The pivotal reason for resurrecting this 400 was to create a budget short-block that could really enhance the 400's inherent torque capacity. Most everyone knows how good a bone-stock iron Vortec head flows. Did you know it's better than the old factory GM Bow Tie iron head? But there are some shortcomings as well. The stock Vortec head uses a very large-diameter valvespring guide that is also very tall, leaving barely enough room for 0.450-inch valve lift. Anything more crushes the retainer into the valveguide seal. Barrington machined our guides for 0.530-inch diameter valveguide seals, which leaves sufficient guide thickness. Unfortunately, this meant we had to purchase different valveguide seals because the Summit supplied seals are intended for 0.500-inch guides, which Barrington claims are too thin given the 0.344-inch valve stem diameter.
All this extra machine work can be avoided by merely ordering a set of modified Vortec heads from Scoggin-Dickey that will come with better springs and the machine work necessary to clear most street cams. While we were talking with Scoggin's Nicky Fowler, he suggested we also test a set of the GM Performance Products large port Bow Tie Vortec heads. These are 225cc-intake-port heads (the standard Vortecs are closer to 170, and the small Bow Tie Vortec is 185 cc), and we've seen flow numbers upwards of 250 to 260 cfm at 0.500-inch valve lift, which is excellent for these budget heads. The Bow Ties come with larger 2.00/1.55-inch valves and are machined with five angles on the seats. One Vortec issue is the specific eight-bolt intake pattern that is completely different from the traditional small-block bolt pattern, requiring its own intake. The Bow Tie heads are drilled with both bolt patterns, so if you choose to go the Bow Tie Vortec route, you can offset the $200 price increase if you already own a good aftermarket small-block intake such as an Edelbrock Performer RPM Air-Gap or a Weiand Speed Warrior. The Bow Tie Vortecs are drilled for both intake bolt patterns, which is convenient. But we discovered you need to seal the Vortec boltholes if you use a standard intake on the Bow Tie heads. The standard small-block intake manifold uncovers the Vortec bolt pattern in the head that will spew oil if the holes are not sealed. We learned this one the hard way too.
After disassembling the stock Vortec heads, Don Barrington Sr. machined the guides to redu
One reason the Vortecs flow so well is the back-cut angle the factory places on both the i
If you want a little more power than the stock Vortecs offer, for a few more bucks you can
Here's what the dead cam looked like after a 25-minute break-in procedure. This was no fau
Our First Test Went Flat
Let's cut right to the chase. We screwed up. We installed the bigger, 130-pound seat pressure valvesprings on the stock Vortec heads expecting that a cocktail of moly cam lube, pressure-lubing the engine, and the prescribed quick run up to 2,400 rpm would be enough to ensure the Summit cam's survival through the break-in procedure. Unfortunately, the cam went flat. We asked a couple of engine building buddies, and the unanimous answer was that 130 pounds of seat pressure and 340 across the nose was way too much spring pressure for break-in. What we should have done, and did for the next effort, was to use the stock Vortec springs, which had enough clearance to avoid coil bind with the Summit cam. These springs measured 80 pounds on the seat and a mere 180 at 0.500-inch valve lift that is low enough to give the cam a chance to establish a wear pattern and to effectively improve the heat treatment of the lobes.
We decided to not take a chance on the second cam, so we ordered a Comp Pro-plasma nitrided Thumpr camshaft. The Pro-plasma heat treat hardens the lobes with a surface treatment that's roughly 0.010 inch in depth, giving each lobe an excellent chance to survive the break-in process. Of course, this also meant a new set of lifters as well as a new set of main bearings when we discovered they didn't survive the short run time due to the iron filings that were circulating through the engine.