Do-It-Yourself Method for Building A Stroker 373ci Small-Block
Remember that old saying, “Speed costs money; how fast do you want to go?” Although the premise of that thought is basically right, most of us are not endowed with wheelbarrows full of cash and therefore must make “selective” decisions when building an engine. The truth is, engine builds headed for street, street/strip or bracket racing generally don’t require all the latest and greatest top-drawer (read expensive!) components a professional program needs.
All of the OEM factories (Chrysler, Ford and GM) and a few aftermarket engine companies saw a window of opportunity for a marketable performance engine, aka a “crate engine.” Current OEM crate engines are built from select, readily-available components, which when compiled make a reasonable amount of power per dollar spent. To coin a popular phrase, “If you build it, they will come.” And so they did.
Even before the advent of the factory performance “crate engine,” many warehouses and performance builders offered “engine kits.” Again, with pre-selected components formulated to a given performance level, they worked when mixed in with the performance enthusiasts’ existing engine.
This particular engine build, the Street/Strip 373, makes well over 415 honest, uncorrected horsepower, has a torque curve as flat as the Great Plains, and can easily be stepped up another 40 to 50 horsepower with simple bolt-on changes at a later date. On the street, the 373 has the torque of a big block and on the track, it revs like a rocket. In plain terms, that flat torque curve means high stall converters and deep rear end gears are not required with drivability an absolute pleasure from an idle to the 5,800 rpm redline.
There are two ways to build a Chrysler 370+ cubic inch small block. The most common way would be to start with a scarce heavy-wall 360 of 1970-1972 vintage. There are two drawbacks to using an LA-series 360 base – first, the ’73 and newer 360 blocks get very thin after only .030 inches of overboring. Secondly, the massive 360 Mopar has three-inch main journals which, by design, take a lot of meat off the main caps. The 340-incher incorporates 2½-inch mains, leaving more meat in this critical area for horsepower development. The only drawback on the 340 today is core scarcity.
Nonetheless, with the following formula, the best part of the 373 is that a Mopar enthusiast can select and adapt the components listed in this story and build the engine as time and money allow. Not a bad way to go.
Mr. Tipz Sez-
How to Tweak Fo’ Mo’ Power
So, the 373 sounds appealin’ to ya but maybe yer lookin’ for a little more power without givin’ up that Olive Oyl torque curve. No problem; use the same short block we just built in the story and drop on some Hughes Magnum heads with their bigger valves. You can expect a solid 30 to 40 hp gain with just this swap. Want even more? Build a “Saturday Night Special” by having your pistons manufactured with a 10.1 or, 10.5.1 compression ratio for another 10 to 15hp. The 373’s hp is now around the 460/475hp range without even a cam change.
Let’s go the other way and say your street rod needs low maintenance but still big power? Use a Holley 600-cfm carb on top of a dual plane MP intake, and slide a 210/215 degree at .050 inch hydraulic cam in the block. You won’t loose much power, but you’ll bring the torque way up. No matter how you slice it, the 373 short-block is a solid foundation for a street, bracket or truck SB Mopar.
The article featured on this page is from the April issue of Mopar Enthusiast Magazine.Click here to read the free digital edition of Mopar Enthusiast now.