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4.6l compression ratio

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Old 12-12-2007, 10:41 PM
  #11  
oxfordgt
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Default RE: 4.6l compression ratio

The 99-02 4v 4.6l all got 4.54cc dish pistons, the 93-98 4v 4.6l all got 2.66cc pistons which is probably where you heard 3cc.

the combustion chamber volume for non pi heads is 52cc, FRPP heads (svo) are 51cc but I can see how you messed that up.Your head gasket thickness is a bit off also

This is the formula I use

Formulas for compression ratio

(CylVolume + ChamberVolume) / ChamberVolume

cylinder volume = pi/4 x bore^2 x stroke

chamber volume = cylinder volume / compression ratio - 1.0

displacement ratio = cylinder volume / chamber volume

amount to mill = (new disp. ratio - old disp. ratio / new disp. ratio x old disp. ratio) x stroke

And here are the specs on the 4.6l 2v engine

Engine Specifications
Description Specification
General Specifications
Displacement 4.6L (2V) (281 CID)
Number of Cylinders 8
Bore and Stroke 90.2 x 90.0 mm (3.55 x 3.54 inch)
Firing Order 1-3-7-2-6-5-4-8
Oil Pressure (HOT 1500 RPM) 138-310 kPa (20-45 psi)
Drive Belt Tension a
Cylinder Head and Valve Train
· Head gasket face flatness 0.10 mm (0.004 inch) max overall 0.050 mm (0.002 inch) total (in head bolt sealing area) 0.025 mm ( 0.001 inch) per 25x25.
Combustion Chamber Volume (cc) 43.9±1.5 cm 3
Valve Seats
· Width—intake 1.3-1.5 mm (0.051-0.060 inch)
· Width—exhaust 1.3-1.5 mm (0.051-0.060 inch)
· Angle 45 degrees
· Runout (T.I.R.) Recommended 0.025 mm (0.001 inch) max 0.050 mm (0.002 inch)
Valve Arrangement (Front-to-Rear) c
· (Left hand): E-I-E-I-E-I-E-I
· (Right hand): I-E-I-E-I-E-I-E
Valve Stem to Guide Clearance
· Intake 0.020-0.069 mm (0.00078-0.00272 inch)
· Exhaust 0.046-0.095 mm (0.0018-0.0037 inch)
Valve Head Diameter
· Intake 44.37-44.63 mm (1.75-1.76 inch)
· Exhaust 35.88 - 36.14mm (1.41-1.43 inch)
· Gauge diameters 42.5 and 34 mm (1.67-1.34 inch)
Valve Face Runout Limit 0.05 mm (0.002 inch)
Valve Face Angle 45.5 degrees
Valve Stem Diameter (Std)
· Intake 6.975-6.995 mm (0.2754-0.2746 inch)
· Exhaust 6.975-6.995 mm (0.2754-0.2746 inch)
Valve Springs
· Compression pressure (N (lb) @ spec length)
· Intake 720.0-800.0 N @ 28.80 mm (161.9 lb @ 1.13 inch)
· Exhaust 720.0-800.0 N @ 28.80 mm (161.9 lb @ 1.13 inch)
· Free length (approximate) 51.77-54.97 mm (2.04-2.16 inch)
Installed Height
Installed pressure (N (lb-ft) @ spec length)
· Intake 42.3-42.9 mm (1.67-1.69 inch)
· Exhaust 42.3-42.9 mm (1.67-1.69 inch)
· Intake 283.0-321.0 N @ 42.56 mm (63.61 lb @ 1.68 inch)
· Exhaust 283.0-321.0 N @ 42.56 mm (63.61 lb @ 1.68 inch)
· Service limit 10% pressure loss
Roller Follower
· Ratio (intake) 2.02 : 1
· Ratio (exhaust) 2.03 : 1
Hydraulic Lash Adjuster
· Diameter (std) 16.000-15.988 mm (0.6299-0.6294 inch)
· Clearance to bore 0.018-0.069 mm (0.000709-0.002717 inch)
· Hydraulic leakdown rate b 5-25 seconds
· Collapsed lash adjuster gap—desired 0.45-0.85 mm (0.02-0.03 inch)
Camshaft
Lobe Lift
· Intake 7.11038 mm (0.28 inch)
· Exhaust 7.4794 mm (0.30 inch)
· Allowable lobe lift loss 0 mm (0.0 in)
Theoretical Valve Lift @ Zero Lash
· Intake 13.00 mm (0.51 inch)
· Exhaust 13.75 mm (0.54 inch)
End Play 0.027-0.190 mm (0.001-0.007 inch)
· Service limit 0.190 mm (0.007480 inch)
Journal to Bearing Clearance 0.025-0.076 mm (0.00098-0.002992 inch)
· Service limit 0.100 mm (0.003937 inch) max
Journal Diameter (All) 26.962-26.936 mm (1.0615-1.0605 inch)
Bearing Inside Diameter (All) 27.012-26.987 mm (1.0635-1.0625 inch)
Front Bearing Location c
Cylinder block
· Head gasket face flatness 0.15 mm (0.006 inch) max overall
· Head gasket surface finish b 0.050 mm (0.002 inch) per 150x150 0.025 mm (0.001 inch) per 25x25
Main Bearing Bore Diameter 72.400-72.424 mm (2.8504-2.8513 inch)
Crankshaft
Main Bearing Journal Diameter 67.482- 67.504 mm (2.66 - 2.661 inch)
Connecting Rod Journal
· Diameter 52.983-53.003 mm (2.085941-2.086728 inch)
Crankshaft Free End Play 0.075-0.377 mm (0.003-0.015 inch)
Crankshaft Runout to Rear Face of Block 0.050 mm (0.01969 inch) max
Connecting Rod Bearings
Clearance to Crankshaft
· Desired 0.027-0.069 mm (0.0010629-0.0027165 inch)
· Allowable 0.027-0.069 mm (0.0010629-0.0027165 inch)
Bearing Wall Thickness (Std) d 2.442-2.453 mm (0.096-0.097 inch)
Main Bearings
Clearance to Crankshaft
· Desired 0.025-0.044 mm (0.001-0.002 inch)
· Allowable 0.025-0.050 mm (0.00098-0.00197 inch)
Bearing Wall Thickness (Std) f 1.919-1.925 mm (0.0756-0.0757 inch)
Connecting Rod
· Pin bore diameter 22.012-22.024 mm (0.86661-0.86708 inch)
· Crankshaft bearing bore diameter 56.866-56.886 mm (2.23881-2.23960 inch)
· Length (center-to-center) 150.7 mm (5.933 inch)
Alignment (Bore-To-Bore Max. Diff.) e
· Twist 0.050 per 25 mm (0.00197 per 0.9843 inch)
· Bend 0.038 per 25 mm (0.00150 per 0.9843 inch)
Side Clearance (Assembled to Crank)
· Standard 0.125-0.475 mm (0.005-0.019 inch)
· Service limit 0.50 mm (0.01969 inch) max
Cylinder Bore and Piston
Cylinder Bore
Diameter f
· Surface finish (RMS) 0.2-0.6 Microns
· Out-of-round limit 0.20 mm (0.007874 inch)
· Out-of-round service limit 0.70 mm (0.027559 inch)
· Taper service limit 0.70 mm (0.027559 inch)
Piston
· Diameter g 0.028 mm (0.0010 inch)
· Coded Red 1 90.185-90.205 mm (3.55-3.551 inch)
· Coded Blue 2 90.195-90.215 mm (3.55-3.551 inch)
· Coded Yellow 3 90.205-90.225 mm (3.551-3.552 inch)
Coated Piston-to-Bore Clearance -0.005-0.025 mm (-0.002/+0.001 inch)
Pin Bore Diameter h 21.008-22.014 mm (0.866-0.867 inch)
Ring Groove Width
· Compression (top) 1.530-1.550 mm (0.06-.061 inch)
· Compression (bottom) 1.520-1.540 mm (0.06-0.061 inch)
· Oil ring 3.030-3.050 mm (0.12-0.12 inch)
Piston Pin
· Length 61.601-62.030 mm (2.42523-2.44212 inch)
· Diameter 22.0010-22.0030 mm (0.87-0.871 inch)
Pin to Piston Fit -0.005/+0.0135 mm (-0.0002/+0.0005 inch)
Pin to Rod Clearance
· Standard 0.009-0.0235 mm (0.0004-0.00092 inch)
· Service limit 0.035 mm (0.001378 inch)
Piston Ring
· Compression (top) 0.050-0.090 mm (0.002-0.004 inch)
· Compression (bottom) 0.030-0.080 mm (0.00118-0.00315 inch)
· Oil ring Snug fit
Ring Gap i
· Compression (top) 0.130-0.280 mm (0.005-0.011 inch)
· Compression (bottom) 0.300-0.550 mm (0.0018-0.0022 inch)
· Oil ring (steel rail) 0.150-0.650 mm (0.006-0.0256 inch)
Piston to Deck 0.035-0.565 mm (0.001-0.022 inch)
Piston Ring Thickness
· Compression (top) 1.480-1.500 mm (0.058-0.059 inch)
· Compression (bottom) 1.470-1.490 mm (0.0587-0.0586 inch)
· Oil ring N/A
Lubrication System
Oil Capacity (Quarts U.S.) 5 ± 0.25 j
a Newly installed—refers to the condition of the "NEW" drive belt before the engine has made no more than one rotation and before the belt has had a chance to stretch or seat into the pulley grooves.
b Time necessary for plunger to leak down 1.6 mm of travel with 222 N force and leak down fluid in tappet.
c Distance front edge of bearing is installed below front face of cylinder block.
d 0.050 Undersize—add 0.025 to standard thickness.
e Pin bore and crank bearing bore must be
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Old 12-13-2007, 03:55 PM
  #12  
stangiac03
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Default RE: 4.6l compression ratio

has anyone ever done this ? what kind of numbers didt it make ?
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Old 12-13-2007, 10:03 PM
  #13  
oxfordgt
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Default RE: 4.6l compression ratio

You will get a bit of a hp gain but not enough to make up for the price of the swap. If you are in need of a rebuild it would be worth it but just doing it to do it its not.
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Old 12-14-2007, 01:21 PM
  #14  
04BlueGT
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Default RE: 4.6l compression ratio

Not to drop in on the thread, but what CR could you run on a 2V and still get away with 91 octane without pulling out all the timing? 9.5:1? 10:1?
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Old 12-14-2007, 03:00 PM
  #15  
stangiac03
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Default RE: 4.6l compression ratio

well i have a stock 4.6l block with the 4.54 dished pistons and rods which are brand new. i was thinking about using the non pi heads i alreedy have just swaping the pi cams into them. would it be much more to go 4v at this poiint. i have the timing cover, intake and heads for 2v but thats it.
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Old 12-14-2007, 03:09 PM
  #16  
jEEd
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Default RE: 4.6l compression ratio

sry not to steal the thread but...

damn oxford you really know your ****s thats amazing. could you tell me possible what my overall compression is if i told you i have an MMR900 Street Mod Cobra shortblock 9.3:1 CR + PI H/C/I ? and if you need the specs of the pistons etc... i'll have to tell you that later when i head over to my dad's...

does the 9.3:1 CR mean my overall CR or just the shortblock?
MMR
Brand new-MMR 4.6 Street Mod 900 9.3 for 96-2004 GT or 8.9 for Cobra (or all 4V)
MMR 4.6 Street Mod 900 (up to 900HP)
*Brand New Cast Iron 2004 Cobra Block, torque plate bored and honed

*New 4340 Forged 3.543 stroke Cobra Crankshaft w/micro polished journals at no extra charge
*New 4340 5.933 Manley H-beam Rods w/ARP rod bolts ( These US made rods are shotpeened, magnafluxed and weight matched to bring you the finest H-beam rod available for your 4.6

*New Forged Manley pistons 3.552 Bore size (High or low compression)

*Speed Pro file fit rings (precision file fit to your application, nitrous, blower, turbo or N/A)
*Speed Pro/Federal Mogul tri-metal Rod and Main bearings

*Complete Pro Assembly and Balancing for the smoothest, highest revving shortblock available.
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Old 12-14-2007, 03:18 PM
  #17  
oxfordgt
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Default RE: 4.6l compression ratio

What piston cc do you have?
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Old 12-14-2007, 03:32 PM
  #18  
jEEd
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Default RE: 4.6l compression ratio

ORIGINAL: oxfordgt

What piston cc do you have?
i'll have to get back to you on that since id not remember and i left the paper w/ all the specs at my dads which im going in 2 hours to drop off my sis & install my brembos.
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