Originally Posted by Volla SA
I am looking to buy a 307 V8 engine. How do I know it is, in fact, a 307 V8 just by looking at it? I don't want to buy from someone claiming to have one, only to get it home and it doesn't fit in my car because it is a 305! Any tips would be appreciated thanks!
Actually if you picked up a pre 1986 305, it would drop right in and you wouldn't know the difference till you took it apart. On the outside anything that connects to or is fastened to the 307 will also go right onto the 305 and the 305 will go into any vehicle that had a 307. Same would go for 283, 327, 350 and some 265s.
Stating in 86 you start see changes, the angle of the center 4 (2 per side) intake to head bolt angle changes from 90 to 72 degrees measured from the head's port face, so this drives a matching intake or modification of the bolt hole angle in the manifold. A change from carbs to injection, Throttle Body Injection (TBI) for trucks and some car models and Tuned Port Injection (TPI) on some car models. Rear crank seal changes from the older 2 piece to a 1 piece, this is is easily accommodated across the change line with the flywheel or flexplate that fits the crankshaft used, everything else still bolts up. The rocker covers morph from the older perimeter bolts to center bolts so the head and rocker cover need to match. For the most part trucks stayed with flat tappet cams, though the block might be provisioned for a roller. Most 305's in cars went to the factory roller cam, from the outside you can't tell. Engines that had TBI or TPI injection use a version of the HEI distributor where the advance is computer generated, these can be changed back to the earlier distributors if you're not using injection and the computer, this is a drop in swap.
So a 305 really wouldn't be an unpleasant surprise nor would a 350, the pre 1986 is a bolt in, the post 86 takes some minor tweaking for the flywheel/flexplate, distributor, and messing around to be sure the heads have the correct rocker cover and intake will bolt up, no big deal. The new versions leak a lot less oil from the crank and rocker covers.