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Discussion Starter · #1 ·
I want to build a 393 on my 351W, the crankshaft that I use is a scat 3.85 with stock rods, stock heads, but have been worked (ported), intake is know 165cc and 58cc combustion chamber, valves are stock 1.84 and 1.54 i think, I need some help to choice the correct piston (302), I heard about compression issues on this 393 stroke
 

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I used the same crankshaft with stock 351w rods and I ordered 302 flat top hyper tonic pistons from summit racing and I an not sure of compression i cant run 87 octane. 89 is fine and 93 is perfect. So i am unsure of compression but it isnt an issue motor runs great. also you wont have the power you wont because of those heads. I have gt 40 heads severly reworked port polished 3 angle valve job and it has a **** load of torque but just not quite the horses i want. after i can get mine to hook like i want im going for afr 205ccs and changing my cam:)
 

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Emilio, you are correct. With strokers, you are compressing much more air into the same space as a stock engine. A piston style that makes 9.5:1 in a 302 will make 12:1 in a 393, or 13:1 in a 427W stroker. While much of your effective (running) compression depends on your camshaft, a static compression of 9.5 to 10.5:1 is typical for iron heads with US or European 'premium' pump gas (US 92 octane, or the equivalent Euro 98 octane). With your smaller 58cc chambers, this will require a pistons with a 20-24cc dish. Here is a simple calculator you can use to check your approximate compression.

David

Popular strokers need deeper dish pistons to maintain reasonable compression for pump gas. 393s like about 20cc or more. The Mahle SBF600030I26 has a 26cc dish that gives about 9.7:1, and the KB364 below with 22cc for 10.1:1 compression:

 

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I concur with what David said. I run a .030 393w with 58cc heads and a .041 thick head gasket. The 8.5:1 302 Probe pistons that I used have a 15cc dish and my final compression is 10.6. See the chart on this piston here:

10684 - Ford 302/393W -15.0cc Reverse Dome SRS Pistons

It works fine with 93 octane at the track and could probably be fine with 91 octane on the street. I have found that it likes 32 degrees of ignition timing, which is also a reflection of using a decent combustion chambered head.



That seems to be the only pump gas streetable piston from Probe for a 393 with a small combustion chamber.

For a more streetable compression that will run 87 octane gas, look for 302 pistons from other manufacturer's that are listed as 8.0-1 (or less) OR instead jump up to a larger combustion chamber head. Do not use a much taller head gasket as a crutch or else you may create further detonation issues. Cam selection and how it is installed also plays a part in what fuel can be run.

The selections that David shows above would be great for a typical street 393w under most conditions.
 

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Discussion Starter · #7 ·
I concur with what David said. I run a .030 393w with 58cc heads and a .041 thick head gasket. The 8.5:1 302 Probe pistons that I used have a 15cc dish and my final compression is 10.6. See the chart on this piston here:

10684 - Ford 302/393W -15.0cc Reverse Dome SRS Pistons

It works fine with 93 octane at the track and could probably be fine with 91 octane on the street. I have found that it likes 32 degrees of ignition timing, which is also a reflection of using a decent combustion chambered head.



That seems to be the only pump gas streetable piston from Probe for a 393 with a small combustion chamber.

For a more streetable compression that will run 87 octane gas, look for 302 pistons from other manufacturer's that are listed as 8.0-1 (or less) OR instead jump up to a larger combustion chamber head. Do not use a much taller head gasket as a crutch or else you may create further detonation issues. Cam selection and how it is installed also plays a part in what fuel can be run.

The selections that David shows above would be great for a typical street 393w under most conditions.
Ok, what do you think about this parts for build my 393:

  • THIS CAR WILL BE STREET CAR (i USE THE CAR EVERY DAY ABOUT 60 MILES TO GO TO MY WORK, BUT IN THE WEEKENG I LIKE TO GO TO THE TRACK AND RACE
  • SEALED POWER ALUMINUM FLAT TOP HYPEREUTECTIC CAST PISTONS AND MOLY RINGS
  • scat 9000 steel crank stroker ford 3.85, model
    942-9351w10
  • Non Roller 351W block
  • <H1 style="TEXT-ALIGN: left; PADDING-BOTTOM: 0px; WIDOWS: 2; TEXT-TRANSFORM: none; TEXT-INDENT: 0px; MARGIN: 0px; PADDING-LEFT: 0px; LETTER-SPACING: normal; PADDING-RIGHT: 0px; FONT: bold 18px Trebuchet, 'Trebuchet MS'; WHITE-SPACE: normal; ORPHANS: 2; COLOR: rgb(51,51,51); WORD-SPACING: 0px; PADDING-TOP: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px" class=vi-is1-titleH1>summit stage II 351w connecting rods, Arp bolts, polished beams, Model
    SMS-5-48-05-121


    </H1>
  • <H1 style="TEXT-ALIGN: left; PADDING-BOTTOM: 0px; WIDOWS: 2; TEXT-TRANSFORM: none; TEXT-INDENT: 0px; MARGIN: 0px; PADDING-LEFT: 0px; LETTER-SPACING: normal; PADDING-RIGHT: 0px; FONT: bold 18px Trebuchet, 'Trebuchet MS'; WHITE-SPACE: normal; ORPHANS: 2; COLOR: rgb(51,51,51); WORD-SPACING: 0px; PADDING-TOP: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px" class=vi-is1-titleH1>
    <H1 style="TEXT-ALIGN: left; PADDING-BOTTOM: 0px; WIDOWS: 2; TEXT-TRANSFORM: none; TEXT-INDENT: 0px; MARGIN: 0px; PADDING-LEFT: 0px; LETTER-SPACING: normal; PADDING-RIGHT: 0px; FONT: bold 18px Trebuchet, 'Trebuchet MS'; WHITE-SPACE: normal; ORPHANS: 2; COLOR: rgb(51,51,51); WORD-SPACING: 0px; PADDING-TOP: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px" class=vi-is1-titleH1>COMP CAM 351W FORD 284 XTREME ENERGY HYD CAMSHAFT


    </H1>
    </H1>
Ford 351W Hydraulic Camshaft
APPLICATION CAMSHAFTS
VALVE SETTING
RPM
OPERATING
RANGE

CAMSHAFTPARTNUMBER
CAMGRIND NUMBER
DURATION
VALVE LIFT @ 1.6:1
LOBESEP.ANGLE
ADV.
@ .050”
IN.EX.IN.EX.IN.EX.IN.EX.HYDRAULIC FLAT TAPPET: Street/strip with 2800+ stall, headers, gears, rough idle.
Hyd
Hyd
2300-6500
35-250-4
XE284H
284
296
240
246
.541
.544
110°



  • Procomp Head 210CC runner size, 60cc combustion chambers. 2.02 1.60 valve size.
  • AOD Transmission with BDR Torque Converter 2500/2800 rpm
  • 8.8" 4:10 rear end

I WILL BE LOOKING FOR YOUR COMMENT
<H1 style="TEXT-ALIGN: left; PADDING-BOTTOM: 0px; WIDOWS: 2; TEXT-TRANSFORM: none; TEXT-INDENT: 0px; MARGIN: 0px; PADDING-LEFT: 0px; LETTER-SPACING: normal; PADDING-RIGHT: 0px; FONT: bold 18px Trebuchet, 'Trebuchet MS'; WHITE-SPACE: normal; ORPHANS: 2; COLOR: rgb(51,51,51); WORD-SPACING: 0px; PADDING-TOP: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px" class=vi-is1-titleH1>


</H1>
  • <H1 style="TEXT-ALIGN: left; PADDING-BOTTOM: 0px; WIDOWS: 2; TEXT-TRANSFORM: none; TEXT-INDENT: 0px; MARGIN: 0px; PADDING-LEFT: 0px; LETTER-SPACING: normal; PADDING-RIGHT: 0px; FONT: bold 18px Trebuchet, 'Trebuchet MS'; WHITE-SPACE: normal; ORPHANS: 2; COLOR: rgb(51,51,51); WORD-SPACING: 0px; PADDING-TOP: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px" class=vi-is1-titleH1>
    <H1 style="TEXT-ALIGN: left; PADDING-BOTTOM: 0px; WIDOWS: 2; TEXT-TRANSFORM: none; TEXT-INDENT: 0px; MARGIN: 0px; PADDING-LEFT: 0px; LETTER-SPACING: normal; PADDING-RIGHT: 0px; FONT: bold 18px Trebuchet, 'Trebuchet MS'; WHITE-SPACE: normal; ORPHANS: 2; COLOR: rgb(51,51,51); WORD-SPACING: 0px; PADDING-TOP: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px" class=vi-is1-titleH1>


    </H1>
    </H1>
 
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