Post up your ported cylinder Artwork

[Maintenance Chief]

48mm ,50mm, and 52mm were the 3 flavors of the 038 cylinders.

 

[Ronie]

48mm ,50mm, and 52mm were the 3 flavors of the 038 cylinders.

What's the difference between the 380 and the 381 cylinders, decomp?

 

[Maintenance Chief]

What's the difference between the 380 and the 381 cylinders, decomp?

Thats all I know about, I mean the 038 series has some pretty serious followers so someone probably could find more differences?
I have a" super" which is the 50mm and built a Magnum for my cousin, which is the 52mm.

 

[huskihl]

Probably similar to the 360/1/. I’d imagine spring a/v on the 381

 

[qurotro]

What's the difference between the 380 and the 381 cylinders, decomp?

381 has decom and the side screw of the engine cover is a bit off from the 038/380

 

[farminkarman]

AM Duke’s cylinder for a FT 660.

 

[Moparmyway]

 

[drf256]

Those are some fine transfers Kevin. I don’t think people easily see how sharp and tight the leading corners of those uppers are.

What’s with the ridge in the band?

 

[Sierra_rider]

My hybrid 500i/066:

 

[Sierra_rider]

Another recent build, 461R:

 

[Sierra_rider]

Do bikes count? The porting numbers come pretty good from the factory. Just slight work on the transfers, slightly staggered timing. Polished the exhaust and increased duration. The factory exhaust port was lower than it needed to be, I think to just make the bike feel easier to ride. Power valve opened several degrees further than the port height at the cylinder wall...with a power valve, you can have your cake and eat it too.

Most of the work was on the head. Stock squish was at .080", I cut it down to .048"(good safe number for a 300.) With cutting the head that far, I had to cut the dome as well, or the compression would've been wayyy high.

 

[Moparmyway]

Those are some fine transfers Kevin. I don’t think people easily see how sharp and tight the leading corners of those uppers are.

What’s with the ridge in the band?

Thanks Doc !!!
Took a while in each one to get them corners proud !

Thats not a ridge, but a witness mark from my aluminum mandrel, it’s tapered at the tip a little bit

 

[supertrooper]

Getting a 365sp roughed in for a friend of mine trying something different than usual
72 120 102 trying smaller transfer tunnels and more case comp.

 

[supertrooper]

On my other 372s I always did 25-27 degrees of blow down and a longer intake. Reading through older threads here, I'm going to try better velocity and work more at transfer angles.

Criticism welcome

 

[farminkarman]

On my other 372s I always did 25-27 degrees of blow down and a longer intake. Reading through older threads here, I'm going to try better velocity and work more at transfer angles.

Criticism welcome

I would do 102, 120-123, 78 and notch out the areas in red all the way to the cylinder base.

Edit- If you are not doing machine work, I might not use those numbers.

 

[supertrooper]

The squish is at 22 thou, what would you do different if it's not getting machined?

 

[Ronie]

I would do 102, 120-123, 78 and notch out the areas in red all the way to the cylinder base.

Edit- If you are not doing machine work, I might not use those numbers.
View attachment 365713

I guy I sold a 371 to sent me this video today, almost the same numbers that you suggested.

EX 102 TR 118/122 IN 79

 

[farminkarman]

The squish is at 22 thou, what would you do different if it's not getting machined?

Depending on what the end user is looking for, I would probably consider leaving the exhaust & transfers lower without doing machine work. I cut 0.050” from the band on mine and it is at 102, 121-123, 78, and that one is pretty even keeled and will pull a 28” bar with authority. I would go higher on the exhaust & transfers if I were doing it as a short bar build.

 

[Ronie]

If I couldn't do machine work, I'd ask someone if they could cut me a pop up out of a 268 closed sided piston.

 

[farminkarman]

If I couldn't do machine work, I'd ask someone if they could cut me a pop up out of a 268 closed sided piston.

Isn’t the 268 50mm?