We're done assembling our budget-conscious 383 stroker mill, and it's time to put it to the ultimate test-the dyno-so we can learn what to expect once it's bolted in a car (yes, we'll do that too). If you've been following along, you'll know that we perked up an ailing 350 with a Powerhouse Engine Components 383 stroker kit in the Sept. '07 issue. Then we showed how to refurbish stock cast-iron cylinder heads in October's Part Two for those of you unwilling or unable to cash in on the bonanza of bolt-on aftermarket aluminum heads available today. Next, in Part Three (Nov.), we torqued it all together and, while we were at it, took a closer look at the new Super Street 215cc aluminum heads from Patriot Performance.
The 383 stroker kit already proved that it can sometimes be more expensive to revive tired factory iron parts than to simply replace them with new components from the aftermarket. Sure enough, the fully assembled Patriot aluminum heads looked to be capable of the same stunt. But the only way to validate these upgrades is to compare them side by side on the dyno. In this month's installment, we'll not only stick the motor on the dyno, but we'll also mix and match heads and intake manifolds to see what works best.
Here's a rundown of the plan: Using our Isky-cammed (0.544/0.547 lift, 284/292 duration) 383 short-block as the basis, we'll start out with the refurbished big-chamber, 76cc iron heads (9.0:1 compression) and a dual-plane intake manifold. Let's call this Test 1. Next, we'll explore the effect of a single-plane intake manifold on the combination in Test 2. Then we'll yank the iron heads and replace them with the small-chamber, 64cc Patriot heads (9.8:1 compression), fed by the same dual-plane intake for Test 3. Finally, we'll top the aluminum heads with the single-plane intake and see what we get in Test 4. OK, the crew at JMS Racing Engines has the 383 perched atop the shop's DTS 4000-G 1,500hp dyno, so let's get started.
Before doing anything, be sure to properly fit any replacement dipstick kit so it is accurate for your particular engine's block, pan, and filter combination. This is no place for assumptions, as oil starvation can quickly destroy any engine. We started by filling the oil pan to its rated capacity-6 quarts in the case of our Moroso Chevy II pan-then added another half quart to account for the oil that will be stored inside the filter. (Tall filters can hold as much as 1 quart, so add accordingly.) Once the pan was filled to the correct capacity, we gave the oil a half hour to settle, then installed the dipstick tube into the block, adding sealant at the base to prevent leaks. Next, we inserted the dipstick in the tube to see if the actual oil level was aligned with the "full" indication line marked on the stick. Our dipstick tube was a little too long, causing a false underfilled reading, so Jeff Johnson used a special compact tubing cutter to remove 1 inch. Then our dipstick reading was spot on.