502EFI exhaust valve seat broke, rebuild time!
05-17-2007, 09:09 AM
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05-17-2007, 11:23 AM
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That's what I thought. What I really would like to do would cost a lot of money and it would be easier to start from scratch and still have a spare motor or sell it to help cover the cost of the new one.
05-17-2007, 01:29 PM
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If your EFi, the maybe look for a Long block to replace yours with. Stock swap and the EFI will work as it did before. You can get a new Long block for around $6000.00 here http://www.1800runsnew.com/NLM/newbase-NLM.html .
Then repair your current engine as you have time and money too.
Then repair your current engine as you have time and money too.
05-17-2007, 02:59 PM
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Thaks for the info Canada Jeff. I just returned from the machine shop and the block and botom end is ok. The block is already hot tanked, honed, and ready for reassembly. I just need a new piston, rings and bearings.
However, the major cause of the this was that my head is cracked, so now I have to try and find a new head. Not many of these around here, so I guess I will be looking on OSO for some heads.
If anyone reads this and has some rectangle heads for a 502 for sale please let me know.
However, the major cause of the this was that my head is cracked, so now I have to try and find a new head. Not many of these around here, so I guess I will be looking on OSO for some heads.
If anyone reads this and has some rectangle heads for a 502 for sale please let me know.
05-17-2007, 03:25 PM
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What about a new set with new valves springs etc ready to go ? How old are your valevs and springs now? may be close to the same price as a couple heads rebuilt ! Go aluminum too if your supercharged. Then just send you computer to Dustin, tell him what your new heads are and they will recal your computer. Probably pick up 40 hp or so.
05-17-2007, 03:31 PM
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All those sound good. I did all that and put the "741 Crane cam" in mine.The stock roller lifters worked on mine but be sure to check them closely. I bored it and used JE pistons. Make sure who ever builds it uses enough clearance on the rings. It is quite a bit larger gap being a marine and SC application. If your heads are fried do a search on here and get recommendations. MIne sounded so much better, it scared the sh*t out of me when it started!
Thats a lot of cam for a 502mpi,any other mods besides the ecm?
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05-19-2007, 08:31 PM
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Rockie:
I just had a similiar experience with my 502's. #8 cylinder on both motors were too lean and the exhaust seat started to come out of one head while the other became warped not allowing the valve to close. These were rebuilt motors with modifications and I did not pay attention to reading plugs when I first started to run it.
During the repair, when I took the heads off and took them to the machine shop, they found one head to be cracked in between the intake and exhaust valve which let the exhaust seat go. Also, the cylinder head was out of true between #6 & #8 combustion chambers (warped .005) so heat was definitely an issue. In my case it was a jetting problem. I too had to buy another head. I think you could have an issue in your fuel system like I had. When you get it all back together, try to get a plug reading.
Gary
I just had a similiar experience with my 502's. #8 cylinder on both motors were too lean and the exhaust seat started to come out of one head while the other became warped not allowing the valve to close. These were rebuilt motors with modifications and I did not pay attention to reading plugs when I first started to run it.
During the repair, when I took the heads off and took them to the machine shop, they found one head to be cracked in between the intake and exhaust valve which let the exhaust seat go. Also, the cylinder head was out of true between #6 & #8 combustion chambers (warped .005) so heat was definitely an issue. In my case it was a jetting problem. I too had to buy another head. I think you could have an issue in your fuel system like I had. When you get it all back together, try to get a plug reading.
Gary
05-19-2007, 08:32 PM
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Canada Jeff, I have went over this time and time again, and for the $4-5 grand to go to aluminum heads, new cam, reporgram ECU. I don't think it is worth the hasle. I would only go probably 3-5 miles faster. So I am going to get it back to where it was and be reliable. Then probably upgrade in another couple of years. I want to get a new boat, but it's not going to be this year. At least I can sell it with a relatively new rebuild. I will be replacing valve springs and such, or putting on new heads as you stated.
05-19-2007, 08:39 PM
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GNJ, I will be replacing all of the maintanence items such as filter and the like. I will also be checking plugs, but I think the problem actually happened at LOTO last year, because that was the last time I used the boat . I really need to read plugs at LOTO this year. The elevation is a lot lower than here so maybe it is running a little lean. I know the ECU is supposed to take care of that, but it is a computer. It's not perfect.
