Originally Posted by hogger52
Well, first off this is my first post on this site and have been reading alot from you guys and hope to learn a few things.
I am old school hot rodder from the golden days of muscle cars. My first project, engine build was a 65 Chevy Impala SS 396 convertible that I bought for $500.00 that was blowing smoke, so I with the help of a couple friends, rebuilt the motor. It didn't go that well as I remember, but that was in about 1971.
So now I have taken up the task of rebuilding a 73 Chevy Cheyenne 4X4 half ton truck. I bought it with a 400 in it and it actually ran pretty good, but I had this vibration problem with it and assumed it was a U joint. I changed them all till I did some reading about the 400 being externally balanced and sure enough at 2800 RPM it was quite severe. I pulled the motor and found that the flywheel looked as though someone shot it with a 9mm. Perfect round dent in it. I am thinking that is the problem, but I decided to sit it on the shelf for now and bought a 350 from the junk guy that was in a 92 chevy truck and it was a TBI motor. I wanted to get a roller cam motor, but this one didn't have the roller cam, but has the bolt holes for the spider and the larger lifter bosses. So at this point I have a 400 block and a 350 roller cam block that both need to be rebuilt. At this point I would say I lean towards the 350 and the reasoning behind that is I am not a fan of an externally balanced engine and am looking into getting the vortec motor to the machine shop to have it de-greased, magnafluxed and possibly bored or line bored.
That's my take on it, for what it's worth. Hope I didn't bore you guys with this long drawn out read.
The heads that came on your TBI engine are known as swirl port
heads. Depending on how you want to build the 350 (stock or towing, or high performance), they may or may not be what you want to use. Basically they're good truck heads, but not so much for high performance.
BTW, your TBI 350 SBC is technically a Vortec engine, but do not confuse that w/the popular L31 Vortec engine, which uses the L31 Vortec
IMO if both need an equal amount of work, I would build the 400.