The valvetrain damage to the Blazer required a bit of thought: Do I replace the heads with a better set of heads or put up with the small-valve "993" castings that are on the engine. Removing the heads and disassembling them produced the answer, because while repairing the head damage would cost only about a third as much as replacing the heads with known performance heads there was little sense in spending money on machining, installing new studs, and installing new valve springs and retainers on a set of heads I knew I wasn't going to keep in the long run.
Removing the heads also allowed me to inspect the camshaft lobes more closely. At this time, I had assumed that the lobes might be OK. When I looked down the lifter bores in the block, I was greeted with a couple of lobes that didn't look too happy. I also discovered at this time that the block is bored 0.040" over standard and was fitted with dished pistons (total displacement of the dish plus the valve reliefs was measured at 10cc).
What did I need to repair the damage? Here's a brief (although incomplete) rundown:
* Edelbrock Performer cylinder heads, 70cc combustion chambers.
* Pushrods, 0.100" longer than stock (this was necessitated by the cylinder heads but wasn't a big deal since I had bent ones anyhow; note that these units are made by Trick Flow and when checked for straightness, concentricity, and length appear to be of superior quality - I will recommend their use in an engine!).
* Rocker arm studs, 7/16" straight shank, ARP (I didn't want 3/8" studs).
* Rocker arms, roller (I got Crane Cams Energizer units in a 1.5:1 ratio, for 7/16" studs - because I had a few dead rocker arms, this wasn't too bad a hit, but I really wanted to get some Competition Cams roller tip Magnum rockers because of valve cover clearance concerns).
* Valve covers, tall, steel (these units only had one hole per cover - no oil filler hole - so I had to modify them to add a bung for my oil fill cap (cut up a stock cover for the bung, and cut and welded the new cover for the bung); I still don't like them - why doesn't anyone make a mid-height valve cover for the SBC? It seems that these covers are WAY too tall for my valvetrain and are butt-ugly. The reason I selected these was because they were inexpensive, were made of steel, and provided baffles for the emissions fittings. These valve covers created problems with my alternator, so I had to search out an alternator belt that was just slightly longer than the one I was previously using).
* Camshaft (I decided that I would get a bit more cam than I had, so I went with a Crower 284HDP grind. Lucky for me that two weeks earlier I had decided to install a Competition Cams two-piece timing cover or I would have had to lift the engine and drop the oil pan in order to perform the cam swap).
* Lifters (new lifters are always necessary with a new cam, so I got Crane Hi-Intensity lifters to provide a little extra bottom-end due to their fast-bleed characteristics).
* Head gaskets (these are necessary whenever R&Ring a set of cylinder heads, but I figured that I'd point out that these are Fel-Pro units with 0.041" crushed thickness and 9.1cc volume).
*Valve cover hold-down/load-spreader tabs (while these aren't strictly necessary, they are nice to prevent long-term valve cover leaks. I got Moroso 4" load spreaders. After comparing them to a number of other aftermarket ones, these appear to be the thickest ones and exude quality. Highly-recommended part!).
* Miscellaneous (gaskets, gasket compounds, spark plugs, fasteners, cleaning solutions, paper towels, coolant, assembly lubricants, etc.).
I lightly oiled each valve around its seat area and applied air pressure to each valve's port. Most of the valves had some seepage. This necessitated disassembling the heads and hand-lapping each valve to its seat. Note that I did this because a friend bought a set of these same heads and had an engine problem associated with leaky valves (he removed his heads and had a complete valve job done on them).
I tapped the drilled-in exhaust crossover ports for 1/8" NPT pipe plugs, in case I ever wanted to plug the crossovers in the future, this creates an easy way to do so by adding pipe plugs. While this isn't "checking work," I figured it kind of fits here because I'm already modifying the heads.
I welded the cups of a couple of the old hydraulic lifters to their bodies in order to check out valve to piston clearance and rocker to valve stem geometry. I had originally purchased a couple of solid lifters for this task. Upon receiving them I found that they are shorter than the hydraulics, throwing the rocker to valve stem geometry. I dropped a couple of "strings" of rolled-up non-hardening modeling clay into the valve reliefs in the piston, and up onto the quench band of the crown of the piston (in order to check both valve to piston clearance and piston to head clearance) on the #1 and #7 pistons. I then sprayed the valves and chambers with oil, installed the head gasket, and torqued the cylinder head onto the block. I then installed the welded (and thoroughly lubed) lifters in the #1 lifter bores, pushrods to them, rockers to their studs set to zero lash, and rotated the engine two complete revolutions. Piston to head clearance checked out at 0.080" on both #1 and #7 (less the 0.041" compressed thickness of the head gasket, that gives me 0.039" piston to deck clearance, which agrees with what I previously measured, so I found no reason to measure the head gasket thickness). The piston to valve clearance checked out in excess of .180" (0.080" is all that's needed on the intake, and 0.100" is all that's needed on the exhaust, so this is more than adequate).
The camshaft is quite a bit more radical than the original cam, and operates outside of the window of operation for which the carburetor is tuned. The carburetor must be re-jetted, so I'm going to play with it. More on this here, later.
I can't stress how stupid I think the valve cover situation is for the SBC. There's no in-between sort of stock-type valve cover that will clear Poly-Locks on roller rockers without having the excessive height for long studs and a stud girdle. Stock Pontiac valve covers clear roller rockers and Poly-Locks without a problem, so I don't see why something with such broad appeal (SBC valve cover that doesn't interere with alternators, A/C, power steering, AIR, etc., looks good, has all of the smog fittings, has baffles, has an oil filler hole, clears roller rockers with Poly-locks on heads with long valves) can't be made profitably and cheaply by some company.