327 block same as 350??

[Nobody_u_know]

My question is whats the difference in the 327 to the 350? I know the obvious things such as the rotating assembly (crank, rod, piston ect...) But the block it self? I know they have a early 60's small journal and later came the large journal around 67 but does that make a difference in the block. Can I put a 350 crank in my original 327 motor and make a 350 out of it? I pulled apart my lower end today and found a crank that sure seen better days. Finding a 327 crank is a job in itself and the $$ makes me wonder why not turn it into a 350 if possible while I have to replace most of the rotating assembly any ways.

[60-66 Nut]

Yes, the first 327 was a small journal engine up until mid 67, when they made the big journal crank. The 307 and 350 were all big journal. Even the mains were smaller on the small journal engine, so the big journal crank will not fit in the small journal block. A 350 crank should drop into a big journal 327 block, provided there is no interference with the crank throws. All small blocks used the same length rods (except for the 400), the difference in stroke length is in the pistons and crank. A 307 crank is the same as a big journal 327. If it were me, I would have the old one turned or get a reman crank kit and keep it a 327, but that's just me. I've had several 327's over the years and I always liked them. What year is your engine?

60-66 Nut

[Hilandr451]

While the heads, cranks & cams may be interchangable, the big difference in a 327 vs. the 350 block is the 327 was a vented block. It had a cylindrical oil baffel at the back of the lifter valley & vented out the back near the distributor. That's how they got away with using clean valve covers without vents. If you're considering converting to a 350 or any other late model block, you won't be able to use the original tin from the 327. (265's & 283's had them too.)

[60-66 Nut]

Yea, I remember the open system on the older 327's I had. My 65' 327 had a pcv valve connected to the fitting behind the distributor with the oil filler on the front of the intake, with a breather-style cap. I put later model valve covers on it with a quadrajet intake, and I blocked off the port on the back of the block. The 68'(big journal) 327 I had came with vented covers but still had the oil filler on the intake with a non-vented cap. The block still had the boss behind the distributor for the vent, but it was not drilled.

The thing I really liked about the older small block engines was the script valve covers. My 409 truck engine has the same style crankcase breather system, but the covers just have a bowtie on them.

60-66 Nut