Heads
08-23-2017, 09:54 PM
#12
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Sorry to hear about your situation. There are tons of threads about mixing different generations of heads and what works on what blocks. It really comes down to using the proper head gaskets.
Honestly, if you have milky oil, it's not the valves...something else is going on. I'd say check the exhaust manifolds and risers. Hopefully it's nothing internal.
Honestly, if you have milky oil, it's not the valves...something else is going on. I'd say check the exhaust manifolds and risers. Hopefully it's nothing internal.
08-24-2017, 06:32 AM
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049 and 781 are pretty good heads. You can get 450-500 with very little port work. Did the mk-4 run well before eating bearings? Oh yeah, where are you? Milkshake, first culprit is intake manifold gaskets and the water passage running across front of intake. Especially with raw water boat motor and more so with salt water. Although the factory mag motor has a brass or bronze piece cast into the alum manifold.
08-24-2017, 04:29 PM
#16
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Are you trying to get thru this season, or looking into what you need for this winter's build? Was mk4 dished or flat pistons? Is this a mag motor? Or a gen 6 that has mag heads on it? And is it still in the boat? Also, what is the boat and how is it run? A lot of people push it to WOT for a few seconds each trip out and spend the day at 3500 to 4k. If that is the case, the ovals are just fine for you. And the alum rectangle mag intake will fit and run just fine on the oval heads.
Last edited by dereknkathy; 08-24-2017 at 04:50 PM.
08-25-2017, 06:37 AM
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Are you trying to get thru this season, or looking into what you need for this winter's build? Was mk4 dished or flat pistons? Is this a mag motor? Or a gen 6 that has mag heads on it? And is it still in the boat? Also, what is the boat and how is it run? A lot of people push it to WOT for a few seconds each trip out and spend the day at 3500 to 4k. If that is the case, the ovals are just fine for you. And the alum rectangle mag intake will fit and run just fine on the oval heads.
08-25-2017, 08:46 AM
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08-25-2017, 08:48 AM
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No, you could run the ovals on the mag just fine. Chambers essentially identical. No piston to head clearance issues. Valves, springs will run on the oe roller lifters. You would have to run the newer pushrods so if pushrod dia are different you will need 3/8 guideplates to fit the 7/16 rocker studs. I have at least one set here. Gen 6 no fuel pump mount. Did the mag come with the water pump-fuel pump combo? Otherwise an electronic fuel pump is necessary. The one pain is if using all the mk 4 brackets, the gen 6 are 7/16 instead of 3/8 and drilling that little bit bigger is no fun. But most attach to the heads, not the block so less holes to adapt. You could have that gen 6-oval beastie together in a couple evenings. You will want to drop the pan and check the rods and mains. I bought 2 different supposedly good engines and found bad bearings after installing the engines.
Last edited by dereknkathy; 08-25-2017 at 08:52 AM.
08-25-2017, 03:43 PM
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No, you could run the ovals on the mag just fine. Chambers essentially identical. No piston to head clearance issues. Valves, springs will run on the oe roller lifters. You would have to run the newer pushrods so if pushrod dia are different you will need 3/8 guideplates to fit the 7/16 rocker studs. I have at least one set here. Gen 6 no fuel pump mount. Did the mag come with the water pump-fuel pump combo? Otherwise an electronic fuel pump is necessary. The one pain is if using all the mk 4 brackets, the gen 6 are 7/16 instead of 3/8 and drilling that little bit bigger is no fun. But most attach to the heads, not the block so less holes to adapt. You could have that gen 6-oval beastie together in a couple evenings. You will want to drop the pan and check the rods and mains. I bought 2 different supposedly good engines and found bad bearings after installing the engines.
