Carbtard

[huskihl]

No sir. It's just a calculator to help me land where my fruity ass THINKS it'll run good. The calculator is so I don't have to do this formula:
View attachment 397977
Because I'm embarrassed to admit, I can't do that formula. I never got that far in math. I simply couldn't do math. I left high school my junior year bacause I simply could not learn algebra and beyond. I acquired my good enough diploma with a Casio calculator. And I assure you no formula like that was on the test.

I used to know how. But I just don’t see it helping now.

 

[NateSaw]

I used to know how. But I just don’t see it helping now.

I'd like to be where you are. The math is less than fun. I'm trying hard not to waste a jug. Perhaps that's the REAL motivation behind my slow approaches. And also the uppers

 

[Ketchup]

I currently have 26* of blowdown. I took 16thou off base to get to 102*,but that's minus gasket. One of the reasons I don't want to raise the exh Is free porting. Using the calculator, I can see piston pin position @ 2.007" for 102* exh, and if I were to lower jug to achieve 78* intake. Seeing that crossover concerned me. That's when the bulb went off in my head as I noticed the tab on the skirt, intake side. In my mind it appears to be close to Freeport already.

The only serious freeporting you need to worry about is if you WIDEN the exhaust or intake beyond the skirt. That’s game over.

There is also freeporting at the skirt. If you drop the jug too far the floor of the exhaust will be too low when the piston is near TDC. Then the piston skirt will be above the exhaust floor and the case will be open on the exhaust side. If it’s only open for a few degrees it doesn’t make much difference but it’s best avoided.

On the intake side, just leave the roof alone and you should never see a ring pin. Your machine work lowers the intake port.

Keep the exhaust low on a 362 to gain torque. Shorten blowdown (raise transfer uppers) to maintain/gain rpm.

It doesn’t matter whether you start your porting strategy from cutting the base or cutting the squish. You’re still limited by how low you want to take the ports. If you started with the base cut, stick with that. Your band cut will end up being in the range @huskihl and @farminkarman said. Remember that you deleted the gasket. That gasket thickness is added to your base cut for the total amount you dropped the ports.

I don’t think your math was wrong. Most 60cc saws will have a 0.040-0.080” base cut. Your calculations are on the high end but you’re trying to buy a much lower exhaust, which takes a deeper cut.

In any case, don’t determine your machining based on intake. You can grind or epoxy the intake to get wherever you want. It’s common to leave the intake where it lands after machining. Widen first if you think it needs more.

You do you, but I recommend you stop looking at the software. Port some saws using basic principles. The simple stuff is still what makes power for me. Find exhaust and transfer numbers that feel strong. Focus on smooth flow and good grinding. Tweak the other stuff as the nuances become apparent.

Sorry. That got long.

 

[Dolkitafreak]

Give rod length, squish, and piston height on intake side and measurements from squish band to top of port (bottom for intake) and it can be calculated very precisely. If you have Rod length I can calculate how much the ex with drop with x amount of cut.

 

[NateSaw]

The only serious freeporting you need to worry about is if you WIDEN the exhaust or intake beyond the skirt. That’s game over.

There is also freeporting at the skirt. If you drop the jug too far the floor of the exhaust will be too low when the piston is near TDC. Then the piston skirt will be above the exhaust floor and the case will be open on the exhaust side. If it’s only open for a few degrees it doesn’t make much difference but it’s best avoided.

On the intake side, just leave the roof alone and you should never see a ring pin. Your machine work lowers the intake port.

Keep the exhaust low on a 362 to gain torque. Shorten blowdown (raise transfer uppers) to maintain/gain rpm.

It doesn’t matter whether you start your porting strategy from cutting the base or cutting the squish. You’re still limited by how low you want to take the ports. If you started with the base cut, stick with that. Your band cut will end up being in the range @huskihl and @farminkarman said. Remember that you deleted the gasket. That gasket thickness is added to your base cut for the total amount you dropped the ports.

I don’t think your math was wrong. Most 60cc saws will have a 0.040-0.080” base cut. Your calculations are on the high end but you’re trying to buy a much lower exhaust, which takes a deeper cut.

In any case, don’t determine your machining based on intake. You can grind or epoxy the intake to get wherever you want. It’s common to leave the intake where it lands after machining. Widen first if you think it needs more.

You do you, but I recommend you stop looking at the software. Port some saws using basic principles. The simple stuff is still what makes power for me. Find exhaust and transfer numbers that feel strong. Focus on smooth flow and good grinding. Tweak the other stuff as the nuances become apparent.

Sorry. That got long.

Don't apologize Caleb. I love it man. I'm on this forum because of the flow of consciousness. And of course because I need help with muh maths. The skirt thing is easy for me. That's a visually physical confine that I can stay within. I'm about to try my hand at a 660 w/ 288 piston, just for the sake of going outside the confines of the stock piston by a smidge. Also, I shouldn't have called it software. It's only a calculator. That's it. It's not going to tell me anything about anything other than help me with the piston dwell factor. I'm aware i could use the ring method to roughly calculate the difference in measurable height between say 100* and 103* atdc. I was using the calculator to be accurate in dwell. As you all pointed out to me early on, intake typically rides near the middle of the piston stroke, where the dwell is at its peak speed. That's why so much meat has to be added or removed to effect a degree change on the wheel, as where less with the exh as its closer to the slow side of the dwell This is the only reason I use the calculator. @farminkarman shared his recipe, so I started crunching those numbers based on piston position, to see where things land in relationship to each other. I've no intention on touching the intake as it's been advised I do not. That's where I found myself looking to see if I could achieve his recommended numbers, both intake and exhaust. When I saw I could not, with ought either going below 106 exh, and raising, or hitting 106 exhaust, and lowering intake, that's when I second guessed my math. You've eased my mind that I'm somewhere in the neighborhood of what's been found typically. I'm thinking I'll roll the dice on getting to 106,and seeing where the intake lands, raising the uppers, to your recommendations for blow down.

 

[NateSaw]

Sorry. I've got turkey belly. I'm backwards. Intake at slow dwell, exh at fast. Phew!

 

[NateSaw]

Give rod length, squish, and piston height on intake side and measurements from squish band to top of port (bottom for intake) and it can be calculated very precisely. If you have Rod length I can calculate how much the ex with drop with x amount of cut.

Are you using a piston calculator? Or are you a math man?

 

[NateSaw]

Happy Thanksgiving fellers. I'm thankful y'all are willing to entertain my pontificating on the subject of flatulence complications.

 

[Dolkitafreak]

Are you using a piston calculator? Or are you a math man?

I enjoy math I derived the equations and made a spreadsheet to calculate port timings and heights; as well as compression, chamber volume, and necessary cuts and compression post cut. It is a helpful tool to see where things will fall with machining to ensure to don’t screw yourself. Some guys shrug off the numbers but they’re easier than guess and check-for example in a head saw I’m building, I knew I wanted my transfers at a certain height, rather than cutting 12 gaskets and trying until they were right-I used the computer and cut one gasket…dead on! It took a bit to sort out the sheet and get it working perfect but overall I am very glad I did.

Happy thanksgiving fellas

 

[NateSaw]

I enjoy math I derived the equations and made a spreadsheet to calculate port timings and heights; as well as compression, chamber volume, and necessary cuts and compression post cut. It is a helpful tool to see where things will fall with machining to ensure to don’t screw yourself. Some guys shrug off the numbers but they’re easier than guess and check-for example in a head saw I’m building, I knew I wanted my transfers at a certain height, rather than cutting 12 gaskets and trying until they were right-I used the computer and cut one gasket…dead on! It took a bit to sort out the sheet and get it working perfect but overall I am very glad I did.

Happy thanksgiving fellas

I appreciate this approach immensely. I suppose this is why I'm willing to struggle through the math. Even though I'm cheating with a Calc. There's something satisfying about the accuracy. And leaving room for further machining, if I'm wanting to make a slow incremental approach. Partly my logic is that I may also trip over a good running recipe on my way to 106*. Just not this time. FYI, 102 with 26* of bd is only slightly better than stock.

 

[NateSaw]

Biggest band/ tightest chamber I've cut yet...
I've my work cut out for me but @farminkarman it fell right in at 106/78. I'll raise the uppers and open the lowers. Had to relieve bore extension to clear case and nip the fly side tunnel a smidge. Looks like this will be a decomp saw. 362,take two. There ain't enough meat left for a take three, so here's to hoping

 

[farminkarman]

Biggest band/ tightest chamber I've cut yet... View attachment 398311
I've my work cut out for me but @farminkarman it fell right in at 106/78. I'll raise the uppers and open the lowers. Had to relieve bore extension to clear case and nip the fly side tunnel a smidge. Looks like this will be a decomp saw. 362,take two. There ain't enough meat left for a take three, so here's to hoping

This is what my last 362 looked like after cutting 0.045” from the squish band:

 

[NateSaw]

Unless I'm setting something up wrong, this is what was required, sans gasket, to fall in @ 106. It's right there too. No touchy roofie. Same with intake. Just right there. No skimmy floory. And the piston position calculator worked accurately. So, albeit I'm taking alot from the uppers to get the blowdown I want, I'm taking the least possible.

 

[Dolkitafreak]

Unless I'm setting something up wrong, this is what was required, sans gasket, to fall in @ 106. It's right there too. No touchy roofie. Same with intake. Just right there. No skimmy floory. And the piston position calculator worked accurately. So, albeit I'm taking alot from the uppers to get the blowdown I want, I'm taking the least possible.

If comp is too high or run into issues from wide band you can always add a secondary angle and narrow the band and drop comp! Good looking cut.

 

[NateSaw]

This is what my last 362 looked like after cutting 0.045” from the squish band:
View attachment 398312

Perhaps our way of timing differs? This thing runs, but I'm not excited. I took 57thou between my two visits. 58 off the base minus gasket is 72. By the ring method I'm at 106.

 

[Ketchup]

What does your muffler look like?

 

[farminkarman]

Perhaps our way of timing differs? This thing runs, but I'm not excited. I took 57thou between my two visits. 58 off the base minus gasket is 72. By the ring method I'm at 106.

How much did you advance the timing?

 

[farminkarman]

Perhaps our way of timing differs? This thing runs, but I'm not excited. I took 57thou between my two visits. 58 off the base minus gasket is 72. By the ring method I'm at 106.

I use the ring method to establish port heights. Is this an older ms362 or a newer one?

 

[NateSaw]

I use the ring method to establish port heights. Is this an older ms362 or a newer one?

2015 Mtronic

 

[NateSaw]

How much did you advance the timing?

7*