port question

[red ghost]

I'm in the middle of working on my port timings.

150 iron-bored to 175,60/110 crank

My current exhaust port is quite standard at 156 deg, now to achieve 160-168, is there a rough guide (or rule of thumb) on how much stock to remove from the top of the exhaust port to achieve to my goal.

cheers

[Rich_T]

yes, you could make a smaller calculation rather than the entire port timing calculation. However this would be negating the influence of rod length which typically is only in the region of 0.1-0.2mm-ish. The calculation is easy to understand but you will still need a calculator with COS SIN function. But you have to ask yourself if you went to this length why not do it properly.

Alternately you could sketch it twice scale on paper and divide that resuly by 2, all you need then is a protractor, ruler and good compas.

[red ghost]

Sir, I really appreciate your responce, but I'm really just looking for a 'less scientific' way, like an 'old hand' method.

[Stampede]

try & error?

remove in small steps and measure again.... if you dont want to calculate...

[Ian Hepworth]

How have you measured 156? Use the same method to mark where you want to be and away you go.

[tarmac tickler]

why are you blinding the man with science?? have a play on here Red


http://www.lambretta-images.com/forumbb/porttiming.php

[carlos fandango]

calculators use a timing disk old skool if you havnt got one i could email you one on pdf. that i did for myself. print it off and glue it to some hardboard or cardboard pm me your email if you want it
Russ

[guygrrr]

yeah, what ian said.
i use a degree wheel, a magic marker, and a scribe. i marker up the bore above the port, set the piston (sans rings) to the desired height/degree, and lightly scribe a line from the head of the piston to bore in the marker. and voila! oh yeah, and use what ever base gasket you're planning on using and torque the cylinder down. i use sockets as spacers on the cylinder studs and it works just fine.
then i cut.

[red ghost]

How have you measured 156?

Hi Ian,
page 41 of the Scooter Centre catalogue and marking it out is blindingly obvious.

cheers mate

[Ian Hepworth]

How have you measured 156?

Hi Ian,
page 41 of the Scooter Centre catalogue and marking it out is blindingly obvious.

cheers mate

I think you shouldn't believe everything written down, Im sure Philipp of SCK will admit a lot of that information is incorrect.

Most of the MB information printed is different to information kept on records by us. Its blindingly obvious EVERY engine casing has a different base height. Rods, cranks, gaskets, cylinders and pistons all vary in size.
This is why, if you want perfect port timings ALWAYS do it individually yourself on your engine and do it with a real timing disc!

Don't trust port timing calculations and theories these are only guides!