Ported intake heads
#2
All the power in a 4 stroke engine comes from the head and chamber design. Its all a compromise on any engine. What makes for good top end ( rpm ) power doesnt do to much for low end torque . Anyone can take a die grinder and wittle away at a head. Some times good , sometimes bad.
You can make some minor improvements just cleaning up the factory work. Minor imperfections in casting lines in the ports can be cleaned up and the seats can be smothed into the bowl behind the valve. After that its time to talk to the pro and get time on a flow bench. If you start to remove metal just to make the port bigger you will not be happy with the results.
You can make some minor improvements just cleaning up the factory work. Minor imperfections in casting lines in the ports can be cleaned up and the seats can be smothed into the bowl behind the valve. After that its time to talk to the pro and get time on a flow bench. If you start to remove metal just to make the port bigger you will not be happy with the results.
#3
I have to agree with NovaSS, either get someone that knows what they are doing or only clean up casting flaws and match the ports to the gaskets, intake manifold only. I've seen several very good motors turned into junk by, "I thought I knew what I was doing" grinding. And a new head ain't cheap. Besides, without improvements in carburation, exhaust and cam, you will probaly never know the difference. I once took a old V-4 Evinrude outboard and was gonna make it better. After screwing it up till it would barely run. I went out and got some later model parts, mainly an upgraded reed cage and tossed all the ground on parts. Ended up with a 25% increase in fuel economy and no change in top speed or 0 to 35 mph times. Seems the factory knew something I didn't, grinding wasn't where it was at. Then again I had a pro motor guy turn a 100 cid 90 hp @ 5000 rpm engine into a 100 cid 175 hp @ 7400 rpm screamer, all with porting changes.
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1ArmBandit
Polaris Ask an Expert! In fond memory of Old Polaris Tech.
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Oct 14, 2015 09:03 PM
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