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View Full Version : What motor would you build for a 18 classic



problemchild
05-23-2007, 08:40 PM
My 400 small block is on its last legs, and the guys at a machine shop say a mild 350 hp 350ci engine would be a good replacement (regular gas and reliability), but coming from a 450 hp engine this might seem a little bland. other options would be to build the 350 to put out more power, put a built 327 in it like what it came with (its a '76) try to save or build my 400 again, or build a 383.

gold-n-rod
05-23-2007, 08:47 PM
There's no replacement for displacement.

If the 400 is just tired, refresh the mo-fo and get it wet!!!!!!!! :)

Lenny
05-23-2007, 08:48 PM
High torque 383, it will get you into all the trouble you will ever need...

http://www.gmperformanceparts.com/Parts/showcase_detail.jsp?engine=0

ZZ if you are 100% a fresh water person...and longer risers

BB's in an 18 do not provide any benefit nowadays. The added 200 pounds does not offset the available horsepower available from a stroker small block. The 18 LOVES the balance provided from the SBC and handles well, and can come off the throttle well.

:)

handfulz28
05-23-2007, 09:39 PM
Vortec 6000
400+HP LS2
500HP LS7 (427ci all aluminum)

MOP
05-23-2007, 10:00 PM
GM HT 383! A real good bang for the buck!!

ITTLFLI
05-24-2007, 05:00 AM
freshen up the 400 or 3-8-3!!!

maddad
05-24-2007, 05:57 AM
Go for as many c.i. as you can. Twisting the crank hard to make power will last longer than twisting it faster. You can add up to 20 inches to your 400, and 420 x a mild 1.1 h.p. per c.i. will get you right back where you were.

LKSD
05-24-2007, 06:33 AM
I too would say 383.. Nice power & torque.. Plenty for that boat.. ;) Jamie / Lakeside

Rootsy
05-24-2007, 07:20 AM
you'll want more after you get used to watcha got... so just go big in the beginning... or stay home...

Craig S
05-24-2007, 09:03 AM
fwiw, I think the 327 was phased-out at the end of the 1968 model year. Maybe a hair longer in industrial packages, but probably not much.

gold-n-rod
05-24-2007, 09:18 AM
fwiw, I think the 327 was phased-out at the end of the 1968 model year. Maybe a hair longer in boats, but probably not much longer.

And the higher HP 327's made their power way up in the rpm range. Not the ideal place for boating horsepower.

The 300 hp 327 (solid lifters) motor in my old race car used to spin to over 7 grand with the stock valvetrain. Dayum, that thing would wind.

Don't stop at 383. As mentioned earlier...... go big!!! (as in inches, not block!)

Eugene Nahemow
05-24-2007, 10:07 AM
Does anyone know the cost of the ZZ383?

Do you need to buy them from a GM dealer?

problemchild
05-24-2007, 10:59 AM
In terms of refreshing my 400ci, i still am considering it, but my buddy at the machine shop didn't like the way the #8 cylinder was scored, its already bored 20 over, the motor has NOT been reliable (i've owned it since march last year, when the motor had only 60hrs on it. I ran it for another 50, and have the top end apart twice on it). We can't figure out why it keeps blowing head gaskets; and there are some signs of overheating in the cylinders, althougth I've never seen the temp guage show anything signs of this. I don't know what would be eaiser-starting over or fixing what I got... :confused:

thanks for all your input
-Alex

RickSE
05-24-2007, 11:38 AM
What casting is the 400 block? Early 4-bolt? Later 2-bolt?

I'd rebuild the 400. If done right it'll make a crap load of HP & torque. I have a mild 400 in my drag car that makes an easy 490-500hp below 6,000RPM with no frills and its full of stock GM parts. The key to the 400 is the rod length. The stock 400 rods make lots of torque but they beat the heck out of the pistons and cyl. walls. I run factory GM 350 rods in my motor.

I've put these pages up before; its old stuff (late 1980's) but still makes for some good reading.

MOP
05-24-2007, 12:35 PM
THe over head gasket issue could be no or plugged steam holes, the cylinders are siamesed so no water passes between them the steam holes allow critical flow between the heads and block. Without steam holes they get hot only in the top of the block kind of a hot pocket which will not show on the temp gauge as the rest of the block flows water Ok!

Phil

mrfixxall
05-24-2007, 01:04 PM
In terms of refreshing my 400ci, i still am considering it, but my buddy at the machine shop didn't like the way the #8 cylinder was scored, its already bored 20 over, the motor has NOT been reliable (i've owned it since march last year, when the motor had only 60hrs on it. I ran it for another 50, and have the top end apart twice on it). We can't figure out why it keeps blowing head gaskets; and there are some signs of overheating in the cylinders, althougth I've never seen the temp guage show anything signs of this. I don't know what would be eaiser-starting over or fixing what I got... :confused:
thanks for all your input
-Alex

Bore it out,,,,030 406,,,060 412.... i built a 406 for my buddies boat a few years ago, i punched it 060 over and never had a issue as of today it still runs like the first day i built it...If your buddy is going to bore it out make sure he uses deck plates which is a must on a 4.185 bore.... I bet your heads are not drilled for the steam ports and thats where your problem lyes..take some pics of your heads and post them...Running the engine at 160 deg wont be a problem,in fact it would be better for a 406. if your worried ablut the block and the overheating problem then replace it with aDart little m block..
check this one out..

http://racingjunk.com/post/850664/434-SHORT-BLOCK-DART-LITTLE-M-BLOCK.html

problemchild
05-24-2007, 02:23 PM
Here's a picture of the block and head gasket, i'm pretty sure that it has steam holes, right? I know the heads have steam holes, also look at how the gasket blew, anybody ever see this before?? its pushed in from the hole where the head bolt goes through. it did this at two places on each gasket. also the casting # is 380817, I think the guy I bought it from said that it was a later 2-bolt.


thanks guys,
-Alex

DON N.
05-24-2007, 02:47 PM
Scorpion Package .

RickSE
05-24-2007, 02:50 PM
Make sure all these holes have corresponding holes drilled in the heads. Non-400 heads won't have the holes unless someone drilled them.

Chevy head bolts tap into the water jacket. It looks like pressure from the water jacket came through the head bolt and into the cylinder.

Yes the 817's were 2-bolt main blocks, car & truck blocks.

problemchild
05-24-2007, 03:06 PM
there are also some hairline cracks between the steam holes and the hole for the head bolt if that means anything

Lenny
05-24-2007, 03:35 PM
Does anyone know the cost of the ZZ383?
Do you need to buy them from a GM dealer?

Here they are $3800 bucks. So figure about $3500 US $$$.

mrfixxall
05-24-2007, 03:45 PM
there are also some hairline cracks between the steam holes and the hole for the head bolt if that means anything


block could be used but i wouldnt trust it with the cracks going into the threaded hole....

How about a pic of your cylinder heads?????

Also looks like their was no sealer on the head bolts too....

problemchild
05-24-2007, 05:45 PM
yes I used sealer, I had already ran a tap through the holes by the time I took the picture. Pictures of the heads coming soon...

MOP
05-24-2007, 09:56 PM
I know you said you used sealer but wanted to bring up the point a little more strongly for those that think they do it right! For an auto app you can get away with just gooping the bolts the anti freeze will save your butt not so on "raw water" cooled marine, When running raw water, it is important to evenly apply a decent dab into the thread bores, clean the entire surface with acetone "NOT GASOLINE" gas leaves a residue and sucks for final clean up, put the gasket in place then set the head on and goop the bolts. By doing it that way the bolts will push sealer down the thread bores giving the lower thread area far better protection. One of my very own kids who has watched me fuss over engines all of his life and who I thought had learned something put together a lightly worked 350 for his 23 Formula, end of the second season he found water in a couple of cylinders. We eliminated the manifolds and went on to pull it apart to find several bolts needing near nothing to remove as the threads were GONE! That was about 20 years ago the little **** still hears about it!

MEAN OLD PHIL

BigGrizzly
05-29-2007, 09:30 AM
In my opinion I would do a 350 for fuel economy or a 383 for the rest. any larger it may become a problem, unless you can find another 400. No real data but it seems that 400 don't seem to fair too well in boats, but do great in trucks. I think it may be the volumetric efficiency.

Eugene Nahemow
05-29-2007, 05:12 PM
In my opinion I would do a 350 for fuel economy or a 383 for the rest. any larger it may become a problem, unless you can find another 400. No real data but it seems that 400 don't seem to fair too well in boats, but do great in trucks. I think it may be the volumetric efficiency.


I have two 400 blocks that were prepped for my Magnum which I never got around to using.

I was told that the 400's were better for a boat due to cooling and that they had a tendency to overheat in a truck.

If this is not so, I have an anemic 350 in my Chevy 2500 Silverado that could use one of these blocks.

Lenny
06-01-2007, 01:44 AM
I have two 400 blocks that were prepped for my Magnum which I never got around to using.
I was told that the 400's were better for a boat due to cooling and that they had a tendency to overheat in a truck.
If this is not so, I have an anemic 350 in my Chevy 2500 Silverado that could use one of these blocks.


Sooooo, does this mean you are selling the 400's ??
;)

Eugene Nahemow
06-01-2007, 02:38 PM
The 400's are definitely for sale.
The two 400 blocks that I have were:
Dismantled,degreased and cleaned.
Magnafluxed.
Cylinders bored 030 over
Cylinder blocks re-surfaced.
Main Bearings line bored & honed fit caps to block with ARP bolts.
Cam bearings precision installed and shaft fit.
Fell Pro seals were used and freeze plugs installed.

Tom Davis
06-01-2007, 03:49 PM
Hey, the last stock 350mag I put in an 18 did over 80mph!

Yup, stock, reliable, warranty...

Tom Davis
Winni Bandits

Eugene Nahemow
06-01-2007, 04:14 PM
Hey, the last stock 350mag I put in an 18 did over 80mph!
Yup, stock, reliable, warranty...
Tom Davis
Winni Bandits


Towed behind a truck!:bonk::biggrin.::biggrin.:

mrfixxall
06-01-2007, 04:23 PM
Towed behind a truck!:bonk::biggrin.::biggrin.:

AND THAT WAS WITH A TAIL WIND PUSHING IT!!!

mABE JUST MABE IF IT HAD A DPX OR A BLACKHAWK BRIVE....

MOP
06-01-2007, 06:24 PM
Towed behind a truck!:bonk::biggrin.::biggrin.:

Nope hooked to a Blackhawk!

problemchild
06-05-2007, 12:04 PM
Got a price on the 383 with, but at $3,750, its alittle more than I can spend right now, (although its probably not a bad price). a mild 350 with my current dart heads, high rise intake, 750cfm holley, crowler rockers, ect..., is supposed to put out 330 with a mild cam and the mercruiser exhaust I have, for about $2000. the 383 would put out around 425hp WITH headers, so about 365hp without them??

I was wondering how much slower my 18 would go if i put in the 350 and bought some headers when I had the money (than I could also run 89 octane gas) than it would with the 383 w/o them?

also, would it be worth just running the 350 and making it into a 383 later on if I wanted???
thanks again,
-Alex

maddad
06-05-2007, 01:57 PM
I put a running 350 that someone else took out of their boat in my boat, and built the motor I wanted in no rush.
Worked out well for me.

Lenny
06-08-2007, 08:41 PM
I put a running 350 that someone else took out of their boat in my boat, and built the motor I wanted in no rush.
Worked out well for me.

Great idea :yes: I think I'll do that ;)

:D :D :D

Dregsz
06-16-2007, 01:19 AM
My 400 small block is on its last legs, and the guys at a machine shop say a mild 350 hp 350ci engine would be a good replacement (regular gas and reliability), but coming from a 450 hp engine this might seem a little bland. other options would be to build the 350 to put out more power, put a built 327 in it like what it came with (its a '76) try to save or build my 400 again, or build a 383.

OK, Chevy quite putting the 327 motor in model year 1968, so I don't know why there was one in a 76 boat.
Merc had the 350 in it's line up long before that too.

If your block is salvageable I'd rebuild the 400 block to a 406 or 421 stroker.
(406 is .030 overbore, 421 is .030 over w a 3.875 crank instead of a stock 3.75 crank)
I probably wouldn't go any bigger then that in a stock GM 400 block/
I'd also build it woth a Hydraulic roller cam and matching lifters. Should be closer to 500 hp.
E

Dregsz
06-16-2007, 01:26 AM
In terms of refreshing my 400ci, i still am considering it, but my buddy at the machine shop didn't like the way the #8 cylinder was scored, its already bored 20 over, the motor has NOT been reliable (i've owned it since march last year, when the motor had only 60hrs on it. I ran it for another 50, and have the top end apart twice on it). We can't figure out why it keeps blowing head gaskets; and there are some signs of overheating in the cylinders, althougth I've never seen the temp guage show anything signs of this. I don't know what would be eaiser-starting over or fixing what I got... :confused:
thanks for all your input
-Alex

Are you sure it's blown HGs and not a cracked head or block?

Even if all this is true it has no bearing if you freshen you the block, you can take 30 or up to 60 over just make sure the main cabs and webbing are good.
probably want some new heads.
Sometimes it helps to switch shops too...

Dregsz
06-16-2007, 01:28 AM
Got a price on the 383 with, but at $3,750, its alittle more than I can spend right now, (although its probably not a bad price). a mild 350 with my current dart heads, high rise intake, 750cfm holley, crowler rockers, ect..., is supposed to put out 330 with a mild cam and the mercruiser exhaust I have, for about $2000. the 383 would put out around 425hp WITH headers, so about 365hp without them??
I was wondering how much slower my 18 would go if i put in the 350 and bought some headers when I had the money (than I could also run 89 octane gas) than it would with the 383 w/o them?
also, would it be worth just running the 350 and making it into a 383 later on if I wanted???
thanks again,
-Alex


My 350 w TRS drive ran 62-64 mph

Dregsz
06-16-2007, 01:29 AM
My 350 w TRS drive ran 62-64 mph


ps, no need for a high rise intake on a motor that's only running 4500-5000 rpm

Dregsz
06-16-2007, 01:31 AM
What casting is the 400 block? Early 4-bolt? Later 2-bolt?
I'd rebuild the 400. If done right it'll make a crap load of HP & torque. I have a mild 400 in my drag car that makes an easy 490-500hp below 6,000RPM with no frills and its full of stock GM parts. The key to the 400 is the rod length. The stock 400 rods make lots of torque but they beat the heck out of the pistons and cyl. walls. I run factory GM 350 rods in my motor.
I've put these pages up before; its old stuff (late 1980's) but still makes for some good reading.

stock rod length in a 350 is 5.7" I ran a 400 block 377 destroker in my racecar w 6.2 rods, I wouldn't hesitate to run a 6" rod in any 400+ CI build up

Dregsz
06-16-2007, 01:33 AM
THe over head gasket issue could be no or plugged steam holes, the cylinders are siamesed so no water passes between them the steam holes allow critical flow between the heads and block. Without steam holes they get hot only in the top of the block kind of a hot pocket which will not show on the temp gauge as the rest of the block flows water Ok!
Phil

Steam hole flow is not critical

Dregsz
06-16-2007, 01:37 AM
I think the guy I bought it from said that it was a later 2-bolt.
thanks guys,
-Alex

2 bolt mains are fine w 400 blocks the caps are much wider then in the 350 block. I've seen 10x more cap failures in 4 bolt 400s due to cracks on the slayed bolt hole

So this is what 10 posts in a row? woo hoo, having fun now.

maddad
07-06-2007, 03:16 PM
Steam hole flow is not critical
Seems like a conflict of opinions here.
I recently did a 400 based build up, and everything I read said avoiding the ultra hot spots at the top of the bores that are caused by steam with no escape route is key to a long lasting motor.
Why do you feel they are not critical?

MOP
07-06-2007, 04:13 PM
Google below then tell us you do not need steam holes!


Chevrolet 400 steam holes

BUIZILLA
07-06-2007, 09:01 PM
how about a stroked and Procharged V6 ??


:) :yes:

zelatore
07-07-2007, 11:01 AM
Man, everybody was so serious. Very few smart-ass replys.

Nobody suggested a triple-nickle or even a turbo rotary. (now there's opposite ends of the spectrum!)

How about multiple briggs and stratons like this: http://www.youtube.com/watch?v=umZpn610AkE


OK, if I was to actually build it myself I'd go for a big-inch small block. Maybe the 427.

Dregsz
07-08-2007, 01:09 AM
Got a price on the 383 with, but at $3,750, its alittle more than I can spend right now, (although its probably not a bad price). a mild 350 with my current dart heads, high rise intake, 750cfm holley, crowler rockers, ect..., is supposed to put out 330 with a mild cam and the mercruiser exhaust I have, for about $2000. the 383 would put out around 425hp WITH headers, so about 365hp without them??
I was wondering how much slower my 18 would go if i put in the 350 and bought some headers when I had the money (than I could also run 89 octane gas) than it would with the 383 w/o them?
also, would it be worth just running the 350 and making it into a 383 later on if I wanted???
thanks again,
-Alex


Why are you afraid to cam the motor?
Give it some cam and you'll get just about enough power out of the 350.
Also, why would you run a high rise intake in a boat?

DonCig
07-08-2007, 06:08 AM
IMO you really need to explore how you use your boat and what is important to you. I went the 427 SBC route and I wish that I had gone with just a little bit smaller of a cam, and I am glad that I went with a Performer RPM dual plane manifold, and probably should have also tried just the Performer manifold. I like my marine engines to have immediate power for pulling water skiers like me, and I like marine engines that do not load up plugs at extended idle. It is not cheap, but adding cubic inches is a failsafe way to build a docile engine with more grunt throughout the rpm range. I have recently changed a few things on my engine to tame it down a little bit. Top speed was more than adequate as it first turned out.
I am able to run on 87 octane gas at 9:49 / 1 compression ratio. I noticed that my Merc. 502 has an 8:75 / 1 comp. ratio with iron heads.
I have gone back to a cast aluminum exhaust manifold (Eddie Marine) from custom fabricated headers. The constant fight with small exhaust leaks with a dual flanged header system was not worth the hassle.
Still very happy with the Demon carb setup. Once you get knowledgeable about tuning them, they are wonderful. Read the tuning book out there for tuning them.
Have learned that I like my outdrive to spin a prop as slow as possible; 1:65 ratio being my favorite if you can get the props and the speed.

Good luck!

wagspe208
07-08-2007, 10:29 PM
Misinformation on the internet is amazing
1) steam holes are not needed for an engine that is usually running over 3000 to 3500 rpm. What is your rpm range?
2) the cracks from the steam holes to the bolt holes mean absolutely nothing. 95 percent of the blocks that have seen any performance time are like that.
3) Compression! your 400 with a very small dish like that has more compression than a 350 (duh) what are your head CC's?
4) the "509" and "817" castings are the preferred blocks to start with. They are all two bolt. The "511" castings are thinner. (don't use these) They were mostly, but not all by any means 4 bolt.
5) Splayed, billet caps (quality ones, not chinese 100 dollar a set caps) will easily hole 750 to 800 hp in a sprint car/stock car style engine. These blocks were used widely in late model engines in the 90's before the dart castings were available.
6) 420 (3.875 stroke) and 434 (4.0) stroke engines can be built in these blocks. It is not for the novice, or backyard builder, or local Napa for that matter. Proper cam (for rod clearance), rods (again, cam lobe clearance), and block clearancing issues will arise if someone isn't experienced.
7) How do I know??? Did/do it for a living
Wags
BTW, I am going to build a 434 for my 18 donzi classic if I can find a 400 block. If not, it gets a 383.

Eugene Nahemow
07-09-2007, 12:54 AM
I have 400 blocks, that are prepped and ready to go.
PM me if interested.


Misinformation on the internet is amazing
1) steam holes are not needed for an engine that is usually running over 3000 to 3500 rpm. What is your rpm range?
2) the cracks from the steam holes to the bolt holes mean absolutely nothing. 95 percent of the blocks that have seen any performance time are like that.
3) Compression! your 400 with a very small dish like that has more compression than a 350 (duh) what are your head CC's?
4) the "509" and "817" castings are the preferred blocks to start with. They are all two bolt. The "511" castings are thinner. (don't use these) They were mostly, but not all by any means 4 bolt.
5) Splayed, billet caps (quality ones, not chinese 100 dollar a set caps) will easily hole 750 to 800 hp in a sprint car/stock car style engine. These blocks were used widely in late model engines in the 90's before the dart castings were available.
6) 420 (3.875 stroke) and 434 (4.0) stroke engines can be built in these blocks. It is not for the novice, or backyard builder, or local Napa for that matter. Proper cam (for rod clearance), rods (again, cam lobe clearance), and block clearancing issues will arise if someone isn't experienced.
7) How do I know??? Did/do it for a living
Wags
BTW, I am going to build a 434 for my 18 donzi classic if I can find a 400 block. If not, it gets a 383.

The Hedgehog
07-09-2007, 09:53 PM
how about a stroked and Procharged V6 ??
:) :yes:

Now that's a novel idea! 1 step closer.

wagspe208
07-10-2007, 09:20 PM
Back in the day...way back when Bush cars were running V-6's and tons of cool hp parts were available, we built a blown alcohol chevy v-6 for a sand dragster. It made 1000 hp and 980 ft/lbs of torque.
200 something cubic inch.
It sounded awesome
Wags

BigGrizzly
09-13-2009, 09:24 AM
We have a twin turbo V6 for sale it is not the grand national engine. but a bush model and marinized.

onesubdrvr
09-15-2009, 06:59 PM
how about a stroked and Procharged V6 ??


:) :yes:
Jim,


We've got a project hull for that one already :D

Wayne

BUIZILLA
09-15-2009, 07:11 PM
dogbreath has an engine...

Tony
10-08-2009, 09:31 PM
This would be the cat's a$$ in an 18;

http://www.volvo.com/NR/rdonlyres/86E8675B-0C64-4A24-82C5-710E96E78EAA/0/kad44_dx.pdf

:beer:

mattyboy
10-09-2009, 09:19 AM
This would be the cat's a$$ in an 18;

http://www.volvo.com/NR/rdonlyres/86E8675B-0C64-4A24-82C5-710E96E78EAA/0/kad44_dx.pdf

:beer:



ummm Tony please come back to us ;)

even spinning 30 pitch props with 10%slip that combo at 1.59 ratio will get you a whopping 61 mph at it's 3800 rpm redline

I do agree with the dpx though and a mild 383 that would be the bee knees

and BTW cat azz??? I thought your hip cool generation called it the cat's pajamas?? :p :) ;) :pimp:

zuit suit riot throw back a bottle of beer

:)


well i could be wrong unless they are swinging 34 + pitch props

Tony
10-09-2009, 10:10 AM
ummm Tony please come back to us ;)

even spinning 30 pitch props with 10%slip that combo at 1.59 ratio will get you a whopping 61 mph at it's 3800 rpm redline

I do agree with the dpx though and a mild 383 that would be the bee knees

and BTW cat azz??? I thought your hip cool generation called it the cat's pajamas?? :p :) ;) :pimp:

zuit suit riot throw back a bottle of beer

:)


well i could be wrong unless they are swinging 34 + pitch props

Yeah, I shoulda figured that someone would crunch the numbers and expose the diesel powerplant for what it probably is - good torque, good fuel efficiency, quiet...but not too terribly swift!

Cat's Pajamas? Yea, I guess I remember that, but what's up with calling it "my" generation? Seems to me that you are close enough to my age to call it "our" generation! :wink:

:beer:

mattyboy
10-09-2009, 10:19 AM
well you started with the cat's azz ;)

I would have went with gnarly, or bitchin :p for that youthful response


yeah I guess there's only a year or two difference there




Hey Mr hand If I'm here and your here isn't it our time??? and what's wrong with having a little feast on our time ???


:) ;)

:beer:

Ghost
12-19-2009, 11:58 AM
a brief aside

http://2.bp.blogspot.com/_yATxh46RxAA/R_EjBkpIDGI/AAAAAAAAAHU/eQhycYgtP34/s400/Phoebe+Cates+Fast+Times+pool.jpg

Bubba Dog
12-19-2009, 04:44 PM
a brief aside

http://2.bp.blogspot.com/_yATxh46RxAA/R_EjBkpIDGI/AAAAAAAAAHU/eQhycYgtP34/s400/Phoebe+Cates+Fast+Times+pool.jpg
Please do, keep it brief.:shades:

Donzinewbee
01-07-2011, 02:15 PM
hey guys, im thinking of buying an 18' donzi with no power. Can you give me some infor as to what I need to get. I've built some chevy cars so Im familiar with the bow tie engine. My problem starts on how to convert a street engine to a marine engine.

The oil pan is probably different, water pump, Rotation?? maniflods, intake, carborator, distributer.

And of coarse the drive its self. I wouldnt even know where to start with that.

fogducker III
01-07-2011, 05:13 PM
hey guys, im thinking of buying an 18' donzi with no power. Can you give me some infor as to what I need to get. I've built some chevy cars so Im familiar with the bow tie engine. My problem starts on how to convert a street engine to a marine engine.

The oil pan is probably different, water pump, Rotation?? maniflods, intake, carborator, distributer.

And of coarse the drive its self. I wouldnt even know where to start with that.

Welcome, I would suggest buying a complete boat, that way you can learn about how it is set-up and see what is needed for a build "down the road".....:wink:

If you buy a "bare" boat and try to do a build with no "marine" experience, trust me, it will be an unpleasant time......:yes:

Pismo
01-11-2011, 05:47 AM
So what finally went into the 18??

joseph m. hahnl
01-14-2011, 09:34 PM
hey guys, im thinking of buying an 18' donzi with no power. Can you give me some infor as to what I need to get. I've built some chevy cars so Im familiar with the bow tie engine. My problem starts on how to convert a street engine to a marine engine.

The oil pan is probably different, water pump, Rotation?? maniflods, intake, carborator, distributer.

And of coarse the drive its self. I wouldnt even know where to start with that.

Marine Camshaft and brass freeze plugs on the block..
Use all marine electrics starter, alternator, etc.
You want heads with bronze valve guides and At least stainless exhaust valves. Rotation is generally standard


As far as the drive goes, we would need to know the year to determine what drive would have been in it.

The spacing between and the height of the through hull exhaust can give insight on weather it had a small, or big block

mrfixxall
01-14-2011, 09:44 PM
To be honest, if i had over flowing pockets of cash i would build a lsx 496 cubic inches and put a crank driven pro charger on it..arneson drive with a extension box like the bravo conversion kit and have a nice day..

maddad
01-15-2011, 12:00 PM
It took a few years but the big bore sbc's are getting votes!

MOP
12-02-2011, 05:51 AM
There are a few differences, pistons ( hypernetic or forged)to handle the higher loads, brass core plugs, better bearings, cam shaft and none sparking electrical components. The pans (though some are coated) are stock as is the rotation, nothing really exotic.

Ghost
12-02-2011, 06:19 AM
In your case, I think I'd just rebuild the 400.

Daydreaming, I'd like a fully-FWC all-aluminum 502 EFI with the good internals, 385 HP and Stainless Marine exhaust. Volvo DP drive.

Lighter than a small block, it'd run well, behave about as well as is possible, very fast cruise at 3800, reasonably fast wide open (if you're not craving 90mph), and last forever. And torquey enough for 5 goesabouts.

Spendy to build though.

mattyboy
12-02-2011, 06:42 AM
well since the thread started there as been a developement from ilmor marine they are making a 430 hp alum 6.2 and a 520 hp 7.4 if you could get one mated to their indy drive or a bravo it would be an interesting combo but right now they look to be for inboards only.

anotherScott
12-09-2011, 06:34 PM
put a ford 351 gt 40 in my 1975 18'......doesnt do 80......but runs like a raped ape...




check out my 24' doral for sale.....tough boat

KenSpiehler
12-10-2011, 09:56 AM
The GM HT383 is unbelievable. If you are using a carburetor, they respond very well to the large (800 CFM) Holley. It sounds like too much carburetor of only 383 cu in, but, trust me, you'll love it. The cam is so mild that it purrs at very low RPM, but has absolute gangbuster torque. The only mods you may want are roller rockers. I used 1.5 ratio on intakes, and 1.6 ratio on exhausts (check guide clearance!) - fantastic.

osur866
12-11-2011, 12:09 AM
600HP whipped 383 good for 90+ and will get your attention very quickly!! Acceleration is off the chart cool, 55-85 happens in 2-3 seconds pins ya back in the seat!! Oh and the lil whine ya hear is pretty cool to at around 5,800-6,000 RPM's :) lol Steve