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350 to 383 conversion RELIABLE

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markkanderson

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I have decided to move forward

I have decided to move forward with rebuilding my 350 to a 383. Does anyone have experience with this that can comment on the reliability of the 383 and also the increase in fuel consumption?
 
"This version of the SBC can m

"This version of the SBC can make for some great torque.
I can offer you some suggestions about building a proper 383 for Marine use.... particularly for cruiser use!
However, (and respectfully and honestly submited) if you are consulting automotive guys on the other side of the fence, it can quickly become a debate that I'd rather not participate in. Unless these guys were to own and operate a cruiser type hull w/ the 383, it would behoove you to consult those who do!
First and foremost, and no more/less important than some of the other selections, is your piston/cylinder head selection rendering a "Quench Effect". Particularly for this engine!

There are several ways to accomplish this, none of which involve the use of the dreaded "dished" piston and none of which will break the bank.

If you care to email me, I'll gladly link you to some good information and images.

."
 
"Thanks Ricardo, I will email

"Thanks Ricardo, I will email you. This is for a cruiser type family boat and I have not consulted with any automotive guys on this. Only Internet and my marine engine builder that I am using."
 
"That statement was not to tak

"That statement was not to take anything away from the auto guys! They know their biz. I want to be clear on that!

Simply put, you are more educated on this if you ARE involved in cruiser boat operation, and know of the little subtle differences that can end up being so dang important.

."
 
"Ayuh,... The 383 is Just as

"Ayuh,... The 383 is Just as reliable as any other SBC built over the last 50 years...
As long as it's built Right...

Fuel mileage is a direct function of the operator's right hand...

I'm puttin' 1 together with Vortec heads,+ D-dished pistons to get the right quench,+ to keep the compression ratio manageable..."
 
"Bondo, good to see that you a

"Bondo, good to see that you also recognize the importance of the Q/E.... many do not!
Being clear on the info that you may get from the strictly automotive crowd, and deliniating between this and Marine, is important!
The differences may be subtle, but none-the-less, they are important ones.
With what I call the "dreaded dished piston", we risk detonation. So we cut back on Ignition TA and as a result, we leave potential horse power on the table.

I'm putting together some info for Mark (MKA) re; a few of the correct Q/E piston selections, etc. Too much to post on the forum here, so an email is being sent to Mark.

As you know, the small chamber heads pose an issue with the 383 or the 400 engine.... Even the larger 76cc chambers pose an issue for correct C/R ......... but very solve-able by using the "correct" Low Compression Quench style, or in your case, the correct D piston.
With the shape of Vortec chamber, this style may not perform quite as well.
However, this may be a better choice for a non Vortec chamber.

edited by moderator per Ricardo's request. See images in message below.

I don't know which cylinder heads he plans to use!

Here is a piston that works very well with the shape of the Vortec chamber wedge area.
Some will list this as a "D" also.

edited by moderator per Ricardo's request. See images in message below.


I won't be getting into cam profile with him. That's another topic!
Maybe you could share some of your thoughts as well.

"
 
Anyone know if there is a 383

Anyone know if there is a 383 GM crate that works well for marine apps?
 
"[b]"Anyone know if there

""Anyone know if there is a 383 GM crate that works well for marine apps?"

Yes there is!
MichiganMotorz.com offers this engine in several varieties... long block/complete engine..... including the MPI.
Problem is for the "purists", is that these all use the Dished Pistons (thank you GM) to accommodate the longer stroke and the small chamber cylinder heads........ of which may not be an issue for some.
For me it would be!
I've never built a SBC Marine with this piston and NEVER will!

."
 
Just remember that vortec head

Just remember that vortec heads do not have a passage to feed water pump bypass into the block passage that leads to the water pump (the extra hole below the water pump mounting bolt on starboard side of block). You need a water pump bypass from intake manifold back to water pump so water can circulate around in block and heads before thermostat opens. Vortec engines in pickups uses a hose from front of intake to top of water pump.
 
"James, I think that you lost

"James, I think that you lost me on that! (not that I am disputing your knowledge here)
We're talking about the marine version of this engine, of which is becoming very popular for marine use these days.
I am not aware of any Circ Pump coolant by-pass that is required and/or is provided by the cylinder heads.
I'd like to learn more about this.

And if there is a coolant by-pass required, wouldn't this be provided by the intake manifold?
Are you thinking of the T heads by chance?

BTW, for marine use, we're better off staying away from the longer rods (for a 383) that the street performance people prefer."
 
"Sounder, that is great.... bu

"Sounder, that is great.... but for the guys who may be wanting more true marine power, these engines will very likely be using the dished pistons unless you were to specify that you did not want them.

That's the issue that I have with the crate engines from GM and/or many of these builders who may not be willing to take these extra measures for Marine use!
The GM 5.0's, 5.7's, 6.2's, to my knowledge, are not using the Q/E pistons...... they are using the fully dished pistons!
Why? I can not answer that, other than a cost saving issue!
Do they work? Yeah.... they do work!
A good Q/E piston requires CNC work in order to manufacture one.
A fully dished piston does not require this at the deck of the piston!

And of course, there will always be those who will find a way to debate the importance of the Q/E.
These will be the same guys who may not fully understand what's necessary to combat marine engine detonation! And this is NEVER accomplished with a fully dished piston in the SBC marine engine...... PERIOD!
This is why I was reluctant to even get into this discussion here and would rather discuss it off forum.
(not that anyone is debating this yet)
."
 
"They are building them specif

"They are building them specifically for marine use. If they don't last then they are warrantied. If you don't build marine motors in the Seattle area you are missing out on a lot of business. Unless you enjoy rebuilding Prius motors.
"
 
"Update:
I had a little boo

"Update:
I had a little boo boo in my previous post with the images!
I noticed that the first piston image that I grabbed was not correct. Second image was fine!
So I chose to ask Andrew if he'd swap images for me. Remove one, replace with two!

Well, apparently I was not as clear as I could have been, so both images were removed and two new ones in their place!
The two that are now shown can be considered a D shape.... sometimes a "low compression Quench".

Anyway...... these are there for an example ONLY!
"
 
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