392 CP Piston Static Compression - Hemi Truck Club
 
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Old 08-29-2011, 09:53 AM   #1
Stu
 
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Ok Jay,

Stu(from Inertia) finally called me with the custom Bullet CP piston specs. I did want to keep it as close to the stock compression as possible. Trying to keep a little flexibility just in case if the turbo setup doesn't work out. I could also add thicker Cometic head gaskets to drop the compression down a little more.

Bore: 3.937 (.020 over bore)
Stroke: 4.050
Head Gasket Bore Diameter(Cometic): 4.100
Head Gasket Compressed Thickness: .030
Chamber: 85cc
Piston Dish: -7.5cc includes .145 int/.080 exh valve clearance notch in piston
Piston Deck Clearance: +.020 (above the deck)

Static Compression: 9.5045226547203:1 (9.5:1)

Your assistance and opinion on this subject Jay is once again highly valued. Stu

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Old 08-29-2011, 09:53 AM   #2
Stu
 
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Ok Jay,

Stu(from Inertia) finally called me with the custom Bullet CP piston specs. I did want to keep it as close to the stock compression as possible. Trying to keep a little flexibility just in case if the turbo setup doesn't work out. I could also add thicker Cometic head gaskets to drop the compression down a little more.

Bore: 3.937 (.020 over bore)
Stroke: 4.050
Head Gasket Bore Diameter(Cometic): 4.100
Head Gasket Compressed Thickness: .030
Chamber: 85cc
Piston Dish: -7.5cc includes .145 int/.080 exh valve clearance notch in piston
Piston Deck Clearance: +.020 (above the deck)

Static Compression: 9.5045226547203:1 (9.5:1)

Your assistance and opinion on this subject Jay is once again highly valued. Stu
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Old 08-29-2011, 11:06 AM   #3
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First, and foremost, I don't want to start a pissing contest on this thread.
That said;
The head gasket you've listed, is for a 6.1, not a 5.7.

Second, unless there's some structural limitations, that I'm unaware of in your combination, I don't see the reasoning for that size dish, then having a +.020 deck hgt. It would be better to have less of a dish, and a -.003 to even deck hight. For example, the Manley piston for yer combination has a 1.5cc dish, (even through they call it a flat top), and a .003 deck hgt. for 9.63 CR.
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Old 08-29-2011, 06:06 PM   #4
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3.941 head gasket bore = 9.58:1 (9.6:1) static CR

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Old 08-29-2011, 06:43 PM   #5
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Quote:
Originally posted by Superjay:
I don't see the reasoning for that size dish, then having a +.020 deck hgt.

I thought the same thing Jay. Something just doesn't seem right.
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Old 08-29-2011, 07:58 PM   #6
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Campbell Enterprise with a (K1) stroker 5.7/6.1 CP Bullet series forged Hemi pistons info also states: C/R as calculated with a 85cc head chamber, +.020 deck height.

Doesn't that mean the block deck is .020 taller than the top of the piston? So that would be a -.020 deck clearance? But, that doesn't add up to 9.6:1 C/R? Or maybe 7.5cc is with the deck height included?

I must have misunderstood what Stu said.

I'll give Stu and CP Pistons a call and get clarification on this one.
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Old 08-29-2011, 08:04 PM   #7
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Quote:
Originally posted by Superjay:
First, and foremost, I don't want to start a pissing contest on this thread.

Who me............
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Old 08-30-2011, 06:17 AM   #8
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Quote:
Who me............
Knot u!
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Old 08-30-2011, 10:59 AM   #9
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Quote:
Originally posted by Superjay:
Knot u!


Cometic, 5.7 Hemi head gaskets:

Right Side PN. H2787SP3030S, 3.950 Bore, .030 Thickness
Left Side PN. H2887SP3030S, 3.950 Bore, .030 Thickness
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Old 08-30-2011, 02:39 PM   #10
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Quote:
Right Side PN. H2787SP3030S, 3.950 Bore, .030 Thickness
Left Side PN. H2887SP3030S, 3.950 Bore, .030 Thickness
I'll buy that better.
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