Critique My First Attempt at Porting Please

[cedarshark]

I am 65 and have read with interest the many threads of people's great reviews of ported saws. As I age, the more I wish better performance from a 50cc saw to make it easier with less weight. The Husky 350 platform seems to be a very good choice. I dug around in the junk pile and came up with a 44mm cylinder that has scoring (that wont come off) above the exhaust port. As I have no experience with porting, I thought it was a likely candidate for a practice first attempt. Many thanks to Brad Snelling, Mattyo and others who graciously contributed to the threads that got me off to a semi-educated start on the basics. As many have stated, its something you have to just get in there and "do" and learn from my mistakes.

Please take a look and let me know your honest thoughts. I did not raise/lower the ports. My intent is not to mess with timing the first try,only let it breath better and increase the compression, probably with a base gasket delete and dump the dished piston. If this attempt (on a trashed cylinder) is "ok", I will try it again on a 45mm 350 that runs well now.

I sincerely appreciate your comments....good and bad

Apologies for duplicate images ...not sure what I did.

My observations:

1) I did not do a good job squaring the edges of the ports. I found this very hard w/ a ball burr.

2) Do you guys port from the outside of the cylinder or do you have to do some from the inside ?

3) I have not beveled the edges of the ports and dont see how I can get to the edges to put a nice bevel(45*) with the Foredom grinder or Dremel. Is it done with a file or something else?

 

[Big Block]

Looks pretty good. Better than what I did on a 555 cylinder. I **** canned that faster than you can say it and I sure wasn't going to share that mess lol. Can you go wider on the exhaust or are you limited by the skirt width?

 

[jmssaws]

Use a saw file and knock the port walls flat.

 

[cedarshark]

Looks pretty good. Better than what I did on a 555 cylinder. I **** canned that faster than you can say it and I sure wasn't going to share that mess lol. Can you go wider on the exhaust or are you limited by the skirt width?

I think I can go wider as it is a non-windowed piston. I just used the exhaust gasket as a guide.

Use a saw file and knock the port walls flat.

OK...Thanks !

 

[alexcagle]

Isn't that bad to have the ring end gaps in an open port?

 

[cedarshark]

Isn't that bad to have the ring end gaps in an open port?

I just stuck the piston in there so I could see if I had a slight arch on the port roof so the rings would "open" gently as the piston traveled past the port.

 

[alexcagle]

Oh. Woops. Sorry.
Wouldn't make much sense to remove the ceiling material off the intake.

 

[jmssaws]

Finish isn't that critical but shape of the port,especially the exhaust roof is very important.

 

[CR888]

Finish isn't that critical but shape of the port,especially the exhaust roof is very important.

Jason, watcha think about the new exhaust port designs on saws like 562xp/ms261-II that have exhaust ports pointing down on a fairly sharp angle. Since Husky started doing this with their layed back cylinder design other OEM's are adopting it too.

 

[jmssaws]

Jason, watcha think about the new exhaust port designs on saws like 562xp/ms261-II that have exhaust ports pointing down on a fairly sharp angle. Since Husky started doing this with their layed back cylinder design other OEM's are adopting it too.

Only cylinder I've done like that is a 056 cylinder on a 1122 chassis, points down bad and can't be helped.
I think it's gotta hurt it some,when it opens it runs straight into the roof and then down.
I'm fixing to port my first 562 and looking forward to it.

 

[rmh3481]

Your best bet is to set your squish first and then work from there.

 

[drf255]

I'd say you did well.

I was worried about that ring pin also, then I realized the jug wasn't mounted.

Square corners aren't necessary and are worse where rings pass by.

Get a diamond ball, use that to bevel.

 

[Chris-PA]

You can do a decent job smoothing port edges with a piece of 220 or 400 grit sandpaper rolled up into a small tube and then flattened. You can pull it back and forth over the port edge, passing it from the cylinder through the port. Also, I don't open the entire port up the way some do, mostly just the the inside up against the piston - unless the port channel seems to be very restrictive. Especially on intakes - compare it to the size of the throttle plate.

 

[cedarshark]

Your best bet is to set your squish first and then work from there.

This was a junk cylinder that is scored through the plating above the exhaust port. Practice only before I try a good cylinder. You are correct, squish should be checked before porting.

 

[cedarshark]

You can do a decent job smoothing port edges with a piece of 220 or 400 grit sandpaper rolled up into a small tube and then flattened. You can pull it back and forth over the port edge, passing it from the cylinder through the port. Also, I don't open the entire port up the way some do, mostly just the the inside up against the piston - unless the port channel seems to be very restrictive. Especially on intakes - compare it to the size of the throttle plate.

Good idea on the sandpaper roll Chris. I did not alter the timing by raising or lowering the floor or ceiling of the ports. I only widened the intake by approx 1/8" on each side of the intake. Your comment about comparing the port size to the carb throttle plate is interesting. Are you saying that the intake will not flow any more than the bore on the carb ?

I left 1/8" of cylinder wall on both sides of the ports for the rings to ride on as the piston travels past the port.

 

[cedarshark]

Warning....a carbide ball burr running at 15000 rpm will wrap up in your "T" shirt and twist the grinder shaft in half. Thank heaven a new shaft for the Foredom is $10.

 

[Chris-PA]

Are you saying that the intake will not flow any more than the bore on the carb ?

Generally in any such passage the most restrictive part will determine the maximum flow, so there isn't much point in making some other part bigger. The portion at the piston edge is different because it is opening and closing like a valve. You want the opening edge of the port to flow as much as soon as possible, so that part benefits from being larger than the overall passage area. When the port is just opening you want the gas to start flowing ASAP, so it should uncover area quickly as it opens.

Warning....a carbide ball burr running at 15000 rpm will wrap up in your "T" shirt and twist the grinder shaft in half. Thank heaven a new shaft for the Foredom is $10.

Topless porting?

 

[blsnelling]

Looks pretty good overall. Simply widening the ports will make a significant difference.

How wide should you go? On a smaller saw like this, I make both the intake and exhaust 70% the width of the bore. Of course, always watch out for skirt edges and ring ends.

Port shapes are critical. That includes squaring up the corners. You want the port to flow as much as possible, as early as possible. There's a careful balance, but the more curved the exhaust port roof is curved, the less it will flow. However, it can't be flat or you risk catching a ring.

I rarely widen the boot end of the intake or the exhaust flange of the exhaust port. The exhaust port is already larger there than at the cylinder wall. I see some people hog it out but I don't see the benefit.

Make your port walls as flat as possible. When I was new at it, I actually used a round file. As you get more experience, you will be able to eye ball it.

Use a round stone of some kind to bevel your ports. The center of the port is most critical. The sides need nothing more than the burr knocked off. Finish up with wet/dry sand paper by hand.

The most notable "flaw" I see are the "divots" on each side of the exhaust port floor. I know from experience how EASY that is to do. Keep in mind, the floor needs to have a concave shape, as the rings pass over it just like the roof. If you have enough piston skirt to work with, I would re-shape that port floor.

I would raise and square up the corners of the exhaust port. Just don't go too far. It's important to keep some radius to the roof, but you have quite a bit more than you need. Just make sure to give it a decent bevel.

I would also square up the corners of the roof of the intake port. Remember, the rings do not travel across this port. Square corners equals more flow, even without changing port timing. You're adding area.

 

[cedarshark]

Generally in any such passage the most restrictive part will determine the maximum flow, so there isn't much point in making some other part bigger. The portion at the piston edge is different because it is opening and closing like a valve. You want the opening edge of the port to flow as much as soon as possible, so that part benefits from being larger than the overall passage area. When the port is just opening you want the gas to start flowing ASAP, so it should uncover area quickly as it opens.

Topless porting?

Had the tee shirt not been there...I would have vented my chest. I need better light(LEDs over my shoulder) and a better way to hold the cylinder.

 

[cedarshark]

Looks pretty good overall. Simply widening the ports will make a significant difference.

How wide should you go? On a smaller saw like this, I make both the intake and exhaust 70% the width of the bore. Of course, always watch out for skirt edges and ring ends.

Port shapes are critical. That includes squaring up the corners. You want the port to flow as much as possible, as early as possible. There's a careful balance, but the more curved the exhaust port roof is curved, the less it will flow. However, it can't be flat or you risk catching a ring.

I rarely widen the boot end of the intake or the exhaust flange of the exhaust port. The exhaust port is already larger there than at the cylinder wall. I see some people hog it out but I don't see the benefit.

Make your port walls as flat as possible. When I was new at it, I actually used a round file. As you get more experience, you will be able to eye ball it.

Use a round stone of some kind to bevel your ports. The center of the port is most critical. The sides need nothing more than the burr knocked off. Finish up with wet/dry sand paper by hand.

The most notable "flaw" I see are the "divots" on each side of the exhaust port floor. I know from experience how EASY that is to do. Keep in mind, the floor needs to have a concave shape, as the rings pass over it just like the roof. If you have enough piston skirt to work with, I would re-shape that port floor.

I would raise and square up the corners of the exhaust port. Just don't go too far. It's important to keep some radius to the roof, but you have quite a bit more than you need. Just make sure to give it a decent bevel.

I would also square up the corners of the roof of the intake port. Remember, the rings do not travel across this port. Square corners equals more flow, even without changing port timing. You're adding area.

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 ??