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Author Topic: LA 46 transfer ports  (Read 1208 times)

Offline Geoff Goodworth

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LA 46 transfer ports
« on: July 27, 2012, 06:05:28 AM »
As I peered deeply into the bore of one of my LA 46s, I noticed that the transfer ports cast in the crankcase do not align fully with the ports cut in the cylinder liner. Both ports are the same so I must assume that it is deliberate

To fully align the cast ports with the liner cut-outs, the liner needs to be rotated about 1/8" clockwise. Such a change would not obstruct the exhaust port but it goes close and I would prefer not to do that.

Does anybody know why the ports would be misaligned like this and is there any benefit to be gained from machining the cylinder liner, the transfer ports or both?

I have to say that I am completely happy with the engine that I am running at present—another from the same batch—so I'm inclined to leave well enough alone.

I'm curious as much as anything.
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Offline Steve Helmick

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Re: LA 46 transfer ports
« Reply #1 on: July 28, 2012, 10:49:15 PM »
I'd check to make sure that the cylinder alignment pin is engaged in the notch in the cylinder flange. Maybe it wasn't assembled (or re-assembled) correctly? Stuff happens!  H^^ Steve
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Offline Geoff Goodworth

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Re: LA 46 transfer ports
« Reply #2 on: July 28, 2012, 11:27:39 PM »
No Steve. It was all assembled correctly. No problem there.

It's a mystery.
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Offline RandySmith

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Re: LA 46 transfer ports
« Reply #3 on: July 29, 2012, 10:11:51 AM »
Quote from: Geoff Goodworth on July 27, 2012, 06:05:28 AM
As I peered deeply into the bore of one of my LA 46s, I noticed that the transfer ports cast in the crankcase do not align fully with the ports cut in the cylinder liner. Both ports are the same so I must assume that it is deliberate

To fully align the cast ports with the liner cut-outs, the liner needs to be rotated about 1/8" clockwise. Such a change would not obstruct the exhaust port but it goes close and I would prefer not to do that.

Does anybody know why the ports would be misaligned like this and is there any benefit to be gained from machining the cylinder liner, the transfer ports or both?

I have to say that I am completely happy with the engine that I am running at present—another from the same batch—so I'm inclined to leave well enough alone.

I'm curious as much as anything.

Hi Geoff

That maybe the case, but it really would not matter at all, even with a misalignment in the intake ports, you will never notice a drop in power, the ports will flow anything the motor needs, and will do it with no problem, just look at the exhaust and using a tongue muffler, that is a VERY bad mismatch, and it still flows plenty with no problems for your use. Even mismatched exhaust areas with tube mufflers causes  no problems

Randy
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Offline Chris Wilson

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Re: LA 46 transfer ports
« Reply #4 on: July 29, 2012, 06:11:04 PM »
The mismatched ports are the same with MVVS engines rotated to rear exhaust as the angled 'Schnurle' ports are fixed fore and aft for side exhaust use and yet even the Pylon racing engines seemed not suffer here. (You would expect some sort of flow problem but perhaps better atomization is a trade off?)

Weird I know.
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Offline phil c

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Re: LA 46 transfer ports
« Reply #5 on: August 16, 2012, 05:38:16 PM »
the probable reason the pots are slightly off is that it looks like OS used the same molds for both the 40 and 46. The 46 case is bored out larger which moves the  of the case port due to the draft angles on the mold core that shapes the ports.

For max torque and horsepower designers generally try to match these things up and optimize the port angles but it isn't for a stunt application.
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