Originally Posted by Ferabel73
Hi I am new to this site even though I have read it before, here is my question can I use a 305 crankshaft on a 307 engine? The reason why I ask its because I have a 1986 chevy Monte Carlo with an original 305 engine, and a friend of mine give me a 307 engine to rebuilt it and use it I have a new set of head for this built and a camshaft but looking at the crank pulley I notice it's smaller than my 305 so I don't think that my alternator , water pump and ac compressor are going to match any suggestions about what should I do? Thanks for any help
Not easily; the 307 has a stroke of 3.25 inches the 305 has 3.48. Both engines use a 5.7 inch rod so the difference in additional stroke length of the 305 crank to keep from pushing the piston out the top is taken in the 305 piston by lowering the pin position by .115 inch compared to the 307 piston. The 305 piston has a diameter of about 3.735 inch compared to the 307's larger 3.874. This is .140 inch which would preclude finding an oversized 305 piston that would fit the 307 bore and bring with the pin position. You could use the shorter 400 rod (5.565 inches) with the 307 piston for an assembled length that's really close to what's needed. But then the piston skirt gets pulled so low in the bore it hits the crank's counterweights.
So this just isn't practical to do, not saying it can't be done, but that won't happen cheaply.
If the 307 is a pre 1973, it may well bore to 4 inches, then you could make a 350 out of it with the 305 crank and rods using 350 pistons.