Finding port timing numbers

[ELECT6845]

Stumpy posted a thread a few years back about finding port timing numbers by using a degree wheel and a flashlight. I know you have to use a degree wheel, but I'm questioning is there a better way to find the port numbers? Instead of shining a flash light thru the plug hole and guessing when the ports are opening? The flashlight seems to work good but sometimes is hard to see the exact point at where they open.

Do the stock numbers really matter when porting? If you know where you want your numbers to end up why even bother finding the stock numbers? Why not lay the cylinder out to the numbers and port shape you want and get to grinding.

 

[Deets066]

Interested where this goes, I'm just getting started doin some portin, even though it's just a fad. I would think that if you stock numbers are too far off from what ideal numbers would be then it may not be feasible to achieve those desired numbers? Just a thought though, no expirence behind this

 

[nmurph]

Use a piston to push the ring to the point where you want it (at the top of the port if you want to check existing timing), then run the piston up against the ring and read the wheel. If you need to lay out new timing numbers, put the ring above the piston and use it to push it until your wheel gives you the desired number. Then remove the cylinder and use a Sharpie to mark where the rings sits.

 

[big t double]

opcorn:

 

[Moparmyway]

When cutting the squish and the base, you need the stock numbers so you can determine how much to cut from the base so your intake ends up where you want it, unless you have done enough of these that you have "known" measurement for cutting the base on each individual saw.

 

[ELECT6845]

When cutting the squish and the base, you need the stock numbers so you can determine how much to cut from the base so your intake ends up where you want it, unless you have done enough of these that you have "known" measurement for cutting the base on each individual saw.

Exactly, I was trying to find an easier way and didn't know if anyone has found a better method.

 

[MillerModSaws]

Use a piston to push the ring to the point where you want it (at the top of the port if you want to check existing timing), then run the piston up against the ring and read the wheel. If you need to lay out new timing numbers, put the ring above the piston and use it to push it until your wheel gives you the desired number. Then remove the cylinder and use a Sharpie to mark where the rings sits.

This is how I do it. Usually get my initial numbers with the flashlight trick because I'm going to change them but the ring method works best for me for changing the timing.

 

[Moparmyway]

Exactly, I was trying to find an easier way and didn't know if anyone has found a better method.

You really cant set your intake untill you determine how much the intake is going to drop, and how much of the base you will loose, eithor to the gasket you are eliminating, or to the base you are cutting.

 

[Deets066]

Great stuff!

 

[MillerModSaws]

You can kind of see here where I pushed the ring in and marked with a sharpie to establish my timing.

 

[ryan.frankum.35]

I need a chainsaw

 

[MillerModSaws]

I need a chainsaw

What do u want? Lol.

 

[Sty57]

When cutting the squish and the base, you need the stock numbers so you can determine how much to cut from the base so your intake ends up where you want it, unless you have done enough of these that you have "known" measurement for cutting the base on each individual saw.

How much do you have to take off the base to change the timing 1° ?

Thanks, Brian

 

[Moparmyway]

Depends on the stroke

How much do you have to take off the base to change the timing 1° ?

Thanks, Brian

1 degree is about 0.015"
2 degrees is about 0.030"

 

[drf255]

I'll add that there's no set amount a port will move in degrees based on amount removed.

The relation is not linear, as rod angle and piston speed varies thoughout the length of the stroke.

Ports that are closer to the center of the stroke (ie Upper transfers) will move more degrees than ports that are near the top and bottom (intake floor and exhaust roof).

For instance, I took .040 out of a Husky 262 Squishband and .026 off the base recently. The exhaust roof moved 7 degrees and the upper transfers 15* with the same amount of jug movement.

 

[Sty57]

Ok, one of the things I'm still trying to wrap my head around is.

Are you cutting the base first to get the timing as close as possible and then cutting the squish band?

Or are you doing the squish band first and then cutting the base? Then adjust port timing from where ever it landed.

Thanks, Brian

 

[Rx7man]

I use a thin feeler gauge (.005") to stop the piston at the edge of the port, I find it gives me repeatable numbers while other methods there's too much 'eyeballing'. DRF is right about it not being a linear relationship.. nmurph's way of finding the new timing works well

 

[blsnelling]

Why let intake port timing determine how much you cut the squishband? You're going to be porting it anyway. There's almost always a little lip I want to take off anyway. I would think you would cut the squishband to get the desired compression and go from there. Of course, there are limits to how far you can go, as with all of the mods you're doing to the cylinder.

 

[mdavlee]

Base first for me...

 

[Moparmyway]

Hmnn ............ a deleted post eh ???

Degrees does throw people off, but once you figure out how to use a wheel correctly, its just a matter of going through the motions and checking to be sure.

Like was already said, the length of the stroke and where the measurement is taken determines how far each degree actually is ................ but the wheel reads what the wheel reads no matter what the stroke distance is or where the stroke is being measured