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  3. Briggs Model 31/33 AVS
OE and Aftermarket Stock and Performance Parts for the Briggs Model 28/31 OHV AVS Engine. We commonly find these as race engines for C/P and G/P Racing Mowers. We have led the way for performance parts and have advanced mower racing to new levels of speed and competition. Not sure if you have a Non-AVS and AVS Block? Major difference between Model 31 Non-AVS & 31 AVS is the dipstick is in the block on the AVS and in the pan on the Non-AVS. Non-AVS engines with small journal crank on pan side measures 1.380” uses fywheel 6611-28. AVS flywheels with large journal crank on pan side measures 1.625” uses 6611-AVS. It’s critical to check your ignition time correctly