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Rebuilding top end of 2000 7.4 MPI - a little help please

Old 06-03-2008, 08:25 PM
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Location: New York, NY
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Default Rebuilding top end of 2000 7.4 MPI - a little help please

So I am sure some of you have seen my posts about the rotting exhuast manifolds and the crumbling heads.

Looks Like I gotta do the whole top end and I have a few questions if anyone cares to help out.

I am going to replace Heads, Exhuast manifolds and considering popping in a cam while I am in there. Of course I will replace the timing chain as well.

Re - Heads: Should I just get a set of stock heads? I have spoken to a couple of people who post here and I can probabaly get a nice set pretty cheaply. Am I correct in assuming I have to get the old heads off and get the casting number before I can order the new ones?

Re - Cam: Whats a good drop in that might give me a little more bite without running the danger of sucking water.

Re - Exhaust Manifolds - I am looking at a set of Eddie Marine... they are aluminum with stainless risers... supposedly breath really well and will drop right in with my stock captains choice.

I am just looking for some quick pointers as I have done this type of rebuild on a car but never on a boat... ultimately it all seems pretty similar but I do not want to get too crazy and then have a pig that I cannot rely on. I use this boat pretty heacy all season and like to go on some really long trips.

Any insight will greatly appreciated....


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Old 06-03-2008, 08:50 PM
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I would think you'd have to pull the engine in order to change the cam. I can't imagine you have enough room between the front of the engine and the front of the engine compartment to get the cam out.

My opinion, for what it's worth, the bottom end won't cost that much more to do. You're already doing the most expensive part in a set of heads. If I remember correctly, this has 950+ hours on it? If it's apart, at all, do it all and be done with it. I know it can be a strain on the wallet. I did my 800 hour 454 Mag MPI last fall because I needed to replace the gimbal ring. I certainly didn't want to pay to have the engine R&R'd twice for when it was time to do the engine. Yeah, I spent money I didn't really have to at the time, but it sure beat wasting money doing the R&R twice and possibly having my known high hour engine finally give it up in the middle of the lake. Just my $.02.

As far as parts suggestion, if you're going to stick with the 7.4 fuel injection and the cast internals, I wouldn't spend money on any high dollar heads. I'd find a set from a shop that have been freshwater heads and have a fresh rebuild on them. No sense in buying new if you can get a good set of used castings with all new parts.
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Old 06-03-2008, 10:42 PM
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The heads aren't going to be that critical. You have to choose between oval port and rectangular. Personally, if you're goingt o go with a warmer but still mild cam, I'd stay with the ovals. Have a good 3-angle valve job done on them and be done with it. I would absolutely spring for stainless steel valves. Look for heads on Ebay- I see them all the time. Or, place a "wanted" on here. Lots of guys upgrade from the ovals. You can also check the classifieds on Boatfreals and Speedwake- alot of the guys from here sell their stuff over there.

On the bottom end- if you're pulling the motor to stick a cam in it, you really should have the bottom end done. If the crank doesn't need turning, you're looking at about $200 in boring. A good set of pistons with rings is going to run you $500 and bearings, gaskets and a new oil pump another $300. You might as well replace the stock rod bolts and resize the rods- another $150. That's going to be better than blowing it up in the first few hours with that new warmer cam.
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Old 06-04-2008, 12:57 AM
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Location: New York, NY
My Boats: 2000 Checkmate 259 Convincer
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So I have thought about this for a while today...

You guys are totally right about just doing the whole enchilada but I am comparing prices here and I think that I am going to be so much better off just finding myself a nice reman. 502 and putting a solid powerplant in place. Seems so much more practical to me to buck up the extra G or two and upgrade. Besides... what's the old addage... there's no replacement for displacement. Of course the forged crank and the 4 bolt mains are a big help as well.

Anyway... I have been checking the numbers all day long and it looks like this is going to have to wait til next year. I do think that I am going to take a shot at just a new set of cheap manifolds and see if I can't get a couple of months of bouncing around the bay out of this thing without casatrophic failure.

All I gotta do is get those busted bolts out of the head... any quick tips on the easiest way to do that???

I do appreciate anyone who takes the time to answer in these posts.


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