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Replacement of 502 mag mpi heads

Old 03-26-2014, 03:48 PM
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Default Replacement of 502 mag mpi heads

I'm looking for suggestion on replacement heads for a 502 mag mpi. I'm not interested in building horsepower, so as close to stock is preferred. I have gotten info on the World 310's which should not require ECM changes but wondering if there are other manufacture? We run a lot of salt water in this area and don't want to have issues. Any input would help with the final decision.
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Old 03-26-2014, 06:08 PM
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What's wrong with yours??? Rotted out???
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Old 03-26-2014, 06:25 PM
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yes sir... last owner must have left the salt water in the motor after every run including storing for the winters? the exhaust valve guides rotted through and cracked causing water to get into the cylinder. time for an upgrade....
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Old 03-26-2014, 07:13 PM
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Originally Posted by JimV
Soon to be available, a replacment head that has the stock ex port positon with all the bolt holes in the stock positions including the extra bolts in between the intakes. The heads will have better quality ex seats and improved airflow on both ports. I think they will be priced low 800.00 per set. All your parts will interchange to the new castings.
There is now a direct replacement for your stock heads. A company is now producing a replacement head cast in USA. We talked to them at PRI and they are now available. Contact JimV for the info on them and where/if he get them for you.
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Old 03-26-2014, 07:58 PM
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Originally Posted by Tib
yes sir... last owner must have left the salt water in the motor after every run including storing for the winters? the exhaust valve guides rotted through and cracked causing water to get into the cylinder. time for an upgrade....
I would be concerned about the blocks then as well. Might be beter off to look for a set of fresh water take out engines.
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Old 03-26-2014, 08:23 PM
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Originally Posted by Griff
I would be concerned about the blocks then as well. Might be beter off to look for a set of fresh water take out engines.
I agree - especially with the Gen V/VI blocks, since the deck is thinner than the old Mk IV blocks. Might be time to cut your losses. Is this a single or twin?
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Old 03-26-2014, 08:30 PM
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Jegs and summit sell pretty inexpensive gm square port replacement heads
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Old 03-26-2014, 09:00 PM
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The problems with this boat started 2 years ago. The #6 exhaust valve guide rusted through inside the water jacket. It allow water into the chamber and hydraulic the cylinder. Well long story short the cylinder cracked and I had to replace the block. The valve guide was a hard issue to pin point. Not something that usually happens.
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Old 03-26-2014, 11:19 PM
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Since the block is replaced, I would just look for a used set of fresh water stock GM rect port heads. They can usually be had for $400-700 a set.
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