Porting a ms260

[drf256]

You don't need to polish the exhaust anymore than you already have. It's useless.

I'm a bit concerned about your intake port. You needed .100, not under a mm (.040) on each side. There are ring gaps there. The area to keep slightly rounded were the roof corners, not the floor corners. Make sure that both ring gaps stay tucked up under your roof. You don't need to run the bottom ring and I wouldn't if it's into/near the port. Be careful with your chamfers. Keep em tight by the intake roof and walls.

How do you plan on raising the transfers? Do you have a right angle tool?

Assemble and look at the geometry. Get your numbers. Draw a line on the piston at BDC. Check your ring gaps. Report back. Don't raise transfers yet.

 

[mdavlee]

Exhaust port looks good. Intake port isn't bad. Like Al said watch the sides since the ring ends are there. Don't want the end right on the chamfer.

 

[drf256]

I looked through some pics I have. The lower ring gap is on the clutch side on the 026. That's the squarer of your roof corners.

The good news is that the rounder corner of your roof should fully cover your upper ring gap on the flywheel side. If it's anything close, just run the top ring. Many performance saws came with a single ring from the factory. It's usually a bit thicker than a dual ring piston ring though.

Your ports do really look great. Helluva lot better than the first ones I grinded. And I've made the mistake of going too wide with my intake as well, so I ran just the top ring and I liked it.

Like you are saying, it's very hard to see what's round and what's square in a bore. A lot of illusions there. The port looks vertically higher than mine. Just make sure that you didn't raise the intake roof into the top ring.

If and when you do the transfers, remember that your piston is domed, so the ring placement will be slightly off for measurements. So if you want 120, push the ring up to 122 for your mark. It's about 2* difference IIRC.

 

[t4driller]

I looked through some pics I have. The lower ring gap is on the clutch side on the 026. That's the squarer of your roof corners.

The good news is that the rounder corner of your roof should fully cover your upper ring gap on the flywheel side. If it's anything close, just run the top ring. Many performance saws came with a single ring from the factory. It's usually a bit thicker than a dual ring piston ring though.

Your ports do really look great. Helluva lot better than the first ones I grinded. And I've made the mistake of going too wide with my intake as well, so I ran just the top ring and I liked it.

Like you are saying, it's very hard to see what's round and what's square in a bore. A lot of illusions there. The port looks vertically higher than mine. Just make sure that you didn't raise the intake roof into the top ring.

If and when you do the transfers, remember that your piston is domed, so the ring placement will be slightly off for measurements. So if you want 120, push the ring up to 122 for your mark. It's about 2* difference IIRC.

Thank you for the sound advice. That bottom ring end gap is close. I was still up in the air about running a single ring, but now I'm pretty sure I will just run one. I'll get the jug bolted back on in a little bit and ch3ck timing again. How is it for longevity running a single ring?

 

[huskihl]

Thank you for the sound advice. That bottom ring end gap is close. I was still up in the air about running a single ring, but now I'm pretty sure I will just run one. I'll get the jug bolted back on in a little bit and ch3ck timing again. How is it for longevity running a single ring?

The last few I've done only have 1 ring. Some aren't fans, but some have done it for years with no longevity issues. Alot of us are running one ring in an 066 with the piston in backwards so we could run finger ports

 

[t4driller]

Just checked timing again.

Ex. 99.5
Intake. 71
Trans. 121

 

[t4driller]

Lowering the intake. Would that give me a shorter blow down? My blow down would be 27 right now if I'm thinking right.

 

[drf256]

No. Blowdown is the difference between the exhaust and transfer opening. Your numbers are good.

 

[t4driller]

Ok. Well ill slap her together and give it a go. Hopefully have a video of it running soon.

 

[t4driller]

just have to finish port matching the muffler and it's all done. I did not do that muffler mod, it was on it when I got it. I'll see how it does and maybe by a cover and do my own muffler mod. [emoji4] [emoji4]

 

[t4driller]

 

[drf256]

Your muffler looks restrictive and not at the same time.

 

[t4driller]

Your muffler looks restrictive and not at the same time.

What do you mean by not at the same time? I can cut that pipe out and make something better. Probably have to get a new cover.

 

[VinceGU05]

Yeah that's s crap mod! I am sure it would interfere when bucking for sure and not very beneficial on top of that.

 

[drf256]

I'd add a deflector to the fly side of the muffler body.

Looks like it will be a nice open outlet from outside, but then you have a small inner opening and a restrictive screen inside.

 

[Redfin]

No. Blowdown is the difference between the exhaust and transfer opening. Your numbers are good.

You like that much bd Al?

 

[drf256]

You like that much bd Al?

I like transfers of 120 on the 026.

Granted, my exhaust is lower, so that gives me 15*. But the effective blowdown is a bit more because my exhaust pressure should be less at opening because of the longer power stroke.

For a new builder who doesn't have (likely-cant confirm) a right angle handpiece, I think it would be safer for him not to touch the uppers.

 

[Jughead]

I'm switching to single ring from now on.tried my buddy steves 026 as a test subject on a few different mods and used my 026 as a base with a shorter bar.the outcome was impressive.done the same with a ms360 but haven't had the chance for comparison on it.

 

[t4driller]

I like transfers of 120 on the 026.

Granted, my exhaust is lower, so that gives me 15*. But the effective blowdown is a bit more because my exhaust pressure should be less at opening because of the longer power stroke.

For a new builder who doesn't have (likely-cant confirm) a right angle handpiece, I think it would be safer for him not to touch the uppers.

I do not have a right angle. [emoji20] yet....

 

[t4driller]

Got it fired up and going lastnight. Made 2 cuts and wife came out yelling to shut that loud thing off. [emoji20] will try and get a video of it running when I get home. ( if she will hold the camera)lol