new 355

[TORY]

Hello I am in the process of rebuilding my Mercruiser 350 bored .30 over. I am looking for any suggestions on a cam duration spec. Is 284 with a 490 lift too much? I would like to make in the 400hp range so I am in the process of tracking down a good set of 2.02 heads. Do you think the dart sportsman is a good place to start? I would like to run 10:1 with 64cc heads. Well any suggestions would great. By the way this is going in my 87 Minx and I am running about 65 with my 330hp sb with a lab finished cleaver prop that I had got made for it. Thanks

[PaulO]

Just my opinion, 10:1 is too much with the constant wide open throttle and the quality of fuel. Most have kept it to 9.5:1. By 284 duration, I am assuming you are talking gross duration not .050? If so, it will work out to around 230 at .050. That is too much duration for stock risers. You need to keep the duration down below 224 with a 110 deg. lobe seperation to eliminate the threat of reversion with stock risers.
PaulO

[TORY]

Thanks for the help Paul and I think I will lower the gross cam duration. As for the heads I am wondering if I should stick with my current heads and have some porting and polishing done but then in the end I would probably have more money spent than a set of new ones. Paul do you think I should just buy a crate motor? I have allocated a 4k budget so i should be able to get something decent.

[woodsy32]

If I were you, and I am in the evalution process of repowering my Donzi '18, Iwould be giving the GM crate motors a good hard look. I do not know if you are running in salt or fresh water, but they have a motor called a "Fast Burn 385". It sells for approximately $3850.00 It is a 350 with all the goodies and a set of aluminum fast burn heads. Supposedly puts out 385HP at 5200rpm. I think the only thing you might have to change is the head gaskets, and I think they are already composite to prevent galvanic reaction between the metals so maybe not. They also have several other crate engine options as well. Add a set of Stainless Marine manifolds and you should be all set. I am trying to find the $$ to accomplish this myself. I am also kind of worried about my OMC King Cobra drive, but thats a whole other story.

Dave

[boxy]

Tory, my local GM dealer figures the fast burn 385 could be bought for around $6000.00 Canadian. I'm in Ottawa, and we run a truck to Ogdensburg New York every day, shipping would be a snap. You may even be able to get it drop shipped to my warehouse in Ogdensburg, and save yourself some shipping , and customs costs.

Everbody else: If you need/find parts in Canada, let me know, we run a cross border trucking company, and your US dollars go far up here, and you can be almost certain that the parts have never been in salt water.

------------------
boxy
mailto:sboxma@sprint.casboxma@sprint.ca</A>
Smuggler's Cove
Ontario

[oldLenny]

Boxy,...Do 18' DONZI PROJECTS fit into your truck, coming into Canada from the Northeastern US states?

[boxy]

Lenny, if you can find it, I can help you with the shipping and customs clearance, or even simpler, we'll bring it in bond to my warehouse in Ottawa, and then re-manifest it in bond to Victoria. It'll travel right across the country, and you can clear it through customs at home.

------------------
boxy
mailto:sboxma@sprint.casboxma@sprint.ca</A>
Smuggler's Cove
Ontario

[TORY]

The only thing that I worry about is running alumunium heads cuase I run about 20% salt water but I flush it every time. the "fast burn motor" looks good but I was wondering if I could build somthing that good for cheaper, who know? woodsy32 is thier any good machine shops around us? i am looking for one to do my block. All I want to do is hit over 70. Thanks

[boxy]

TORY, are you in Watertown New York... if so there are some great shops just north of the border.

------------------
boxy
mailto:sboxma@sprint.casboxma@sprint.ca</A>
Smuggler's Cove
Ontario

[woodsy32]

Tory...

The two really good shops in MA that come to mind are Forte's Parts Connection (They are at all of the custom auto shows and I have heard they do good work) The other shop is in Westford MA right near me... I think it's is called KD Auto Machine. I had him work on an old 289 Ford project of mine. His work was excellent, but its pricey. He has a dyno and builds all sorts of race motors. I am a firm believer in you get what you pay for. I also want to hit 70mph, but to do that I think I will need a little more motor than 385HP. That give approximately 355HP at the prop. It might get to 70 if the conditions are right, but I would not bet the house on it. The descripition of the fast burn heads on the GM performance website indicated that they made almost 500HP on a 383 @ 6000RPM. A little too much rev for my OMC King Cobra I think. If you intend to stick with your 350, do yourself a favor and put in the 400 crank to get to a 383. Also, spend the extra $150 to $200 to have the motor balanced. The extra cubic inches and the balancing will add a lot of smoothness to the motor, not to mention a few extra ponies. I would also put in high strength bolts, and bolt kits for 350's are cheap. If you ever intend to run a blower or nitrous, make sure you use a a forged piston. I would not go over 9.5:1 for a compression ratio... Boat motors are always loaded up and detonation is a KILLER. I think the crate motor is cheaper than what I could do myself only because if I built it myself, I would not be at all happy unless everything inside the motor was bulletproof, and bulletproof costs big $$$.

Dave
dave_wood@millipore.com

[rayjay]

Tory,

Look into running a "closed" cooling system even if you do not run an engine with AL heads. This has many advantages besides allowing you to run AL parts like heads. Rather than repeat this, search for previous messages on "closed" or "fresh" water cooling systems to learn more about this.

From what I have seen, the "fast" burn engine would be a real good choice. AL heads are more efficient at getting rid of heat and generally let you run an additional .5 point of static compression compared to an FE head before you have detonation problems, plus the additional compression will give you more power.

rayjay

[BigGrizzly]

I think I like where your going. 10.5 is what I have its got over three seasons on it. My compression ratio is measured, not somebody's pistons they say is 10.5, the real thing. Need more specs. Sounds like a high lift short duration cam. If your looking for top speed and 400 hp that set up is not going to do it! Your going to need more duration-230- and a dual profile cam. If you do this then any thing less then 10.0 will be a waste of time and money. The dart iron heads are good, especially if you are raw water cooling. Remember at 160 deg f salt crystalizes and then alum. heads are trash. How many times have you seen someone build a motor and has some wild cam that goes slower then before. Chances he keep the low compresson pistons. I would explain, but i have in many eailer posts read them than make your own decision. Also look at all the different engine configurations on the prop&speed post they all go the same realitive speed-65mph give or take a few. Strange isn't it!

[This message has been edited by BigGrizzly (edited 09-25-2000).]

[GeneD]

Wow!
All that was really great. Big G, you are awesome!
My suggestions?
Keep all the stuff you have and make it better. Port those heads, replace those pistons. Get some good rings. And if you really must have a new cam, go with the pros. They have all the info on cards and can make a very good choice for you.
How about some nice roller rockers? Supposed to add 5-30 HP depending on application.
Maybe a factory roller cam?
If you keep your motor costs down, you could afford to buy all those other goodies. A nice set of racing exhaust manifolds! Nice carburator? How about a fuel injection system?
And really, for about $5K, you could come down to Florida in April and buy a Merc motor new in the crate!
Lots of possibilities for you.
Man...wish I had $4K to spend on a motor!
Hey bud, I think your boat is going plenty fast for what it is. Did you say 330 HP with the 350? What do you have on it now that makes 330 HP?
Go baby go!

------------------
GeneD
007
Melbourne, Florida

[Jamesbon]

Just about everything spoken of in this thread, sits in my new 388 stroker that should be dropped in the 21 GT in the next couple days. (registry # GTX2100021). If you have any questions, please let me know.

388 cu in. Chev. (350 block, .060 over, 400 Scat crank), GM Fast Burn Alum. heads, Bullet solid lifter roller cam - .540 lift, 290+ (??) duration, JE forged alum. pistons, 10.01 calculated C.R., stainless Marine long tube manifolds and risers, (long tube enables the use of radical cams w/o fear of reversion), fresh water cooling conversion (for Alum. heads), Quadrajet marine carb sitting on an Edelbrock Vic. Jr. Vortec intake, Mallory LED distributor.

If I don't get lazy, I'll be able to provide the first performance reports within a week or so. The engine's ready to drop in with exception of 2 accessory belts. (still have to pick'em up) I also need a rev limiter, but will go ahead and break it in and test drive w/o one.

[TORY]

Thanks BigGrizzly for the info and GeneD plus all of the other responses. I think I will take Biggrizzly's advice. I think I will look into the dart Iron heads and get a good port and polish job. I know a shop that could extrhone it (sp?)As for Pistons I was wondering what type to buy this week? if any of you could give me a proper cam spec and manufacturer that would be great. The roller cam is also a choice, is thier any disadvantages? Sorry for all the Questions. My current motor is a 355 4bolt main(originaly a tempest motor) Steel crank. I added a 274 degree cam and trw flatops. (what I remember)I had the heads done over and I had them polished and a little port work done. I had them mill the heads a little also. On top I have an iron manifold with a rebuilt Q-jet with the butterflies modified. It goes nice but not over 65. well thank you for the advice everyone. I just do not want to get a running motor that will underperform. I also have a lab finished prop that I had balanced and sharpened, it is a cleaver and I have it bent to 22.

[This message has been edited by TORY (edited 09-26-2000).]

[Jamesbon]

As I see it, the only disadvantage of a roller cam is the cost. Otherwise, it's a "winner."

Personally, I would go with TRW forged pistons. Hypereutectic pistons are okay if you're on a budget and will stay away from nitrous, turbo's, blowers...

If you can, get the combustion chamber size in C.C's to determine what compression ratio you'll achieve using whatever pistons you choose.

I like the Q-Jets, even though some Holley's may be slightly faster. The Q-Jets have always awarded me faster, no throttle starts, ease of tuning, and "leak free" operation. I would trade the cast iron intake in for an aluminum unit to save a few lbs., But I guess if you're running raw water cooling, iron may be better. However, I ran an old Torker intake in salt water for 8 years with no signs of leakage. However, the water passages were just about shot, so......

[Randy Hibbard]

Tory, I also have a 1987 Minx which I recently modified. What I would suggest is to consider the future of all your modifications. My boat had low hours on it and the 350 mag Alpha set up worked perfect. Being a die hard hot rodder, I wanted more speed so after confirming the short block was fine, I took advantage of cheap SBC prices and instaled; World Torguer heads, Comp Cams Extream Marine cam, their roller tip rockers, preformer rpm intake and the oversize 750 edelbrock marine carb- which did need the Holley marine fuel pump. All was assembled with proper marine parts, cam degreed, ect. I left the centerrise Merc exhast manifols in place. The cost of all that was only around $1500 so it was worth it, even if just to freshen up the top end. Now the Minx is a great riding but heavy boat, and if you have a factory Alpha drive, you know the limits of it`s power handeling. On my second speed run, Mine blew out the upper gear assy. I went for a new Merc complete unit for $2900 ouch. I just wanted dependability. Do`nt want to break down under the Golden Gate Bridge, I`ve seen the Great Whites on the Discovery Channel out there! My top speed has only sightly increased and the acceleration has greatly increased from the mods. I run a 23p Stileto at only 4500rpm. The HP exhast manifolds might help at this point but how much? Will the hook in the hull even permit more than 65 mph? I`m thinking not with a SBC. If I had to do it all over again, I would be happy with my current set up, as you have now, and save for one big future investment; a big block with Bravo One. It just makes sense if you plan on keeping the boat. The speed would be amazing and reliability of a factory Merc motor unbeatable. Why deal with alum. heads and reversion problems when your boat needs a BB anyway. Please forgive the long post, just wanted to give some advice to a fellow Minx owner. Thanks to the others for their input, now I want those Stainless Marine Manifolds. Maybee Paul.O will buy them and let us know.......... California Randy

[PaulO]

Thanks Randy,
I guess I have been somewhat of a test case for others! I would love to try the exhaust mods but, when I look at those cavernous center riser manifolds and risers and compare them to the so-called performance exhaust I have had on my cars, I can't believe there's that much to be gained. I know, I know, Grizzly, seperation of the pulses and length of runners.... but exhuast tuning only addresses a relatively narrow RPM range blah, blah, blah, sorry for rambling.
PaulO

[CDMA]

I read somewhere that you can get chromed water jacketed headers from Basset Racing for something like $750 dollars. Might be worth a look. I don't care if they work they look SO cool.

Chris

[MattM]

CDMA, those basset headers are water injected, not water jacketted. I looked into them.
Tory, did you look into the Edelbrock Performer RPM package? I built a 454 with their Performer RPM recipe and was really happy with it. Nice sounding idle, stock power below 3000 and then it pulled hard to 5800 RPM. At that time (1994) they advertised the package for the 350 and showed 420 Hp with it with mildly worked over big chamber factory iron heads with 2.02 and 1.60 valves. They sell you the matched carb, intake, and cam and tell you how to build everything else, it's all matched so there's no guessing about cams and stuff. A few years ago they added their own aluminum heads to the mix, but if you want to stay away from them I'm sure you could prod them to dig up the mods list for the factory iron heads. Good luck

[rayjay]

Air Flow Research, aka AFR, http://www.airflowresearch.com/ has some very nice FE heads as well as AL heads. They also have CNC porting available, and from what I have seen their CNC porting does work. CNC porting has a great advantage in that every head is done the same and the bowls come out really nice. CNC porting leaves some extremely fine lines in the port which probably help the intakes a little bit, although may catch a little carbon in the exhausts. If you talk to them, they will work with you on getting the correct port size, intake and exhaust, for your combination. rayjay

[TORY]

Well this gets me thinking again, If i do go with the Aluminium heads, I think the edelbrock package may be right but I am scared even though I run 80% fresh water. The 420hp edelbrock uses a cam spec of 234 deg at .050. This could be a little much but that is ok. The idea of a big block is nice but then the budget would go to 8k with a new outdrive. Not in my plans for now but someday. The q-jet is in question becuase of the years of reliability I had with it.

I think the best bet is to listen to you guys and find something we all agree on and I will just do it. I hope that with these mods I will at least hit 70mph. If not I will be bummed but that is ok. Looking at the thread on top speeds, It looks like it may be a little more difficult to run than I expected. Any one now where I could get some custom side glass for the MInx, Thanks

[This message has been edited by TORY (edited 09-26-2000).]

[CDMA]

Tory,

With your budget it is a simple decision. fresh water cooling. $700.

Chris

[PaulO]

Tory,
Not to bum you out but, 70 real miles per hour is a pipe dream with a 350 modified in the way it sounds you are going. Also, keep the Q-jet. I ignored past experience and "upgraded" to an expensive 750 Holley on my 383. It runs great but, no faster than the Q-jet.
PaulO

[BigGrizzly]

Just sit back JamesB is doing all the home work for you. Wait untill he gets it done. If you like it use it, if not go your own way. Boats are close enough to evaluate. Sounds like he is going in the right direction. I would Like more cam specs. opening and closing etc. Pistons are a good reliable brand they custom make my race bike pistons. Ross is the other brand I use. As for exhaust being narrow power band, well of my three exhaust systems go the CMI have the broadest power band, by 650rpms, on the dyno. I have eight different cams for that motor and the result is the same on all of them. The power band is at different places with each cam but the result is same, except for the 45-29 with 106 lobe centers when it is 800+rpms.

[This message has been edited by BigGrizzly (edited 09-26-2000).]

[Jamesbon]

Awaiting a home..... http://albums.photopoint.com/j/ViewPhoto?u=1229726&a=9073806&p=29370310

[RickSE]

One thing you guys may want to think about is the fact that the new Mercruiser 6.2L (377 c.i.) engine is rated at 320 (about 340 at flywheel) propshaft horsepower and has no problem pushing an 18 over 70 MPH. 1HP/c.i. can be obtained with 10 to 10 1/2:1 compression and a good induction combination. Theoretically a 350HP 350 should be able to break 70 with the right combination, this includes drive, ratio & prop. PaulO something still seems wrong with your combination, your 383 should be able to break 70. Maybe you need to mess with the cam timing or change your drive ratio? What was your HP supposed to be?

[CDMA]

I am convinced the difference lies in the x dimension. The hulls are the same, they weigh similar amounts the only thing that really could be that much differnt is the x dimension. That is why the new 18's have a raised hatch cover. Just my two cents.

Chris

[BERTRAM BOY]

Chris,
I have to say that I agree with your X-dimension reasoning. I only have 260hp And I'm almost at 65!!! So far I've only hit 62 (GPS reading) but that was with full fuel and 2 people ( 1 to hold the GPS). I think with less fuel, 1 person and maybe a tune up I MIGHT be able to hit 65. That's with only 260hp and the X-dimension raised 3 inches.
However there are disadvantages. There is a big 'ol hole in my deck that the flame arrestor is sticking out of, and doesen't really look that good.
BERTRAM BOY

[RickSE]

I think the Donzi Guy told me the current "X Dimension" for the 18-Classic is 14 1/2". I'd have to check though, I have it written down somewhere.

[GeneD]

Here we go again!
I think the difference is made in two areas. And by themselves, don't make much of a difference.
One...the X dimension. I am raised 2.75 inches from the norm by using the Alpha SS.
Two...my Alpha SS is specially geared. Probably the only one in the country with this gearing.
The gearing woke this boat up. Of course, I had to go to a bigger prop. I'm now runing a 25. I think I am the only one running a 25 - anyone?
And my top speed is unknown, but if I could use my speedo as a comparison, without the gear change, the Alpha Super Sh*t was getting the boat to around 56 MPH. After the gear and prop change, the Alpha Super Sport was pegging the needle. It formerly went past 60 over past zero, and into the 10 MPH range. All this with a stone stock 260 Mercruiser.
My new motor? Who knows. I'm hoping to get back to 20 MPH!
Dream away Gino, dream away!

------------------
GeneD
007
Melbourne, Florida

[PaulO]

I think that Chris (CDMA) is on to something. My question is this: What is the trade off of the raised x-dimension or the SS? (besides the hole in the hatch) There has to be a trade off!! Hole shot? Ventilation during acceleration? Poorer cornering?
PaulO

[CDMA]

I have been giving this x dimension thing way too much thought. I ran it past a prof here and his explanation went as follows ( close as I can remeber):

The boat at high speed gains in a few ways with a raised x dimnension. First of all, which is readily apparent, is that there is less drive in the water therfore less drag. When I asked him why it made such a big difference on a Donzi the first thing he said was let me guess it is a deep v that is realitively heavy right? Well I thought that was correct. So above and beyond the reduceded drag it can actually do the following. A boat skimming over the surface of the water makes turbulance so lets say hypothetically a Donzi's turbulance reaches 18 inches bellow the surface ok? So with a regular drive the top edge of the propeller is about 18 inches bellow the water. So if you raise the x dimension the top of the propeller, which provides little to no forward thrust) gets into the turbulance. Now since the turbulance is more air it is less dense than water so the propelller has less drag. Seemed a little far out but I mean this guy has been around for ever. He is know as the father of the modern propeller. He is like 82, still teaches and designed or supervised the design of most of the props for all the nuclear navy subs. Really a pioneer in his field. So then he gave another reason which I really did not follow but he said it was right so I will convey it to you all and take it as you want. He went on about how raising the x dimension will create more stern lift. I sort of balked at this because it is against all I know about lever arms and the such but he was sure. I really could not get a good explanation but he went on how due to increased upward forces the stern is lifted higher off the water making less wetted surface in the water hense more speed. Which would also explain why it makes such a big difference on the vee hull because there is inhgerintly so much surface area in the water. Now he teaches a complete years course Junior year. If he is still alive I ought to know more about it then. Sorry some of this stuff is so vague he really is old and it sort of is hard to follow him. Now some other time I want to corner him and pick his brain on surface drives because personally I think there is a lot more to be had in Geoo's boat. It it by far the wildest thing but personally I think it needs more lift. I am so interested cause as soon as he sells that thing it is mine....keep all your pesky hands off....

Oh Bertram Boy you are right it is a tremendous difference. With one person light fuel I barely get 58 more like 57.something in reality. Bummer.

Chris

I like this boat school thing

Except I have a math test tommorow ... ewwww

[Tim Howland]

Tory,

Good to hear from another MINX owner. If you have the factory wings on your boat you could send them to Dave Cunningham at Sea View Marine. Both of the wings on my MINX were badly checked and cracked. I purchased the 2370 bronze plexiglas from Cadillac Plastic in Manchester N.H. sent the raw material and the rh & lh wings to Dave and he did an excellent job with the angles, holes, and final finish sanding on the bottom routered edges. Worth a call, 813-933-1739 leave message, Dave is good about calling back. I put an new Rochester Quadrabog on my small block, more durable long-term than the Holley's.

Tim

[GeneD]

The trade off between the SS and the Alpha One is, from my perspective, having used both, is that the SS doesn't provide a lot of bow lift. I have also noticed that the cornering is not as good.
But this is something that I got used to rather quickly, seeing how the thing is so freaking faster than the Alpha One.

------------------
GeneD
007
Melbourne, Florida

[BigGrizzly]

Chris he gave you the answer to the stern lift. Listen to what he said about turburlance--prop runs in air then when it hits the non aireated water, on the down strock it lifts thr stern. Like on twin offshore boats-counter-rotate in one direction it lifts the stern , the other way itpulls the stern down thus lifting the bow. listen to ewery word he says. The answer is always there. Is this the guy the use to call "Doc Prop"?

[CDMA]

So a raised x dimension gives more lift. But only stern lift not entire boat lift.....ok. So this could cause Geoo's boat to run bow down with more drag hence slower speeds


Chris

[Forrest]

. . . and in many cases, you don't want or need "bass-boat" bow lift. My 16 Ski Sport uses an Alpha SS with 1.5 gears and turns a 23" cleaver at 5000 RPM. The gimbal is mounted about 1/2" high which puts the cavatitation plate about 3-1/4" above the bottom of the boat. This combination is NOT a bow lifter. I have limited my trim to about two ticks from all the way down, and this is high enough. If I let it trim above two ticks, the bow doesn't go much higher, but the prop starts to loose bite. Even at two ticks up, the boat is very loose and is about as fast as you would ever want to go in a 16. Hay, just ask "white knuckled" Emmo! The Alpha SS made a huge difference in top end and handling over the stock #1 (Alpha type) drive.

------------------
Forrest

[PaulO]

So, are there other ways to acquire an Alpha SS? Do they still make the castings and the internals? Can you assemble one? It's a shame no one makes them after-market. Is it only the lower unit or do both need to be swapped?
PaulO

[GeneD]

I DO beleive there is a joint that is making a similar unit. But I don't know who they are.
GEO would know, I think he checked into it once.
The guy that told me he knew the location of 2 units won't respond to my emails. So that is out.

------------------
GeneD
007
Melbourne, Florida

[GEOO]

GeneD, I think the name of the outdrive company was Stern Power. I'll look into it.
I'm psyched about your new power!!! Sould be sweet!!!!!
GEOO

[BERTRAM BOY]

Hey Gene,
Awhile ago a company by the name of Konrad was supposed to make the "Alpha SS" but never really heard anything.
BERTRAM BOY

[BigGrizzly]

Try Imco, saw one on a way trick triple step Eliminator. the unit looked like a merc but way short.