Big Block Clones LLC
72mm Bore Clone Block
72mm Bore Clone Block
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Reinforced tall deck GX200 clone block with 72mm bore. Deck is taller than the 135.5mm Tillotson blocks so you can fit a longer stroke with a long enough rod for an acceptable rod/stroke ratio.
Combine with our 59mm crank, ARC 6269 rod, and a "550" (.906" compression height) flat top piston and it will sit 0.003" below zero deck, which works perfectly for a 0.035" head gasket. Add our Stage 1 head and intake combo and a 308 cam for an inexpensive and SNAPPY 240cc combo with loads of torque!
Bore: 72mm \ 2.835"
Deck Height: 136.8mm \ 5.385"
Weight: 5.68lbs
**Rotating assembly combos will all need some clearancing on the top and bottom of the base of cylinder, the roof and front wall of the crankcase. 58mm shouldn't need grinding between the lobes of cams preclearanced for the Predator 224, but you will need to grind there for 59mm and 60mm cranks. It may also be necessary to grind just a bit on the crank counterweights if using a "550" piston and shorter rod.**
Math for computing exact crank, rod, and piston assembly height:
Will it fit inside your block?
(block deck height) - (half of stroke) - (piston compression height) = (connecting rod length for zero deck at top dead center)
(zero deck length) - (actual rod center to center length) = (amount above or below the cylinder deck, positive number is below deck, negative number is above)
(connecting rod length) / (stroke length) = (rod/stroke ratio)
Common Piston Compression Heights:
Clone "550" flat top = .906"/23mm
GX200 and clone "570" dish top = .927"/23.5mm
Wiseco 2 ring and 3 ring = .640"/16.256mm
Wiseco 2 ring large bore = .595"/15.11mm
**You can cut up to .100" off of a Wiseco 2 ring, but never cut a 3 ring piston.**
Here are some rotating assembly combinations that you can build with this block and our 58, 59, and 60mm cranks:
STACKUP w/ rod and piston | BORE X STROKE | DISPLACEMENT | PISTON CROWN DISTANCE TO DECK AT TDC | Rod/Stroke Ratio |
Use 72mm "550" - 0.906" CH flat top piston | ||||
54mm Crank + ARC 6771 - 3.403" | 72mm x 54mm | 220cc | 0.014" under the deck | 1.60:1 |
55mm Crank + ARC 6771 - 3.403" | 72mm x 55mm | 224cc | 0.005" above the deck | 1.56:1 |
58mm Crank + ARC 6271 - 3.323" | 72mm x 58mm | 236cc | 0.015" under the deck | 1.46:1 |
58mm Crank + ARC 6266 - 3.343" | 72mm x 58mm | 236cc | 0.004" above the deck | 1.46:1 |
59mm Crank + ARC 6269 - 3.313" | 72mm x 59mm | 240cc | 0.003" under the deck | 1.42:1 |
59mm Crank + ARC 6271 - 3.323" | 72mm x 59mm | 240cc | 0.013" above the deck | 1.42:1 |
60mm Crank + ARC 6270 - 3.303" | 72mm x 60mm | 245cc | 0.005" above the deck | 1.40:1 |
60mm Crank + ARC 6269 - 3.313" | 72mm x 60mm | 245cc | 0.015" above the deck | 1.40:1 |
Use Wiseco 17-2835XC 0.640"CH 3 ring piston | ||||
58mm Crank + ARC 6234 - 3.595" | 72mm x 58mm | 236cc | 0.007" under the deck | 1.57:1 |
59mm Crank + ARC 6234 - 3.595" | 72mm x 59mm | 240cc | 0.013" above the deck | 1.54:1 |
Use Wiseco 11132P273 0.640"CH 2 ring piston | ||||
54mm Crank + ARC 6268 - 3.707" | 72mm x 54mm | 220cc | 0.024" above deck (cut the piston crown) | 1.74:1 |
55mm Crank + ARC 6268 - 3.707" | 72mm x 55mm | 224cc | 0.044" above deck (cut the piston crown) | 1.71:1 |
60mm Crank + ARC 6234 - 3.595" | 72mm x 60mm | 245cc | 0.030" above the deck (cut the piston crown) | 1.52:1 |
**Always maintain a minimum of 0.030" clearance between the bottom of the head and the top of the piston using the correct thickness head gasket** | ||||
Common Block Deck Heights | ||||
BBC 70mm tall deck block deck height is 138.6mm | ||||
BBC 72mm bore TC225 block deck height is 136.8mm | ||||
Predator 224 block deck height is 136.5mm | ||||
Tillotson racing block deck height is 135.5mm | ||||
Predator 212 non-hemi deck height is 135.5mm | ||||
Predator 212 hemi block deck height is 135mm | ||||
Available ARC GX200 Clone rods | ||||
1.181" main journal X .709" wrist pin (550 flat top piston) | ||||
6267 | 3.283" | |||
6734 | 3.293" | |||
6270 | 3.303" | |||
6269 | 3.313" | |||
6271 | 3.323" | |||
6266 | 3.343" | |||
6270 | 3.383" | |||
6271 | 3.403" | |||
1.181" main journal x .490" wrist pin (.640CH pistons) | ||||
6234 | 3.595" | |||
6268 | 3.707" |
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