Hello Inmates, I'm looking for assistance in diagnosing a problem with a recent engine build. My boat is a 2007 Conquest Top Cat II which was originally equipped with a 496 Mag/HO. I recently built a new 540 cubic inch motor to replace the 496. Most all parts were purchased from Larry at Raylar Engineering. The Block is a Brand new P.S.I. Short-block with all forged internals and 10:1 compression. The heads are Raylar's aluminum heads. The head gaskets are Cometic M.L.S. at .040" The motor has approximately 10 hours of run time on it. I have noticed that when running the motor at between 3,000 and 4,000 rpm it looses approximately 24oz. of coolant every 2 hours or so. There is no water in the oil under these conditions so it appears it is entering the exhaust system and then exiting the boat. My original thought was that I had a leak in the heat exchanger, so I ran a test where with the boat on the trailer. I began by removing the end caps from the heat exchanger and then drying it out completely. Then I pressurized the coolant system and left it sitting for several hours. The first few times i did this I only pressurized it to 9 or 10 psi. I did not notice any loss of coolant. I then began pressurizing to 13 to 14 psi and noticed a loss of approximately 32 ounces of coolant over a period of several hours of continued pressurization. There was no evidence of coolant in the heat exchanger. I then checked the cylinder bores with a flexible scope and noticed evidence of water in the #4 and #5 cylinders. I then drained the oil and found the missing coolant in the pan. I don't believe it's a problem with the head gaskets because the engine has not gotten over 165 degrees ever. The only other issue which may have a bearing on this, is when I originally put the engine together I used ARP thread sealent on the head studs. After running the engine I noticed that the head studs were weaping coolant where the head stud nuts and washers contacted the heads. I pulled each stud individually and applied a new sealant (Permatex aviation sealer) and re-torqued each stud. I did not remove the valve covers and re-seal the studs under the covers, as I was not seeing any evidence of water/coolant in the oil. My next plan is to pull the valve covers and re-seal the studs under the cover, but I really can't see this being my problem. Another possibility is that I may have reversed the head gaskets which are right and left side specific. I was aware of this possibility during assembly, and really don't think this happened, but who knows.
Apparently when the motor is running the coolant is getting into the combustion chamber and immediately being forced out the exhaust, so no coolant in the engine oil. When pressurized and not running, the coolant is entering the combustion chambers and then leaking past the piston rings into the oil pan. I really don't want to pull the heads to replace the head gaskets, but if the re-sealing of the studs under the valve covers doesn't solve my problem, the head gaskets are my next option unless someone here can offer some other possibilities that I haven't thought of.
Thanks very much,
Any theories will be greatly appreciated. Sorry for the long winded thread.
Apparently when the motor is running the coolant is getting into the combustion chamber and immediately being forced out the exhaust, so no coolant in the engine oil. When pressurized and not running, the coolant is entering the combustion chambers and then leaking past the piston rings into the oil pan. I really don't want to pull the heads to replace the head gaskets, but if the re-sealing of the studs under the valve covers doesn't solve my problem, the head gaskets are my next option unless someone here can offer some other possibilities that I haven't thought of.
Thanks very much,
Any theories will be greatly appreciated. Sorry for the long winded thread.
