to move the piston to minimize and scoring on the cylinder walls.

Sorry to hear this is the issue.
 
You sayin with all the plugs out it won't crank on the starter? Or turn with a wrench? You may have bent a rod, other damage. How's the oil look? Coolant, water in the oil?
 
moparodbuster said:
I need some seriously good advice. My 340 12.6:1 pro streeter was running fine for days and days after overheating but after not running for about 5 weeks I went to start it and it ran really rough like it had a fuel issue. When I finally did get it to fire it ran like it was on 5 cylinders and really rough. I thought it might be old fuel or a stuck jet so I tried to clean it out by giving it some revs but it wouldn't idle and eventually died. When I tried to crank it over again it turned over a few times without firing then did not want to turn over at all and I felt a solid resistance in the block when turning the key. I haven't taken the spark plugs out yet but I'm thinking I've got hydraulic lock from a leaking head gasket into the cylinders. Any advice on what to look for what to watch out for and how to identify what size head gasket to get would be helpful all I know from the previous owner is that it's a 30 over 340 from a '71 Cuda with x Heads.
I work away and only home 1 day a week. have to pay a mobile mechanic by the hr to come do it while I'm away so I need to educate myself as much as possible to make sure I'm directing him to do everything right. He's not a mopar guy just a heavy equipment mechanic. So I'm basically paying him to be my hands and eyes.
Soooo... I'm guessing pull plugs, tap starter and look for water coming out of cylinders and see if she turns over, if I see water, mark that cylinder and then pull heads and look at gaskets, cylinder walls and check piston heights for possible bent rods then put straight edge on heads to check for warp... am I right? Am I missing something?
Click to expand...
 
moparodbuster said:
I need some seriously good advice. My 340 12.6:1 pro streeter was running fine for days and days after overheating but after not running for about 5 weeks I went to start it and it ran really rough like it had a fuel issue. When I finally did get it to fire it ran like it was on 5 cylinders and really rough. I thought it might be old fuel or a stuck jet so I tried to clean it out by giving it some revs but it wouldn't idle and eventually died. When I tried to crank it over again it turned over a few times without firing then did not want to turn over at all and I felt a solid resistance in the block when turning the key. I haven't taken the spark plugs out yet but I'm thinking I've got hydraulic lock from a leaking head gasket into the cylinders. Any advice on what to look for what to watch out for and how to identify what size head gasket to get would be helpful all I know from the previous owner is that it's a 30 over 340 from a '71 Cuda with x Heads.
I work away and only home 1 day a week. have to pay a mobile mechanic by the hr to come do it while I'm away so I need to educate myself as much as possible to make sure I'm directing him to do everything right. He's not a mopar guy just a heavy equipment mechanic. So I'm basically paying him to be my hands and eyes.
Soooo... I'm guessing pull plugs, tap starter and look for water coming out of cylinders and see if she turns over, if I see water, mark that cylinder and then pull heads and look at gaskets, cylinder walls and check piston heights for possible bent rods then put straight edge on heads to check for warp... am I right? Am I missing something?
Click to expand...
 
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