Re: 350 to 454 upgrade?
A few years ago I did what you're thinking about doing - going from a 350 to a 383 in my heavy single engined cruiser.
I learned a few things during and after that might help you along:
First, you will see and feel the extra power, but not like those who have light boats with big engines. I'm glad I did it, but will admit that at first I was a bit underwhelmed. As it turned out my expectations weren't realistic; I didn't fully understand the mechanics of pushing that big a boat across the water, nor did I understand just how much additional power it takes to gain each additional MPH. To be sure, you probably aren't going to pick up 10 MPH at the top. After that realization, I found several things that make me glad to have done the swap: I can now cruise at a lower RPM (and at the same speed as before), my boat doesn't "feel" underpowered, and it is quite bit more responsive to my right hand.
I know all about eyes glazing over as you look over the parts selection. What I ended up with has worked for me so far. YMMV. As mentioned before, you don't
need forged pistons. For that matter, you don't
need a forged crank either. You will want to keep your compression in check (my machinist said he wouldn't touch anything over 9:1 on a heavy boat, and would really like to see 8.5:1 so that's what we did). I ran the Vortec heads because it's rather cheap horsepower when you're building from scratch (you're going to get the valve job anyway so the only real price difference is the price of the heads). I also used a late model Vortec block (casting #880) - if you can find a long block core and the heads are the right casting number you'll pretty much be able to offset the cost of getting stuff separately, plus you'll be set to run roller lifters.
As far as free stuff - just be careful. The bad economy cuts both ways in that respect. People with junk are actually moving it more easily now because everyone is looking for a steal. And many times that desire to get a bargain clouds sound logic. I have this conversation on an almost weekly basis - people ask how I justify my prices, tell me how much they can get it for elsewhere, then call me back two weeks later when they have a problem. I politely decline; some people's children just aren't worth the brain damage of dealing with. People who have good stuff (and know it's good) aren't as interested in giving it away as cheap as some people think. And it's probably still true that you do get what you pay for. The real interesting thing here is that in a lot of cases free stuff on the front end can end up costing
more. Where this really shows up is in the amount of machining your block is going to need. A "free" core can end up costing you a few hundred dollars in extra machine work. Point being, it pays to know what you're buying yourself into when you pick something up.
Probably the most important decision you'll have to make will be your camshaft selection. I got so much varying information that I called a bunch of cam companies. I told them I wanted a cam tailored to the specifics of my system. They continually steered me to their off the shelf cams, and three different ones at that. I finally broke down and got a custom design. That will set you back a couple bills extra, but in my opinion it's money well spent. You know the drill...cut once.
Somebody earlier mentioned rods - if you end up with a Vortec core, those rods are pretty good. Get them resized, which would be as good a time as any to upgrade the bolts. For a few bucks more you can get an aftermarket set, but my machinist had one fail and ever since has refused to use aftermarket rods (at least the ones at that price point). That choice is really comes down to what you're comfortable with.
2 bolt or 4 bolt also comes down to your comfort level. If memory serves, Mercruiser factory 350s are 2 bolt. I think that myth (that all boats are 4 bolt) started on a forum somewhere.
As far as crate vs. machine shop - it has been my experience that for the same money, a reputable machine shop will give better quality end product (in terms of machining, and likely free up some money that can be either saved or put into upgrading parts).
The last thing I learned is that your time most certainly is not free. I hear people say (and I used to subscribe to this), "the only thing I'll be out is my time." I don't know anyone who feels they have too much time in a day; time is typically our most scarce resource. Even when you aren't working, your time spent on this project will come at the expense of something else (sleeping, spending time with friends/family, etc.). Keep that in mind, because when you consider that your time isn't free, you tend to make better decisions about whether you should do something yourself or farm it out. If you still think that your time spent outside of work is "free", I have plenty of projects around here that would benefit from free labor
.
Sorry for the long post, but I remember the long hours I spent with glazed eyes and a spinning head; hopefully I can save you a bit of that.
