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2002 5.7 rebuild, questions about piston design

Brians Bryant

New member
I was reading some post about piston design on the SBC. Did I read correctly that the piston design can be changed without changing the ECM mapping. If this is true, does anyone have a part # for the best piston design?
 
Re; your first question, if you target the same Static Compression Ratio (via piston dish volume) I don't believe that you'll need to make any other changes. FYI, the S/C/R can be increased some with a proper quench dimension!

A good Q/E will allow for a few more degrees of ignition advance and will place the LPCP closer to where it needs to be.
It will also reduce the likelihood of Marine load detonation.

As for a piston part number, you can use one of the on-line static compression ratio calculators.
You will plug in your known values (bore dimension, combustion chamber volume, piston deck height, etc) along with your other target values (piston deck height, compressed head gasket thickness, piston dish volume, etc.)
Once you determine the piston dish volume
(that you came up with during your calculations), you will look for a piston that offers a quench surface that mirrors your cylinder head quench surface.
A LCQ piston works well with the SBC Vortec cylinder head.


Starting at post #7 in this thread, you may find some info that will help explain the advantages of building a Q/E into the SBC combustion chamber.

http://www.marineengine.com/boat-forum/showthread.php?394668-V6-to-V8-engine-swap


Good luck with the project!


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Brian, you will not be changing valve timing nor the stoichiometric mixture.
By going to a quench style piston (with the correct quench dimension), you will be ensuring that the flame front has little to no place to hide, of which will more effectively force the gasses into the combustion chamber.
With the right piston profile selection, you can create the same Static Compression Ratio as to what you now have.

If you can increase the ignition TA by a few degrees only, you will be able to create a much better LPCP.


SBC Quench Effect image 8.jpg

SBC Quench Effect image 9 .jpg



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Last edited:
Hello, It's been a few weeks, but I started on the boat last week. I tore the engine down, the heads were busted as well and the cam was already pitted.
I shopped around and ended up buying a new all stock engine so I could keep the fuel injection.
The intake and most of the wiring were already removed. There is a black wire with an extra black insulator over it with a #10 ring terminal on the end
that I can't figure out where it goes. It is right by the MEFI control box.
 
It has a #10 size screw hole eyelet on it, and it wont reach the bell housing. I am apparently to stupid to figure out how to upload pictures on here.:mad:
 
It has a #10 size screw hole eyelet on it, and it wont reach the bell housing. I am apparently to stupid to figure out how to upload pictures on here.:mad:
 
Hello, It's been a few weeks, but I started on the boat last week. I tore the engine down, the heads were busted as well and the cam was already pitted.
I shopped around and ended up buying a new all stock engine :( so I could keep the fuel injection.


The intake and most of the wiring were already removed. There is a black wire with an extra black insulator over it with a #10 ring terminal on the end that I can't figure out where it goes. It is right by the MEFI control box.

In a 12 vdc system, we will have a Positive and Negative only (ground as in Earth Ground, is a term used for AC current).
Since it is black and equipped with a ring terminal, it is no doubt a Negative.
Your engine block is your System Negative Common source, and that is where you will want to attach this wire.


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