Speaking of the cool GMPP valve covers. They don't come with any provisions for a breather, so we welded these Moroso baffled breather tubes on. And capped them off with Moroso clamp-on breathers. We secured the covers using ARP stainless studs and hardware.
To finish our baby Rat we added a CSI electric water pump for dyno cooling (an Edelbrock pump will go on the street) and a CSI upper radiator hose neck. XRP supplied the -10 push-lock hose and fittings for the front-to-rear water connections in the manifold. Hindsight tells us that -10 hose is too bulky and looks out of place so next time we'll run -8 or -6.
We bolted the baby Rat on Burbank Speed and Machine's Stuska dyno and topped it off with a 750-cfm Speed Demon carb and bolted on 1 3/4-inch Hooker headers.
The engine was fired and carefully watched over by Akard himself while it broke in for 10 minutes to seat the rings and warm up.
After its initial warm-up, we lashed the valves to Comp's recommended specs (0.016-intake/0.018 exhaust) and changed the oil pouring in 7 quarts of 10W-30 Mobil 1 for the power pulls.
Burbank Speed's dyno rookie Jesse checked ignition timing for us. After several pulls we learned the engine liked 38 degrees total advance so we left it there for the whole day.
The Speed Demon idled fat, blackening the plugs' inner threads and most of the electrode. The fat idle was traced to all four mixture screws being turned out way too far. We screwed them in until they were about 1 1/4 turns from bottom and the idle cleaned up and the plugs began to color fairly well so we moved on.
We moved jets up and down in search of power and found the best numbers with 76 primary and 83 secondary jets with the 6.5 power valve left in the carb.
Comp Cams beltdrive allowed five-minute cam timing changes and we advanced and retarded the bumpstick until the best power was found at four degrees retarded. Advancing the cam made a bit more low-end torque, but we wanted horsepower so we left it retarded.
We're pretty confident that the engine would have made about 15 more top-end horsepower if we'd installed Edelbrock's Victor Jr. 454 O intake manifold. Comp Cams also makes a bigger street roller grind that might push this little Rat over the 525hp mark. Maybe we'll make some changes and return to the dyno to see how much power we really can squeeze out of this baby with off the shelf parts and no behind the scenes trickery.