365 BB Kit

[AUSSIE1]

I am sorry to keep beating this horse, but do you think there is enough arch on top of this port to tuck the ring properly or do I need to work it over more?

The very last bit of light should be at the centre.

 

[bjorn773]

So I should probably take more out. It still looks a little flat at the very top. I'll have to work on the outside corners of the transfers too.

 

[AUSSIE1]

So I should probably take more out. It still looks a little flat at the very top. I'll have to work on the outside corners of the transfers too.

Yes just a little.
Your comp will not be as high as it could be with .029 squish as it is, so just a little.

Yep, do what your gasket tell's you.

 

[bjorn773]

I'm considering milling the cylinder. Say I take .010 off, then running gasketless I should end up at .019 squish. Would I be better off taking more off so I can use a gasket and still end up with around .020?

 

[AUSSIE1]

I'm considering milling the cylinder. Say I take .010 off, then running gasketless I should end up at .019 squish. Would I be better off taking more off so I can use a gasket and still end up with around .020?

Yeah for sure.
Take into account the compressed measurement of your gasket.

 

[bjorn773]

I just miked my old gasket, it's .017 thick. So at .029, I would need to take .026 off to end up with .020 if my math is correct.

 

[AUSSIE1]

I just miked my old gasket, it's .017 thick. So at .029, I would need to take .026 off to end up with .020 if my math is correct.

Yep, sounds good.
Keep us all posted on it's progress.

 

[bjorn773]

Aussie, this is what you were referring to, yes? I got as close as my tools will get me, gotta get some smaller bits to get any closer.

 

[AUSSIE1]

Aussie, this is what you were referring to, yes? I got as close as my tools will get me, gotta get some smaller bits to get any closer.

Yep, and that little bit of cyl.
I don't really go deep here (in the transfer), mostly just blend.

Also don't forget to sharpen that bit of cyl running around along your transfers as this hangs in the c.case. Don't go to low if you know what I mean as you don't want to weaken it.

BTW this bit of cyl isn't even present in the 385's!

Make sure everything is nice and smooth with no lumps, bumps or divits, just nice smooth lines.
Attention to detail is good.

 

[bjorn773]

Well, I was hoping to mill my cylinder, but my machinist(father-in-law) is not comfortable enough with his rotary mill to do it. So, I think I may have to deal with .029 squish. How much difference will .009" make in compression? I'm cutting firewood, not competing. Am I just getting too obsessive about this?

 

[TRI955]

Well, I was hoping to mill my cylinder, but my machinist(father-in-law) is not comfortable enough with his rotary mill to do it. So, I think I may have to deal with .029 squish. How much difference will .009" make in compression? I'm cutting firewood, not competing. Am I just getting too obsessive about this?

Too obsessive.....I don't think so. I've had the BB kit off my Makita twice last week and plan on one more time this week after following this thread....

Your also asking the wrong people about being too obsessive anyway!!!!

Mike

 

[bjorn773]

I had the machinist we use for our shop work pick up my cylinder yesterday. I'm gonna have him shave .026" off the cylinder. With the gasket in place, that should put me at .020" squish. I figured I've gone this far with porting and the larger cylinder, why not get the compression as high as I can. I'll update when I get the jug back.

 

[Evan]

very good thread

 

[wheelman]

Before you mill the cylinder be sure to for free bore at the bottom of your ex port. A couple of BB kits that I have used had low bottoms in the ex port even with the gasket.

 

[bjorn773]

Before you mill the cylinder be sure to for free bore at the bottom of your ex port. A couple of BB kits that I have used had low bottoms in the ex port even with the gasket.

I checked for free porting with it set up gasketless and it appeared ok. The cylinder has probably already been milled by now, so I'll cross my fingers.

 

[bjorn773]

Hindsight is 20/20, right. In the future, I should probably measure squish and determine if I'm going to mill the cylinder BEFORE doing any porting. Then I would know how much I can play with on the bottom of the exhaust port. I didn't lower it other than putting a better arch on it to help the ring tuck, so I should be ok. I'll be thinking about it until I get my cylinder back.

 

[wheelman]

If you end up with a little free bore I would not sweat it much. I have 2 660s with BB kits With a little free bore that are suffering no ill effects.

 

[bjorn773]

I talked to my machinist today. He is welding up a fixture to hold the cylinder in the mill. He was nervous about clamping onto the fins, so he's gonna weld something up to bolt to the exhaust. Still anxiously waiting.

 

[rmihalek]

lathe

Ask your machinist if he can chuck the cylinder in a lathe. Perhaps there are some long jaws for the chuck that can fit inside the cylinder to hold it true. With a slow feed, the nikasil lining should not be damaged by the jaws.

Also, the exhaust port looks fine. I've seen many exhaust ports more square than yours that have not hung a ring. Don't hog out the transfers too much because gas velocity through the transfers is very important in scavenging the cylinder between power strokes. If you make them too big, the velocity drops and the scavenging goes to sh!t.

You're on the right track and your photos are worthy of a screen saver!

 

[bjorn773]

Well, I'm taking matters into my own hands with the cylinder milling. My machinist has really been dragging his feet on this one. I took the initiative to learn how to run my father-in-law's lathe this weekend. I cut a plug to fit into my old 365 cylinder and shaved it down .010" just for practice. Today, I'm picking up my BB cylinder and am going to shave it down tonight myself. I'll post pics tomorrow.