Streamer,
The Cleveland has plenty of room in the crankcase for a long stroke crank, however, there are several other considerations. One is the rod length to stroke ratio, some engine builders put more emphasis on this than others. Another consideration is the piston's compression height, the distance between the piston's top and the center of the wrist pin. There needs to be enough room for the ring package AND the deep intake valve notch peculiar to the Cleveland. A last consideration is how far out of the bore the piston is pulled at BDC.
Scat sells a 4.00" stroke kit that utilizes a 6.00" long rod. That results in a pin height of 1.2" which is pushing the limit for a standard ring package that can be expected to last 100,000 miles. It also requires using a piston where the wrist pin intersects the oil ring groove, which results in an engine that burns oil. And finally this combination of parts results in the piston being pulled very far out of the bore at BDC.
I know of a Cleveland engine being built for a Pantera owner, by a very big name engine builder. This builder has chosen to use a 4.00" crank with a 6.2" rod, this builder obviously is of the school that puts importance on the rod length to stroke ratio. His custom pistons will only have a compression height of 1.00". He is getting away with the reduced compression height by very carefully mapping the valve motion near top dead center and having the depth of the intake valve notch reduced as much as possible. All of this trouble in order to achieve a rod length to stroke ratio of 1.55:1 instead of 1.50:1.
The crank you suggest using is not commercially available, it would have to be custom manufactured for you. Assuming you used custom pistons with the same 1.00" pin height as in the motor I described previously, this would allow you a maximum rod length of 6.115", which would require a custom set of rods as well. These rods with your 4.170" stroker crank result in a rod length to stroke ratio of 1.46:1. The wrist pin at BDC would be 0.030" higher in the bore compared to Scats 4.00" crank kit, but the 1.00" compression height compromises piston stability. You might find an engine builder willing to build this motor if you have the budget. He would have to be of the school that doesn't put as much emphasis on the rod length to stroke ratio, but he would have to be as skillful as the guy who is building the motor with the 6.2" rods.
This motor would be expensive and the return in your investment would be questionable, other than the bragging rights for having a 427C. After all, you are only gaining 19 cubic inches. I can't answer the reasonable question for you, I'll leave that up to you. I'll just say it would definately be swimming against the tide.
Compression is NOT a big power maker in regards to street engines burning gasoline. Nor is it a parameter that you build a motor around. Just the opposite, the compression ratio will be determined by your cam grinder, based upon the fuel to be utilized, the camshaft specifications and the design of the cylinder heads. The compression ratio will compliment these factors to optimize your engine's performance. I can specify that your compression ratio will fall somewhere between 9.0:1 and 11.0:1 depending upon those factors.
Your friend on the DTBB, George
