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Can anyone tell me what Horsepower this engine is? It is on a used mower that my son-in-law has on a Craftsman lawn tractor. The tractor says it has a 20.0 HP, but the cowling on top of engine says it is a 17.5HP. I suspect the engine was worked on in a shop and somone may have put the wrong cowling on the engine but maybe they just replaced the engine altogether. I am having to replace the camshaft because the compression release was not working. I have a question for the timing also. I know to line up the divets on the cam and crank, but what position should the crankshaft be. You could actually have the timing 180 degrees out.

The stickers on the cowl are pretty meaningless, as is the engine numbers stamped into the rocker housings when you are looking at a used engine.
The cowls interchange between a massive number different engine capacities and the rocker covers interchange between all inteks, even the twins .

reelton said:

Can anyone tell me what Horsepower this engine is? It is on a used mower that my son-in-law has on a Craftsman lawn tractor. The tractor says it has a 20.0 HP, but the cowling on top of engine says it is a 17.5HP. I suspect the engine was worked on in a shop and somone may have put the wrong cowling on the engine but maybe they just replaced the engine altogether. I am having to replace the camshaft because the compression release was not working. I have a question for the timing also. I know to line up the divets on the cam and crank, but what position should the crankshaft be. You could actually have the timing 180 degrees out.

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Impossible to get the timing 180 degrees out of time on a single cylinder Briggs as long as the timing marks are aligned. First the crankshaft to camshaft turns ratio is 2 to 1. Second these engines uses wasted spark so for every full turn of the crankshaft there is a spark. All you got to do is align to two timing marks.

Also the 310000, and 330000 series all use the same camshaft.

As for HP 310000 series can be labeled anywhere from 15.5 hp to 19.5 hp depending the the actual configuration. Also with Craftsman they like to put different hp labels on different mowers with the same exact engine. I once had three Craftsman is the shop at the same with the old opposed engine (I mean the same model and type numbers) one mower was labelled 18.5 hp the next was labelled 19.5 hp and the last one was labelled 20.5 hp. This why there was a class action lawsuit over the engine HP ratings and now we mostly torque ratings. Even the HP rating system was change from the engine having to with in around 80% of the labelled gross HP to 95% of the labelled gross hp rating so we can see engine that once rated for 20 hp being rated at a low HP and same be the same engine.

But answer your question Briggs has the 31C707-1346-B1 rated at 17.5 gross hp per Briggs Power Portal..

I forgot to ask about the valve adjustment. I understand it is critical for the compression release.
Thanks, Star Tech, Bertsmobile1, & Mechanic Mark.

IN .003"-.005"
EX .005"-.008"

So I have a 46hp Briggs I/C on my Snapper RER. Good to know. Joke

I've noticed the engine hp rating deal too. Check bore and stroke, identical as Star Tech said. Cam, same part numbers. Compression, Briggs engines are normally all 8:1. Hmmmm.

slomo

Thanks Star Tech & Stomo