Porting question

[xspike77x]

Ok, so from everything I have read on porting these OHV engines the focus on the intake side is definitely on smoothing the corner short side radius and then grinding down the valve guide that is protruding into the intake. Then smooth things out, but not too much so as to still allow the fuel to atomize on its way in. Smooth down the edge around the valve seat so that the seat blends smoothly into the bowl for both the intake and exhaust, and then smooth out to a mirror finish the exhaust port. Now after starting to attempt this for the first time I finally see what people mean when they say short side radius (without pointing it out the explanation does not provide much to the average individual. Now, I logically can understand why the work on the short side radius is beneficial for flow in that is allows for an easier and smoother path of travel for the air/fuel mix on its way in without a sharp corner or obstruction of the valve guide. However, what I don't understand is, if this makes sense for improving flow on the way in (intake), why would it not also make sense for the exhaust gases on their way out? Why would you not also want to smooth out the short side radius on the way out? Is it what way the gases enter/travel down the ports?

[minidragbike]

I have givin out a ton of porting advice over the years. But what I notice is that many get the head ported, but are running the incorrect parts with the head work.

So let me ask you this:

How much power are you trying to make?
What parts are you using?

BTW the short side is gone on both of my ports, not just the intake.

[boogyman]

Originally Posted by minidragbike

I have givin out a ton of porting advice over the years. But what I notice is that many get the head ported, but are running the incorrect parts with the head work.

So let me ask you this:

How much power are you trying to make?
What parts are you using?

BTW the short side is gone on both of my ports, not just the intake.

Yep,that how we do it

[xspike77x]

I have a billet rod and flywheel, AGK intake with a PZ22 carb and open header, no governor and aftermarket springs of course. Oh 6* advance too. Nothing major. Just looking for 8-10, thought I would do light port work just to help things flow a bit better. Am I incorrect to do so?

[ccarruth]

Not at all. With the mods you have you will benefit from a mild port job. Porting is one of those "less can be more" mods. Not saying that you will or have done this but most first time porters just cut everything they can. The one thing that I stress the most to new guys wanting to do it themselves is that port shape is more important than port volume. Find the smallest point of the intake or exhaust runner and measure it. There is no need for any point beyond that to be larger in diameter because it's limited to volume the smallest point can flow. Think of a mandrel bent exhaust tube, That is the best way I can describe it. You don't want the volume of the runner changing from large to small over and over, it will only hurt the flow. Be careful and take your time and you'll be fine. Good luck and don't forget the pics.

[minidragbike]

Originally Posted by ccarruth

Not at all. With the mods you have you will benefit from a mild port job. Porting is one of those "less can be more" mods. Not saying that you will or have done this but most first time porters just cut everything they can. The one thing that I stress the most to new guys wanting to do it themselves is that port shape is more important than port volume. Find the smallest point of the intake or exhaust runner and measure it. There is no need for any point beyond that to be larger in diameter because it's limited to volume the smallest point can flow. Think of a mandrel bent exhaust tube, That is the best way I can describe it. You don't want the volume of the runner changing from large to small over and over, it will only hurt the flow. Be careful and take your time and you'll be fine. Good luck and don't forget the pics.

All good info, no need to go all out until your ready for it.