The large counterweight on the 4.750 crank needed a "little finessing" to clear the thick portion of the Dart block.

After the initial inspection, de-burring and cleanup it was time to measure the cylinder bores and pistons. It was the 4.600" bore block and it was almost exactly 4.600. The problem was Jay had to remove about .008" to get proper piston clearance. That is OK, but after talking to Jay about the time it took him...let's just say these Dart blocks are made from a very dense HARD material and he doesn't have a $200,000 CNC block prepping machine. He got it dead straight and after that it was one more cleanup and then put the bearings in and the crankshaft.

Well, the 4.750" Ohio Crankshaft Pro-Max crank slid in perfectly, but...it would not rotate. The counterweights hit the block on the inside of the casting and it took an hour or so with a die-grinder to get the clearance required for the crankshaft to rotate freely. Cleaned everything up again and then time to drop the pistons and rods in.

You can see where Dart did some basic CNC machining for rod clearance but with the 4.750" stroke we needed more. I was not aware the block could be ordered clearanced and ready to go. My mistake. When you order one be sure to ask the salesperson about extra clearance work.

This picture shows you the rod clearance issue. We had a way to go but it got done and worked out great. A special thanks has to go out to Jay for taking the time to do this right. It was time consuming and I appreciated it.

Well, this time it was rod clearance to the block. Basically there wasn't any clearance for the 4.750" stroke and the I-beam Ohio Crankshaft connecting rods. This is where the "serious grinding" took place. I am not sure how long Jay was leaning over the block carefully carving away to get the correct clearance but let's just say it took several cans of soda and a lot of patience to get it right and not nick anything.

On a side note, I did call Dart and ask about this and they said the blocks could be ordered with clearance for 4.750" stroke cranks and rods. They do it before shipping with a CNC machine and it saves hours of manual labor. Doh! OK, I am a dumbass, but now I am smarter. For a couple hundred dollars you can get the Dart Big M block CNC-machined at the factory and save yourself a lot of grief. If I order another one I'll get it CNC-machined for the max stroke even if I'm running a smaller stroke.