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Nutball

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Echo CS-4910 with now more traditional entrance angle intake side upper transfers. Lots of grinding!

View attachment 326858 View attachment 326859
How about a picture through the exhaust port, it's kind of hard to see the angle otherwise. Is it much less up angled, I assume? I haven't seen inside a 4910 yet.

I like this a lot, especially for cylinders that do not have a lot of material. Do you have an idea of how much it reduces compression having a small patch of the cylinder missing? I'm sure it could be offset with a pop up top. Would it be better to widen/square off the exhaust port or leave the original shape and notch the piston like this?
Probably a minimal amount of compression lost, not nearly enough to worry about, but it may have some negative effects as far as squish and trapping fuel that might not get burned. I notched the piston so I wouldn't have to square the port and risk catching a ring.
 

srcarr52

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How about a picture through the exhaust port, it's kind of hard to see the angle otherwise. Is it much less up angled, I assume? I haven't seen inside a 4910 yet.

These are goofy saws, the stock entrance angles of the intake side transfers are around 60deg.
 

Shibby

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Question about the finishing, and I'm not sure if it matters on such a small engine. Is it better to have a completely smooth finished surface or a slightly rough or "machined" type surface. I remember years ago drag racers who had their cylinder heads ported would leave a slight rough sand finish to prevent air from "sticking" and create micro turbulence due to the pulsing of the air as valves opened and closed. Like I said, this is mostly curiosity since I doubt it matters on such a small engine.
 

NWWrench

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huskihl

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Question about the finishing, and I'm not sure if it matters on such a small engine. Is it better to have a completely smooth finished surface or a slightly rough or "machined" type surface. I remember years ago drag racers who had their cylinder heads ported would leave a slight rough sand finish to prevent air from "sticking" and create micro turbulence due to the pulsing of the air as valves opened and closed. Like I said, this is mostly curiosity since I doubt it matters on such a small engine.
I use a burr or stone finish in the transfers and 80 grit on the exhaust and intake
 

Canadian farm boy

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Very nice work CFB. Probably my favorite saw to run ported the 372 OE. I have ported 372 and 375's not alot of difference between the two. Very nice finish work on your cylinders.
My question is what do use to mount your cylinders on during porting? Can you show a picture and is this something you made yourself, very interested.
Thanks Ryan
I don’t use anything but my left hand to hold the cylinder when porting. Sometimes I’ll hold it against my knee if I’m really hogging out material.
 

Canadian farm boy

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Question about the finishing, and I'm not sure if it matters on such a small engine. Is it better to have a completely smooth finished surface or a slightly rough or "machined" type surface. I remember years ago drag racers who had their cylinder heads ported would leave a slight rough sand finish to prevent air from "sticking" and create micro turbulence due to the pulsing of the air as valves opened and closed. Like I said, this is mostly curiosity since I doubt it matters on such a small engine.
I do almost the same as Kevy. Diamond burr finish in the transfers. 120 grit in the intake. 220 grit in the exhaust. Sometimes I’ll go 1 step further on the exhaust with a small piece of red scotch brite in a split mandrel to just give a bit of a polish to the port.
 

Bigmac

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Some blaster stroker action, the customer wants mid top for his little girl, and he said I don’t care about bottom end power! I am on my the edge for trusting what he wants,, so I set it up for mid top and put a shim gasket to get him there but also set it up to be a mid motor without the shim gasketA874DA77-E71D-4F33-BF57-D9A4422A2BD7.jpegCB82A832-833B-43FB-AB2A-9CDB358A7355.jpeg EA1D2190-FFB4-4A1E-83B4-4406F0EB34E7.jpegD84DC6D8-E481-4B8A-B003-3CFD59604894.jpeg
I think the mid motor will be better, but people want what they want

this is the before intake B2CC1D72-A5CC-43ED-A8FF-2C09A08AF1FB.jpeg
 
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