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Big Block Clones LLC

72mm Bore Clone Block

72mm Bore Clone Block

Regular price $79.95 USD
Regular price Sale price $79.95 USD
Sale Sold out

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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