Port Timing Calculator Guide

[Martinm210]

I tried and used this calculator with good success, but it's a little tricky to understand.

First here is the calculator:
http://www.modelenginenews.org/design/tcalc/TCalcForm.php

There is a decent explanation on the bottom, but you still have to add up some numbers on the side.

Here is a visual guide I made up to help understand how you figure it out.

Stroke is most easily figured out using the specifications in a service manual, the rest can be easily measured with some calipers. It's probably easier to just measure everything in metric millimeters, down to at least .1mm.

Here are the port maps I made for my old stock 066 and BB 066:

And this was my input and output from the calculator:

Have questions about what's good or bad on port timing? Ask one of the many experts here in the forum, I am clueless and trying to understand that myself.

Anyhow, thought this might be helpful so I spent a few minutes working up the visual guide.

Cheers!:chainsawguy:
Martin

Update: Fixed the missing stroke/2 length...

 

[yo2001]

Thanks. I was trying to figure out how to use that caculator.

 

[nitrousbaby]

nice! thanks for that one

 

[teacherman]

Thanks! I guess a degree wheel is in order, to find these points on a particular saw.

 

[blsnelling]

Interesting that the port timing is early identical on the two cylinders. I'm surprised to see the exhaust that high, especially on the BB kit. I wouldn't expect very high compression but good RPMs.

 

[Friar-Tuck]

Printable degree wheels

This link should lead to several Printable degree wheels.
Size,Print, Cut-Cut, apply to anything from Cardstock to sheet metal.

http://forum.grumpysperformance.com/viewtopic.php?f=50&t=417&sid=76ce4e3445496a9d878a6e9b60010e32

Tuck\o/