OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Two types of 3hp Briggs ?

Our most valuable (and friendly) decal supplier "silenmessor" was selling the 3hp decal reproduction as a 127cc. (pics attached) So I asked him to check if this was an error as my 3hp Scotty Hawk Rotary said 148cc. To confuse further I have attached another pic of a 3.5 hp that is 148cc. Can the ODK Masters let us know if this is normal to have Briggs make different capacity engines with the same horse power? Many thanks. Chris.

Just read the Model Number on the engine. The first digit, or first two digits if it is one of the larger engines, are the engine capacity in cubic inches. One cubic inch is about 16.4 cubic centimetres. So the answer to the question is, if the Model number begins with 8, the engine is about 130 cc. If the Model number begins with 9, the engine is about 148 cc. Note that Briggs round the number to the nearest cubic inch, so the 8 cubic inch engines may well be 127 cc. I think from memory some of the Briggs 80000 series engines were 3 hp, while others were 2.5 and I know that some of the 90000 series engines were 3 hp. Most of the 90000 vertical engines were originally 3.5 hp, then were de-rated to 3 hp when they reduced the governed speed to 3,000 rpm instead of 3,600 for safety reasons in about 1980.

Yes, Briggs did overlap the horsepower versus engine size ranges. In particular, there were horizontal 60000 series engines with the same power as some 80000 series engines. As far as I can interpret what they did, Briggs took the view that in those days fuel was cheap, so supplying the customer with a bigger engine than he or she strictly needed was no bad thing. Remember that Briggs used a great deal of poetic licence in their advertised horsepower anyway, in those days. They probably didn't actually lie, but they used (and still use) a "Gross Power" test for rating purposes. Gross power allows them to test without the air cleaner and muffler, and with "optimised" ignition timing and air fuel ratio, rather than the timing and mixture the production engines have. I think they are allowed to leave off the fan and cowl, as well, thus avoiding accounting for the power absorbed by the fan. The omission of the muffler, and using probably about 30 degrees of ignition advance instead of about 6 degrees, makes a profound difference to measured power. (The fan's power requirement is no small matter either, on air cooled engines. Back in those days the VW Beetle engine was rated under an (American) SAE test procedure instead of the (German) DIN one, seemingly just because the SAE test was run without the cooling fan, and the DIN test with the fan. The fan absorbed several horsepower, at a time when the car's advertised gross power was only 36 hp.)

Just a few years ago Briggs and other manufacturers settled a highly publicised lawsuit on that subject and then largely stopped advertising horsepower at all, to keep from having further problems.