QuestionQUESTION: I need to change a 5hp B&S engine into an 11hp or 12hp engine. Can you tell me how this is done?
ANSWER: Alcohal and about $500. Bore cylinder, advance timing, stroked rod, lower compression ratio.
If you are building a race engine you will need racing parts to get that kind of HP out of a 13 cubic inch block.
If you are replacing a 5hp engine will a larger engine you will have to relocate engine mounting bolts as the engine base plate footprints are different.
What exactly are you trying to accomplish or build?
Eric
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QUESTION: i want to up the horse power on a 5 horse briggs for use on a gocart
AnswerAbout the only way to tell really noticable HP is to really deck out the engine. Of course this costs some bucks buying all the race goodies.
A cheaper start you might want to try is replacing the head gasket with a thinner race type to increase compression, adding a header and purching a race carb that has been flow tested with mods plus an after-market high flow air filter. This might gain noticable increased HP. The most accurate way to see the HP gain is with a dynometer usually only found in high end race machine shops.
Porting, polishing, stroking, boring, angled valves all take machine tools to perform. If you really want to make power visit this site:
http://www.hscsupercharger.com/
This is supposed to be a decent header:
http://www.eautoworks.com/product-Hooker-Headers-226169.htm
Many of the parts from the Briggs Raptor engine can be bolted on to your engine.
http://www.briggsracing.com/racing_engines/raptor/
It may be cheaper to just buy a higher HP engine but of course it is not near as much fun as building it yourself.
Eric
