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piston choices for 5.7 vortec heads? are these acceptable?

C

centerline

Regular Contributor
after being reading several forums and articles, and being told NOT to use the common stock full dish pistons with vortec heads, so I have been looking for alternatives.

It has also been said that I should locate a a piston/ engine parts supplier that is familiar with marine engines to help decide what I need, but I cannot find a parts supplier who is knowledgeable about marine engines. JEGS is the only supplier who even claims to have someone who is familiar with a marine engine build, and is willing to put together a custom kit for me.... but I dont trust their piston choice, as the photo they sent me shows a narrow quench ring...

in an attempt to find a piston that works, I have searched the internet and have came up with 5 choices of SBC pistons.... I am posting the links in hopes that someone can take a look and tell me if any of these are the style of piston I should be looking for..... some of the choices shown are a bit expensive, and may not even be the right size for my application, but I need help finding the correct STYLE, and then I will locate the correct part number in that style.

the back story is, I have a '99 Vortec 5.7 roller block (68cc heads) that im converting to a 383. I have rebuilt many stock automotive and truck engines (gas and diesel) but this is my first attempt at a marine stroker conversion...or dealing with a vortec engine.

I am not trying to build a 400+hp motor, so i dont feel I need forged pistons, forged crank or H beam rods, but im only wanting to build a dependable motor that will deliver a bit better performance than the stock 5.7, at a reasonable cost....

5 piston choices below...
KB135
KB121
IC734
H890CP
139632-8 .......... Thank you for any help you may be able to give.
 
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Ayuh,..... Yer lookin' at the right Style of pistons,.... D-dish, aka: inverted dome pistons,....

Which ones exactly will depend on the compression numbers ya come up with,.....
 
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centerline said:
after being reading several forums and articles, and being told NOT to use the common stock full dish pistons with vortec heads, so I have been looking for alternatives.
Good for you!

It has also been said that I should locate a a piston/ engine parts supplier that is familiar with marine engines to help decide what I need, but I cannot find a parts supplier who is knowledgeable about marine engines. JEGS is the only supplier who even claims to have someone who is familiar with a marine engine build, and is willing to put together a custom kit for me.... but I dont trust their piston choice, as the photo they sent me shows a narrow quench ring...
That would most likely be the GM style full dished piston, of which offers a quench band only.
Most will be equipped with double valve reliefs of which allows one part number to fit all 8 bores.
This is a lazy man's piston!

in an attempt to find a piston that works, I have searched the internet and have came up with 5 choices of SBC pistons.... I am posting the links in hopes that someone can take a look and tell me if any of these are the style of piston I should be looking for..... some of the choices shown are a bit expensive, and may not even be the right size for my application, but I need help finding the correct STYLE, and then I will locate the correct part number in that style.
We first need to know which SBC you will be building...... 5.7L or a 6.3L ....... I.E., bore, stroke, combustion chamber volume, etc.

the back story is, I have a '99 Vortec 5.7 roller block (68cc heads) that im converting to a 383.
OK..... that would end up being a 4.030" bore (first over) with a 3.750" stroke.

I have rebuilt many stock automotive and truck engines (gas and diesel) but this is my first attempt at a marine stroker conversion...or dealing with a vortec engine.
Look closely at the Vortec cylinder head's combustion chamber!
You will see that the quench surface extends out in between the valves some. This is the portion that creates the swirl.
The GM full dished piston CANNOT take full advantage of this feature!
In fact, the large dished area (when in close proximity to the quench surface) gives a portion of the flame front a place to hide, causing detonation potential.

I am not trying to build a 400+hp motor, so i dont feel I need forged pistons, forged crank or H beam rods, but im only wanting to build a dependable motor that will deliver a bit better performance than the stock 5.7, at a reasonable cost....
You are certainly thinking and planning correctly!

5 piston choices below...
Good choice with the Hypereutectic alloy.


KB135
This profile requires the 5.7" connecting rod..... good choice for the Marine SBC.
You chambers are most likely 64 or 65cc, which gives you a S C/R of 9.7:1

KB121
This is a D-dish profile. Not as desirable with the Vortec cylinder head.

IC734
This piston has a raised wrist pin location requiring the 6" connecting rods, and would NOT be a good choice.


H890CP
This is a reverse dome piston. Not much info, so I cannot comment.
Info says "wrist pins not included".


139632-8
This profile may work, but you will want to specify the dish volume.
Click to expand...


Take some time and read this thread beginning at post #7. See my images and in particular the image in post #15.
In post #20 I give a brief explanation of LPCP and the importance of it for the Marine SBC.

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


You can also do a search and read what people like Dennis Moore, John Erb, Jeff Smith, have to suggest about properly building the SBC Marine Engine.


You may find that many Automotive Engine and even Marine Engine machine shops will not know what you are talking about when you mention Quench Effect.
You may get that "deer-in-the-headlights" look as you do!
So...... you may end up needing to provide your own build specs to your machine shop.
They will be fully capable of doing a Q/E build for you.

Knowns:
Bore = 4.030" (first over to clean up cylinder walls)
Stroke = 3.750"
Chamber volume = 64cc or 65cc...... you will want to verify this.
For the 6.3L build (aka 383 cu in), your quench dimension should be approx .045" or so.
(this will be a combination of the piston deck height and the compressed head gasket dimension)
DO NOT use the 6" connecting rods for this Marine Engine build! The 6" rods require a raised wrist pin location which creates the need for shorter piston skirts.
While the HP Auto enthusiasts like this, the Marine version SBC will not fair well with short piston skirts!

You will want to run your build specs through an "on-line" Static Compression Ratio calculator.
Be sure to include the piston deck height, compressed head gasket thickness, etc.
You will vary the piston dish volume until you come up with a desired S C/R.


Camshaft choices:
If you plan to replace the camshaft/cam followers...... once you have determined the build, I would suggest that you contact a reputable camshaft company.
Give them your build specs and intended usage.
They should be able to recommend a camshaft profile for you.

By the way..... the GM Marine Roller Camshaft and Roller cam followers will go for hours and hours........ often these are very reusable.




Whether carbureted or equipped with FI, the Q/E build will prove to be a real plus.
When done correctly, you will now be able to use a slightly more aggressive Ignition TA and obtain a good LPCP.



.
 
RicardoMarine said:
............................

Chamber volume = 64cc or 65cc...... you will want to verify this.


the GM Marine Roller Camshaft and Roller cam followers will go for hours and hours........ often these are very reusable.
Click to expand...

"Chamber volume = 64cc or 65cc...... you will want to verify this."
the KB135 piston is the first one that caught my eye, and with the specs given for these heads at 68cc (head p/n 10239906 A288), im thinking (without calculating) the compression will be a bit closer to 9.5

Question... does the .038 Quench still apply to the 383 marine build, or should one stick with the .043?

"the GM Marine Roller Camshaft and Roller cam followers will go for hours and hours........ often these are very reusable."
The OEM donor engine was TBI from a Tahoe, and not a marine 5.7... so it has the automotive parts that will all be replaced with the correct marine parts... and it will be Carbureted...
 
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also, another question for Rick..

also, In another thread I was reading, you made this statement...
"Building a good quench and good quench dimension into a SBC is very simple. Most any engine builder can do this for the asking, and it should not affect the warranty whatsoever!
It will however cause the need for multiple piston part numbers and extra alertness during the assembly."

does this mean the same piston part numbers are NOT all the same in all cylinders of the SBC engine?
 
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centerline said:
"Chamber volume = 64cc or 65cc...... you will want to verify this."
the KB135 piston is the first one that caught my eye, and with the specs given for these heads at 68cc (head p/n 10239906 A288), im thinking (without calculating) the compression will be a bit closer to 9.5
With a good Quench dimension, the 9.5:1 S C/R should not be an issue.
Here is an article by Jeff Smith.
http://www.superchevy.com/how-to/97458/

Question... does the .038 Quench still apply to the 383 marine build, or should one stick with the .043?
With the longer stroke of the 6.3L Marine Engine build, the Q dimension can be increased some. .043" would be OK.

"the GM Marine Roller Camshaft and Roller cam followers will go for hours and hours........ often these are very reusable."
The OEM donor engine was TBI from a Tahoe, and not a marine 5.7... so it has the automotive parts that will all be replaced with the correct marine parts... and it will be Carbureted...
Note that some Vortec cylinder heads have a limit as to valve travel.
If a higher lift is used, the valve guide height may require machining.
Your automotive machine shop staff will know what to do.

You may want to double check re; the combustion chamber volume.
I found this for the casting #10239906:
Notes: 350, Vortec 5700, L31, 64cc chambers, 170cc intake ports, 1.94/1.5 valves​

The rocker arm stud towers can be pinned or threaded.
I would NOT have the studs pinned! Drilling for the pins weakens the tower!
I would go with threading and cutting the tops of them and using threaded studs.
Click to expand...
 
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.....................................
centerline said:
also, another question for Rick..

also, In another thread I was reading, you made this statement...
"Building a good quench and good quench dimension into a SBC is very simple. Most any engine builder can do this for the asking, and it should not affect the warranty whatsoever!
It will however cause the need for multiple piston part numbers and extra alertness during the assembly."

does this mean the same piston part numbers are NOT all the same in all cylinders of the SBC engine?
That would be correct!
This is due to the wrist pin off-set (Right bank/Left bank) and the Int/Exh valve relief locations.
These ports are exh/int/int/exh/exh/int/int/exh, of which means that the un-equal valve reliefs must correspond to each valve.

Any machine shop person who is worth his salt should know what to do.
Click to expand...
 
RicardoMarine said:

"the GM Marine Roller Camshaft and Roller cam followers will go for hours and hours........ often these are very reusable."
The OEM donor engine was TBI from a Tahoe, and not a marine 5.7... so it has the automotive parts that will all be replaced with the correct marine parts... and it will be Carbureted...
Note that some Vortec cylinder heads have a limit as to valve travel.
If a higher lift is used, the valve guide height may require machining.
Your automotive machine shop staff will know what to do.

You may want to double check re; the combustion chamber volume.
I found this for the casting #10239906:
Notes: 350, Vortec 5700, L31, 64cc chambers, 170cc intake ports, 1.94/1.5 valves​
Click to expand...

"Note that some Vortec cylinder heads have a limit as to valve travel.
If a higher lift is used, the valve guide height may require machining."

it is my understanding that using the vortec heads with the correct pistons in a lower rpm engine, such as a standard marine build, there is little sense in using a high lift cam... im looking at somewhere between .350 to .400 lift as according to the numbers ive seen, the engine seems to be able to breath as well as it possibly can at 4600 rpm at this lift..

thank you for double checking the head spec I posted, I will check again and see where the number I posted (68cc) went wrong...
 
Docksidemarineservices said:
Seems like you are talking with yourself.

I asked an important question and it was passed over.

As for post count. Not my purpose on this page.
Click to expand...

im so sorry, when I read the particular post of yours that I quoted, I thought you may be trolling... I sincerely apologize.
I did answer the question you posed but did not quote you specifically, but just included it in reply #5, at the bottom. it will be a carbed engine... and as for me talking to myself, yes, I believe im old enough to start doing that... :)
 
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centerline said:
.....................
I did answer the question you posed but did not quote you specifically, but just included it in reply #5, at the bottom. it will be a carbed engine...
Whether carbureted, FI or drip system, you are wise to explore the idea of building a Quench Effect into your combustion chambers.
The SBC that is destine for Marine service should NEVER be built using that silly GM full dished piston. :mad:

and as for me talking to myself, yes, I believe im old enough to start doing that... :)
You are not alone...... I am also old enough to start talking to myself....... as a matter of fact, I do it quite often! :)
Click to expand...


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centerline said:
Rick, I double checked the head chamber volume from the site I originally got the info from... http://outintheshop.com/faq/casting/heads.html and it does show 68cc.... but another site shows them being 64cc as you said you found.... I suppose I will have to keep searching and take an average ;-)
Click to expand...

Whether the chambers are 68cc or 64cc in volume , you will want to know this value in order to run the Static Compression Ratio calculations.
If your entered data is off by 4cc's, your S C/R calculation will be off!
Just for fun, try changing the value by 4cc's........ you'll be surprised at how much difference it makes!

If in doubt, you can turn the cylinder head upside down and fill the chamber with a measured volume of ATF.
A difference of 4cc's should be obvious.



NOTE: some of the on line S C/R calculators require that we enter a - or + when typing in the piston dish volume value.




.
 
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centerline said:
im so sorry, when I read the particular post of yours that I quoted, I thought you may be trolling... I sincerely apologize.
I did answer the question you posed but did not quote you specifically, but just included it in reply #5, at the bottom. it will be a carbed engine... and as for me talking to myself, yes, I believe im old enough to start doing that... :)
Click to expand...

If your engine is Carbed you can build it anyway you like. If it was EFI with Computer controlled timing. You have to build it to the original specs unless you have a the ability to change the tables in the ECM.
 
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Docksidemarineservices said:
If your engine is Carbed you can build it anyway you like.
If it was EFI with Computer controlled timing. You have to build it to the original specs unless you have a the ability to change the tables in the ECM.
From what I read, centerline is building a '99 Vortec 5.7L into a 6.3L and will be using a carburetor.
Click to expand...

faztbullet said:
A lot of overkill if your putting in the Bayliner IMO.

I would love to hear your reasoning behind that statement!
Click to expand...
 
Chris, all due respect........ you are very knowledgeable as seen by your contributions here on the forums.

I have to ask:

1..... are you suggesting that a person who would be building a Marine version of the SBC 6.3L (aka SBC 383 cu in stroker) and using the Vortec cylinder heads (whether it is to be carbureted or equipped with EFI, TBI, MPI or MEFI)....... NOT use a quench style piston in lieu of the GM Full Dished style for this build?

2..... are you suggesting that this same person (using the above build) NOT change the tables in the ECM ?

3..... if you are against doing this build, and if you believe that the GM F/D piston is a better choice (even while knowing that the ECM tables can be changed), please explain why!



******************************************


Mr. Centerline, as you know, the 6.3L build gives this build an increased stroke of .270".
The .270" increase is all the more reason for getting away from the GM style F/D pistons!
Also, due to the .270" increase in stroke, the quench dimension should be increased from .038" to perhaps .043" or so.

Now..... I would never suggest that a person build a HP Automotive version of this SBC engine for Marine use.
However, and for a comparison ONLY....., the GM HP Auto version will typically incorporate a piston profile that mirrors the Vortec quench surface.
In other words, it would NOT be built using the GM full dished pistons that are not capable of creating a Q/E!


My suggestion: take the time to read some of the great articles written by Jeff Smith (SBC HP expert), Dennis Moore (Small Block Chevy Marine Performance), John Erb (Chief Engineer Kieth Black Performance ), Larry Carly (engineer) and more.




Keep us up to date regarding your research and what you have decided to do! :D


Photo below:
Note that this is viewing the front of a Std LH Rotation engine, therefor the crankshaft (as viewed) is rotating in a CW direction.
When looking at the cylinder to the left, the "burn" is forcing the piston downward during the "power stroke".
This image represents a crankshaft angle when the burn is at maximum expansion.
The engine build must be correct so that "ignition" can occur early enough (yet not cause detonation) in order to achieve this 12* to 14* LPCP.
 

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faztbullet said:
A lot of overkill if your putting in the Bayliner IMO.
Click to expand...

possibly.... it depends on ones point of view I suppose.

but if one was to keep in mind that I can afford to do it, I have the time to do it as the engine I have in the boat now is perfectly fine and runs well, AND I have the tools to do it.... this is only a project that im interested in doing and im and learning something new by doing it.... its not so much of an overkill, but I would agree that it is not an absolute necessity....

the only down side is, after putting this much power in front of the cobra drive, I will be needing to replace it at some point also.. but thats plan anyway.
 
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I am moving forward with the project.
I have the block and heads in the shop being prepped for the build... it should be ready towards the end of next week.

as I have said earlier, this is not going to be a high rev'ing, or high horse power engine, but only a basic stroker, put together as a marine engine for a cruiser, using the best information I can gather from other people who have experience building a 383..

the piston choice seems to be the easy part, but the suggestions for a cam is a bit more elusive.

I have read a lot on the conversion process, but all I have read so far in choosing the internals is to not uses a full dish piston, and try to keep the C/R below 9.5 (this is agreed on by all performance builders)....and that a vortec engine is built to breathe well without a high lift cam, and the vortec engine with an rpm range up to 4600 can very effectively use a cam with a lift of .350 to .400 to the engines full potential at that rpm... yet I have no idea of what duration would be normal for a marine build like this, because so far I have not been able to find someone who can (or is willing to) make an educated guess at it...
the guy at Summit who I spoke with has NO IDEA of what a "marine" build even means.... and the guy at JEGS pretends to have someone on staff who know, but evidently doesnt, because his piston choices were wrong and he didnt know what the quench area was on a piston, or what it meant (which I didnt either 6 months ago, but im not in the business of selling parts or building marine engines either)...

I think once I have a cam picked out, all the other decisions will be easy....
 
I think once I have a cam picked out, all the other decisions will be easy....
Click to expand...

Ayuh,..... In the cam catalogs, the usable rpms are listed for each cam,....

Ya want to pick a cam that builds it's max power from Idle, to 4800 rpms,.....
Usually known as a Marine cam, or better known as a R/V cam,....
 
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centerline said:
A lot of overkill if your putting in the Bayliner IMO.
Click to expand...
possibly.... it depends on ones point of view I suppose.

but if one was to keep in mind that I can afford to do it, I have the time to do it as the engine I have in the boat now is perfectly fine and runs well, AND I have the tools to do it.... this is only a project that im interested in doing and im and learning something new by doing it.... its not so much of an overkill, but I would agree that it is not an absolute necessity....
And that is the attitude that is needed. I'm with you!

the only down side is, after putting this much power in front of the cobra drive, I will be needing to replace it at some point also.. but thats plan anyway.
FYI...... the OMC Cobra drive is a candidate for the Volvo Penta SX or DP-S drive conversion. SX = single prop.... DP-S = Duo Prop.
This conversion will get you a stronger drive and cone clutch gear engagement. (no more Dog Clutch..... no more ESA)
Click to expand...

centerline said:
I am moving forward with the project.
I have the block and heads in the shop being prepped for the build... it should be ready towards the end of next week.

as I have said earlier, this is not going to be a high rev'ing, or high horse power engine, but only a basic stroker, put together as a marine engine for a cruiser, using the best information I can gather from other people who have experience building a 383..
Correct...... our boats require torque, not necessarily high horse power.
The 3.750" stroke will give you much more torque.

the piston choice seems to be the easy part,
Yes.

but the suggestions for a cam is a bit more elusive.
As said earlier, contact a major camshaft company and give them your build specs.

I have read a lot on the conversion process, but all I have read so far in choosing the internals is to not use a full dish piston,
Correct!

and try to keep the C/R below 9.5 (this is agreed on by all performance builders)....and that a vortec engine is built to breathe well without a high lift cam, and the vortec engine with an rpm range up to 4600 can very effectively use a cam with a lift of .350 to .400 to the engines full potential at that rpm... yet I have no idea of what duration would be normal for a marine build like this, because so far I have not been able to find someone who can (or is willing to) make an educated guess at it...
Companies like Jegs and Summit sell parts.
I would go directly to a manufacturer. They will have experts on staff who will be able to steer you in the right direction.
Then you can place your order through _______ or ????

http://www.compcams.com/tech-help/Support.aspx

800-999-0853


http://www.lunatipower.com/

662-892-1500


http://www.iskycams.com/

310- 217-9232



https://www.crower.com/

619-661-6477





the guy at Summit who I spoke with has NO IDEA of what a "marine" build even means.... and the guy at JEGS pretends to have someone on staff who know, but evidently doesnt, because his piston choices were wrong and he didnt know what the quench area was on a piston, or what it meant (which I didnt either 6 months ago, but im not in the business of selling parts or building marine engines either)...
It would appear that you have witnessed the "Deer-in-the-headlights" look when you asked.
Don't be too surprised...... I have heard this song played many times.

I think once I have a cam picked out, all the other decisions will be easy....
I would feel safe if I was to make my rotating assembly parts decision first..... but that is your call!
Click to expand...


Side note.... whether done by the machine shop or by you, when initially adjusting your hydraulic cam follower plunger depths, I would suggest using the Static 8 stop procedure..... not the 2 or 3 stop! Do this and you should not need to go back through them.


Have fun and keep us up to date. :D





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thank you for the contact numbers...

as for the rotating assembly, I think I know what I need, and have it picked out and have been quoted, but they didnt include individual item part numbers or pictures and im holding off until they send me some more information, so I KNOW what I have ordered..... the cam they have included is still in question.

I have found one with the correct lift and rpm range, but it is a flat tappet cam... im waiting to hear back from Comp what they have for a roller equivalent...
 
centerline said:
thank you for the contact numbers...

as for the rotating assembly, I think I know what I need, and have it picked out and have been quoted, but they didnt include individual item part numbers or pictures and im holding off until they send me some more information, so I KNOW what I have ordered..... the cam they have included is still in question.

I have found one with the correct lift and rpm range, but it is a flat tappet cam... im waiting to hear back from Comp what they have for a roller equivalent...
Click to expand...

Unfortunately (for the Marine Engine enthusiast) most SBC "stroker" kits are intended for HP automotive use, and will typically include the longer rods and shorter piston skirts (i.e., reduced compression height). This is OK for the HP Auto version, but is not as desirable for the Marine cruiser engine.

Also, these companies almost always omit describing the piston deck profile. They will include the word "Hypereutectic", etc..... but rarely any profile info.

https://en.wikipedia.org/wiki/Hypereutectic_piston


As for the cam and cam followers....... your cylinder block is set up for the roller tip followers. I would certainly stay with that and benefit from the reduced friction and the more efficient cam ramping profile!


Suggestions:

Your 3.750" stroke crankshaft requires a different harmonic balancer (it should be included in the kit). While the balancer has not yet been installed, have it indexed up to approx 35 degrees btdc. Some kits may include an indexed harmonic balancer. (this will be useful when checking ignition advance)

Also, you may want to ask that #1 TDC be verified by having them perform a PPS procedure. (use a 30* +/- split..... not 10* +/-)



 
I finally have my parts ordered...

after searching for someplace to source the parts, who knew anything about what I was talking about, I finally ended up at SCAT. they have marine rotating assemblies, BUT in their "stock" kits, they normally include the full dish pistons... Luckily they are very helpful and easy to work with, AND willing to substitute for desired parts if requested. so I got the KB135-.030 pistons... the rods are the new style "stroker" rods, with the claim that very few blocks have to be machined to allow journal bolt clearance when using the stroker rods, which also happen to be H-beam rods.

the cam and roller lifters are coming from Crower.
its a .410 lift custom marine cam... their "marine" cams are a different duration and overlap than street cams so the chance of ingesting water back into the engine is minimized... 800-4800rpm range.

all parts except the cam is in stock (the custom cam has to be built, but will ship within 12 days they said) so I should have everything within 2 weeks....
 
Good for you! :D

Since you have ordered a rotating assembly, I assume that you have determined the cylinder head combustion chamber volume.
Just curious...... what were they... and what S C/R are you shooting for????

Also.... FYI.... your cylinder heads 10239906 are equipped with the smaller valves...... 1.94 intake and 1.50 exh.



Rick
 
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