Clam shell porting?

[1990Husky262]

ya way to big to be of any use

 

[paragonbuilder]

Iv already did a mm and that helped it a lot. Might shave a little off fly wheel key now too.
I dont think ther is much i can do for porting it. Kind of a bummer but i learned something new to look for.

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If you can't widen the intake, you can add duration.

 

[merc_man]

If you can't widen the intake, you can add duration.

Im still quite green to this porting. What would that do as a end result?

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[XP_Slinger]

Im still quite green to this porting. What would that do as a end result?

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Gets you a bigger "gulp" of fuel/air mix. I've never only added intake duration but I imagine it would raise your torque a bit. I would offer a number to shoot for but I've never worked on one of those saws. I'm sure someone will give you a target number.

 

[Chainsaw Jim]

There's no need to enlarge the intake any larger than the boot that feeds it. That would be like using a plastic pop bottle with a hole in the bottom of it as a drinking straw.

 

[XP_Slinger]

There's no need to enlarge the intake any larger than the boot that feeds it. That would be like using a plastic pop bottle with a hole in the bottom of it as a drinking straw.

I was talking about increasing intake duration, not enlarging the intake area. That's a hell of a metaphor though...perfect!

 

[Motorhead]

Doesn't matter if you grind the top bottom or sides it still makes the hole bigger.

 

[XP_Slinger]

It does matter. Grinding .020 off the bottom edge gets the intake open sooner as the piston is traveling up, which increases the length (duration) of the intake vacuum pulse. Some guys accomplish this by taking a small amount of material off the piston skirt which is a controversial practice. You can add intake duration without adding hardly any additional area to the port itself by grinding a slight bevel on the bottom edge of the intake port. Deleting the base gasket adds intake duration in the same way. There is a big difference between adding duration and making the entire intake port and passage bigger...in my mind there is anyway.