Block Dimensions

[duck454ss]

i'm building a large displacement stroker. 5.0L minimum. looking to determine vertical distance from the center of the crank to the lowest point of the cylinder bore in the 4.0L block. i need this number to determine stroke, connecting rod and cylinder wall cleanrance. obviously i'm not using a stock 4.2L crank. any help would be greatly appreciated.

thank you

can't measure myself because i havent torn the block appart yet. cant tear appart the block till i have my parts in one place to start the build. cant order parts till i know these numbers. nasty circle i know.

[gradon]

My brother and I are working on a 4.9l using +.060" ross pistons and an offset-ground 258 crank from 505 Performance that has a 4.060" stroke. Diamondeac here has a stroker w/ +.080" custom diamond pistons. You would either need a +.100"(4.95l/302cu.in. like the older mustangs) or +.120"(5l/305cu.in like the older chevys) piston w/ the 4.060" crank to get your magic 5.0, but you would also need a magic 4.0 block(some claim that some renices can be taken out to .125") that has thick walls or has been sleeved. Ask 505 if they can get a little more stroke out of the grinding, but I think they have the formula down w/ the non-Jeep 6.125" Eagle rods they use in conjunction with the 4.060" crank's smaller journals(maybe they can use bigger rod bearings).

[racing89]

Been racing the same block(4" bore) for 10 seasons. Had another block punched .0125 with 4.06 stroke crank(306 cid?) Ran last race of the season a month ago . Works good!

[duck454ss]

i have my own magic blend going on with a much longer rod, custom pistons (my specs), and the crank will be getting something special all of its own. this combinatino will put 505 to shame. i have a few rod and stroke combinations in mind but i need that vertical dimension to determine if the rod will contact the cylinder wall.

[I6FAN]

You'll probably have to determine the dimension somehow. I think actual blue prints for these engines are rare? On max bore, a similar question came up on the Hesco forum in which Lee stated that the later blocks can be safely bored to 4" (still need to sonically verify). Plectan, on this site, runs that bore. Lee said the best stroker blocks were the old Mexican AMC blocks (282cu) where the bottoms of the cylinders bores were not as high as in the 4.0l block. The distance was the same as on the 4.2l block, but had a much larger bore already than that block. The "roof" height was changed when they went to the 4.0l giving it a greater distance from crank CL to bottoms of cylinder bores. This gives better piston stability at BDC when stroking, and would enable a longer stroke than commonly done. They are supossedly rare, and hard to obtain.

[johnj92131]

You might want to look at this thread:

http://www.jeepstrokers.com/forum/viewt ... 601&p=6727

used a 4.20" stroke and kept the piston in the bore. Read the whole think - he has a lot of numbers in the thread and some great pictures.