Bc419

oilcanhenry

Well, if it indeed a 1975 350 cubic inch motor, it looks pretty good to me, in the photos you supplied. What you _really_ need to be concerned with are the various load-bearing surface materials "wear and tear" over all of these years, assuming that it was not remanufatured or rebuilt, of course. It's unlikely OE original, but it's possible, but not with new pistons installed.

You won't want to find out, after you install this motor, that they are out of spec and your oil pressures are too low, or that you have noise/clatter that should not be there. On the plus side, the pistons look very good, and with little carbon build-up too!

I would definitely chuck the oil pump, no matter what, as well as replace all the seals. I'd install a Cloyes timing chain as well, You'll never have to worry about it again. They are built as solid as a rock, in my experiences, and not just with Chevrolet's engines either. A good carburetor would also be of high priority to me, as well. Holley, first choice; Carter/Edelbrock in 2nd.

Those mid-1970's motors, not just GM, but all of them are what I refer to as "Smog Motors", so your compression ratio is likely 8 to 1, or 8.5 to 1, Not exactly as powerful as thier predecessors, but all the vehicle manufacturers had to meet the US emission standards of the day, and dropping compression ratio's was one of those long-abandoned notions, way back then.

Bc419

oilcanhenry

Non necessarily, as to the shaved deck. There is no way that I can tell if your engine has been modified in that manner. Too, the use of closed-chambered heads, would most certainly increase your compression ratio, so that is something that you might want to consider, along with thin head gaskets and a performance camshaft, as well.

When GM switched to open-chambered heads, due to the smog laws, horsepower ratings dropped like a rock. My father replaced a 1969 C-60 closed-chambered 366 C-I Chevrolet motor with a 1975 366 open-chambered mill and the sudden drop in performance was _VERY_ noticeable, as well as decreased fuel mileage to boot. I finally swapped out the heads, and the engine ran as it had before it was swapped, with a few other modifications done as well. Medium-duty trucks are exempt from smog laws.

Ultimately, what kind of 350 cubic inch Chevrolet motor that you want to build will depend on the "Vehicle Emissions testing" or "SMOG" laws in your particular state. BTW, 1975 was the first year that catalytic converters were made mandatory in all 50 US states on light gasoline vehicles. Back then, the catalytic-converters depended on the A.I.R. system to control air-pollution, but today's modern vehicles no longer need a "smog pump", thankfully.

If you live in a state that tests for "smog" you may be limited in what you can do, in regards to passing any emissions testing for registration of your vehicle. Had this been a 1974 vehicle, or if you choose to install the motor into a pre-1975, non-CAT vehicle, you can do whatever you wish to do in any US state, to the best of my knowledge.

Bc419

oilcanhenry

All I could find out in regards to your block number is that is correlates to a 1975 GM 350, per the TXL designation. Didn't come up with anything on the 05413429.0 number at all.