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Pros & Cons??

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I'm thinking of having my 13hp rebored, probably .30 over, polish the intake and the exhaust. What are the pros and cons on having this done? I already have the motor tore done. One of the guys I work with said reboring is only $10.00. The major cost would be new piston and rings. Thanks for your thoughts. Jeff

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I just got the engine for my Dads 3314H back from the machine shop. It was already bored .30 over so they sleeved it back to standard bore. New piston and rings New conecting rod and wrist pin New valves ground and seated New crankshaft bearings Gasket set New crankcase breather Carberator rebuild kit Air filter Parts and labor added up to about $500, sounds high but IMO well worth it.

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Jeff, You will gain some horsepower by porting and polishing but I do not think you will notice much for the time required. The exhaust can be pollished to a mirror finish. The intake should not be cleaned up more than the grit of 320 sand paper. If it is to smothe the fuel will form droplets and the will stick to the intake walls. This will cause a loss of performance. If it was my motor I would make sure that the gaskets match the intake and the block. This is just my two cents. For tools and some info on porting try http://ccspecialtytool.com/

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I agree that polishing the ports is a waste of time. Polishing is all about flow at high volume and thats just not the case unless your putting big bucks into a pulling tractor. Some of the old school mechanics would even go so far as to say that smaller/rougher intake runners improve low end torque/horsepower because to get 35 CI's of fuel/air through a half inch bore in .3 seconds at 800 rpms it has to move at roughly twice the speed it would to get through say an 11/16th bore. So the mix in the combustion chamber is better, As said before there is less time for droplets to form out of the atomized fuel etc etc. Sorry if this was more than you were looking for. Good luck on your re-build..

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