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port and polish

2797 Views 5 Replies 4 Participants Last post by  wreckedGT
in about a week i will be cleaning the the intake manifold. Im thinking of porting and polishing it or is it just a waste of time and money?
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Unless you know what you are doing I would skip the P&P. Do you have flow bench, and how much additional flow and subsequent hp do you think can acheive with a P&P?

I'm into vintage 2-stroke street bikes and a typical way increase hp here is to port cylinders and match port intakes and carburators and some will go so far as to polish their intakes and exhaust ports. Actual dyno testing in these applictions indicates that the best bang for the buck is port matching the carbs to the intakes and exhaust to the muffler flange. Polishing, while looking and sounding cool had no appraciable performance enhancement. All that being said I have never been inside an Ody motor nor do I plan to be.

All motors are in essene a large air pump. IMO you would need to improve the entire air delivery and exhaust circuits to see any appreciable performance improvements. But let us know how you fair if you break out the die grinder and polishing wheels.
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i guess ill just be cleaning it with lots of brake cleaners then. lol:)
This would be such a waste of money.

BTW what motor are we talking about here?
If you already have everything apart and can get it done cheap, go ahead. It won't hurt anything. also port matching on intake is not neccisary it is better to have a step (the manifold side slightly smaller.
When air moves through the manifold towards the valve and the valve slams shut the air compresses and pushes back up towards the manifold just a bit before the valve opens again and the piston pulls the air back into the cylendar. The small step causes some resistance to this backflow making giving a better fluid dynamic to the overall airflow. It may seem insignificant, but that tiny difference multiplied by 1000s of RPMs over however long you drive adds up. a more efficient engine is ALWAYS better weather you are going for power gains, or MPG gains.
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