ReedRacing33
Member
Anybody know where I can find WKA Limited Flathead rules?
WKA Limited Flathead
- Thread starter ReedRacing33
- Start date
meracer9
Site Supporter
SECTION 14 - Briggs & Stratton Flat Head Limited Modified
14.1 Block; Must be stock Briggs & Stratton 5hp FH (or approved aftermarket) item. Maximum
bore allowed is 2.643” (+.080” over stock.) Must be as produced with no alterations or
reworking except minor grinding for rod clearance permitted. Block may be welded or
repaired as long as no performance enhancement is involved. No bushings of any kind allowed
except bushings approved in this tech manual. DU bearing may be installed location on the
flywheel side. Sleeving of the block with ferrous sleeves is permitted. Repair of coil posts
permitted. Valve guides that meet stock physical dimensions may be replaced, guide material
optional. Must have flywheel shroud but head and cylinder shroud non-tech.
14.1.1 Ports – Porting allowed. Intake Port .880” No-Go, exhaust port 1.005” No-Go. Finish is
non-tech, no addition of material allowed. The block cannot be machined on the intake or
exhaust port gasket surfaces. No grinding is allowed on the underside of the intake
valve seat.
14.1.2 Valves – Stock valves only. Must be one angle and polishing and/or lightening prohibited.
Intake valve maximum diameter is 1.115” and seat angle is 30°. Exhaust valve maximum
diameter is .990” and seat angle to be 45°. Margin on both valves to be .035” minimum
14.1.3 Valve Springs – Valve springs and retainers non-tech.
14.1.4 Valve Seats – Must meet stock specs. One angle only, intake angle is 30° and exhaust
seat angle is 45°. Intake seat I.D. is 1.004” maximum no-go with a minimum/maximum
thickness of .199”/.215”. Exhaust seat I.D. is .880” maximum with a minimum/maximum
thickness of .199”/.215”.
14.2 Side Cover; Must be stock Briggs & Stratton 5hp FH (or approved aftermarket) item. Pin
punching gasket surface and additional breathers allowed.
14.3 Cylinder Head; Stock Briggs & Stratton 5hp cylinder head (or approved aftermarket) only.
Head cannot be machined below flat cylinder portion of the head. Machining of two pockets
for valve clearance or a single continuous relief are from side to side across valve area is
permitted. In no instance may the relief area touch either the back or sidewalls of the head
and should be done in a manner as to not affect airflow. No O rings allowed.
14.4 Crank Shaft; Must be stock Briggs & Stratton 5hp FH (or approved aftermarket) item.
Stroke is 2.437 +/- .010”. Crank to be stock appearing in shape and finish (except minor
grinding for cam clearance.) Heat treating allowed. No polishing allowed. Minimum journal
diameter is .990”
14.5 Camshaft; Cam and lifters non tech. No roller cams allowed.
14.6 Carburetor: Any commercially available butterfly type Tillotson HL series allowed.
Minimum/Maximum venturi = .850”/.900”. Minimum/Maximum throttle bore = .990”/.1.010”.
Metering holes are non tech. Filter cups, adapters and air filters non-tech items. Pulse type
fuel pumps only permitted.
14.6.1 Fuel-Methanol only, no other additives.
14.7 Intake Manifold; aluminum only and must be one piece.
14.8 Ignition System; Stock unaltered Briggs & Stratton coils are required. Spark plug wire and
connector non-tech. Resistance from plug wire to be from 2,000 to 5,000 ohms.
14.9 Flywheel; Approved flywheels only. 4lb 6oz minimum weight. Must be ran as supplied, no
alterations allowed. The following flywheels are approved. ARC #6608, Clements #BAFWL &
#FWSLTD, J.R. Racecar #555-3284 and United Machine and Fabrication #1001.
14.10 Piston; Piston, wrist pin and rings non-tech. Flat top pistons only. Deck height non-tech.
14.11 Connecting Rod; Non-tech, aluminum only. Bolts non-tech.
14.12 Starter; Non-tech, auxiliary or pull starters allowed.
14.13 Miscellaneous Non-Tech Items; Gaskets, fasteners and breathers.
14.1 Block; Must be stock Briggs & Stratton 5hp FH (or approved aftermarket) item. Maximum
bore allowed is 2.643” (+.080” over stock.) Must be as produced with no alterations or
reworking except minor grinding for rod clearance permitted. Block may be welded or
repaired as long as no performance enhancement is involved. No bushings of any kind allowed
except bushings approved in this tech manual. DU bearing may be installed location on the
flywheel side. Sleeving of the block with ferrous sleeves is permitted. Repair of coil posts
permitted. Valve guides that meet stock physical dimensions may be replaced, guide material
optional. Must have flywheel shroud but head and cylinder shroud non-tech.
14.1.1 Ports – Porting allowed. Intake Port .880” No-Go, exhaust port 1.005” No-Go. Finish is
non-tech, no addition of material allowed. The block cannot be machined on the intake or
exhaust port gasket surfaces. No grinding is allowed on the underside of the intake
valve seat.
14.1.2 Valves – Stock valves only. Must be one angle and polishing and/or lightening prohibited.
Intake valve maximum diameter is 1.115” and seat angle is 30°. Exhaust valve maximum
diameter is .990” and seat angle to be 45°. Margin on both valves to be .035” minimum
14.1.3 Valve Springs – Valve springs and retainers non-tech.
14.1.4 Valve Seats – Must meet stock specs. One angle only, intake angle is 30° and exhaust
seat angle is 45°. Intake seat I.D. is 1.004” maximum no-go with a minimum/maximum
thickness of .199”/.215”. Exhaust seat I.D. is .880” maximum with a minimum/maximum
thickness of .199”/.215”.
14.2 Side Cover; Must be stock Briggs & Stratton 5hp FH (or approved aftermarket) item. Pin
punching gasket surface and additional breathers allowed.
14.3 Cylinder Head; Stock Briggs & Stratton 5hp cylinder head (or approved aftermarket) only.
Head cannot be machined below flat cylinder portion of the head. Machining of two pockets
for valve clearance or a single continuous relief are from side to side across valve area is
permitted. In no instance may the relief area touch either the back or sidewalls of the head
and should be done in a manner as to not affect airflow. No O rings allowed.
14.4 Crank Shaft; Must be stock Briggs & Stratton 5hp FH (or approved aftermarket) item.
Stroke is 2.437 +/- .010”. Crank to be stock appearing in shape and finish (except minor
grinding for cam clearance.) Heat treating allowed. No polishing allowed. Minimum journal
diameter is .990”
14.5 Camshaft; Cam and lifters non tech. No roller cams allowed.
14.6 Carburetor: Any commercially available butterfly type Tillotson HL series allowed.
Minimum/Maximum venturi = .850”/.900”. Minimum/Maximum throttle bore = .990”/.1.010”.
Metering holes are non tech. Filter cups, adapters and air filters non-tech items. Pulse type
fuel pumps only permitted.
14.6.1 Fuel-Methanol only, no other additives.
14.7 Intake Manifold; aluminum only and must be one piece.
14.8 Ignition System; Stock unaltered Briggs & Stratton coils are required. Spark plug wire and
connector non-tech. Resistance from plug wire to be from 2,000 to 5,000 ohms.
14.9 Flywheel; Approved flywheels only. 4lb 6oz minimum weight. Must be ran as supplied, no
alterations allowed. The following flywheels are approved. ARC #6608, Clements #BAFWL &
#FWSLTD, J.R. Racecar #555-3284 and United Machine and Fabrication #1001.
14.10 Piston; Piston, wrist pin and rings non-tech. Flat top pistons only. Deck height non-tech.
14.11 Connecting Rod; Non-tech, aluminum only. Bolts non-tech.
14.12 Starter; Non-tech, auxiliary or pull starters allowed.
14.13 Miscellaneous Non-Tech Items; Gaskets, fasteners and breathers.
meracer9
Site Supporter
I found this post from a thread posted on here a few years ago. From my understanding limited flathead rules have been the same since around 2014 per WKA, maybe I'm wrong.
I could always contact WKA for a updated rule book and see!
Jon Brogden
Member
WKA rules allow the 1.060 TB carbs , we built them for limited Modified class for years as they flow a tick more .
stevevaughn31
Member
The venturi is a tech not throttle bore. The head has to be a minimum of .400 in the spark plug area. The ARC billet stick stroke crank is legal also.
Skidude
Member
Are you sure about the bore? I was thinking the max bore was 1.060 and max Venturi .900.
stevevaughn31
Member
Yes. There us no tech on throttle bore. Only .850 minimum and .900 max on venturi