5.7 engine build

[alldodge]

Does decking mean flattening the area where the heads are bolted on? Do I need to know which piston I want to use before this is done?

The deck is the flat area where the pistons are and the head sits on top. The factory deck on a block is a bit higher then the height of the pistons when they are at Top Dead Center (TDC).

The normal method of decking a block is to shave the surface down to where the top of the piston is at the same level as the deck, called 0 deck. If the deck is higher then the pistons, this is in the positive side (exp 0.010 deck), if the pistons stick above the block, this is negative deck (exp 0.005). The zero deck is what is most often used.

Then if you have a 0 deck and use a 0.040 or 0.038 head gasket you have your quench (0.040 or 0.038)

To add on to the piston responses, if you use pistons which are taller then factory, you will want to deck the block less or maybe none. So as Scott mentioned, don't start cutting on anything until you decide what components you will be using. crank, rods, pistons, and if head or block needs to be flattened

 

[FreeBeeTony]

if your running vortec heads, you want the dish to mirror the combustion chamber.

something like this http://static.summitracing.com/globa...890CP60_xl.jpg

this style piston will give you the most quence/squish which gives you the most torque.

if your piston looks like this, it will produce much less power

Just curious, how would these pistons work w/ Vortec heads?

 

[Bondo]

Ayuh,.... That's the piston Chevy used with the vortec heads Tony,....

Not the Best choice, but it could be worse,....

It can't give the "Ideal" quench, like the D-dished or Inverted dome pistons,....

 

[Scott Danforth]

Tony, they work OK, however they are not going to make anywhere near the torque of the proper pistons in a quality high torque SBC build with vortec heads because they do not have an adequate quench zone. the pistons you show are the typical cast dished with 4 reliefs that GM put in everything because they were inexpensive and could be stuffed into the block by a guy on a Monday morning without coffee

 

[FreeBeeTony]

Thanks for the responses.........
Doesn't make much difference now, engine has been in the boat for years and performs very well.
Was just looking for info for possible projects in the future....
How much of a difference would the optimal pistons make? Would it be noticeable?

 

[Bondo]

How much of a difference would the optimal pistons make? Would it be noticeable?

Ayuh,.... If done as part of a full on rebuild, Ya it'll make a difference,....

Shorten the quench to .040", 'n bring the static compression up to 10:1, 'n Then yer where it oughta be for down low torque,.....

 

[FreeBeeTony]

Would the difference be noticeable?

 

[Scott Danforth]

Would the difference be noticeable?

significantly noticeable

 

[Bondo]

Ayuh,..... Throw in a Stroker crank, 'n ya get to the "Holy Ship" category of improvement,.....

 

[NHGuy]

God bless me, I'm gonna get holy ship! 9.8:1 compression, Dart Heads, .040 quench, boo yah. And yup, I won't go wide open on holeshots.
BTW marine engines need a bit more ring gap. That's adjusted with a special filing device that won't burr or damage the ring surfaces where they are filed at the gaps. Each piston ring manufacturer has a statement on how to calculate the optimal gap.

 

[FreeBeeTony]

If I only knew then what I know now................

 

[Scott Danforth]

God bless me, I'm gonna get holy ship! 9.8:1 compression, Dart Heads, .040 quench, boo yah. And yup, I won't go wide open on holeshots.
BTW marine engines need a bit more ring gap. That's adjusted with a special filing device that won't burr or damage the ring surfaces where they are filed at the gaps. Each piston ring manufacturer has a statement on how to calculate the optimal gap.

Dont forget just a bit more piston to bore clearance.

If your running an alpha, the holeshot will need to be a roll-on, not a slam the throttle. The worst part (and what blows up most alphas) is the sudden unloading when flying across a wave, followed by the sudden re-loading as the boat hits the water again. If you become airborne, simply back off the throttle when in the air.

I know of quite a few healthy 383 strokers in front of alphas with nothing more than synthetic oil in them.

 

[flipbro]

1979 if you get new pistons you will need to have the hole rotating assembly balanced.Make sure the pistons you buy do not wiegh more then then the ones your replacing. You do not want to have to add heavy metal to balance. Again thats part of planing.A stroker my sound tempting but if youve never buit a sbc my be a little over your head.

 

[1979 Quartermasters]

To be honest, I'm already over my head. Learning lots. So now, I also have to watch the weight of pistons, and rods? How do we balance this assembly.

 

[alldodge]

If you do a standard rebuild nothing is needed more then bore, check flatness, use over size pistons and the rest is standard rebuild process. The standard rebuild process is involved some what, but not as much as building a stroker, higher compression or higher rpm motor.

Agree rebalancing is better and is accomplished by taking the lightest piston being used and making sure all the others match the same weight (in grams). They drill out the under side of the pistons to remove weight.

I would suggest doing your first rebuild maybe go the simple way, but if you want to get way into it we can help.

 

[1979 Quartermasters]

How advanced is what they've been talking about in all the previous posts. I like the idea of upping the compression to 9.4 with the Vortec heads roller valve train. I'm trying to get my head around the pistons so I can get the block and crank machined. They will be calling tomorrow to ask how I want to proceed. I will get Comp Cams to set me up with cam, lifters, rockers and valve springs. I will be using the factory crank. I guess I need know which pistons and rods I'm going to use to figure out how to machine the block, right? Right now, that where I'm kinda stuck. I realize I need the kind of piston that was pictured earlier in this thread but don't know how to begin to find it. I want to learn this as long as I'm not leaning too hard on you guys. The amount of info and people willing to help is awesome. I would love to be able to say " I built this motor".

 

[flipbro]

Bore .030 over. 3.48 stroke. 0 deck .041 head gasket. 14 cc Ddish pistons .64cc chamber vortecs puts you at 9.4.1 compression..Have the mains line honed. Have the rods big end cheaked for roundness. And 100 % Get the rotating assembly balanced. You dont want to take a chance with bob wieghts being off or all the machine work and prep build will be for nothing.

 

[1979 Quartermasters]

Are you suggesting using the original rods?

 

[flipbro]

Sure am. You would have what they call powder metal rods. Have them checked over by machin shop. Those rods are fine for up to 400 hp.

 

[alldodge]

The flywheel and harmonic balancer is manufactured to the crankshaft. Quality pistons are manufactured to within a few grams of each other, some less expensive ones are not, hence the reason to have some pistons balanced.

The engine when originally manufactured is balanced, to within a given range. As rpm's increase above factory max there is a need to rebalance the rotating assembly to a finer degree. Having the rotating assembly balanced to a finer degree is always better IMO, but this only reduces the internal vibrations. How much the reduction in vibrations will be noticed if it is done is unknown.