upgrading to a 383 stroker

boating maniac

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Hey guys. I have a 1989 abermarle 24 with a volvo penta aq271c which is a 275hp 350 chevy and a dp-a volvo penta outdrive. I bought the boat last year and the second trip out I noticed the ujoint bellows slipped off. Anyways, something in the outdrive is binding up now stalling the engine and I just want to totally redo the outdrive and engine since i'm sure the u joints/pds bearings are probably shot now and the outdrive/engine needs to come out anyways to replace those.

I bought a rebuilt volvo penta dp-a outdrive that has been gone thru, repainted and resealed for $2900.00

Now for the 383 stroker I got a quote of $12,000 for a brand new 383 stroker complete drop in engine fresh water cooled with the old style manfolds/risers, so I just use the existing y pipe that works for the older volvo outdrive. Now I got to thinking, how about I have the existing engine rebuilt vs buying a brand new engine?


My reasons for going with a brand new drop in engine are:

-Comes with a 2 year warranty
- I don't have to worry about marginal parts being reused
- I don't know of any good machine shop/engine builders
- My old original engine doesn't have vortec heads it has 12 bolts not 8
- Its due for new manifolds/risers (7 years old)
- I get all new power steering pump, alternator, raw water pump. etc
- The fresh water cooling tank is corroded from bilge water hitting it at the bottom, so I want a new one of those also, preferably position horizontally in front of the engine so this doesn't happen again.

Opinions?

I don't know a whole lot about how the machine shop engine building thing works and what all can be done. $12,000 sounds pretty steep though vs just rebuilding what I have and turning it into a 383 stroker. The goal is to make it so I have confidence in the engine/outdrive so I can feel like I can go anywhere with it and not break down. With everything being 30 years old now I think it's just a matter of time before something goes wrong with it even thought the current engine is relatively simple with no electronics on it hardly.
 
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boating maniac

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Also i'm going to have a shop do the work and they also have a machine shop they use, then they install the tin. Although I don't know who they use or if they are any good, but they say they haven't had any issues with them. (what else are they going to say) lol
 
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jerryjerry05

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Make sure the crank matches the old flywheel.
They used a light duty 2bolt crank and the crank and flywheel didn't always hookup.
 

Scott Danforth

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$12k is extremely steep a brand new 6.2 MPI from mercruiser is only $11k and that includes all the plumbing which will plug up and fail, and a bunch of other mercruiser hypercomplexificated parts

all the following assume you will transfer over the accessory drive and accessories, and transfer over the 715 CFM holley to a new manifold

to build a brand new stroker long block, will cost you about $4200 and you control the components. then if you want to add a half system, thats another $1500. that is a new GMPP block, new vortec heads, new SCAT rotating assembly with KB LCQ style pistons, new damper, new flywheel this is about 350hp at the prop. add $1100 more if you want 420 at the prop

to buy a brand new 377 stroker long block, that is $4200. that is a run-of-the-mill GM motor. then you add the HX to that http://centerstateengine.com/new-ma...rine-base-engine-replaces-years-1996-present/ this is 320hp at the prop

https://www.michiganmotorz.com/377ci-stroker-base-marine-engine-2000-2019-replacement-p-545.html

if you want to take your motor and rebuild it to a stroker, it will cost you about $3000-3800 depending on your machine shop. the only thing you would be using is the block. the heads you have on the motor are really good compared to the heads that mercruiser used. they are actually 64cc crate motor heads for Hi Po applications. however they are not vortec heads.

finding a good machine shop is easy. find where the race teams and marinas in your area take their engines

here are some other threads https://forums.iboats.com/forum/eng...outdrives/10798315-stroking-a-volvo-penta-5-7

you may also find this thread interesting https://forums.iboats.com/forum/eng...rds/10101672-bbc-build-don-t-tell-the-admiral

you need to rebuild your PDS - read this https://forums.iboats.com/forum/eng...s-engines-outdrives/10343318-pds-shaft-issues

you dont need a whole new drive, you need new u-joints and to rebuild the upper (transmission). a new seal kit is $200, the bearings to rebuild the upper, about $60

if you want a new power steering pump, that is $47. you need to still re-use your can, as the reservoir is VP only use. to rebuild your PS pump, its $11 for the kit

a new alternator is $100

if you need reconditioned pulleys for your 271C, PM me, I have all my 271C parts I didnt use on CL right now.

you will need new exhaust manifolds. no, you cant add a full cooling system with most exhaust manifolds for VP's. I have asked the chief engineer at Volvo back in 2011 that very question. too much restriction in the manifolds water jacket for a HX

you can add a set of hi-tek manifolds http://www.hitekmarine.com.au/ https://www.cpperformance.com/m-78-hi-tek-marine.aspx

or you can add the Volvo Penta Neutra Salt system http://www.volvopentastore.com/Neutra-Salt-Engine-Flushing-Kit/dm/store_id.366--view_id.352393
 

Scott Danforth

Grumpy old guy who plays with boats
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I forgot to add. the PDS on your 271C wont take a 168 tooth flywheel, only the 153 tooth.

remember that when you get the motor balanced. your machine shop will most likely recommend zero balance. if so, get a zero balance crank to start with (bigger bob weights)
 

boating maniac

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I forgot to add. the PDS on your 271C wont take a 168 tooth flywheel, only the 153 tooth.

remember that when you get the motor balanced. your machine shop will most likely recommend zero balance. if so, get a zero balance crank to start with (bigger bob weights)



You're sure I have the weird 153 tooth smaller 12-3/4" flywheel? How do I know the bolt holes will line up to the crank like the other poster said?
 

boating maniac

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Also the $12k was for the complete long block with everything assembled, power steering, pulley's, old style risers/manifolds installed and an aftermarket fresh water cooling half kit. This is Michigan motors that said they would build it like this for me. He also said the engine is neutrally balanced, so I guess that means it will work with the smaller 153 tooth flywheel?
 

Scott Danforth

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You're sure I have the weird 153 tooth smaller 12-3/4" flywheel? How do I know the bolt holes will line up to the crank like the other poster said?

I guarantee you have a 153 tooth flywheel. the 168 tooth flywheel WILL NOT FIT IN THE VP PDS, AND YOU CAN NOT MODIFY THE PDS TO FIT IT. I have been there, done that and bought the tee shirts. I went thru that in the link I provided when I went to build my BBC to put in place of the 271C SBC

all factory SBC's from 1986 and later have a 1-piece Rear main seal and use the same bolt pattern. all factory SBC's from 1954 to 1985 have a 2-piece rear main seal and share the flywheel mounting with the BBC's (aftermarket can be either)

all post 1986 1-piced RMS 153 and 168 tooth flywheels for a stock balanced small block are "neutral balanced" this means that you have +/- 30 grams per each piston/rod combo to hit. it means that your motor will have some imbalance and will be RPM limited. me personally, vs spending that much money on a stock internal motor would prefer to build a real motor and have it "zero balanced" that means the rotating assembly is truely balanced and not a "spec build balance" for example, my last build, each piston/rod assembly was balanced within 1 gram and there is $800 worth of malory metal pressed into my crank bob weights to zero balance the crank to allow that motor to spin at any RPM I want to hold it at.

I would also suggest SFI rated damper and flywheel, especially if you plan on holding 5000 RPM for long periods of time. the stock cast $70 flywheel is just that..... cast. a steel billet SFI rated flywheel is $110. an SFI damper is a bit more

when you buy a flywheel or damper, you must know the balance of your motor.

for $12k, that $4200 motor with a $100 cast-iron intake manifold, $1500 heat exchanger and $500 manifolds better be installed in your boat.

you are not getting a bargain if you know how to turn your own wrenches.

and the stock 377 GM crate motor they are starting with uses a 168 tooth flywheel

you could buy the same $4200 motor from the link I provided, install a $200 edelbrock RPM air-gap manifold, spend $30 on gaskets, mount a set of stock manifolds and be ahead. I can walk you thru a HX installation like I did. (I bought mine for $600, and built the bracket)
 

Scott Danforth

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nothing special about neutral balance of a stock motor. However the 1-piece RMS crank from GM is externally balanced (damper and flywheel) unless you specifically order the aftermarket stroker crank with neutral balance. the stock GM 377 gen 1 1-piece RMS crank is not neutral balanced.

https://www.gmperformancemotor.com/parts/12489436.html

you can order SCAT or Eagle cranks with either. however most builders wont use Eagle components as they are usually out of spec.

HX is Heat Exchanger

OC is oil cooler (you dont have one)
FC is fuel cooler (you dont have one)
PS cooler is power steering cooler
 

boating maniac

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I see. I may just let the shop have their machine shop build me a 383 with the existing engine I have. Although I do want vortec heads to be put on. Unfortunately I'm not really set up to do this stuff myself. I need either a forklift or an a frame to remove the engine and I don't really have convenienent access to either. The shop I had to fix my engine mount lag bolts quoted me 20hrs labor time to remove, reinstall and change over the tin. I'd bother go with new parts, like the harmonic balancer, new flywheel, etc and then make sure it's internally balanced.
 

Scott Danforth

Grumpy old guy who plays with boats
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Vortec heads are fairly inexpensive at $800 a pair. you will need them modified for higher valve lift (requires cutting the seal tower)

https://www.gmperformancemotor.com/parts/12558060.html

(cheaper thru Scoggin Dicky) when they have a sale https://sdparts.com/i-23901396-sdpc...der-head-with-0-525-valve-spring-upgrade.html

however a good used set of vortecs can be had from nearly any machine shop that supports racing for about $400 already to run, already modified for screw-in rocker studs and high lift cam. rules changed, they no longer run vortec heads on 1/4 mile cars so there are hundreds of sets of heads awaiting new customers.

I would get the heart-shaped LCQ style piston from KB in the SCAT rotating assembly. they are basically an inverted vortec combustion chamber.

you only need hypers, you wont need forged unless you want to spin it at 5500 RPM all day long and maybe have a power adder such as a blower.

https://www.competitionproducts.com/Scat-Chev-SB-383-Street-Strip-Assemblies/products/2868/
 

boating maniac

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I'm liking the idea of letting the shop use their guy then if a problem occurs, they can't come back and 've like well you gave us the engine, it's your problem. Honestly I'd prefer new heads for the $800 I don't want something that's been I a 1/4 mile drag strip. Lol
 

boating maniac

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I don't want this engine to blow up after 500hrs. I'd like it to last 2-3000hrs like the good old 350 did. Will the forged piston be more durable I'm assuming? I prefer to overbuild something then just make it marginal.
 

boating maniac

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Also can I still buy a long block then have the machine shop balance the crank and installed different pistons, etc? Or is that counter productive to have to take a brand new long block apart.
 

Scott Danforth

Grumpy old guy who plays with boats
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It will cost you about $1200 for them to take a long block, tear apart, balance, and put together

A brand new GM block is $1100 (reconditioning your block will be about $600)
A brand new rotating assembly is $1100-1200
A new cam k-kit is about $850
A new set of GM heads about $800
New bearings, oil pump, gaskets, hardware about $500

At that point balancing will be about $400

Talk to your machine shop
 

boating maniac

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I got ya. Do you if a vortec block is any different than a non vortec block? What i'm saying is I can take vortec heads and put them on my my block that had the old style pre vortec heads without issue, correct?
 

Scott Danforth

Grumpy old guy who plays with boats
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the heads only are what makes it a "vortec"

I put vortec heads on my 271C

https://forums.iboats.com/forum/eng...o-performance-upgrades-for-an-aq271c?t=503800

the heads will bolt up fine

the SBC is like Mr Potato head. lots of things will bolt to it.

however your block is not a roller block, its a flat tappet. it does have the 1-piece RMS crank (1986 was first year of the 1 piece RMS)

you can run a conversion setup for a roller cam. your block simply doesnt have all the machining that later blocks have to allow easy conversion to roller cam.

you need to talk to your machinist on costs of baking the block, cleaning the block, line-honing the mains, decking, boring and honing. also if you want to convert to a stroker, what he charges for clearancing the pan rail . in some cases, the cost to do all that is the same as buying a new block.

here is a GMPP block already clearanced for the new stroker rotating assembly. https://www.gmperformancemotor.com/parts/88962516.html

(same, however cheaper because of the rebate) https://www.summitracing.com/parts/nal-88962516

if your block was ever used in salt water, you would want a new block anyway. its almost impossible to clean all the rust out of a salt water block. however if you have had a heat exchanger on it from day one, the block would be fine
 

boating maniac

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So all the marine 350 and even standard automotive engines have been neutral balanced for the last 35 years? 5000 is about as high of an rpm as I'm going to run it.
 
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