Small Engines (Lawn Mowers, etc.): 16hp twin cylinder briggs exhaust, twin cylinder engine, recoil starters

Question
Hi.. i have an old sears lawn tractor.. with a Briggs vertical shaft 16hp opposed twin cylinder engine.. i was thinking of taking the muffler off.. and using pipes and making dual exhaust stacks, with no muffler. and wanted know if doing this is going to wreck the engine.. will having no muffler ruin the engine? or will it be fine. it will be louder and maybe run faster.. but i will control the speed of the engine. i just want to know if and engine with no muffler is going to expire faster or last just as long..?
thanks
i also have a areins lawn tractor with a Briggs 10-12hp engine that has a leaky crank case gasket and bad carb and bad ignition system.. the model no. are
model: 252707
Type: 0186-01
Code: 80121117 or 1111. i cant read the last no.
but i want to know if you can find a replacement engine or someone who sells ones.. WITHOUT electric starter motors, just a pull start..
if not.. i just need a new engine..
thanks
with respect Matthew

Answer
How long do you plan to make the exhaust pipes?  Too short of pipes may not provide enough back pressure and you run the risk of burning the exhaust valves.  This is not a big problem for racing applications as they plan on replacing valves often anyway.  The older 16hp engines tend to wear out sooner than the 14 or 18hp versions.  This is because the 16hp engines are actuall 14hp blocks with increased engine speed.  What are you planning on using the engine for?

As for the second question, those crankcase gaskets are prone to leaking because the front oil pan/sump bolts tend to loosen, just a little, causing the gasket to fail.  Briggs fixed this problem by adding lock washers and loc-tite to the bolt threads are later engines.

If you are really looking for a pull start version I'd look for old Snapper rear engine riders.  You can find 8-12hp engine with recoil starters.  To convert an electric start engine you would need a recoil starter, starter clutch and an adapter post for the crankshaft or a new crank.  I've seen adapter posts but they are difficult to find these days...don't beleive Briggs even still makes them.  It would be easier to buy a new engine or track down an old Snapper engine.

Let me know if this helps.
Eric