Muscle Mustangs & Fast Fords
Ford Small-Block Engine Shootout Part 2 - 363ci Stroker Vs. 363
Battle of the 363's!
Last month we introduced the premise and core components of this build. Based on Ford Racing Performance Parts' 363ci crate engine, we're comparing a short-deck (8.2-inch) 363 with a similarly sized tall-deck (9.5-inch) Windsor. The purpose is to compare and contrast the two, and see which makes more horsepower (and torque) and where in the rpm range it's made.
The general consensus is that the longer-stroked (3.5-inch) tall-deck engine will make more low-end torque, and the shorter-stroked (3.4-inch) short-deck engine will make more top-end horsepower. But how much better will each be, if at all, and how that will play out on the engine dyno will be revealed over the next few issues.
There are obvious advantages, especially to Fox-body Mustang owners, to sticking with a short-deck engine. But when more cubes are desired, a 351 Windsor swap is a common choice. But things like header fitment and hood clearance are just a couple of many hurdles that 351W swaps pose. But is a comparably sized short-deck engine just as effective as the big Windsor?
Fair and Square
How is it going to be possible to make this test fair? Well, we've enlisted a team of experts to help us along with this build. On the roster are reps from FRPP and Comp Cams, and our engine builder, Auto Performance Engines' (APE) Kevin Willis. Willis is overseeing both engines from the unboxing of all the parts to hitting wide-open throttle on his in-house engine dyno. His 25 years of experience in building high-performance engines will certainly be utilized.
After determining the exact displacement of the 363 short-block that FRPP sent us, which is 363.32 ci, we needed to determine how much we needed to overbore our 351W block to achieve as close of a displacement as possible. Willis determined that we needed to order 0.060-over pistons (4.060-inch), which will make our displacement 362.31 ci. Though not technically 363 ci, it's roughly 1 ci less than the short-deck engine. We'll discuss the internals of the tall-deck engine in Part 3.
Another major factor is compression ratio (CR). We want both engines to have the same CR, so we're taking much care in determining the actual ratio. There are a number of factors that determine static CR, including stroke length, deck clearance, piston volume, bore size, head gasket bore size, head gasket thickness, and combustion chamber volume (on the cylinder head). Willis has formulas to determine the actual compression ratio, but we won't bore you with the math.
After taking all of those things into account, we determined that our short-deck engine has a CR of 10.2:1. Though 0.2 points higher than the crate engine is rated, we think this is what the crate engine should actually be listed as, because we're using the same cylinder heads and head gaskets that FRPP uses in the crate engine versions.
We also want to make sure that the heads are the same. We ordered two sets of FRPP's Z304DA heads that come standard on the 363 crate, but Willis wanted to put them on his flow bench to be sure they were exactly the same. We only tested the first pair this time, but we'll compare them to the other pair in Part 3, when we introduce the other engine.
A component that we know will be different will be intake manifold, though we ordered equivalent pieces from Edelbrock. Obviously, rod length, piston size, and stroke will be different, so we're simply trying to make those the only variables. The 800-pound gorilla in the room, though, is the camshaft.
Cam You Dig It?
This is where Comp Cams comes in. Camshafts are chosen based on nearly every internal component in an engine, and bore and stroke are huge contributors that decide which camshaft is best for that particular engine, as well as the purpose of the engine. That being said, which camshaft should we go with? One that is perfect for the short-deck won't help the tall-deck engine achieve maximum performance, and vice versa. We considered a middle-of-the-road camshaft that would be fair for both, but it's hard to say exactly where the "middle" of the road is.
The solution: have Comp Cams grind a custom camshaft to suit each engine. The benefits are two-fold. First, maximum performance for each application will be achieved. Comp knows which cylinder heads, intake manifolds, carburetors, fuel type, and octane we're using, and can maximize output based on those parameters for each engine. The other advantage is that we'll be closer to maximizing each engine's power potential, which means big numbers on the dyno.
The profile that Comp chose features 0.580/0.585-inch lift, 236/242 duration at 0.050-inch, and 107 degree lobe separation. The tall-deck engine will feature different specs, but we'll get into that next time. For now, we're at Auto Performance Engines in Auburndale, Florida, to follow along with Kevin Willis as he prepares our short-deck 363.