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Turning a 350 into a 383 stroker

Ok so what I need is: new intake, LC Q pistons, Vortec Heads, New cam, New Crank, machine my block for new crank. It almost sounds like I could sell my long block and buy a 383 long block for around $3,500 and switch over all my accessories. I would just have to make sure the engine builder used the correct pistons. Building an engine has always been a dream of mine but I would just hate to screw it up and have the thing blow up. The other thing I'm hearing since I've been doing research is that Malibu has had problems with their 383's in the new boats. They say the 383 doesn't like low rpm's. Some guys have had to replace the engine with under 500 hrs on it. Thoughts?
 
holinwtr said:
Ok so what I need is: new intake, LC Q pistons, Vortec Heads, New cam, New Crank, machine my block for new crank. It almost sounds like I could sell my long block and buy a 383 long block for around $3,500 and switch over all my accessories. I would just have to make sure the engine builder used the correct pistons. Building an engine has always been a dream of mine but I would just hate to screw it up and have the thing blow up. The other thing I'm hearing since I've been doing research is that Malibu has had problems with their 383's in the new boats. They say the 383 doesn't like low rpm's. Some guys have had to replace the engine with under 500 hrs on it. Thoughts?
Click to expand...

Ayuh,... Unless it's got the wrong cam, or poorly tuned, That's Bullship...
 
Just to be clear...... my comments were intended to be suggestions only.... it's up to you to decide how you want to build this.

holinwtr said:
Ok so what I need is: new intake, LC Q pistons, Vortec Heads, New cam, New Crank, machine my block for new crank.

It almost sounds like I could sell my long block
You certainly could.
I good running 5.7L is worth more than the sum of all parts that you could otherwise source out yourself.


and buy a 383 long block for around $3,500 and switch over all my accessories. I would just have to make sure the engine builder used the correct pistons.
Yes, and this is where we'll occasionally get that "deer in the headlights" look (that I mentioned earlier) when the alternate build is suggested to these guys..... unless they understand what this means.

You may also be persuaded to use the longer connecting rods that the auto guys like to use for this build.
As mentioned, this causes an unnecessary change to the piston pin height and skirt profile for the Marine version.


Building an engine has always been a dream of mine but I would just hate to screw it up and have the thing blow up.
You'll be OK, and you won't blow it up unless you do something silly.

The other thing I'm hearing since I've been doing research is that Malibu has had problems with their 383's in the new boats. They say the 383 doesn't like low rpm's. Some guys have had to replace the engine with under 500 hrs on it.

No Marine engine likes low rpm heavy loads for any duration, and in particular if the spark lead is incorrect.
This is when detonation may occur.

Of these engines that are failing, I'd be very curious to find out about the build.
GM does offer a 377 version (6.2L)...... and I can just about guarantee you that the GM style full dished pistons are used in these.
Click to expand...

A quench or squish type piston selection is very simple. With your "known's" (i.e., bore/stroke, rod length, cylinder head chamber volume, quench surface shape, and desired S/C/R), most any good piston supplier representative can speak with you and help you make a selection.
There's no need to break the bank with a $950+ set of pistons. A good quality pressure cast Hypereutectic piston will do just fine.

The clearancing of the block will be pretty much the same between an Auto build and Marine build.
Boring cylinders, checking deck height, selecting a C/H/G thickness will also be in the "norm" category for the builder.
However, they will need to know that the Quench dimension can be tightened up for the Marine build (.038" or so).



.
 
Are you shure Malibu uses a 383 in there boats?

I was not aware that OEM/GM released a 383 production motor pre LS motor. That is where Merc would get it from and malibu would simply install it.

If it is a LS motor then that is a different animal all together.

I know gM released a 383 but have never heard of it going into a boat as a stock marine engine.



The bottom line is, what ever you choose to do, if you biuld your own, get with a engine biulder and put a parts combo plan together that siuts your needs.
High tourque at low rpms........STart there and then adjust the rest of the components for good power. Most boats rarely go past 5000 rpms so keep that in mind.

$3500 is a healthy price and I would suspect it is for a new motor and not a rebiult one.

Also understand that with todays parts availability making a standard 350 cubic inch motor a tourque monster is not that difficult.

Good heads, cam, pistons and as stated get the piston profile, quench and valves correct and you will have a motor of good power where and when you needed it with very high reliability.
 
I guess as long as the OP is OK with this, we'll keep going here. Good stuff anyway! :D

kghost said:
Are you shure Malibu uses a 383 in there boats?

I was not aware that OEM/GM released a 383 production motor pre LS motor.
To my knowledge, GM did not. The LS3 6.2L version was for the Corvette I believe.

That is where Merc would get it from and malibu would simply install it.
GM does produce a "stroker" for Merc's Horizon 6.2L, of which is a 377 cu. in. (standard 4.000" bore)
The 383 cu. in. version (6.3L) would be a remanufactured, in that the bore now becomes first over (4.030").

If it is a LS motor then that is a different animal all together.

I know gM released a 383 but have never heard of it going into a boat as a stock marine engine.
That would be Merc's Horizon 6.2L or 377 cu. in.
MercMX62Horizon-inboard.jpg

Once again.... keep in mind that GM used their full dished pistons in these.
Look at the specs here and here.
This is another example of how all of the components are mentioned, with exception to the piston profile.
When a certain good feature is absent from the specs (in lieu of a lessor feature), no one is going to capitalize on it.
However, when a certain good feature is used, you can bet that they're going to capitalize on it.

I will give them credit for listing a more honest horse power rating.


The bottom line is, what ever you choose to do, if you biuld your own, get with a engine biulder and put a parts combo plan together that siuts your needs.
Yes.... ditto that one!

High tourque at low rpms........STart there and then adjust the rest of the components for good power. Most boats rarely go past 5000 rpms so keep that in mind.
Hence the reason for the shorter connecting rods and longer piston skirts.... AND the tighter quench dimension.

$3500 is a healthy price and I would suspect it is for a new motor and not a rebiult one.

Also understand that with todays parts availability making a standard 350 cubic inch motor a tourque monster is not that difficult.
Not quite as torque'y as it's cousin the 377/383 with the .270" longer stroke, but with a good quench, you can gain some torque.
Anything to bring LPCP closer to where it needs to be.

Good heads, cam, pistons and as stated get the piston profile, quench and valves correct and you will have a motor of good power where and when you needed it with very high reliability.
Fully agree.
Click to expand...

BTW.... MichiganMotors is now willing do a quench build for the asking.


.
 
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Malibu did come stock with an Indmar 350 Monsoon. the 383 Hammerhead was an upgrade option for a number of years. They stopped using it because of problems. Not sure when Malibu switched from Merc to Indmar. BTW, I'm fine with you guys adding to this thread! All this stuff is great!
Thanks again for all the helpful info! I've saved this thread to my browser favorites
 
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You can save some time and effort, possibly money if you get a Dart SHP Block. Clearanceing already done, Splayed 4 bolt mains and heavier casting. Much stronger than old GM blocks. Blind headbolt holes many other features good for a boat motor. They are about $1500.00 but after boring, Decking, cleaning, align boring possibly, and the purchase price of a rebuild-able core you would be ahead for the start of one tough motor. Search for Dart heads/blocks watch videos, good info there.

Repeating everyone else watch your head cc's piston dish and quench. 10+ compression ratios not good for boat. Get a good marine cam, by the whole kit, cam,lifters, springs and keepers. Pay attention to what they say about break-in.

I used a Comp cams Marine roller cam, the smallest one, rated idle to 5000 rpm good economy. Max torque 3200 max hp 4800. It's in a 350 "wish I had done a 383". 4800 Lb cabin cruiser, up on plane at 3000 rpm with a 15x18 prop will still over speed and out runs my ski boat. Love the torque, would still be better with 383.

Check out Dart's heads and Edlebrock's heads. Edlebrock heads are a little more expensive but have less fussy setup. Aluminum heads are good for marine with closed cooling. They will give you more options in head cc's than vortec but use the smallest intake.port volume you can get. Dart has a 175 cc intake iron head that basically is a Vortec for about $400.00 or less for a bare head.
 
I think that those are great suggestions for building a high dollar HP Automotive 377/383.
For our Marine Cruiser engine version, the GM blocks seem to be holding up just fine.

As for cylinder heads, there's always room for improvement over that of the GM cylinder heads, so no disagreement there. :)


.
 
Not necessary of course, but I spent way to much on machine work on my old block that to finish cost not far from a new Dart block. Particularly after $200.00 for old truck 4 bolt with crack in oil galley .
If I had not paid for cleaning and check it would have been in my boat.

If doing a 350 there are less things to deal with. But with a 383 the crank has to miss the block so you need to spend time with grinder often to clearance block, or have someone else do it.
You need to be sure crank will not hit cam. You have to buy it anyway, call aftermarket mfg, and tell them what you are doing and they will provide what you need.

Dart block already clearanced ready to go. Much stronger than any factory block. No junk yard block problems only final honing to pistons.

Good alternative would be to by a 383 short block that a rebuilder built, but check everything! You really don't want a Chinese crank and rods ect. Some are good but you have to know, I don't.

They like to use flat top pistons for a 10+ to one compression ratio. Vortech heads will have to have dished pistons on a 383.

I leaped before I looked could have had a much better motor for no more than $600.00 difference. Probably less.

The reason for the roller cam is this motor will spend hours trolling at 1200 rpm. Flat tappet cams are not supported well by today's oil,
they are missing scuff protection. At low rpm this gets magnified and flat tappets can round off.

Roller cam good for 10 free friction reduced hp, and lower oil temps. I did add roller rockers, for long life
steel not aluminum. Another 10 free hp with friction reduction.

The roller cam and rockers were as much for curiosity as anything
but the results are some where around 6 to 8 gallons per hour at just over plane, about 3200. I need to check this closer agreed, but I don't think I am far off.
oil temps stay at 120 degrees, too cold i know. I need to get it hotter but have no oil cooler even now, may have to add cooler to use water temp to get oil hotter.
Machine shop told me the roller stuff would keep oil temp down, They were right.

If I did it again I would dump the purchase of the 2 blocks and machine and clean-up costs. by one, expensive agreed, Dart block. by the way you don't get the best price from the Mfg
they don't under cut their sellers.

The roller stuff worked out, love the marine roller cam, smooth idle, torque right at cruse 3200rpm, and hp below 5000 rpm.
rollers have much broader torque curves than flat tappet and more in line with today's oil.

Would build 383, possibly just make it a 400.

Also, yes I would love to have the same motor in Comaro or a Corvette.
 
onegreatsteak said:
1. They like to use flat top pistons for a 10+ to one compression ratio.

2. Vortech heads will have to have dished pistons on a 383.

3. Would build 383, possibly just make it a 400.
Click to expand...
We're sorta re-hashing what's already been addresses in this thread.

1. F/T's with the 3.750" stroke (even with 76cc chambers) creates too high of a C/R for Marine Cruiser use.

2. Yes, but best if a LCQ piston is used as to offer a quench effect.
I'd certainly not use the GM style full dished piston.... especially in the 377/383 version.

4. While it makes great torque, the 6.6L, with Siamese cylinders, is a poor choice for a Marine application.
 
The Dart though it has Siamese cylinders is a complete different recast of the chev block. Different metal, don't know what they did cooling not a problem. Not actually related except in parts compatibility.
Many are running in boats. They sell a lot for use in heavy mining equipment. Some running in Homebuilt aircraft.
 
Moot point...................leave it till spring........


not enough interest this time of year especially for the details..............been there done that on here tooooo many times.........
 
Don't know the forum here. I built motors in machine shop 30 years ago. Was fun doing a new one again. Just wished I had found out what was available now, before jumping on the build.
Found even old engine tech for an engine first built in I think 1956 had continued to evolve so much.
 
As fun as it is to biuld your own, on most forums most participants do not typically have the knowledge,time or money to do it themselves, thus they come here to ask.

Most who have worked in the field do not waiste time in biulding a motor from scratch........too much time and effort. time is money......


With the availablility of almost any motor allready biult or rebiult for a fair price it is more cost effective to go that route.

The changes that have occurred over the last 20 years are extremely difficult to keep up with. Only engine biulders and real sharp hot rodders have the knowledge.

30 + years ago most all biulds were of a typical type, easy and only so many parts available to do them.

Making a 350 a more powerful motor than a standard 260 - 300 hp is very easy today. biulding a 383 is also as easy........

I cant speak for anyone else here but when someone I know needs an engine for there boat I do a remove and replace. I purchase a remanufactered marine motor with the same basic specs and do the swap.

What it all boils down to is money, how much they want to spend.

If money is not an object then a higher HP motor is obtainable you just have to do your research and make sure the components selected will give the desired results.......

With the new LS style SBC motors vs the older standard SBC there is much greater power available just due to there beter designed components.
Not to mention the life span of the new vs old.......

time for a coffee.........
 
Unless I missed it, I read nothing about SBC piston selection in Ken Weber's article.

As you may know yourself, most all GM SBC's today (that end up as Marine Cruiser engines), are fitted with the full dished pistons at the factory. This is NOT a good choice! In fact, this is a very poor choice due to the SBC cylinder head combustion chamber design!
Nothing wrong with the chamber itself, per 'se, if a quench style piston is put underneath it, and when the correct C/R and clearances are incorporated.

Because Ken mentions zero about this in his article, I'd question his authority somewhat!
I don't want to be misunderstood here, or sound like an authoritiy myself.... as he does make quite a few excellent points.




.
 
Hope he's running in fresh water cz there ain't no such animal as a cast iron Vortec intake. If there is, I'd like to see a pic or better yet have a part number.

EDIT: Looks like my google skills need work. They're out there, but awfully expensive. Nearly $500 for a 4 barrel one.
 
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Article is a bit dated, from 1997. In general I think it's mostly correct.

I probably should have said it was dated, It says former owner of Marine Engine Service, Inc at the end of the article year 1997 so his viewpoint is probably further back. And I think real respect for proper quench seems to be in the last 5 - 7 ? years. With further study the advice is good.

Many things for a full how to build it article were left out. Probably since he was writing to pro builders probably assuming much knowledge and the need to do research of the customer needs and application.
 
onegreatsteak said:
It says former owner of Marine Engine Service, Inc at the end of the article year 1997 so his viewpoint is probably further back. And I think real respect for proper quench seems to be in the last 5 - 7 ? years. With further study the advice is good.
Click to expand...
Just an FYI:
The very first GM SBC 265 cu in V-8 was fitted with F/T pistons. The cylinder heads used a "wedge" style chamber. This piston style creates a quench/squish effect. This was continued until the 70's when GM made the decision to begin using the full dished pistons, and this was due to the emmision control requirements.
Chambers became smaller, so rather than doing this correctly, they took the cheap way out.

.
 
RICARDO: My apologies for sending you a private message. Frankly, it will sound dumb, but I didn't realize "PM" stood for private messages. HUGE thanks for all the time you have put in here to help people. I am working on bringing a classic back (as close as I can get) to showroom condition. She is a Tolly 26 Sedan and came out of Portaland, OR. I live in the Seattle area, so we are neighbors. I found Dennis Moore's paperback on Amazon, used for $200 and I'm still studying that book. His information supports all of the things you have said here. I am closing in on my engine specs. Based on what I have learned so far, here is my existing, goals, and specs:

EXISTING ENGINE:

  • 1983 Crusader 270 (hp – Chevy 350) with Borg Warner 2:1 Velvet Drive
  • Fresh water cooling
  • Original Crusader exhaust system
  • Was able to hit 3,300 RPM and 26 MPH with three bad cylinders (51, 54,91psi), but with very little weight on board including fuel.
  • Existing power was adequate for low weight ~10,500 LBS, but when loaded will reach closer to 12,000 LBS.
TARGET GOALS – MARINE QUENCH BUILD :

  • Quench Effect engine is a “must have” no compromise. Stroker?
  • Adequate power when boat is fully loaded – 270 is probably not enough and a little go-fast capability is desired. Current target estimate is up to but no greater than 350 HP.
  • I do NOT want a hot-rod engine. I do NOT want 500hp. I want an engine as strong as possible at low RPM – high torque at low RPM.
  • LPCP 12-14 degrees ATDC
  • Prefer keeping the existing Crusader exhaust system.
  • Efficiency/fuel burn – improve low-end torque to hold a plane at low RPM. I want to operate this engine below 3400rpm. Ideally, if it can hold a plane at 20 knots and 2800rpm, that would be incredible.
  • An engine much stronger than it needs to be for durability and reliability in tough conditions.
  • Looking for EFI with matching electronic ignition.
SPECS:

  1. Quench Effect engine, 355 – 383 cu. in. (moderate marine-build stroker)
  2. Quench tolerance: .038” - .040”
  3. Compression Ratio 9:1
  4. 4-bolt main – prefer aftermarket splayed 4-bolt main bearing caps. Decking critical (0-Decked?), align boring critical.
  5. D-Dish quench pistons. Piston deck surface needs to mirror the head as close as possible.
  6. Non-Vortec combustion chamber ported and polished heads to match the pistons, (combustion chamber cc. 76cc ? - TBD) Non-GM heads are certainly an option.
  7. Top quality crankshaft, steel connecting rods, pistons. Hi-quality pressure-cast Hypereutectic pistons are fine. QUESTON: “Raised-pin” pistons ?? – shorter connecting rods, longer piston skirts better for durable marine, but do I miss out too much by not going for a pure 383 stroker.
  8. Top quality moderate marine roller camshaft and lifters. Focus on torque, long term durability, and staying close to 350hp.
  9. Roller-bearing cam & lifters is a “must-have”

THANKS AGAIN!
Brian
 
Brian, this thread was started back in January of 2013. It is always best to start a new thread on your topic. But..... since we're here.............

bhedmondson said:
RICARDO: My apologies for sending you a private message. Frankly, it will sound dumb, but I didn't realize "PM" stood for private messages. HUGE thanks for all the time you have put in here to help people.
You are welcome!

I am working on bringing a classic back (as close as I can get) to showroom condition. She is a Tolly 26 Sedan and came out of Portaland, OR. I live in the Seattle area, so we are neighbors. I found Dennis Moore's paperback on Amazon, used for $200 and I'm still studying that book. His information supports all of the things you have said here. I am closing in on my engine specs. Based on what I have learned so far, here is my existing, goals, and specs:

EXISTING ENGINE:

  • 1983 Crusader 270 (hp – Chevy 350) with Borg Warner 2:1 Velvet Drive
  • Fresh water cooling
  • Original Crusader exhaust system
  • Was able to hit 3,300 RPM and 26 MPH with three bad cylinders (51, 54,91psi), but with very little weight on board including fuel.
  • Existing power was adequate for low weight ~10,500 LBS, but when loaded will reach closer to 12,000 LBS.
TARGET GOALS – MARINE QUENCH BUILD :

  • Quench Effect engine is a “must have” no compromise. Stroker? You will pull more torque from the increased stroke of the 6.3L SBC.
  • Adequate power when boat is fully loaded – 270 is probably not enough and a little go-fast capability is desired. Current target estimate is up to but no greater than 350 HP. I'd not make HP the focus....... I would focus on the Q/E build that when tuned correctly, will lead to increased torque.
  • I do NOT want a hot-rod engine. I do NOT want 500hp. I want an engine as strong as possible at low RPM – high torque at low RPM. Keep in mind that Detonation is more likely to occur at low RPM while under heavy load! I would be shooting for a cruise RPM of 3,600 or so.
  • LPCP 12-14 degrees ATDC This can only be achieved when Detonation potential has been greatly reduced and the ignition advance can be increased.
  • Prefer keeping the existing Crusader exhaust system.
  • Efficiency/fuel burn – improve low-end torque to hold a plane at low RPM. I want to operate this engine below 3400rpm. see above. Ideally, if it can hold a plane at 20 knots and 2800rpm, that would be incredible. Again...... see above.
  • An engine much stronger than it needs to be for durability and reliability in tough conditions.
  • Looking for EFI with matching electronic ignition.
SPECS:

  1. Quench Effect engine, 355 – 383 cu. in. (moderate marine-build stroker) The 5.7L stroke of 3,480" would be increased to 3.750"
  2. Quench tolerance: .038” - .040” The .038" quench dimension has been suggested for the Marine built 5.7L SBC. The Marine built 6.3L SBC Q/D would be increased a bit.
  3. Compression Ratio 9:1
  4. 4-bolt main – prefer aftermarket splayed 4-bolt main bearing caps. Decking critical (0-Decked?), align boring critical. Why ZERO for deck height?
  5. D-Dish quench pistons. Piston deck surface needs to mirror the head as close as possible.
  6. Non-Vortec combustion chamber ported and polished heads to match the pistons, (combustion chamber cc. 76cc ? - TBD) Non-GM heads are certainly an option. The D-dished piston with 76cc combustion chambers may work but you will want to run the Static C/R calculations in order to select a dish volume.
  7. Top quality crankshaft, steel connecting rods, pistons. Hi-quality pressure-cast Hypereutectic pistons are fine. QUESTON: “Raised-pin” pistons ?? This makes for short piston skirts. I would avoid doing this for a Marine build.
  8. – shorter connecting rods, longer piston skirts better for durable marine, but do I miss out too much by not going for a pure 383 stroker. I may not be following you....... the connecting rod dimension will not change the Bore/Stroke and/or engine displacement. 4.000" bore w/ 3.750" = 377 cu in or 6.2L ........ and the 4.030" bore w/ 3.750" stroke = 383 cu in or 6.3L
  9. Top quality moderate marine roller camshaft and lifters. Focus on torque, long term durability, and staying close to 350hp.
  10. Roller-bearing cam & lifters is a “must-have” I'm not sure what a Roller Bearing cam is. What we call a roller cam is supported with the same type of hydrodynamic bearings as with any SBC camshaft. The cam followers (aka lifters) will be roller tip equipped to reduce friction.

THANKS AGAIN!
Brian
Click to expand...
 
On another website I give bad info on, a guy stroked his Mopar 360s to 392 cubes--and they perform brilliantly! Took the usual hot rodder route and did the heads and intake up as well.

So...a 383 sounds like a good idea to ,e.


Jeff

PS: THis was a cruiser application, by the way. Goes like stink!
 
RICARDO! Thank you! Sorry about not starting a new post. I posted here because I thought keeping 383 Stroker discussion should be in one place. Please let me know if I should start a new thread.

I love your advice and the way you give back. I am going to contribute too. It' my understanding that the Tollycraft club lost all of their forum data a while back, including all their posted projects information. That was a pretty big hit. I am documenting my boat restoration and engine rebuild. My son has an audio video business and we have already build a drone video covering the engine extraction under a 16' hand-made gantry. I have hundreds of photos I am assembling along the way. This engine build will be part of that. I am an Instructional Designer by trade.

U R the best!
B.E.
 
fastjeff said:
I'm a fan of Rick as well, and I like Tolleycrafts too. Nearly bought one years ago.

Jeff
Click to expand...
.

Thanks Jeff! My wife named her "Symphony." It is my understanding that Tolly built 850 of these. Ours is hull #837. She has great bones and all the stuff needed to put her in showroom condition is stuff that is easily done... note that I didn't say "cheaply done." And now she's going to get a Dennis Moore Q/E engine... borrowing Rick's terminology. She is just about as big as you can get and still yank it down the highway. She has a 10' beam. Schooner Creek down in Portland helped me get her up here. I added a new ($10k) Venture trailer from Word Boats in Spanaway.

Symphony_001reduced.JPG
 

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