Former winner Tony Bischoff could enter the small-block or nitrous class with his Hemi.

Following the successful debut of a new five-class format, the Amsoil Engine Masters Challenge is accepting applications for the 2016 competition.

Tighter rules will prevent some radical ideas like Jon Kaase’s 8-4-2-1 headers in 2013.

A revamped lineup will pit engine builders in five categories, one winner being determined each day during the October 3-7 competition. Final rules for each of the five classes were just announced, and drawing the most attention will likely be the debut of a nitrous class and the return of the Ford Modular engines to competition following a two-year absence due to either being banned or no class opening.

Also returning to competition is the highly popular Vintage class that last year saw Ford Y-blocks, a Chrysler Poly head engine and a Packard enter. Under revised rules, those engines will not be allowed to return, but the class this year will be opened up to inline six-cylinder engines — so it will be interesting to see what choices this year’s engine builders will enter.

Competition involves three dyno pulls over a specified rpm range. Average corrected torque and horsepower are added together to achieve scores. If engines of different sizes are allowed, then a displacement factor will be added to the final calculation formula. Prize money will be awarded in each category.

Here are capsule looks at the rules for each of the five classes:

Day 1 – Small-block shootout

Dyno pulls from 3,500 to 7,500 rpm with a displacement factor. Minimum displacement is 350ci but there is no maximum. Cylinder blocks (aluminum or iron) must be cast OEM or available aftermarket replacement. Cylinder heads are limited to two valves per cylinder and must be OEM or available aftermarket. Heads must also retain passenger car production port configuration. Titanium valves and springs prohibited. Heads can be ported but welding or filling inside the ports prohibited.

SAM Racing is always tough in the small-block class.

Single 4150- or 4500-style carb allowed, with restrictions on throttle-shaft diameter and throttle plate thickness. Fuel injection is allowed but with a single injector per cylinder and commercially available throttle body that has a 4150 or 4500 footprint. Knock sensors prohibited. Camshaft must retain OEM journal diameter and lifters must commercially available. Intake manifold must be commercially available designed for a single four barrel. Tunnel rams prohibited.

Commercially available steel rods required. Pistons must be commercially available and support three rings with minimum thicks of .040, .040, 3mm. Compression ratio limited to 11.75:1. Any commercially available rocker arm allowed, and headers must be of a chassis-style exhaust. Oil pump must mount in factory location. Oil pan must be commercially available but there are restrictions on dimensions. Oil will be supplied at the competition. All engines will run on VP 101 unleaded gas.

Day 2 – Spec big-block

Dyno pulls from 3,500 to 6,500 rpm. Maximum displacement is 470ci but there will not be a displacement factor in the scoring calculation. Any domestic OEM block (aluminum or iron) or aftermarket replacement allowed. Billet cranks prohibited. Edelbrock cylinder heads required (the rules have a full list for AMC, Buick, Chevy, Ford, Olds, Mopar and Pontiac applications).

Porting allowed but no welding, and valve angles must remain as cast within a degree. Valve size allowed to go .005 over or under .015 under. OEM style rocker arms and Spec Edelbrock intake manifold required. Spec MSD distributor also required. Single 4150-style carb required with specified modification restrictions (see rules). Comp Cams camshaft designed for the block required but any grind allowed. Comp Cams hydraulic roller lifters required. Compression ratio limited to 11.5:1. Steel rods and pistons must be commercially available. Vertical gas ports prohibited and .040/.040/3mm minimum ring package. Chassis style headers required. Fuel is VP 101.

The Ford Modular engine is back in action following a two-year absence.

Day 3 – Coyote 5.0 Showdown

Dyno pulls from 3,500 to 8,000 rpm. Any OEM production Ford Coyote 5.0-liter engine with cross-plane crankshaft permitted. Must retain stock 3.63 bore x 3.65 stroke and production cylinder heads with OEM valve seats. Any commercially available steel valve allowed. Unlimited porting but no welding. No carburetors, and fuel injection limited to single injector per cylinder. Maximum fuel pressure of 65 psi.

Any camshaft with a commercially available drive. Intake must be commercially available with forward-facing throttle body. Steel rods and 3-ring pistons must be commercially available. Compression limited to 12:1. OEM cam followers required. Chassis style headers. OEM oil pan required, and no vacuum pumps. Fuel is VP 101.

Day 4 – Vintage

Dyno pulls from 3,500 to 6,500 rpm with displacement factor. Any normally aspirated OEM domestic passenger car V8 engine introduced in 1954 or earlier.

Additional antique families include Nailhead Buick, Packard V8, Y-block Ford, FoMoCo MEL-Series and Chrysler 1956-1967 A-Series Polyspheric small block. Also allowed are inline 6-cylinder engines introduced in 1964 and earlier. Any displacement and any commercially available crankshaft. Billet cylinder heads and titanium valves prohibited. Cylinder heads must be OEM production or available aftermarket. Unlimited ignition and carburetion.

Unlimited EFI but 65 psi maximum fuel-line pressure. Unlimited camshaft and intake manifold. Steel, iron or aluminum connecting rods allowed. Unlimited pistons, rocker arms and compression ratio. Dry sump prohibited but oiling pretty much open except for some dimension restrictions. Chassis style headers. VP 101 fuel.

Day 5 – Nitrous Power Adder

Dyno pull from 3,500 to 7,200 rpm with scoring between 4,500 and 7,200. There is no displacement factor. Team leader triggers nitrous at any point between 3,500 and 4,500 rpm and must continue activating spray throughout run. Legal engine types limited to: AMC; Buick; Cadillac; Chevrolet small-block, General Motors LS; Chrysler LA-series, Magnum small block, Gen III Hemi; Ford Windsor or Cleveland; Modified; Pontiac. Maximum displacement is 367ci.

The nitrous division allows a single plate, and organizers will supply the nitrous jet to help ensure equality.

Cylinder blocks, crankshaft and cylinder heads must be commercially available. No titanium valves or cylinder head welding. Single 4150 carb, no fuel injection. Any camshaft but must retain OEM journal size. Intake manifold must be commercially available. Steel connecting rods, and pistons have .040, .040, 3mm minimum ring pack.

Compression ratio limited to 11:1. Commercially available oiling with some restrictions on dimensions. Competitors will use a plate system between in the intake and carburetor. The event staff will supply the nitrous jet targeting 150 horsepower. Fuel jet will be at the engine builders discretion. Details of the nitrous jet, bottle pressure and size will be furnished in rules update.

Additional rules covering water pumps, mufflers, balancers, etc. are in the complete rules package listed on the Engine Masters website.