394 Basic Porting

[jacktheripper]

Hey, I’m thinking I might do a little bit of basic grinding on my 394 with KS cylinder. Still need to map it out, but I do know that it has pretty big squish even with the base gasket removed. I might try sanding it on a glass plate and taking measurements to remove about .007”-.010” from the base. I will be doing some milling with it, so I won’t go too far.

In terms of numbers, I see that people tend to like 101,120,78. Does that sound right?

Any tips on port shape, etc? I assume the lower transfer lips should be smoothed, but I shouldn’t go too far so as to increase case volume. How about exhaust and uppers? Any tips there?

Thanks.

 

[srcarr52]

Hey, I’m thinking I might do a little bit of basic grinding on my 394 with KS cylinder. Still need to map it out, but I do know that it has pretty big squish even with the base gasket removed. I might try sanding it on a glass plate and taking measurements to remove about .007”-.010” from the base. I will be doing some milling with it, so I won’t go too far.

In terms of numbers, I see that people tend to like 101,120,78. Does that sound right?

Any tips on port shape, etc? I assume the lower transfer lips should be smoothed, but I shouldn’t go too far so as to increase case volume. How about exhaust and uppers? Any tips there?

Thanks.

394 has a cylinder extension that goes into the case so sanding on a pane of glass wont be easy.

Those numbers are good for a tamer ported saw. I'd bump up the ex to 100.

 

[jacktheripper]

394 has a cylinder extension that goes into the case so sanding on a pane of glass wont be easy.

Those numbers are good for a tamer ported saw. I'd bump up the ex to 100.

Ah, you’re right. I forgot about the extension.

 

[farminkarman]

Ah, you’re right. I forgot about the extension.

I can cut the base, or base and squish for you if you need/want.

 

[jacktheripper]

I can cut the base, or base and squish for you if you need/want.

Thanks for offering that! I actually started talking with a local guy yesterday who ports saws for his friends and himself. He has a lathe and tooling for machining jugs. I might be meeting with him next week and handing off some cylinders. If that doesn’t work out, I’ll reach out to ya.

 

[jacktheripper]

Ok, so with the base gasket removed exhaust sits at 104 and transfers at 127. Seems like I probably shouldn’t raise the exhaust any more without raising the transfers, correct?

 

[huskihl]

Ok, so with the base gasket removed exhaust sits at 104 and transfers at 127. Seems like I probably shouldn’t raise the exhaust any more without raising the transfers, correct?

I wouldn’t raise the exhaust without raising the transfers. You’ll end up with a saw that won’t hold RPMs in the cut

 

[jacktheripper]

I wouldn’t raise the exhaust without raising the transfers. You’ll end up with a saw that won’t hold RPMs in the cut

Sounds good. After talking with Steve, I’m going to shoot for closer to 120 transfer duration and maybe a hair more exhaust duration. Any thoughts on intake duration?

 

[huskihl]

Sounds good. After talking with Steve, I’m going to shoot for closer to 120 transfer duration and maybe a hair more exhaust duration. Any thoughts on intake duration?

You can square it up a little bit but I wouldn’t lower it much if at all