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383 Inboard(V-Drive)build

Bracker

Bracker

Member
I have decided to go with a 383 with Vortec (062 casting) heads, 22cc volume reverse dome hyper pistons, 5.7” rods, Comp XM264HR camshaft and Scat forged crankshaft. As currently configured it should have a SCR of 9.27:1 and a DCR of 7.62:1. Someone ran the specs through DynoSim6 for me and the torque numbers were exactly what I was looking for.

However, I’m still trying to settle on a manifold/carb combo. It will have a full FWC kit, but as you guys know, Dennis Moore recommends using a cast iron manifold with cast iron heads (besides the corrosion factor) due to the expansion rate differential between iron and aluminum and how that affects the head gasket. What are your opinions on this matter? If I do go with the cast iron manifold, I believe all that are Vortec compatible are configured for a spread bore. I know there are square bore adapters but I’m ocd and I’ve read several places that this isn’t ideal.;) The forum’s thoughts and advice will be appreciated. Thanks!
 
Sorry, I was rereading my post and noticed I wrote head gasket when I meant manifold gasket.:rolleyes:
 
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Bracker said:
I have decided to go with a 383 with Vortec (062 casting) heads, 22cc volume reverse dome hyper pistons, 5.7” rods, Comp XM264HR camshaft and Scat forged crankshaft. As currently configured it should have a SCR of 9.27:1 and a DCR of 7.62:1. Someone ran the specs through DynoSim6 for me and the torque numbers were exactly what I was looking for.
Have you plugged your numbers into one of the better on-line Static Compression Ratio calculators?

However, I’m still trying to settle on a manifold/carb combo. It will have a full FWC kit, but as you guys know, Dennis Moore recommends using a cast iron manifold with cast iron heads (besides the corrosion factor) due to the expansion rate differential between iron and aluminum and how that affects the manifold gasket. What are your opinions on this matter?
If people were having trouble, we would not see it being done as often as it is being done.
Plus, with a Full Closed Cooling System, there should be no concerns about galvanic action.
(sorry... I have an aversion towards the term FWC )


If I do go with the cast iron manifold, I believe all that are Vortec compatible are configured for a spread bore. I know there are square bore adapters but I’m ocd and I’ve read several places that this isn’t ideal.;) The forum’s thoughts and advice will be appreciated.
I too do not like the idea of an adapter plate.
Nor would I be afraid of an aluminum intake manifold since you are going with a Closed Cooling System.
Click to expand...

Side notes:

Good choice on 5.7" rod length.

With the additional .270" stroke dimension, I would target a quench dimension of .044" or so, as apposed to .038".

Make sure that your Vortec cylinder heads are capable of offering enough valve travel for your selected cam profile.

When building this engine, perform a #1 TDC verification. You can do this prior to the cylinder heads being installed by using a PPS tool, or you can do it afterwards with a spark plug port PPS tool.

You will be using the equivalent of a SBC 400 harmonic balancer. I would get one that is degree indexed as to allow you to ignition time this engine while seeing Real Degrees in Real Time.




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Thanks for the reply! Thank you for easing my worries concerning the aluminum intake. Allowing myself that option makes things simpler. For this build would you recommend zero decking the block?
 
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Bracker said:
Thanks for the reply! Thank you for easing my worries concerning the aluminum intake. Allowing myself that option makes things simpler. For this build would you recommend zero decking the block?
Click to expand...



In order to zero deck the cylinder block, you would first need to fit the pistons and see where they are.
Unless you have some concerns regarding the deck surface, I would first fit pistons and check the piston deck height.

For example:
If the pistons are at .016" in the hole, you would need a compressed head gasket thickness of .028" to gain a quench dimension of .044".


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So I bought the first component for my build. I’m pretty stoked about it. I got a set of Wiseco forged 4032 alloy 20 cc volume reverse dome pistons.
C67DD733-B6E7-4B1D-A415-554A2CF1FF05.jpg
Something I was wondering about was what size/make/model of carburetor would everyone recommend for a 383 with Vortec (Scoggin-Dickey modified version) heads and the below cam specs? There’s a Holley 600 cfm marine model I’m interested in but I think a lot of guys would say 600 cfm is too small for my application even though the online carb calculators put me in that ballpark.
5077D7E7-E82A-44A9-AEAA-BAB3C8151AF4.jpg
Thanks in advance for any advice!
 
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Bracker said:
So I bought the first component for my build. I’m pretty stoked about it. I got a set of Wiseco forged 4032 alloy 20 cc volume reverse dome pistons.
View attachment 21947

Run your new numbers through one of the many on-line compression ratio calculators to see what your S C/R will be.
Don't forget to consider the quench dimension!!!!

https://www.google.com/search?sxsrf=ACYBGNREPx_U-S-mVzqfQQzfaMmmq8VhOw%3A1570632970460&source=hp&ei=CvWdXcWOGrL19AOG67_gDA&q=online+static+compression+ratio+calculator&oq=on+line+static+compression+ratio&gs_l=psy-ab.1.0.33i299l2j33i160.2160.12356..14883...0.0..0.196.2754.29j4....2..0....1..gws-wiz.....10..35i362i39j35i39j0j0i131j0i67j0i10j0i13j0i13i10j0i13i30j0i13i5i30j0i8i13i30j33i22i29i30.29L2B-W8kRM


Something I was wondering about was what size/make/model of carburetor would everyone recommend for a 383 with Vortec (Scoggin-Dickey modified version) heads and the below cam specs? There’s a Holley 600 cfm marine model I’m interested in but I think a lot of guys would say 600 cfm is too small for my application even though the online carb calculators put me in that ballpark.

Run your numbers through an on-line CFM calculator using approx 4,000 for the RPM value.
You'll be surprised at how little CFM is required at our Marine Cruising RPM for the 6.3L SBC.

https://www.google.com/search?sxsrf.....1..gws-wiz.......0i71j35i304i39.k_EHqD9IFho


View attachment 21949


At .488" and .495", make sure that the cylinder heads will accommodate that amount of valve travel.


Thanks in advance for any advice!
Click to expand...
 
Thanks for the reply! The Scoggin-Dickey modified Vortecs can accommodate up to 0.525” of lift and at around 500 bucks a piece they seem like a great value. What brand/model of carb do you prefer?
 
I’ve decided to run ethanol free gas which is readily available (but not cheap:rolleyes:) in Florida and it’s most common form is 90 octane. I figured it should accommodate the higher compression. With the cam I’m going to use my DCR should be below 7.8. Below are the cam specs. Sound plausible?
DD633D64-7888-409C-AE95-F66F4C8BBB78.jpg
 
Bracker said:
I’ve decided to run ethanol free gas which is readily available (but not cheap:rolleyes:) in Florida and it’s most common form is 90 octane. I figured it should accommodate the higher compression. With the cam I’m going to use my DCR should be below 7.8:1.
Below are the cam specs. Sound plausible?

View attachment 21961
Click to expand...

As a general rule, the camshaft profile selection would be made after having selected piston profile, cylinder head chamber volume, quench dimension, etc.
and is something that I would run past a reputable camshaft company sales tech/expert.
The expert would also need to know that this is being built for a Marine Cruiser application, and not for a street rod application.

I also noticed that the specification card does not mention a rocker arm ratio! I presume 1.5:1!


On an unsolicited note, when it comes time to adjust the cam follow plunger depths (what some call "adjusting the valves"), I would strongly suggest using the tried and proven 8 stop static procedure, rather than the 2 or 3 stop. (I can explain if interested).
Do this, and you will not need to go back through them later on!


Good luck and keep us informed on your progress.
Pictures would be great!
 
Thanks Rick! That is Comp’s mildest marine SBC cam. Those specs are at a 1.5:1 rocker arm ratio. And yes I would definitely like to hear that explanation. I need all the quality guidance I can get.
 
Bracker said:
You think I’m too close to detonation at that DCR and SCR with 90 octane?
Click to expand...

Forgive me..... this is not easy to fully and adequately explain in short, but I'll do my best!


Most gasoline engine engineers will agree that Pre-Ignition and Detonation are two entirely different phenomenon.

Pre-Ignition causes:

Early spark ignition source. Could be ignition spark, could be from hot spots, carbon build up, etc.

"Anytime something causes the mixture in the chamber to ignite prior to the spark event it is classified as pre-ignition. The two (detonation/pre-ignition) are completely different and abnormal phenomenon."

It's doubtful that you will have Pre-Ignition issues if this new engine's ignition system is set up correctly, you avoid carbon build up, and if you use the correct spark plug heat range, etc.


Detonation causes:

Poor cylinder combustion chamber design that may give the flame front a place to hide.
Excessive compression.
Higher than desired cylinder temperatures.
Poor quality fuel (low octane rating).
Extremely lean fuel/air mixture.
Incorrect spark plug heat range, of which may also cause pre-ignition.
Carbon build up on piston decks and valve faces, of which may also cause pre-ignition.


This where things get a bit tricky and and where you may see a few contradictions appearing:

We want to initiate combustion BTDC in order to properly place LPCP (location of peak cylinder pressure) where it needs to be..... generally between 12* to 14* ATDC.
If Detonation is a result of too much ignition advance, we cut the advance back as to move us away from the detonation threshold.
(this is what the Marine companies do with their silly GM full dished piston SBC engines!)

However, cutting the ignition advance back also changes the LPCP, of which is what creates torque, of which is what we are after for the Marine Engine!



From the choices that I see that you are making, you are building a good combustion chamber design into this engine.
Running non-ethanol fuel is also a plus!

Keep the quench dimension tight (perhaps .043" to .045" for the 3.750" stroke), make sure that your fuel delivery system is providing the correct feul/air ratio, make sure that your ignition advance curve is spot on for this build, and I think that you will not have any detonation concerns.




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I haven’t added everything up to the penny. Probably in the 10K ballpark. I have an aversion to moderation.:D It’s a piece in a SeaCraft resto puzzle. The plan is to take my time and enjoy the journey.
 
That is nice to not be restricted by a budget.
Unless you flaunt ridiculous amounts of cash in front of the machine shop owner, I fail to see how you would have any where near $10k into this engine build.
 
It could come out to less. It just seems 99% of the time things cost more than you initially plan so I didn’t want to sound overly optimistic.:D
 
Nah, I know, but I’m enjoying the research, education and planning aspects of the venture. That would definitely be the way to go if I was in a hurry to repower and get a boat back on the water. I’ve enjoyed projects since I was a kid and I think planning exactly what I want and building it myself will be a satisfying accomplishment.
 
This is similar to what you'd have with the factory built Mercruiser 383 Mag MPI engine.

489732d1357002294-350-mag-mpi-engine-upgrade-options-photo-46-.jpg




This is similar to what Bracker will have in his build.

shinny_sbc.JPG
 
RicardoMarine said:
This is similar to what you'd have with the factory built Mercruiser 383 Mag MPI engine.

489732d1357002294-350-mag-mpi-engine-upgrade-options-photo-46-.jpg




This is similar to what Bracker will have in his build.

shinny_sbc.JPG
Click to expand...

In a marine engine, I will take the top one. Proven to work under harsh loads with crappy and slightly phased gasoline.

All the money he will spend on this with just book knowledge and what he read on the internet will be wasted. The possibilities of complete engine failure are real and not backed by a company warranty.
 
As for the comment regarding this build being book knowledge, Internet based info and wasted money...... who are we to tell Bracker how to proceed with his project and what to do with his money?
Bracker says; "I think planning exactly what I want and building it myself will be a satisfying accomplishment."

As for the comment re; not backed by a company warranty....... Bracker will receive whatever warranty the machine shop offers, regardless of his piston selection. And no... it will not be the same as what GM or Merc can offer for their build.


Let's back up for a minute!

Understand the the Quench Effect and/or Squish Effect are nothing new. The Chrysler Wedge Head boys, the Ford 335 series boys and the SBC boys have known about this for many years.
Although these people are primarily involved in the High Performance Auto Versions, if a person Foo Foos this build and believes that there is ZERO benefit to it, you may as well say that Dennis Moore (SBC Marine Performance), Jeff Smith (Super Chevy and well known SBC enthusiast), Marlan Davis (Hot Rod Network) Larry Carley (expert on engine combustion), John Erb (Chief engineer KB pistons), Jon Cobalt (crankshaft coalition) are all out to lunch!
And of course, we know that isn't true!

I think that some people (by way of misunderstanding) believe that by incorporating a Q/E into the combustion chamber, that this automatically creates a High Performance engine that may not be suitable for Marine Cruiser use.
Not so!
The quench effect is not affected by the piston dish volume nor by the combustion chamber volume. This means that we can stay within any C/R range that we choose for our build. The quench effect will vary depending on which piston profile is used, and with that profile's ability to "mirror" the cylinder head's quench surface.

The primary reason for the Marine quench build is to lesson the likelihood and potential for Marine Load Detonation. And again, it is NOT necessarily a feature used for a High Performance build ONLY.
As a result of a good Q/E, the C/R can be increased slightly as well as the Ignition TA without further risk of Detonation.
In general, this equates to better performance as a result of a correctly placed LPCP (location of peek cylinder pressure) at/near 12* to 14* ATDC.
Also understand that the GM Full Dished piston cannot possibly create a Quench Effect, nor will it allow for a proper LPCP! In fact, it makes for a lazy LPCP.


NOTE: the image below shows two types of combustion chambers.
Wedge shaped chamber on the left (quench capable), and a hemispherical on the right (no quench possible nor needed).
A good LPCP applies to either.
fetch






Just for fun, read post #23 (in the V6-to-V8-engine-swap thread) regarding fuel burn.



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