393 stroker CR help?

3

351vic

New Member

Jun 13, 2007

33

0

0

Pierz, MN

Jan 25, 2008

#1

• Jan 25, 2008

• #1

Hey guys, I'm putting together a 393 stroker, I have the bottom end already but the guy i got it from said it would be 10.5 CR and I just ran all the numbers on the compression ratio calculator and I came up with 11.3:1! So therein lies my dilemma.... Is that WAY too much compression for the street with aluminum heads or will I be okay? Thanks

 

B

bnickel

Founding Member

Aug 21, 2002

5,640

3

77

lubbock, texas

Jan 25, 2008

#2

• Jan 25, 2008

• #2

11.3:1 is a little high for the street even with aluminum heads. combustion chamber volume is the best place to adjust compression if you haven't already bought the heads. i'm assuming the heads have either 58 or 60cc chambers and if you went with a 64cc head instead you'd probably be closer to the 10.5 number. either that or run a really thick head gasket

 

4MuscleMachines

Member

Jul 20, 2005

417

1

17

South Texas

Jan 27, 2008

#3

• Jan 27, 2008

• #3

Clevelands love compression, having said that, you also would not want too much for the street on pump gas. I had my extra engine rebuilt to match Boss 351 engine specs for my 71 Boss. The CR is 11.3:1 on iron heads, but I run on the street octane booster, 93 pump gas, and take it easy on the timing. NO problems whatsoever, so far .

Also, the cam grind you use can help you run on the street.

 

4MuscleMachines

Member

Jul 20, 2005

417

1

17

South Texas

Jan 27, 2008

#4

• Jan 27, 2008

• #4

dup

 

PUNISHER RACING

Active Member

Aug 27, 2007

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36

FORD CITY, PA.

Jan 28, 2008

#5

• Jan 28, 2008

• #5

That is not that bad for alum. heads just run 91-93 octane fuel.

 

SoCalCruising

Founding Member

Jul 25, 2000

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SoCal

Jan 28, 2008

#6

• Jan 28, 2008

• #6

If you wouldn't mind, would you post the variables you used for CR?

 

3

351vic

New Member

Jun 13, 2007

33

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Pierz, MN

Jan 28, 2008

#7

• Jan 28, 2008

• #7

And by variables you mean........ What?

 

67topless

Member

Mar 31, 2006

203

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16

Raleigh, NC

Jan 28, 2008

#8

• Jan 28, 2008

• #8

I think he want's to know what numbers you used to come up with the 11.3:1 compression.

 

3

351vic

New Member

Jun 13, 2007

33

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0

Pierz, MN

Jan 28, 2008

#9

• Jan 28, 2008

• #9

60cc chambers, 8cc piston head volume, .040 gasket thickness, 4.060 bore, .0143 deck clearance, 3.85" stroke. Came to like 11.275:1 or something to be exact

 

SoCalCruising

Founding Member

Jul 25, 2000

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SoCal

Jan 29, 2008

#10

• Jan 29, 2008

• #10

I get 11.18 - my spreadsheet takes in one or two more variables, chiefly piston to wall volume. You can run this CR if you also choose a healthy cam to bleed off some dynamic compression. If I were you, because I am not a can expert, I would consult with a custom cam grinder.