Hidden in the shadows of NASCAR lies the oldest automobile racing sanctioning body in the United States known as IMCA. IMCA is based on enforcing fair and consistent rules that promote affordability as the foundation of racing in America. Through the promotion of the "grass roots" weekly racer, IMCA has seen remarkable growth since the late 70's in what are mostly 1/4 mile to 3/8 mile dirt or clay circle track venues in small towns across the nation. Click here for tracks.

While founded in 1915, it wasn't until previous IMCA owner Keith Knack introduced the Modified Division did IMCA really take off throughout the United States. Keith Knack has since sold IMCA to Kathy Root who has championed Knack's vision to make circle track racing relatively inexpensive and competitive from coast to coast. IMCA Modifieds are known as the "calling card" of IMCA.

IMCA Modifieds
IMCA Modifieds have become the calling card of IMCA, thrilling legions of new local dirt circle track fans every year from coast to coast.

Key IMCA Modified Rules

1964 or newer OEM perimeter American rear-wheel drive passenger car frame only.

Minimum wheelbase 108 inches, maximum 112 inches, both sides. No part of frame can be lower than four inches from ground except front crossmember.

No composite body panels allowed. Body must be same width, front to rear, and parallel to OEM frame.

All front suspension components must be steel, unaltered OEM, in OEM location, and replaceable by OEM parts, with some exceptions.

No rack and pinion steering. All components must be steel, unaltered OEM, and in OEM location with some exceptions.

No independent rear suspension. All components must be steel.

Must use unaltered Hoosier Race tire, G60-15 (8.75" width) with IMCA stamped on sidewall.

View Complete Rule Book

IMCA Modified Division
Modifieds achieved their popularity due to a carefully crafted set of rules that lower the barriers of entry found in the IMCA "Late Model" Division or any other competitive circle track division for that matter. Along with having to run a '64 or newer domestic passanger car frame and the 8.75" wide tire limit, the engine "claimer" rule helps keep a level playing field in terms of costs and horsepower.

Claimer Rule
Realizing that racers at this level have a wide range of budgets, and that this can make for lopsided races, IMCA utilizes an "engine claim rule." Roughly put, the top four finishers at any event are subject to an "engine claim" by any racer from 5th place back. What this means is, if you sink $5000 or $15,000 into your block, rotating asembly, heads, valvetrain, and intake (carb, headers, distributor etc. not included in a claim) then your competition can claim your motor for a mere $550, or exchange for his engine. It's a great rule in spirit, but unfortunately rarely does it play out as written because the winner can decline to honor the claim and simply put up with a three race suspension.

What is particulary fun regarding the engine requirements or lack of in the IMCA Modified Division is there is very little in the way of limitations as to what parts you can or cannot use to make up your motor. However, on any night you could be claimed. That means the challenge is to build as much horsepower as possible and as cheaply as possible. And for an enterprising engine builder, this can be a lot of fun. The key is to understand which components in the engine will give you the greatest bang for your buck and which components you should save a few bucks on.

IMCA Modified Engine rules are as follows. Take note there is no displacement limit, this means even big blocks and or strokers are permitted. Also, keep in mind that running a Ford can work in your favor since 95% of IMCA Modified cars are bow-tie powered... this means 95% of your competition wouldn't want to run your motor, even if their claim was honered by IMCA officials. This gives the Ford IMCA Modified racer a bit more comfort in extra engine development and investment.

"Any American make steel engine block allowed. Aftermarket and OEM performance blocks allowed. Steel heads and oil pan only. Flat tappet cam/lifters and stud-mounted rocker arms only. No stud girdles. No mushroom lifters, lifter diameter and configuration must match OEM passenger block. OEM firing order cannot be changed. No crank triggers. All engines must be able to be used in conventional passenger car without alterations. Engine mounts cannot be removed or altered. Castings and fittings must not be changed. No machine work on outside of engine. All belt driven accessories must be on front of engine. ‘Wet’ sump oiling system only. External oil pumps go with engine if claimed."

Tmeyer Inc. Small Block Ford 454 Build
As you probably surmised, due to the intensely competitive nature of the modified class, engine builds are a closely guarded secret. Not many racers (at least the winning ones anyway) are willing to reveal what goes into their powerplants. Recently Tim Meyer of TMeyer Inc. allowed us to get a rare look at 351W based 454 stroker that he was building for a client. This particular racer has always run 351W based 396 cid strokers in his race car, and this season wanted to up the displacement to 454cid. This engine will be used in this seasons IMCA Modified series - however, not revealed to us was the drivers name, car number or anything else that would allow someone to identify where the engine you see below is going to be run!

This build starts with a new TMeyer Cast Iron 351W block. The blocks are offered with either a 4.000" or 4.125" bore sizing, the latter was selected for this build. The blocks come ready for finish machining. Tim Meyer finish hones the bores and mains, surface mills the deck, and runs a hone through the lifter bores.
The H-beam rod assembly comes TMeyer. The 6.250" rod is 4340 forged steel and comes with ARP 8740 cap screws.



In This Article...
FordMuscle takes you inside a IMCA Modified Small Block Ford 454 build at Tmeyer Inc.

SBF 454W Quick Facts
Application IMCA Grand American Modified Series - Circle Track
Fuel Alcohol
Bore x Stroke x Rod 4.125" x 4.250" x 6.250"
Block TMeyer Cast Iron 351W - Factory 9.500" Deck
Rods TMeyer 6.250" Forged 4340
Crank TMeyer
Forged 4340
351W with Cleveland Main Journals
Heads RHS Cast Iron 215cc Runner and 58cc Chamber
Intake Edelbrock Victor
Carburetor 750 cfm Willy's prepped for alcohol
Cam Ultradyne
Flat Tappet, 639/619 @.050 Lift, 263/267 Duration
Pistons Probe SRS Forged Aluminum Flat Top
Compression 13.7:1

RHS ProAction 215cc
PN 35306-01
Available in iron or aluminum (iron used in this article due to IMCA rules.) These heads are available with 58cc or 64cc combustion chambers, and support up to 8500rpms and .700" lift out of the box. They are the ideal heads for stroked 302 and 351W Ford motors.

20° intake and exhaust valve angles
2.08" int and 1.60" exh values
314 cfm intake flow at .700" lift
202 cfm exhaust flow at .700" lift
Radius exhaust valve seats
Improved valve guide design
Highly efficient water jacket
Manganese intake valve guides
Bronze exhaust valve guides
Hardened valve seats
Extra-thick deck faces

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Probe Sportsman Race Series Piston: SRS 454W PN:14427

Style - SRS Flat Top
Material - 2618-T6 forged aluminum
Bore - 4.125"
Stroke - 4.250"
Rod - 6.250"
Compression Height - 1.115"
Pin - .927" x 2.500"
Valve Relief Volume - 4.5cc

Compression with RHS 35306 58cc Combustion chamber: 13.7:1

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