Heymow - Lawnmower Racing Forum

Engine Help => Briggs Flathead => Topic started by: bikerider on August 07, 2018, 02:04:34 pm

Title: Seeking advice on adding power to Briggs and Stratton engine
Post by: bikerider on August 07, 2018, 02:04:34 pm
Hello all, I have a 6.5hp Briggs and Stratton vertical shaft engine and am wanting to add power to it. I have been researching performance for small engines lately and have a ball park idea of what I'd like to do but would like some feedback from the community here. I would like to remove the governor, billet connecting rod, bigger cam, 18 lb valve springs, remove airbox in favor of a cone intake, larger carb jet, and straight pipe exhaust. My ideal top rpm would be 5500-5800. How does this sound?


Edit: Moderator, if you could please move this to the flathead briggs section I would appreciate it. I posted in this section by mistake. Thanks.
Title: Re: Seeking advice on adding power to Briggs and Stratton engine
Post by: HotRodBriggs on November 11, 2018, 02:17:47 pm
My personal advice would to take the money you were going to spend on that and buy a bigger engine.

If you still want to build that..
Port and polish, relieve the transfer area (shave the eyebrows), stiff 18lb valve springs require a billet flywheel and billet connecting rod, bigger cam, do some head work around the valves, search for some titanium valves if they exist,  new intake manifold, new carburetor I suggest tillotson, large cone filter, straight pipe exhaust,  alternative fuels, adjust timing,. Reduce weight of chassis!

I got a 2hp to rock a minibike from just some porting, shave eyebrows, and reducing overall weight of the chassis and engine.
Title: Re: Seeking advice on adding power to Briggs and Stratton engine
Post by: Leon_Johansson_ on November 11, 2018, 02:43:05 pm
You could get arund 5500 with a removed governor, porting and polishing, and shaving the eyebrows. If you have the time and money you should get a billet rod and flywheel, atv carb, straight pipe exhaust, maybe a cam and upgrade the whole valve train and do some porting and polishing and shave the eyebrows a little, dont go crazy on the eyebrows, only slope up to the top of the cylinder and never polish the intake!