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Chainsaw Porting Theory

Keith Gandy

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Could the Venturi effect be how it overcomes exhaust pressure initially?
I think so. When the charge starts in it is probably acting sorta like a venturi effect and taking a deep breath and creates negative pressure/vaccum at the intake port exit or negative pressure in the combustion chamber . Too much back pressure would damper that venturi effect? After theres a reduction in back pressure and a negative pressure then the full blunt of the case compression will be enough to transfer the charge and blow the exhaust on out? Im seeing getting the exhaust/blowdown and intake out of wack with each other pretty easily? Just a few ideas I have been pondering :couch:
 

jmssaws

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Some epoxy might bring it back J, those are some huge fingers
The lowers are filled and my 66 runs great and has bigger fingers than it.

It ran terrible before fingers, the transfers are to high,I'm going to try some more intake,it's 80

Fingers are at 113 mains 115
 

merc_man

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The lowers are filled and my 66 runs great and has bigger fingers than it.

It ran terrible before fingers, the transfers are to high,I'm going to try some more intake,it's 80

Fingers are at 113 mains 115
what do those fingers do ya cut in.
New to porting Just trying to learn. never seen that before.
 

jmssaws

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what do those fingers do ya cut in.
New to porting Just trying to learn. never seen that before.
Direction mainly but I suppose it will help filling the cylinder with fresh charge.

I've had them work and I've had them do nothing,I probably won't use them anymore.

The last couple I've done had no fingers or bridges and ran great.

I think if they work then your transfers are off a little.
 

Keith Gandy

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Direction mainly but I suppose it will help filling the cylinder with fresh charge.

I've had them work and I've had them do nothing,I probably won't use them anymore.

The last couple I've done had no fingers or bridges and ran great.

I think if they work then your transfers are off a little.
I would think a progressive transfer would achieve the same as a finger?
 

Keith Gandy

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So.... What if you had bridges, fingers, and sloped uppers?
Id probably say lost velocity and very quick to progress backwacks instead of gaining. Ive been thinking lately on 25% of the transfer on the intake side adjusted to desired port # and leave the other close to factory?
 

Keith Gandy

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U may would have an initial purge to that one side with increased velocity then the rest of the transfer opening and pushing charge on in?
 
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