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I have looked at several 500 cc Briggs engines that have different hp ratings. the lower rated engines are also lower in price. I am repowering a smaller rider(30") and am wondering just where the extra horsepower comes from,with the same cc displacement. Compression,carb,what?
TIA
Sam

Could be a slight difference in cam lift or timing. Could be different jets in the carb, Could be a few other things. By law to get the different hp ratings they have to change something on the engine.

Thank you. I have the intake and carb still on one of my bad engines that is a 17.5 Intek AVS. I am looking at a 13.5 Intek AVS,both are 500 cc engines. easy to swap the intake+carb. However,13.5hp most likely will be ok on the mower. 17.5 hp may have been overkill. Mower is a Snapper RER 30" cut deck.

Swapping the carb is an invitation for trouble. At the very least you will VOID any warranty on the new engine.

Engine HP is a result of intake port design, valve size, compression ratio, cam timing, ignition timing, and 10 other things. Very little of that is carb. The design and jetting of the carb is in response to all those other engine specs.

Your plan is to bolt a bigger tail onto your Chihuahua and get a German Shepard. It may have worked that way on the family car back in the 1960's, but that's not the way modern engines are designed.

Thank you for that additional information,Born2mow. I actually have the choice of replacing the 11hp on the mower with a 10.5 or a 13.5hp,with the 13.5 actually being a bit less $.

I might add that the 11hp is the original factory engine,,not a '1960's' style hop-up. I agree,this isn't that era any more..

SamB said:

Thank you for that additional information,Born2mow. I actually have the choice of replacing the 11hp on the mower with a 10.5 or a 13.5hp,with the 13.5 actually being a bit less $.

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I ran into the same thing a few years ago were a 13 hp was cheaper than an 8 hp briggs, I shoehorned a 13 HP on a rear engine snapper.

ILENGINE said:

I ran into the same thing a few years ago were a 13 hp was cheaper than an 8 hp briggs, I shoehorned a 13 HP on a rear engine snapper.

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I also have a Snapper 33" Extra Tough RER that I have a 18 hp flathead twin2 on that works quite well. It was originally an 11hp. I had a 17.5hp on it but put it on my Husqvarna zero turn that oem was a 17.5. The AVS weights broke apart on it and trashed the engine on it.. It ain't the '60's anymore,vehicle-wise,but one can still have a bit of fun with things that for the most part are still 'old school'.

SamB said:

It ain't the '60's anymore, vehicle-wise, but one can still have a bit of fun with things that for the most part are still 'old school'.

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It only "looks" old school. These days, because of EPA compliance, the carbs are so leaned out and so closely matched to the engines that swapping major parts around is really a no-no.

You can certainly try it, but I'd take a bunch of cylinder head temp readings before and after for comparison just to be on the safe side.

Born2Mow said:

It only "looks" old school. These days, because of EPA compliance, the carbs are so leaned out and so closely matched to the engines that swapping major parts around is really a no-no.

You can certainly try it, but I'd take a bunch of cylinder head temp readings before and after for comparison just to be on the safe side.

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Nope,totally taking your advice and not going to mess with it at all. Brand new right out of the box will be how the engine will stay. Fiddling with and experimenting with an old engine is one thing, not a brand new ($$) one. I.m heeding your advice and keeping my warranty intact!

SamB said:

I'm heeding your advice and keeping my warranty intact!

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Good.
That way I won't need to send you my rear view mirror dice or my cheery bomb mufflers !!

I don't have any place to hang the fuzzy dice,so I'm ok with that. I always favored Walker Blue Swingers over the Cherry Bombs,as they were just a bit quieter than the CherryBombs.(local cops issue!) Am I dating myself? Here again,using the Old School termimnology! :-D

I have one question and I don't know where to post it. On the 500 cc engines,is anyone familiar with different color governor springs that control the rpm? TIA.