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Author Topic: Compression and exhaust port  (Read 306 times)

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Offline The Ripper

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Compression and exhaust port
« on: September 24, 2014, 09:09:47 pm »
Bought a R16 partner and couldn't resist removing the base gasket and compression jumped from 155 to 176psi, question is this compression jump acceptable for a working saw using 87 octane ?  The gasket was .027,so how will this effect the timing and power outcome when removed?

On the exhaust port there seems to be some  casting flaw that protrudes slightly up from the floor,should this be removed flush with the floor and then slightly radius the bottom edge inward. Also the bore is 44MM so would opening up the E/P to 29MM be acceptable, don't want to push it to the edge. 
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Offline farmboy

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Re: Compression and exhaust port
« Reply #1 on: September 24, 2014, 09:55:51 pm »
You need to check the squish too tight is bad news detonation, etc.  44mm I'd suggest .020 no less than .018 squish.  Rule of thumb on widening ports for work saw is bore x .65 yours is 44mm x .65=28.6 29 should be fine.  The casting on the floor of ex port is anti reversion ridge.  Porters are actually cutting them in on some saws.  I've seen that ridge in Partners, Jonsered, and Husky.  Having said that I'd leave it.  87 is OK.  Most of us run premium non-e (if available) @ 32:1 w/synthetic mix oil.
Shep
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Offline mdavlee .

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Re: Compression and exhaust port
« Reply #2 on: September 24, 2014, 10:08:29 pm »
87 has worked fine with up to 230lbs of compression.
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Offline The Ripper

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Re: Compression and exhaust port
« Reply #3 on: September 25, 2014, 09:14:09 pm »
Double checked the squish and it comes in at .035, Which I prefer as I'm not a big fan of those super tight squishes. As for the  anti ridge,I just worked the corners when widening and didn't touch the middle. Opened the port from 23.5 to 27mm mostly on side as the other side was already  a straight shot. Hope to fire it up this week-end. Thanks for the mix ratio tip.
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