help! cracked heads?
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04-13-2003, 08:27 PM
#3
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heres the real post!
Sorry about that, heres the real post. I have trailer started my boat twice, all seemed ok. Today was the first water ride. It’s a 97’ Baja boss 232 with a gen 6 502 and merlin cast iron heads, carbed. The boat ran fine at first, started good, warmed up good, got up to around 150. Hit WOT, around norm at 5100 rpm and 70 mph, had 70 gallons of gas and 4 adults.
Ok, heres the trouble, dropped off two of the people and headed back out, tried WOT again and it only hit 4500 rpm around 60 mph, not good. Raised the hatch and found oil/water mix had sprayed out starboard side valve cover breather, right above cylinder #8. Pulled out both valve cover front breathers and had water/oil stuff almost pour out, was more clear like water than oil, had slight green sludge stuff in it, looked almost like seaweed. More of it on the starboard side. Put my had over the breather hole while friend reved up engine, didn’t really feel any back pressure. The underside of the breathers were milky and where the breathers go to the flame arrestor was milky on the arrester screen. Pulled oil dipstick, found only a trace of milky residue (running royal purple 40w oil). I headed back to dock, only a few minutes away.
Went home, pulled plugs, 5 look normal, #3 and #4 were slightly white/brown and pretty dry/clean looking, #8 was more white and dry. Checked compression, 5 were normal at 150psi, #3 and #4 were low at 120psi and #8 was really bad at 95psi, did this test a few times, didn’t change. Drained the oil, didn’t see any traces of water in it. Im thinking possible cracked head(s) or blown head gasket(s). Water in the cylinders I think would clean the plugs making them look like they did. If the water is burning in the cylinders then it may not reach crankcase, but why then so much water in valve covers and breathers, why spraying out, blow-by by chance? I could please use some help here, the boat was winterized but who knows. Any ideas before I tear it down and get the heads checked? Is there any common problems with these setups? Please tell me I missed something simple, I’m ready to boat! Thanks Derrick
Ok, heres the trouble, dropped off two of the people and headed back out, tried WOT again and it only hit 4500 rpm around 60 mph, not good. Raised the hatch and found oil/water mix had sprayed out starboard side valve cover breather, right above cylinder #8. Pulled out both valve cover front breathers and had water/oil stuff almost pour out, was more clear like water than oil, had slight green sludge stuff in it, looked almost like seaweed. More of it on the starboard side. Put my had over the breather hole while friend reved up engine, didn’t really feel any back pressure. The underside of the breathers were milky and where the breathers go to the flame arrestor was milky on the arrester screen. Pulled oil dipstick, found only a trace of milky residue (running royal purple 40w oil). I headed back to dock, only a few minutes away.
Went home, pulled plugs, 5 look normal, #3 and #4 were slightly white/brown and pretty dry/clean looking, #8 was more white and dry. Checked compression, 5 were normal at 150psi, #3 and #4 were low at 120psi and #8 was really bad at 95psi, did this test a few times, didn’t change. Drained the oil, didn’t see any traces of water in it. Im thinking possible cracked head(s) or blown head gasket(s). Water in the cylinders I think would clean the plugs making them look like they did. If the water is burning in the cylinders then it may not reach crankcase, but why then so much water in valve covers and breathers, why spraying out, blow-by by chance? I could please use some help here, the boat was winterized but who knows. Any ideas before I tear it down and get the heads checked? Is there any common problems with these setups? Please tell me I missed something simple, I’m ready to boat! Thanks Derrick
04-13-2003, 11:54 PM
#5
I would do a leak down test before tear down. That could tell you if it is a valve or something else. Unless you just know that your are going to tear it down then have the heads checked after it is apart. Water (lake) temperature is cold this time of year. Are you running a thermostat with your cross over and do you know what your water pressure is in the block and oil temperature is. Very cool engine temperature can cause condensation. Low compression and blow-by well thats something else. 
04-14-2003, 12:23 AM
#6
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Just a thought-
What about loose or improperly torqued head bolts? I don't know if the Gen 6 502 block has blind bolt holes- but water can and will come up past head bolts if the head bolt holes go into water jackets. If a cylinder has run hot it can cause the bolts to loosen up, too.
It sounds like a head gasket will need to be changed.
What about loose or improperly torqued head bolts? I don't know if the Gen 6 502 block has blind bolt holes- but water can and will come up past head bolts if the head bolt holes go into water jackets. If a cylinder has run hot it can cause the bolts to loosen up, too.
It sounds like a head gasket will need to be changed.
Last edited by Bulldog; 04-14-2003 at 12:29 AM.
04-14-2003, 05:57 AM
#7
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Merlin heads....... I had a defective casting which had a pin hole in the exhaust port water jacket. I think it was #2 or #6. Just a thought to check that.
04-14-2003, 12:32 PM
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Sounds like a head gasket problem to me!! If the builder is not experienced with MK V and VI blocks, he could have used head bolts for the MK IV. If he did, the bolts bottom out and do not hold the head down. Seen this more than once!! Also, the incorrect head gasket will cause similar problems. At any rate, time to remove the head(s)!!!
04-14-2003, 01:08 PM
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when my heads cracked water was in the pan and all over the motor and it was running hot.
when i ran with new heads and my crossover without a thermostat condensation was in the valve cover area and mixing with the oil. the pan was clean.
change the oil and put in a thermostat run it if the oil is clean after it gets hot your good if not pull heads.
when i ran with new heads and my crossover without a thermostat condensation was in the valve cover area and mixing with the oil. the pan was clean.
change the oil and put in a thermostat run it if the oil is clean after it gets hot your good if not pull heads.
