IMCA Modified Spec Racing Engine

• New IMCA Modified spec engine from Speedway Motors Racing Engines 
• More power and torque than a 604 crate while maintaining drivability 
• Modifieds can run the same spoiler allowed with crate engine 
• Low maintenance hydraulic roller cam  
• Unsealed engine gives racers the freedom to maintain their engine 

A New Engine Option for IMCA Modifieds 

IMCA Modified rules for 2025 allow for a new “spec” engine. Racers running a spec engine are allowed the same spoiler as those running a crate in an unsealed, user serviceable engine with a hydraulic roller camshaft. Speedway Motors Racing Engines worked closely with IMCA to develop this engine package.

A Rebuildable Alternative to the 604 Crate Engine, with a Roller Cam 

This is the engine that racers have been asking for. It’s an alternative to the sealed crate motors that still has a roller camshaft, unlike the flat tappet cam required in the claim engine. Plus, Modified racers running the new IMCA spec engines are allowed the same rear spoiler as those running a crate. Per the IMCA Modified spec engine rules, Speedway Motors Racing Engines spec engines are based on stock roller cam blocks and displace between 355 and 360-inches. Each engine uses 3.480” stroke stock-appearing steel crankshaft, IMCA-approved SCAT Pro-Series connecting rods, and forged flat-top pistons yielding the required 9.0:1 compression ratio. 

IMCA-approved Dart cast iron cylinder heads are assembled by Speedway Motors Racing Engines using Ferrea hollow-stem valves and the same beehive valve springs used in the 604 crate engine (or Melling VS2254 alternative) per the IMCA spec engine rules. Speedway Motors spec engines use a custom grind Comp cam selected for a balance of power and drivability along with OE-style hydraulic roller lifters for low-maintenance dependability. Each engine is topped with an MSD Pro Billet distributor and the required Edelbrock 2975 Victor Jr. single plane intake manifold. Spec engines are designed to run methanol fuel only.   

Designed and Built by the Experts at Speedway Motors Racing Engines  

Speedway Motors Racing Engines worked closely with IMCA to develop the spec engine as a more powerful, unsealed alternative to the 604 crate. An emphasis has been placed on an engine that makes more power and torque than the crate, but retains the drivability that crate motor racers are used to. 

All of this is assembled by the crew at Speedway Motors Racing Engines with the same expertise and precision that has won countless track and national championships in everything from Stock Cars to 410 Sprints. Each engine is broken in on the dyno using a proprietary program and then tuned to guarantee the power and reliability to put you at the front of the pack, night after night.  

Specs: 

• OEM GM cast iron roller cam black, 1-pc. rear main 
• Displacement: 355-360 cubic inches 
• Stock-appearing steel crankshaft 
• SCAT Pro Series connecting rods 
• Forged two valve relief flat top pistons 
• 9.0:1 compression ratio 
• Dart IMCA-approved cast iron cylinder heads 
• Comp Cams hydraulic roller camshaft – custom grind 
• Edelbrock 2975 Victor Jr. single plane intake manifold 
• Cast aluminum perimeter-bolt valve covers 
• Steel 7 quart oil pan with IMCA required 1” inspection plug 
• Fuel: methanol