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Where to buy SBC Marine pistons?-gctid360463

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  • 2850Bounty
    replied
    Giddy-Up wrote:
    I have had all of that info before I started all of this. The head casting numbers are 14096217 .. They are 64 cc.

    With 1.94 and 1.5 valves.. They can handle either the rollers or non-roller.

    [COLOR]"#0000FF" wrote:
    That would appear to be correct.

    I come up with cylinder head casting number 14096217 = 5.7L 1.94/1.50, 64cc chamber, 1990-up crate engine heads. [/COLOR]

    The engine that was in the boat had 9.3:1 cr. 260 hp. (see pic)

    [COLOR]"#0000FF" wrote:
    With the full dished pistons, this may have contributed to the detonation. [/COLOR]

    Engine Casting: 14093638 14093638 = 350 cubic inch 1988 through 1994 were the years this block was made Roller or Flat Tappet Cam was used

    2 or 4 bolt mains were used 1-piece rear seal

    [COLOR]"#0000FF" wrote:
    I come up with block casting 14093638 = 1986-1988, pre-roller cam blocks if OEM in your boat.

    Not a deal breaker by any means, but doubt that it is roller cam ready.[/COLOR]

    The piston I am going to use is



    I want you to know that I do understand what you telling me.. My problem is learning how to do it. I want to go a little more on the HP as well as everything else. I would like to get it up to say 300 HP. as well as keeping the Quench Affects in control.

    [COLOR]"#0000FF" wrote:
    Understood, and I'm trying my best to help you in that direction. [/COLOR]
    Jim, you'll want "torque" as much as you want horse power. In particular, you want mid range and above torque for this hull.

    The single valve relief F/T pistons is a good choice when used with the 76cc.

    [COLOR]"#FF0000" wrote:
    You have 64cc heads according to your last post![/COLOR]

    If you run the calcs using 64cc chamber cylinder heads and with those F/T pistons (using a -2cc relief volume), here's what you get:

    Enter Bore/Stroke Designation Type 1 = Inches 2 = Millimeters ......................... 1

    Enter Cylinder Bore Size .................................................. ..................................... 4.030"

    Enter Piston Stroke Length .................................................. ................................. 3.480"

    Enter Head Gasket Bore Diameter .................................................. ..................... 4.030"

    Enter Compressed Head Gasket Thickness .................................................. .......... .022"

    Enter Combustion Chamber Volume In CCs .................................................. ......... 64cc

    Enter Piston Dome Volume In CCs Negative For Dished Pistons (Use '-') ............... -2cc (this is close... may be -1cc larger/smaller)

    Enter Piston Deck Clearance Negative If ABOVE Deck (Use '-') : ............................. .016"

    Based on the above data, the Calculated Engine Static Compression Ratio will be [COLOR]"#FF0000" wrote:
    10.4643:1[/COLOR]


    This is clearly a C/R used by the Automotive guys.... not the Marine guys, and certainly not in cruiser type applications............ not without extra and more costly modifications.

    NOTE: if the machine shop fattens up the compressed head gasket thickness to compensate....., you loose a great portion of the quench or squish effect.
    • The same F/T pistons with 76cc chambers = 9.1428:1 static C/R.
    • The LC Quench, D dished, or Rev Dome piston with your 64cc chamber = 9.1428:1 static C/R. (dish volume of -14cc)
    • Close the dish volume to -12cc, and you'll get a 9.3368:1 static C/R.
    • Open the dish volume to -16cc, and you'll get a 8.9576:1 static C/R.




    It took me all of 10-12 minutes to do this....., or about the same time it would have taken a piston supplier representative while on the telephone.

    Jim, this is none of my business, but I have a hunch that you are being influenced by automotive enthusiasts (who are not acknowledging the subtle differences), rather than people with SBC Marine Cruiser experience.

    I've given this my best shot, and I do wish you good luck and I hope that it works out for you!


    Edit:

    BTW, Jim, if you want to do the roller cam, the front area of the block must be machined for the thrust plate that controls lateral camshaft movement...............



    ....... and you'll need these threaded bosses for hold-down tray mounting bolts (red arrows), and the casting reliefs for the cam follower keepers (yellow arrows).

    If memory serves me, none of this machining showed up until the early to mid 90's.

    Attached files http://baylinerownersclub.org/media/....jpg[/img]

    Leave a comment:


  • Guest's Avatar
    Guest replied
    I have had all of that info before I started all of this. The head casting numbers are 14096217 .. They are 64 cc. With 1.94 and 1.5 valves.. They can handle either the rollers or non-roller. The engine that was in the boat had 9.3:1 cr. 260 hp. (see pic)

    [img]/media/kunena/attachments/vb/669756=25911-OMC Corbra Specifications.jpg[/img]
    Engine Casting: 14093638 14093638 = 350 cubic inch 1988 through 1994 were the years this block was made Roller or Flat Tappet Cam was used 2 or 4 bolt mains were used 1-piece rear sealThe piston I am going to use is

    [img]/media/kunena/attachments/vb/669756=25910-flat top ebay_12.jpg[/img]I want you to know that I do understand what you telling me.. My problem is learning how to do it.I want to go a little more on the HP as well as everything else. I would like to get it up to say 300 HP.as well as keeping the Quench Affects in control..Regards, Jim

    Leave a comment:


  • 2850Bounty
    replied
    Giddy-Up wrote:
    Yes I did go to the sites that you sent me to and a few more that I have found along the way..

    1..... Those pistons that I bought are not quite right for the job but there are a few things that I read that can be done to make them work..

    2..... But I am getting different ones..

    3.... If I can get the ones that I have returned I will get the ones with just the two valve reliefs.

    4.... I also ran across a set that were totally flat.. How would they be to use.. I would not get them because of the cost

    I was just wondering how they would be to use?

    I think I understand it all, but I hope no one ever asks me about it. I would just look at them with a blank look on my face..

    5.... From some of the numbers that I gathered it looks like I should be in the 10:1 area for cr.

    6.... I will be cc'ing the heads when I get them back So I have a more accurate figures to work with..

    7..... I am also going to measure the piston to deck height and a few other measurement Just to be as accurate as I can..

    8..... As far as the machine shop goes, he understand what it is.. He got a better understanding after I sent a fax to him with pic's. of what you have explained to me.. I actually understood, but I had no idea of how to do it all..
    Jim, you really can't go any further here until we know which cylinder heads you plan to use. Meaning; cyliner head combustion chamber volume!

    Your cylinder head casting numbers will give you this information.

    It will be right there underneath the valve cover area.

    With this number, you can go on-line to a SBC casting number web site.

    http://outintheshop.com/faq/casting/heads.html

    http://www.castingnumbers.info/site/browse/m/Chevrolet

    http://www.nastyz28.com/sbchevy/sbch.php

    You are looking for a two digit number (i.e., 58cc, 64cc, 65cc, 76cc, and so on) .... not intake runner or exhaust port volume..... we're talking combustion chamber volume.

    Once you know this, the other numbers [desired C/R, bore (4.030" if first over), and stroke (3.480"), deck and compressed gasket thickness ] will get you started on a piston selection.

    As I said:

    If the chamber volume is 76cc, then a F/T piston will bring the C/R to just about where you want it to be.

    If the chamber volume is 64cc, then you can NOT use the F/T piston as the C/R would be too great!

    [SIZE]4 wrote:
    Perhaps re-read posts #21 and #23 again. [/SIZE]

    1..... If these are what I believe them to be, this would be a high grade version of the GM Full Dished piston.

    They are pretty and shiny and well constructed... no question about it, so I'll give you that!

    But no matter how nice these are and look, they are not a good Marine Build choice with any SBC cylinder head (no quench surface).



    2..... Good! But again, you must begin with the cylinder head combustion chamber volume. This, and the desired C/R, is what will determine your selection.

    3.... Again, you must begin with the cylinder head information.

    The single valve reliefs -vs- the double reliefs is secondary to the more important aspect of the piston shape complimenting the chamber.

    4.... Again, you will only be able to use a F/T piston if your cylinder head chamber volume is 76cc..... and only for the 5.7L stroke.

    I was just wondering how they would be to use?

    5.... I'd say NO! For Street Use 10:1 would be a good C/R, but you are building a SBC for a Marine application.

    Not only Marine, but for a somewhat heavy 2556 SDN F/B boat.



    6.... Your casting numbers will give you this information.

    7..... This will be protocol for your machine shop person. They do this routinely.

    8.... If he truly understands, then he will be instrumental in determining the chamber volume, and will then go from there for the piston selection.

    This selection is nothing more than plugging the data in, and doing some easy math.

    Take another look at Dave's quench style pistons.

    Note the large flat surface that mirrors the cylinder head "wedge" area.

    Also note the dish volume that compensates for the smaller 64cc chamber heads, and keeps the C/R where it needs to be.

    If this dished area was flat, the actual combustion chamber volume would be reduced, thus the C/R is increased beyond what Dave could use.



    If Dave was using the larger 76cc chamber heads, he'd probably be using a piston more like this, and knowing Dave, I'm sure that he'd opt for the single valve relief pistons.





    Jim, this would be on my build menu if I owned your 2556:


    Target C/R of 9.0:1 to as much as 9.2:1..... and with an extremely good "quench" perhaps 9.3:1.

    No long skirts.

    No extended connecting rods.

    No HP Automotive high ring landings.

    Large valves both intake and exhaust.

    No Extreme Valve Spring pressures.

    Piston deck height of .016" or so.

    Compressed Head Gasket dimension that offers a total quench dimension of .038" + / -.

    Normal assembly protocol.

    8 Stop initial static cam follower adjustment prior to intake and oil priming.

    A fully degreed Harmonic Balancer for Dynamic Ignition timing.

    A PPS TDC procedure to ZERO in the harmonic balancer.

    I would punch mark the inner/outer balancer components for future checks against slipping.

    [COLOR]#ff0000 wrote:
    I would also consider having your ignition distributor fully tested and re-calibrated.

    Something contributed to the Detonation Damage that occured previously, and you DO NOT want a repeat of this: [/COLOR]

    http://www.baylinerownersclub.org/fo...6&d=1331675418

    I think that the rest of this is best left in the hands of a qualified Engine Builder -slash- Machinist.

    And one that appreciates this for a more True SBC Marine build.

    Jim, at the risk of sounding gruff, if your machine guy can't speak this language better than I, he's probably not the right the man for the job.

    However, if he does speak this language, and knows the perameters, he'll do just fine for you.

    .

    Leave a comment:


  • Guest's Avatar
    Guest replied
    2850Bounty wrote:
    Well, sort of and almost!

    The intake and exhaust valves are located within the combustion chamber. The target quench dimension for the SBC Marine is .038".

    But we can't talk about the quench area without understanding which part of the piston creates the quench, and/or if it's even the right piston to create a quench.

    Had you visited any of those linked to articles, you'd have seen this.

    This image shows a cross-cut view of cylinder, combustion chamber, wedge area, and piston (including skirt, wrist pin and deck).

    It exaggerates the squish/quench dimension.... (actually only .038" or so) ..... I suppose for illustration only.



    As you can see, the wedge area is off to the side of the combustion chamber..... actually, higher up on the SBC engine, and towards the intake system.

    The combustion chamber is down lower, closer to the exhaust manifold side.

    What this image does not show, is a perspective view of the piston dished area related to the wedge area.

    http://"http://t2.gstatic.com/images...nd wedge area)

    With the SBC, we have to start with a piston who's deck surface "mirrors" the wedge best it can, then we can build an effective quench or squish area, but only with this certain style piston.

    The D dished, Low Comp Q piston, and/or Reverse Dome piston can do this.

    Let's flip this piston around 180* and bring the D shape over to our left side.

    Now let's bring this piston deck up underneath the D shaped wedge surface in the image above.

    When these two D shaped surfaces are brought to within close proximity of each other, we essentially have the beginning of a Quench or Squish area.



    Meanwhile, the open combustion chamber and the piston dished area are over/under each other.

    Now let's bring this full dished piston up underneath the D shaped wedge area.

    You'll see that the dished area is underneath the wedge and there is ZERO Quench occuring here ....... in fact, we have a small void there.



    The full dished can't possibly create a quench or squish..... there is no flat deck surface to this style piston!

    There's so much more to this than pistons, cam profile, fuel delivery, ignition, etc. and it has to do with LPCP (location of peak cylinder pressure).

    We want the largest process of expanding gasses (from combustion) that we can have.

    This makes for greater cylinder pressures that push the piston down in the bore.

    We also want this process to reach it's peak pressure at approx 12* to 14* ATDC.... that's AFTER Top Dead Center when the piston is pushing the crankshaft down.

    This would be for any piston engine..... 4 stroke, 2 stroke, diesel, gasoline, etc.

    Here's a key point:

    The placement of PCP (in terms of crankshaft angle) is all determined by when the combustion process begins.

    If the process begins too early, then PCP occurs to soon and we can undergo detonation.

    If the process begins too late, then PCP occurs much further after the desired crankshaft angle, reducing crankshaft torque.

    So why can't we just time the ignition differently to make this happen????

    The full dished piston does NOT offer a quench, in fact, it provides a place for the flame front to hide, causing a potential secondary burn and shock waves.

    These are destructive to the cylinder.

    So we must hold back ignition timing when this piston is used.

    When we hold back ignition timing, we also delay LPCP to perhaps 16* to 17* ATDC..... making lousy torque and horse power.

    When we build a quench or squish area, we reduce detonation potential, and can now give the engine some more spark lead (Ignition Advance).

    When we give the engine more ignition lead we bring the LPCP back to a much more desirable 12*- 14* ATDC... making better torque and horse power.... and at the same time, greatly reducing the risk of Detonation.

    The gain:

    A greater chance of LPCP at 12* to 14* ATDC, more low end torque, and a much reduced risk of detonation, of which is a real concern for Marine loads.

    This is nothing new. Your machine shop person should know exactly what all of this means. He just may not be considering how well it applies to the SBC Marine build.

    Also, Jim, this build requires no other major changes. Assembly procedure is identical.

    He'll still be checking deck height, fitting pistons, choosing the correct head gaskets, etc.

    Edit: If I gained any Rep Power points for content here, I certainly lost more for Verboseness.
    [SIZE]3 wrote:
    [FONT]Calibri wrote:
    [COLOR]#000000 wrote:
    Yes I did go to the sites that you sent me to and a few more that I have found along the way.. [/COLOR][/FONT][/SIZE]

    [SIZE]3 wrote:
    [FONT]Calibri wrote:
    [COLOR]#000000 wrote:
    Those pistons that I bought are not quite right for the job but there are a few things that I read that can be done to make them work..[/COLOR][/FONT][/SIZE]

    [SIZE]3 wrote:
    [FONT]Calibri wrote:
    [COLOR]#000000 wrote:
    But I am getting different ones.. If I can get the ones that I have returned I will get the ones with just the two valve reliefs. [/COLOR][/FONT][/SIZE]

    [SIZE]3 wrote:
    [FONT]Calibri wrote:
    [COLOR]#000000 wrote:
    I also ran across a set that were totally flat.. How would they be to use.. I would not get them because of the cost[/COLOR][/FONT][/SIZE]

    [SIZE]3 wrote:
    [FONT]Calibri wrote:
    [COLOR]#000000 wrote:
    I was just wondering how they would be to use? [/COLOR][/FONT][/SIZE]

    [SIZE]3 wrote:
    [FONT]Calibri wrote:
    [COLOR]#000000 wrote:
    I think I understand it all, but I hope no one ever asks me about it. I would just look at them with a blank look on my face.. [/COLOR][/FONT][/SIZE]

    [SIZE]3 wrote:
    [FONT]Calibri wrote:
    [COLOR]#000000 wrote:
    From some of the numbers that I gathered it looks like I should be in the 10:1 area for cr. I will be cc'ing the heads when I get them back[/COLOR][/FONT][/SIZE]

    [SIZE]3 wrote:
    [FONT]Calibri wrote:
    [COLOR]#000000 wrote:
    So I have a more accurate figures to work with.. I am also going to measure the piston to deck height and a few other measurement [/COLOR][/FONT][/SIZE]

    [SIZE]3 wrote:
    [FONT]Calibri wrote:
    [COLOR]#000000 wrote:
    Just to be as accurate as I can.. As far as the machine shop goes, he understand what it is.. He got a better understanding after[/COLOR][/FONT][/SIZE]

    [SIZE]3 wrote:
    [FONT]Calibri wrote:
    [COLOR]#000000 wrote:
    I sent a fax to him with pic's. of what you have explained to me.. I actually understood, but I had no idea of how to do it all..[/COLOR][/FONT][/SIZE]

    [FONT]Calibri wrote:
    [SIZE]3 wrote:
    [COLOR]#000000 wrote:
    [/COLOR][/SIZE][/FONT]

    [FONT]Calibri wrote:
    [COLOR]#000000 wrote:
    Regards, Jim[/COLOR][/FONT]

    Leave a comment:


  • 2850Bounty
    replied
    Giddy-Up wrote:
    Ok... if I understand this right.. Essentially the less space between the piston head/edge to the head the better it is.. Right? Not counting the area where the valve is..
    Well, sort of and almost!

    The intake and exhaust valves are located within the combustion chamber. The target quench dimension for the SBC Marine is .038".

    But we can't talk about the quench area without understanding which part of the piston creates the quench, and/or if it's even the right piston to create a quench.

    Had you visited any of those linked to articles, you'd have seen this.

    This image shows a cross-cut view of cylinder, combustion chamber, wedge area, and piston (including skirt, wrist pin and deck).

    It exaggerates the squish/quench dimension.... (actually only .038" or so) ..... I suppose for illustration only.



    As you can see, the wedge area is off to the side of the combustion chamber..... actually, higher up on the SBC engine, and towards the intake system.

    The combustion chamber is down lower, closer to the exhaust manifold side.

    What this image does not show, is a perspective view of the piston dished area related to the wedge area.

    http://"http://t2.gstatic.com/images...nd wedge area)

    With the SBC, we have to start with a piston who's deck surface "mirrors" the wedge best it can, then we can build an effective quench or squish area, but only with this certain style piston.

    The D dished, Low Comp Q piston, and/or Reverse Dome piston can do this.

    Let's flip this piston around 180* and bring the D shape over to our left side.

    Now let's bring this piston deck up underneath the D shaped wedge surface in the image above.

    When these two D shaped surfaces are brought to within close proximity of each other, we essentially have the beginning of a Quench or Squish area.



    Meanwhile, the open combustion chamber and the piston dished area are over/under each other.

    Now let's bring this full dished piston up underneath the D shaped wedge area.

    You'll see that the dished area is underneath the wedge and there is ZERO Quench occuring here ....... in fact, we have a small void there.



    The full dished can't possibly create a quench or squish..... there is no flat deck surface to this style piston!

    There's so much more to this than pistons, cam profile, fuel delivery, ignition, etc. and it has to do with LPCP (location of peak cylinder pressure).

    We want the largest process of expanding gasses (from combustion) that we can have.

    This makes for greater cylinder pressures that push the piston down in the bore.

    We also want this process to reach it's peak pressure at approx 12* to 14* ATDC.... that's AFTER Top Dead Center when the piston is pushing the crankshaft down.

    This would be for any piston engine..... 4 stroke, 2 stroke, diesel, gasoline, etc.

    Here's a key point:

    The placement of PCP (in terms of crankshaft angle) is all determined by when the combustion process begins.

    If the process begins too early, then PCP occurs to soon and we can undergo detonation.

    If the process begins too late, then PCP occurs much further after the desired crankshaft angle, reducing crankshaft torque.

    So why can't we just time the ignition differently to make this happen????

    The full dished piston does NOT offer a quench, in fact, it provides a place for the flame front to hide, causing a potential secondary burn and shock waves.

    These are destructive to the cylinder.

    So we must hold back ignition timing when this piston is used.

    When we hold back ignition timing, we also delay LPCP to perhaps 16* to 17* ATDC..... making lousy torque and horse power.

    When we build a quench or squish area, we reduce detonation potential, and can now give the engine some more spark lead (Ignition Advance).

    When we give the engine more ignition lead we bring the LPCP back to a much more desirable 12*- 14* ATDC... making better torque and horse power.... and at the same time, greatly reducing the risk of Detonation.

    The gain:

    A greater chance of LPCP at 12* to 14* ATDC, more low end torque, and a much reduced risk of detonation, of which is a real concern for Marine loads.

    This is nothing new. Your machine shop person should know exactly what all of this means. He just may not be considering how well it applies to the SBC Marine build.

    Also, Jim, this build requires no other major changes. Assembly procedure is identical.

    He'll still be checking deck height, fitting pistons, choosing the correct head gaskets, etc.

    Edit: If I gained any Rep Power points for content here, I certainly lost more for Verboseness.

    Leave a comment:


  • Guest's Avatar
    Guest replied
    2850Bounty wrote:
    Jim, perhaps this will help.

    NOTE: neither of these pistons would be used in a 5.7L SBC Marine build w/ the 76cc chamber cylinder heads..... it simply is not needed since the F/T piston (w/ the correct quench dimension) accomplishes what we need.

    So we're talking about the use of the smaller chamber cylinder heads here (64cc or so).

    If your build includes the use of the 76cc chambers, we'd be back to a Flat Top piston choice...... in which case you need to read no further.

    But assuming that your combustion chambers are 64cc:

    Here are two piston types (grabbed from a Google search.... so these are random images only).

    This is a full dished piston.



    This is a Quench style... actually a D dished piston.



    Either piston offers a dish volume that allows us to control C/R with a given cylinder head chamber volume.

    First piston offers a dish volume, but absolutely ZERO quench or squish ability.

    Second piston offers a dish volume, but also offers a quench or squish ability due to the piston deck surface coming up and underneath the cylinder head "wedge" area.

    Given that both piston dish volumes would be the equal (again, I grabbed random images):

    The Static C/R end results will the same.

    However, the performance results will not be equal.

    .
    Ok... if I understand this right.. Essentially the less space between the piston head/edge to the head the better it is.. Right? Not counting the area where the valve is..

    Leave a comment:


  • 2850Bounty
    replied
    Jim, perhaps this will help.

    NOTE: neither of these pistons would be used in a 5.7L SBC Marine build w/ the 76cc chamber cylinder heads..... it simply is not needed since the F/T piston (w/ the correct quench dimension) accomplishes what we need.

    So we're talking about the use of the smaller chamber cylinder heads here (64cc or so).

    If your build includes the use of the 76cc chambers, we'd be back to a Flat Top piston choice...... in which case you need to read no further.

    But assuming that your combustion chambers are 64cc:

    Here are two piston types (grabbed from a Google search.... so these are random images only).

    This is a full dished piston.



    This is a Quench style... actually a D dished piston.



    Either piston offers a dish volume that allows us to control C/R with a given cylinder head chamber volume.

    First piston offers a dish volume, but absolutely ZERO quench or squish ability.

    Second piston offers a dish volume, but also offers a quench or squish ability due to the piston deck surface coming up and underneath the cylinder head "wedge" area.

    Given that both piston dish volumes would be the equal (again, I grabbed random images):

    The Static C/R end results will the same.

    However, the performance results will not be equal.

    .

    Leave a comment:


  • Guest's Avatar
    Guest replied
    Ricardo???

    Leave a comment:


  • 2850Bounty
    replied
    Jim, I did not know your name until just now.

    This piston is an OK choice. The single valve relief's would be better, but this is still better over a full dished piston.



    This piston is a single valve relief.



    NOTE:

    Both of the above pistons are Flat Top pistons.

    Because there is no dish volume, either must be used with the larger 76cc chamber cylinder heads in a 5.7L SBC build to keep the C/R where it needs to be.

    (has to do with the 5.7L 3.480" stroke).

    This is important to note.

    Jim, I'm putting this in bold red text... no offense, just want to stress these points.

    [COLOR]"#FF0000" wrote:
    You'll need to know your cylinder head combustion chamber volume in order to run the calculations in order to determine piston dish volume. [/COLOR]


    You'll know the stroke (3.480"), you'll know the bore (4.030"), you'll know your chamber volume.

    You just need to determine the piston dish volume which will lead you to the correct piston part number.

    [COLOR]"#FF0000" wrote:
    Your machinist will know the piston deck heigth which will lead him to the compressed head gasket thickness. Both play a role in the correct quench or squish dimension.

    For our SBC Marine engines, a quench/squish dimension of approximately .038" is recommended. This is a tad bit tighter than what the HP Auto guys use since we do not turn the higher RPM.

    With a good quench, our Marine C/R can be increased a point or two. [/COLOR]


    Giddy-Up wrote:
    Ok I am totally confused now.. The pistons in the third pic. They are calling flat top.. Correct me here if I am wrong, was it not suggested to me that flat top is not what I needed. But to use dished?

    These are what they are calling flat top..



    But I should be using correct?
    Two things:

    1.... I understand the confusion!

    First, we need to back up here and find out which chamber size cylinder heads will be used.

    You'll find two common chamber volumes.... 64cc and 76cc.

    You can not select a piston without this information and we really can't select a cylinder head without piston information.

    When the smaller 64cc chamber cylinder heads are used, we need piston dish volume to bring the Static C/R down to where it needs to be.

    This can be accomplished with a Full Dished piston :thumb (not a good choice), or a more correct Low Compression Quench style, D dished, or Reverse Dome piston, such as what Dave M. shows.

    The full dished is what I'm suggesting that we NOT use.

    It was a 70's emmission control piston, was poor design in the 70's, and it's a poor design today.... especially for SBC Marine use with a wedge off to the side of the combustion chamber.

    2... You'll want to get clear on what "Full Dished" means -vs- a partial dished piston as per the above.

    Jim, I'll be bold once again here, and will suggest that if your machine shop person is unable to explain the differences to you, and/or the benefits of a quench or squish effect for a SBC Marine build........., then he is the wrong person to be using.

    http://"http://www.marineengine.com/... included.</b>

    .

    Leave a comment:


  • Guest's Avatar
    Guest replied
    What Rick said is spot on - you need to talk to the machine shop and make sure they understand marine builds. Have them prove they have built engines for heavy cruisers, and understand the build specifics of marine engines.

    To answer your last question you want single relief flat top pistons or "D" dish pistons, BUT you need to calculate your finished compression ratio before you purchase ANY piston - this is what the machine shop should do (or if you know how to do it yourself).

    A GENERAL answer is you want to be no higher than 9.0 c/r.

    Leave a comment:


  • 2850Bounty
    replied
    Well, I'm glad that you took no offense to my being so adamant about the SBC Marine build. I'm rather passionate about this!

    Not all are on board with this because they simply have not bothered to educate themselves.... plus they tend to listen to the Automotive guys.... and not the Marine guys.

    Just a re-cap for you:

    In post #1 you asked about pistons and what the differences were.

    I offered a brief explanation, even linking you back to your first thread where I had explained how the full dished piston contributes to Detonation, of which your piston damage highly suggests.

    In post #10 of that thread, I offered you #1 through #5 suggestions and primarily because this fresh engine is headed for a 2556 which is a small version SDN F/B boat...... I.E., rather heavy.

    In a 2556 you're running a single prop KC drive and you'll be loading this new engine much more so than if in a car/truck.

    The full dished piston does ZERO against detonation potential.

    If you end up using the full dished piston, you'll want to be conservative with your ignition advance, or you will risk damage.

    Conservative ignition advance leaves horse power on the table.

    And the full dished build will not produce the torque that you want for this hull.

    Early in this thread, in post #6, I explained how to select the correct quench style piston using the online Static C/R calculator.

    Your machine shop person should be extremely familiar with this process!

    Post #7 Dave chimes in..... "NO Full Dished Pistons!"

    Post #8, Carl chimes in.... "Be careful using just any machine shop's advice!"

    So this isn't entirely a Rick thing!

    The machine shop that you chose is very likely much more involved with Automotive than Marine..... and that is understandable!

    To recommend the stronger connecting rods and full floating wrist pins, and yet NOT recommend a quench effect suggests this to me.

    The guy is obviously not considering Marine Loads -vs- automotive loads.... even when considering HP Auto.

    Apples/Oranges!

    I think that you need to sit down and have a heart-to-heart conversation with this person. If you can't get him on board, then you may need to pull the reins in a bit.

    He is working for YOU!

    If you still can't get him on board, then quite frankly, he's the wrong guy... period!

    .

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  • Guest's Avatar
    Guest replied
    Ok I am totally confused now.. The pistons in the third pic. They are calling flat top.. Correct me here if I am wrong, was it not suggested to me that flat top is not what I needed.But to use dished?These are what they are calling flat top..

    .jpg][img]/media/kunena/attachments/vb/668845=25856-140[6].jpg[/img]But I should be using correct?

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  • Guest's Avatar
    Guest replied
    2850Bounty wrote:
    I'm curious as to which of these Digital Diamond Profile style pistons you decided upon!

    This piston with the correct cylinder head and compressed gasket thickness, offers you a quench..... but the partial dish volume must compliment the combustion chamber volume..... or visa-versa... to obtain the correct C/R.



    While this piston is not the Devil that the GM full dished piston is, I would once again steer clear of this style piston..... regardless of a machine shop recommendation.



    BTW, there's no need to any of these to be double valve relief.

    The unused reliefs are unnecessary carbon and heat holding devices.

    Edit:

    I'm not sure if you are just bringing us up to speed, or if you're asking for any further feedback.

    If just bringing us up to speed..... understood!

    However, if asking for feedback, again I'll suggest that the first piston shown would be a better choice between the two.

    This piston for a 5.7L Marine build must be used with the 76cc chamber cylinder heads..... and this is if the dish or valve relief volume is correct.

    If not, and when used with the 64cc chambers, then your static C/R will be too great.

    If you do a correct 5.7L SBC Marine quench build using the smaller 64cc chamber heads, your assembled engine block will look similar to this.



    If you do a corrrect 5.7L SBC Marine quench build using the larger 76cc chamber heads, your assembled engine block will look similar to this one.

    Note the double valve reliefs (top) -vs- the more favorable single valve reliefs (bottom).





    If the quench build just seems rediculous to you......, then your assembled engine block may look like this.



    .
    The pic of the second block is what it will now look like. The third pic I think I can do if it is the best one.

    to do.. I'll get right on that and check back.. The bottom is what it use to look like..

    Damn, I wish I had asked for advice first.. I just don't like bugging people..

    I will order the other piston style and hope I can exchange the other later..

    Regards, Jim

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  • Guest's Avatar
    Guest replied
    2850 Bounty, I thought I was just updating, but now I see that I should be asking for advice..



    I have seen pistons in my search that have only two reliefs.. Should I be getting them instead..

    That seems to be close to a flat top..

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  • Guest's Avatar
    Guest replied
    2850Bounty wrote:
    I'm curious as to which of these Digital Diamond Profile style pistons you decided upon!

    This piston with the correct cylinder head and compressed gasket thickness, offers you a quench..... but the partial dish volume must compliment the combustion chamber volume..... or visa-versa... to obtain the correct C/R.



    While this piston is not the Devil that the GM full dished piston is, I would once again steer clear of this style piston..... regardless of a machine shop recommendation.



    BTW, there's no need to any of these to be double valve relief.

    The unused reliefs are unnecessary carbon and heat holding devices.

    Edit:

    I'm not sure if you are just bringing us up to speed, or if you're asking for any further feedback.

    If just bringing us up to speed..... understood!

    However, if asking for feedback, again I'll suggest that the first piston shown would be a better choice between the two.

    This piston for a 5.7L Marine build must be used with the 76cc chamber cylinder heads..... and this is if the dish or valve relief volume is correct.

    If not, and when used with the 64cc chambers, then your static C/R will be too great.

    .
    [SIZE]3 wrote:
    [COLOR]#000000 wrote:
    [FONT]Calibri wrote:
    Great.. Then I got the wrong Piston.. Because I ordered the second set.. Ok.. I'll send them back and exchange them.. Thanks for letting me know this.. It may be a hassle now but [/FONT][/COLOR][/SIZE]

    [SIZE]3 wrote:
    [COLOR]#000000 wrote:
    [FONT]Calibri wrote:
    a much bigger one later on.. [/FONT][/COLOR][/SIZE]

    [FONT]Calibri wrote:
    [SIZE]3 wrote:
    [COLOR]#000000 wrote:
    [/COLOR][/SIZE][/FONT]

    [SIZE]3 wrote:
    [COLOR]#000000 wrote:
    [FONT]Calibri wrote:
    Thank you Sir for your guidance [FONT]Calibri wrote:
    and experience ..[/FONT][/FONT][/COLOR][/SIZE]

    Leave a comment:

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