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Thread: Building a 350: newbie finer points?

  1. #1
    curtis73
    After reading some good posts here I have some final questions on a powerplant for my Baja 190 supersport. It currently has a wasted 305 and a good alpha so I'm replacing it with a 350. I know very little about I/Os, but I have a good bit of experience assembling engines so I thought I'd save some cash and build it myself instead of paying someone else $1300 for a shortblock... jeez that stuff is expensive.
    Anyway, I'm shooting for 300 hp with a top RPM of 5000. I need to know some things before forging ahead. The dyno simulation below was made using desktop dyno with an off-the-shelf Comp 212/218 marine roller and as-cast vortec iron heads.
    - Given the power curve, should I tune for 5000 rpm with out any load in the boat so I still have plenty of power at 4500 and up for the extra weight?
    - Is my torque peak at an OK place? Will I be putting too much torque to the Alpha? Will I be on plane by 3000 ya think? That dyno simulation is with a roller cam... should I consider switching to a flat cam to bleed off some of that torque?
    - Does a stock marine exhaust manifold flow better or worse than a typical stock automotive manifold? A little better? A lot better? A lot worse?
    - I may buy a marine shortblock. If I do, what do I look for in a quality build? I know about brass freeze plugs. Do the crank, rods, pistons need to be forged? Are 4-bolt mains necessary, or just a benefit? What should I look for in the oiling system?
    - I have a friend at a plating shop here in town and I already have an aluminum intake... can I just have my intake plated with brass or something? Do I need a marine intake?
    - 90% of my boating is in fresh water. Can I get by with aluminum components during the 10% saltwater time? Is a cathoded piece of aluminum as good as an unprotected iron piece?
    I know I ask many dumb newbie questions, but I gotta learn somewhere. I have some books coming that should reduce my number of questions.

  2. #2
    SmokinLowriderSS
    I think you have a very good looking build there. Someone other than I will have to comment on the durability of a Merc Alpha drive. The torque pull sure should help holeshooting it onto plane, especially if you strap on a couple skiiers or a tube. You may also find you can pull several inches more prop and get better mileage (if you can keep your hand (throttle) out of it).
    Usually in my simulations on DD, I run High-perf Manifold w/ mufflers, but I am usually hooking a big block up to log-manifolds on jet. I think that may still be more accurate, unless you are running thru-hub. Then, the stock may be more accurate.
    I do know folks who have put the cutout systems on a small-block, and gained nothing so the hub-exhaust isn't to bad on the small motors.
    A "marine" block is the same cast iron one in a car, usually just brass freeze plugs. The build parts inside depend entirely on how hard you are trying to work the engine. My 454 is making 400HP (loafing, i know), spinning a cast crank, and the engine builders here have no concerns for me unless I want to spin it up beyond 6-large (which I do not), even to 600 HP. It's a 2-bolt as well.
    This 300 HP 350, if built with care, toleranced properly (IMO, factory stock tolerances, ABOVE THE MID-RANGE of each tolerance (ie, slightly "loose")), a cast crank if you have one should be fine, stock rods should be fine. Cheap insurance on the rods would be a set of ARP rod-bolts and a re-size on them. Forged pistons are not a must (my cast ones been running 28 years, even sipping 75HP of Nitrous), but, since a set of Speed-pro Powerforged's will set you back under $400, if you have the $$, and need pistons, why not upgrade for nearly nothing. A set of casts will cost likely over $300.
    IF the boat sits in the lake, engine ful of water, all summer, you will have galvanic corosion problems with an Al intake. If it only sits all weekend, or maybe a week on a big holiday, then comes out to the trailer & sits dry 98% of it's life, you will have no trouble.
    Salt water is a different issue.
    Rinse the snot out of it, and rinse it some more, then rinse it again. There are helpful products out there, others must fill in here as I do not make it to oceans with Lowrider.
    IMO, for 95% of the uses, the stock oiling system is plenty up to snuff, especially for a moderate build level. Put in a windage tray, a oversize pan is not a bad thing, but I ran 28 years so far on a stock-sized one (a larger one is in planning, but will be a while), stock pump too. As long as you get (and can maintain) 10psi per 1,000 RPM, you are OK. A long hard run will heat the iol, thinning it. If it is severe enough, a cooler will be needed. Depends a lot on how you drive. I've not been able to run more than 3 or 4 miles, flat out, and no issues, but I am also pushing my engine harder as I update things, and I am watching.
    Clean out any flashing (casting excess) from the block drains before you have the block cleaned/clean it, this helps keep drain-back from being interfered with.

  3. #3
    curtis73
    Excellent info!!! Thanks for such a complete response!
    I was considering running cutouts to a transom exhaust just for sound I like the sound of it open, but heading up the lake at 5am to catch some bass might seriously tick off the rest of the campground
    Good advice on the aluminum components. This boat was purchased mainly for the 2 months on the lake in the summer, then local lakes and maybe some salt on the weekends the rest of the year, so I'll stick with iron stuff. The 305 currently has an iron manifold that I could re-use, but aren't the newer ones aluminum with a plated water passage? What are they plated with, and can I just have my buddy electroplate an Edelbrock Performer?

  4. #4
    Ryan00TJ
    Smokin is right on his is above post. Spinning to 5000rpm max will be fine with a cast setup. 2 bolt is fine, my current is an all cast Jasper shortblock 2 bolt. I spin it 5600rpms and 69mph w/ no problems. Your Alpha should also stay very healthy at that power level and rpm level. Just remember the Alpha does not like full throttle hole shots. Most problems with the drive revolve around an all out hole shot. When your up on plane have no worries hammering down. My Alpha has been going strong since 92 with some stout small blocks and 6500rpms.
    My boat has always been in freshwater and sits May-Sept every year. I've used both Performer RPM and Victor Jr intakes with Felpro gaskets with no corrosion problems. 7 years on one setup was the longest. Key here is strictly freshwater. Salt is whole new ballgame.

  5. #5
    SmokinLowriderSS
    Nobody runs plated passages in manifolds. In cars, the anti-corrosion additives in the coolant keep corrosion shut down. Same in salt water as you switch to closed loop cooling, anti-freeze, and a water to coolant heat exchanger.
    Since you run an I/O, you already have anti-corrosion Zinks in place. Maintain them and use a good manifold like a Performer. The Zinks sacrifice themselves saving Alum parts like Drive housings, manifolds (intake & exhaust), Alum props, etc, from the Iron engines and Stainless prop shafts & hardware.
    I think I took over 50 pounds off my boat pulling the iron dual-plane and replacing it with a Performer RPM Air Gap. First time I heaved on it, and it didn't move, I looked again to make sure I hadn't missed a bolt someplace. I just hadn't pulled hard enough. I'll swear it's at least 70 pounds.
    When you bolt the intake down, LIGHTLY RTV the coolant passages on the intake gaskets, or they tend to leak, also retorque several times, at least 1 of them after first heat-cool cycle. If not, they will leak water soon, usually INTO the engine. Then you have an annoying mess to straighten out.
    Also RTV the corners where the gaskets meet LIGHTLY, to avoid an oil leak here, same for the oil pan. Too much just becomes a mess inside the engine.
    In fact, torque EVERYTHING that gets a torque spec at least 3 times, then check them again, tripple-check the bottom end a few more times, just to make certain nothing got missed before the pan goes on.
    A buddy bough a jet boat with blown-up 460. I helped him dissassemble it. #8 rod UNSCREWED a con-rod nut, then threw the rod, ruined block, crank, pan, and 3 rods total (parts pin-balling arround). HAD to have been an improper torquing, either missed or insufficient. We found the side of the rod, still together (broken completely off the rod end), minus nut, and the undamaged nut, in the pan sump.
    If you want to stiffen the 2-bolt lower end up a bit, cheaply, stud it. ARP set, roughly $50. Some folks think the mains need to be align-honed after, some do not. I fall in the not category since they are not aligned by the bolts like rods are but by the cuts in the block. You decide.
    You don't need fancy for rings & bearings either. I was advised Clevite 77 bearings, and I am happy. Moly rings, I happened to get double-moly, same price. I have not seen much use of gapless rings, and some folks I know have seen very little, very specialized, good uses for them. I know others who swear by them. Seems to be ring flutter problems, aespecially double-gapless ring sets (gapless #2 compression). Personally, I have zero trouble with old-school standard rings, they work great and I am not trying to chase every 1/2HP there is.
    There is a co-worker who swears they are better than the bread slicer, but then he told me I am loosing 30% of my available HP (no typo, thirty percent) by letting my engine run 120* WFO instead of 190 like his cars. His advice is now dubious and suspect.

  6. #6
    curtis73
    Great. I just put in a bid on a cam on Ebay. Its listed as a NIB Melling marine flat cam for chevy. It specs out to 202/213 on a 110 LSA (ground 2* retarded) with just over .4" lift. I simulated 1.6:1 rockers for a little help and the dyno simulation spit out:
    -301 hp @ 5000 using "h.p. manifolds" in the simulation
    -285 hp @ 5000 using "stock manifolds" in the simulation
    *mumbling to myself* Let's see, 2175 lbs for the bare boat, 230 for my fat butt, a little gas, guessing 2600 lbs, carry the 4, 10% loss through the outdrive for 257-270 hp at the prop, 10% prop slip***
    yehaw!!! I'm knocking on 70 mph either way. That makes me happy. :rollside: I really wanted a roller cam and I might still do it for the sake of those long months when it sits letting the lobes dry out, but I'm perfectly happy with those numbers.

  7. #7
    SmokinLowriderSS
    Your Alpha should also stay very healthy at that power level and rpm level. Just remember the Alpha does not like full throttle hole shots. Most problems with the drive revolve around an all out hole shot. When your up on plane have no worries hammering down. My Alpha has been going strong since 92 with some stout small blocks and 6500rpms.
    Yes, and the power used to pull a skiier (or even 2) isn't usually what you use trying to beat some low-slung big-block jet onto plane. Pulling a skiier you more "roll quickly" into about 3/4 throttle or so, not a slam from idle to full. From what I have read, I understand it's the upper gearset that gets unhappy with lotsa torque applied too harshly to it. On plane, not a problem to wind it out. You will get a problem I do not, which is drive oil heating, keep an eye on that, you MAY need a drive shower if you tend to go a long ways pretty hard and get it hot. The big boys with big engines NEED them, badly, often on stock 496/502's & bravo drives.

  8. #8
    SmokinLowriderSS
    Great. I just put in a bid on a cam on Ebay. Its listed as a NIB Melling marine flat cam for chevy. It specs out to 202/213 on a 110 LSA (ground 2* retarded) with just over .4" lift. I simulated 1.6:1 rockers for a little help and the dyno simulation spit out:
    -301 hp @ 5000 using "h.p. manifolds" in the simulation
    -285 hp @ 5000 using "stock manifolds" in the simulation
    *mumbling to myself* Let's see, 2175 lbs for the bare boat, 230 for my fat butt, a little gas, guessing 2600 lbs, carry the 4, 10% loss through the outdrive for 257-270 hp at the prop, 10% prop slip***
    yehaw!!! I'm knocking on 70 mph either way. That makes me happy. :rollside: I really wanted a roller cam and I might still do it for the sake of those long months when it sits letting the lobes dry out, but I'm perfectly happy with those numbers.
    Those "long months", really shouldn't hurt anything. My Taylor, dad's boat, he bought new, sat, sometimes a couple YEARS between trips near the end of his ownership. She was spun enough getting her started every time that she never was "started dry" oil-wise. The cam was perfectly fine when I took it out 2 winters ago, lifters too. Just tossed tho, nobody was going to want a BBC cam specing .480"/.472". :cry: Heck, I'm still pretty mild at .565".
    Again, personal preference here, but I'd prefer to buy a new cam, kit style, with springs included, all to fit together. This way I know the condition. If you buy that one, I hope it isn't worn badly. If you are unsure what to look for on the lobes, get advice from a pro somewhere. My buddy's in the 460, is about 1/2 shot, from likely a poor break-in procedure, which surprises neither of us as we know the prev owner of the boat, who likely rebuilt the engine itself (threw the rod at about 10 hrs). Probably short-sheeted the cam break-in too. If the cam is good, I'd prob buy new lifters, and re-break it in, just for peace of mind. Did the seller get the lifters all marked correctly? Who knows, hope so. Get one on the wrong lobe, it's all screwed.

  9. #9
    curtis73
    If the cam is good, I'd prob buy new lifters, and re-break it in, just for peace of mind. Did the seller get the lifters all marked correctly? Who knows, hope so. Get one on the wrong lobe, it's all screwed.
    Actually its a new in the box cam, but thanks. I don't re-use my own cams or lifters, let alone anyone else's
    My concern with dry lobes is that lifters today (and today's oil... long story so I won't go into it) don't let lifters last nearly as long as they should. The problem is, any movement of the flat lifters on the lobes while they're "dry" can score the lobes. Since cam lobes rely entirely on oil slung from the crankshaft, no amount of priming the oil will prevent cam lobe failure on an engine with "dry" lobes.
    I agree, its not much of an issue in the real world, but I deal specifically with a lot of low-mileage classic cars. I have a 73 Chevy that I bought with 58,000 miles and it had sat for three years. The seller primed the oil and started it and it was only a matter of 200 miles until I had three flat lobes for the same reason. I guess my line of work just rubs my nose in flattened cams day after day so I'm a bit paranoid
    There are methods where you can drill a .010 hole in the base of the lifter to positively oil the lobes and that might be something to try. At least that way spinning the pump would put oil on the lobes. I've also toyed with the idea of using a piece of stainless brake line tubing with 16 holes drilled in it and install it above the cam. Bend it up at the back and drill a hole up through the intake for it to pass through. Then oiling the cam is as easy as squirting from an oil can. Just pressurize that little manifold and you're set. I come up with weird ideas like that all the time. I would have made a great Amish Farmer.
    Oh.. and definitely a drive shower. I'm an ounce-of-prevention kinda guy
    I'm really liking this dialogue and I'm learning soooo much. Thanks!!!!

  10. #10
    curtis73
    By the way... I just won the cam for $33. Now, does anyone have a 350 block for me? I just missed a 4-bolt block on Craigslist for free

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