GT40P Compression with SpeedPro Pistons

If you MILL the heads, your compression will INCREASE.

An easy and less expensive way to measure CC per cylinder is to buy a syringe like this, Universal Pump Dispenser, by Hyde Tools, at most paint or hardware stores (Item #30460) for about $5.00, then buy a small piece of thin plexy glass..drill a very small hole(1/8th, about 3/4 from the edge of the plexy glass). Add grease around the combustion chamber, put the plexi glass over the C-Chamber.

Now keep filling the combustion chamber with water and keep track of how many CC's are added to it.

Use the attached image to tape over the syringe to know how many CC's are being added into the syringe.

Make sure your spark plug is IN the hole.

Also , I would personally just give it a quick spray of WD40 and wipe it down before doing this, because it will cause flash rust.

Now after you have done each cylinder head, and made sure each one is even @~61cc per chamber, then you read everything below and figure it out!

If your head CC is not matching, nothing a dremel cant handle. Remember one glob of water is one CC(size of a DIME almost).

I know this is for a CHEVY, but same concept.

The calculation of compression ratios (CR) is based on the following formulae:

Compression Ratio = (Swept Volume + Top Dead Centre (TDC) Volume) divided by TDC Volume

Swept Volume = (pi x Bore Diameter x Bore Diameter x Stroke) divided by 4

TDC Volume = Head Volume + Gasket Volume + Deck Volume + Dish/Dome Volume

Head Volume is published or measured in cubic centimeters (cc).

Gasket Volume = (pi x Gasket Bore x Gasket Bore x Compressed Gasket Thickness) divided by 4

Deck Volume = (pi x Bore Diameter x Bore Diameter x Deck Clearance) divided by 4

Dish/Dome Volume is published or measured in cc.

Note: Any volume below the piston compression height is a positive value. Any volume above the piston compression height is a minus value.

Dimensions: When calculating, use cubic centimeters (cc) or cubic inches, but not both. Refer to the following conversions:

1 inch = 2.54 centimeters (cm)
0.061 cubic inch = 1 cc
1 cubic inch = 16.387 cc

Example: Find CR for a Chevy 350 using 0.03 inch oversize pistons with a Dish/Dome Volume equal to 5 cc:

Head Volume = 76 cc = 76 x 0.061 = 4.636 cubic inches

Dish/Dome Volume = 5 cc = 5 x 0.061 = 0.305 cubic inches

Gasket Thickness = 0.035"

Gasket Bore Diameter = 4.166"

Deck Clearance = 0.005"

Deck Volume = (pi x 4.03" x 4.03" x 0.005") divided by 4 = 0.064 cubic inches

Gasket Volume = (pi x 4.166" x 4.166" x .035") divided by 4 = 0.477 cubic inches

Swept Volume = (pi x 4.030" x 4.030" x 3.480") divided by 4 = 44.389 cubic inches

TDC Volume = 4.636 + 0.305 + 0.064 + 0.477 = 5.482 cubic inches

COMPRESSION RATIO = (44.389 + 5.482) divided by 5.482 = 9.097

Now, those of you who only sleep well at night having measured Head Volume and Dish/Dome Volume yourselves are undoubtedly saying, "published values can introduce error into compression ratio calculations". Well, you're right, and if cc-ing equipment is at your disposal, using it can help achieve an accurate compression ratio, which in turn can be used to calculate the optimum camshaft profile for the application.

All in all to sum it all up: This is a basic formula...

Compression Ratio
CR = ( V1 + V2 ) / V2
CR is compression ratio
V1 is cylinder volume at exhaust closing
V2 is combustion chamber volume

GOODLUCK!
Pete

Also for boost it is great to go under 9:0 or stay at 9.

Oh yea, email me for the syringe, I cant upload images.