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flat head briggs carb swap 8 to 11hp?

1507 Views 2 Replies 2 Participants Last post by  NDwrench
I am re-powering a mower that has an 8hp briggs with an 11hp industrial, the 11hp has been sitting for a long time and the carb is very crusty, so I was wondering if I can use the carb from the 8 hp?
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If it bolts up and the linkage fits, you can use it. You might find that you have less than the 11hp that you expect. Compare the venturi diameter or throttle plate diameter as that would be the limiting factor. The 8 might have a smaller diameter, and thus when installed on the 11, it will not flow the same amount of fuel mix as orginal.
Most mowers do not work with the throttle plate wide open all the time, so the carbs are designed around that fact, giving good mix in the 'middle ground' with partial throttle, but may have the mix 'off' a bit when full throttle is called for.
I *think* you might not develop the full hp of the 11. But it should work. It's kind of like having a 4 barrel or a 2 barrel carb, either can be put on a small block, or a large block, but one will develop more hp & torque than the other. They used to install 2bbl carbs on large engines for economy. Get the large block torque for acceleration in traffic, with good throttle response and control of a small venturi 2 bbl. The 4 kicked in at full throttle, but the fuel was generally not well controlled. More like dumped.
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