I won't be touching them again until Monday.
A Tale of Three Saws
- Thread starter blsnelling
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I won't be touching them again until Monday.
I don't anticipate any more videos until both the 660 and 390 are both ported.
parrisw
Tree Freak
What do you normally do for setting squish? Just remove the gasket?
I make a gasket out of what ever gasket thickness is needed to get the squish I want.
parrisw
Tree Freak
I see. Makes sense. I just like doing pop-up's, well, because I can I guess.
parrisw
Tree Freak
No need to show off...
ha ha. sorry! you know your pistons and cylinders are welcome here anytime! Even you too!
Not to take over this thread or anything, but from my limited experience and from limited testing, it's my opinion pop-up's give you very little if anything in a normal woods ported saw. Tightening things up by removing the base gasket or turning down the base is the way to go for a normal woods saw IMHO. I've also noticed some saws seem to like more compression than others. Take this for what it is, as I'm no engineer.
Andre.
Andre.
AUSSIE1
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Not to take over this thread or anything, but from my limited experience and from limited testing, it's my opinion pop-up's give you very little if anything in a normal woods ported saw. Tightening things up by removing the base gasket or turning down the base is the way to go for a normal woods saw IMHO. I've also noticed some saws seem to like more compression than others. Take this for what it is, as I'm no engineer.
Andre.
Just that some need both popup and base turned, the 385/390 being a couple of them.
Just that some need both popup and base turned, the 385/390 being a couple of them.
That's exactly what I was referring to.
I've only seen small gains if any on most saws. A race saw is a different story. Theoretically more compression will give you more power, however you often have limitations with crown and base thickness. Most pop-up's with the limitations will only net 10 to 20 pounds of added compression, not really enough to make a difference, and not worth the effort IMHO.
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AUSSIE1
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That's exactly what I was referring to.
I've only seen small gains if any on most saws. A race saw is a different story. Theoretically more compression will give you more power, however you often have limitations with crown and base thickness. Most pop-up's with the limitations will only net 10 to 20 pounds of added compression, not really enough to make a difference, and not worth the effort IMHO.
Yep, admittedly I couldn't say I could feel a 10-20psi increase but my thinking has been that a combination of some minor improvements may add up.
35-45psi to my 385 would be a welcome increase though.
Yep, admittedly I couldn't say I could feel a 10-20psi increase but my thinking has been that a combination of some minor improvements may add up.
35-45psi to my 385 would be a welcome increase though.
I completely understand where you're coming from, I was there not so long ago myself.
However after some recent testing, in my opinion a pop-up in a good woods ported saw, for the most part gives you nothing. It actually may be somewhat detrimental in the long run. IMHOYup 34-45psi would be worth the effort. The 7900 in this thread has a significant pop-up and the compression jumped up pretty good, and it definitely added some power. However Brad and Nik did pushed the limits of what could be done with the machining.
Andre.
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MCW
Somebody's talking crap here & it ain't the tree!
I'd like to see the stock compressions on both the 390 and 660 if possible Brad, just out of interest
arborjockey
ArboristSite Guru
Getting more compression is only one part of the puzzle while building any small engine. Getting your charge in and out is #1. Porting is a fine art. The power go's up and go's up as you port a little more and a little more then it falls flat on its face. Same with intake etc. Some so called modified motors when set up against stock have less power. :monkey:no joke.raising compression is a miner gain. Although the compression go's up from a thinner base gasket you have now lowered your ports. so theirs now porting involved and more work. The B.M.E.P is high on saws but i prefer slight exhaust porting and they run forever.I completely understand where you're coming from, I was there not so long ago myself.
Yup 34-45psi would be worth the effort. The 7900 in this thread has a significant pop-up and the compression jumped up pretty good, and it definitely added some power. However Brad and Nik did pushed the limits of what could be done with the machining.
Andre.
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MCW
Somebody's talking crap here & it ain't the tree!
Getting more compression is only one part of the puzzle while building any small engine. Getting your charge in and out is #1. Porting is a fine art. The power go's up and go's up as you port a little more and a little more then it falls flat on its face. Same with intake etc. Some so called modified motors when set up against stock have less power. :monkey:no joke.raising compression is a miner gain. Although the compression go's up from a thinner base gasket you have now lowered your ports. so theirs now porting involved and more work. The B.M.E.P is high on saws but i prefer slight exhaust porting and they run forever.
You're right. I dropped the base gasket out of one of my modded 7900's and the cold compression went from 180psi to just over 200psi. The throttle response and power in the cut was instantly noticeable. Completely different saw now.
flushcut
Addicted to ArboristSite
opcorn:opcorn:
little possum
Crash and Burn
That there isnt JTs work, but that saw is strong too :monkey:
He did do the 5100 though.
Anywhos, Brad, are ya done yet???
