Critique My First Attempt at Porting Please

[Laslabjohn]

Thank you(and everyone else) very much for some helpful constructive points. I will work on those as soon as my ball stone(for bevels) and grinder shaft get here.

Question : I tried to port match the mouth of the exhaust flange to the muffler gasket opening and then hogged out the inside of the flange to match what I took off the flange. Is it necessary to grind the muffler inlet as well ??

Yes it is, if you match the exhaust gasket and not the muffler you are creating a barrier that restricts flow. And hinders everything you have done to the exhaust port.

 

[cedarshark]

Yes it is, if you match the exhaust gasket and not the muffler you are creating a barrier that restricts flow. And hinders everything you have done to the exhaust port.

Good answer....now I have something to work on until the grinder shaft gets here. I can use the dremel.

 

[Red97]

Looks pretty good for a first shot.

Biggest thing is getting a feel for how each cutter removes the material.

I don't do a lot on most intakes. Raise them back up, make sure the piston isn't hanging into it at tdc. The intake on a 350 can be completely square as the ring never gets into the port.
Leave my intakes with a 80 grit finish.

On the widths, I try to stick in the 60-65% range, not a big issue with full skirt pistons, but window pistons can limit your widths.

On the ex I try to keep a stright shot out, most get raised so that means raising the outside too. I like a nice curved roof on the ex port.

Match the gasket, and muffler to the new exhaust outlet size.

I would suggest getting some 1/8 shank split mandrels, and a diamond coated ball assortment for bevel ing 150 grit works well.

I use some 320 by hand to smooth the bevels just a bit.

Like to use the split mandrel to finish shaping/smoothing my exhaust ports. Normally 150 grit.

 

[cedarshark]

Looks pretty good for a first shot.

Biggest thing is getting a feel for how each cutter removes the material.

I don't do a lot on most intakes. Raise them back up, make sure the piston isn't hanging into it at tdc. The intake on a 350 can be completely square as the ring never gets into the port.
Leave my intakes with a 80 grit finish.

On the widths, I try to stick in the 60-65% range, not a big issue with full skirt pistons, but window pistons can limit your widths.

On the ex I try to keep a stright shot out, most get raised so that means raising the outside too. I like a nice curved roof on the ex port.

Match the gasket, and muffler to the new exhaust outlet size.

I would suggest getting some 1/8 shank split mandrels, and a diamond coated ball assortment for bevel ing 150 grit works well.

I use some 320 by hand to smooth the bevels just a bit.

Like to use the split mandrel to finish shaping/smoothing my exhaust ports. Normally 150 grit.

Thanks for the input Joe. I had no idea the rings did not reach the intake port on a 350. I have the 1/8 split mandrels and use them to clean cylinders on occasion.

 

[Red97]

Thanks for the input Joe. I had no idea the rings did not reach the intake port on a 350. I have the 1/8 split mandrels and use them to clean cylinders on occasion.

I love those little mandrels, as I have hundreds of yards of sand paper to use up.

The cartridge rolls are ok, but the cheap ones in the corse grits just like to spin.

While your playing with the 350 it may be helpful if rotate the crank, and watch the piston at various points along the stroke. Try to envision what the air/charge is trying to do inside the jug.

 

[blsnelling]

Is it necessary to grind the muffler inlet as well ??

If it's smaller than the gasket and port, yes.

 

[1Alpha1]

I used to port dirt bikes, but that was long ago. Emphasis was on very smooth and shiny ports.

I don't mess with chainsaws. So I can't say how well you did.

But.....you do take some damn fine pictures.

 

[cedarshark]

I realize there are always more than one way to skin a cat. I interpret Brads input to mean the roof of the intake port needs to be curved with the roof edge beveled to not catch a ring. Joe's post above leads me to believe the 350 piston rings never enter the port. I do not have a 350 partially torn down to rotate the crank to test how far into the intake the piston actually travels. I must be misinterpreting some info from one of you. You both have thrown out some great help to a guy with little to no experience.

 

[cedarshark]

I used to port dirt bikes, but that was long ago. Emphasis was on very smooth and shiny ports.

I don't mess with chainsaws. So I can't say how well you did.

But.....you do take some damn fine pictures.

Thanks,just a point and shoot Canon. I was especially proud of the way I hit enough buttons downloading the pics to make the same pic show up 2 and 3 times.

 

[Red97]

I realize there are always more than one way to skin a cat. I interpret Brads input to mean the roof of the intake port needs to be curved with the roof edge beveled to not catch a ring. Joe's post above leads me to believe the 350 piston rings never enter the port. I do not have a 350 partially torn down to rotate the crank to test how far into the intake the piston actually travels. I must be misinterpreting some info from one of you. You both have thrown out some great help to a guy with little to no experience.

On a 350 the ring does not enter the port on the intake side. The skirt is what controls the intake open/close.

It does cross both sides of the exhaust port. The crown is what dictates port open close.

The crown also is where transfer timing is measured from.

Bevels are important on all the ports. Especially the wider you go.

 

[cedarshark]

On a 350 the ring does not enter the port on the intake side. The skirt is what controls the intake open/close.

It does cross both sides of the exhaust port. The crown is what dictates port open close.

The crown also is where transfer timing is measured from.

Bevels are important on all the ports. Especially the wider you go.

That makes perfect sense. I thought the rings dictated the ports opening and closing. You and Brad are both saying the same thing. Thanks.