I found a 1989 350 ‘M’ motor and had the short block bored .030 between business trips to Albuquerque. This is a one-piece rear main seal 4-bolt truck block.
If you want to look for this block in the boneyard, check the casting number on the back of the block behind the passenger side cylinder head.
Roller Cam Provision Hiding Under the Intake
A big advantage with this older block is that it has provision for the mechanical fuel pump, so I can use the carburetor Vortec intake mainfold that came with the retrofit kit I used to build my Ram Jet. There are other choices or intakes depending upon whether you want use a single or multiple carbs, a Quadrajet, or square-bore carb.
Ideal 1-Pc 350: Roller Cam Plus Fuel Pump Pad
I hoped to use a TBI fuel injection system from an Impala, and one vendor recommended the GM 330HP 350 HO was a great base engine for TBI. This is an older GM Performance Parts crate engine, but it can be easily made using this recipe, or this one. It calls for pistons 12361371, but I needed them in a +0.30 oversize. The Pace Performance description shows a 12514101 piston. The Silv-O-Lite index at Beck Racing cross-references the 12514101 piston to an H1476 piston, hypereutectic, destroked .020″, 3.14 diameter head recess .070″ deep with four valve reliefs. This equates to an approximate 11.5cc dish. This piston uses 2-5/64″ rings and 1-3/16″ ring. The closest +0.30 piston and ring kit I could find is Z8KH423NCP30, which has a 10cc dish. Close enough, I hope.
Special Use Only - Mmmmmm...Special....
The rest of the parts I needed to make the 330HP engine is the 24502476 hydraulic cam and 1.5 ratio self-aligning rocker arms 12495490. Most 350 pushrods and timing kits will work with this combination. The rockers are the ones on the head to the left.
VortecZZ5DT Comparison with 8060 Conventional Head
The cylinder heads I am using were a discontinued Pace Performance special reworked head called the VortecZZ5DT. Pace took a 8060 head and machined it for screw-in rocker studs plus dual valvesprings to accommodate a .550″ lift cam. In addition, they drilled the intake face to accept a pre-1986 12-bolt conventional intake manifold, using special Fel-Pro gaskets. My plans have evolved since I purchased the last pair of these they stocked. They will be total overkill for the 330HP cam, but I can always upgrade the cam and lifters later.