Reed valve

bubba22349

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How would you get the reeds close to the valves would you machine like a slot in the valve cover area or bottom of the head to slide it in?
 

pmuller9

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How would you get the reeds close to the valves would you machine like a slot in the valve cover area or bottom of the head to slide it in?
One way is to find a reed valve assembly to fit inside the intake port but the small reed assembly might obstruct high rpm flow.
A second way might be to use a larger reed assembly that sits between the intake manifold and the head.
 

Wesman07

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So I was doing some work in my buddy’s air plane hanger today and I see a ktm 65 stuffed in the corner. I said “Jay, do you have a reed valve laying around for that thing?”. Sure enough, he did.

The sizing is very close. My only concern is the inlet on the reed valve is too small. I don’t know if it can be modified or if that’s all the air it will flow.

My next step is to take a junk head and run it through his band saw. I really need to see how much I can open the entrance of the intake port. Also, I’d like to see if I can recess the reed flush with the head surface.
 

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pmuller9

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It looks like the round part of the inlet can be removed so it can make a larger rectangular inlet?
 

Wesman07

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After thinking about it a little more. I wouldn’t modify these V force reeds. They use a click together design that eliminates screws through the peddles. They have a tendency to warp if over heated as is. Removing material might make that worse.

The aluminum boyesen or factory ktm reeds should be more forgiving.

ps. Thanks pmuller9 for running the math for pressure against the reeds.
 
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bubba22349

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Interesting was your idea to then machine like a little stepped ledge at the port opening for a reed to set into where its flush with the gasket surface, either in the intake manifold or into the head?
 

Wesman07

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Yes, that was one of the options I’m exploring. It would be nice to set the reeds as far as possible to minimize the volume behind the intake valve. The other nice thing about that is any exhaust/ intake combo would bolt right up.

The other option would be to modify the intake or exhaust flange to adapt.

Looking at FTF’s cut away photo, it will be close. The water jacket above the intake port does look like a spot that could be filled with epoxy.
 

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Wesman07

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So I found a reed valve that is more promising from a flow standpoint. This one is about the maximum size I am hopeful will fit into the intake port. I think I can do some porting to the cage and modify the reed peddle stops to squeeze a little more flow out of it at the cost of longevity.

The next step is taking a cylinder head to a band saw. Once I see a cross section of the intake port entrance, I will know what I really have to work with.
 

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Wesman07

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Quick update. I picked up a third reed valve to try and I also made some decent sections of a junk head.
With one of the reeds I have now, I should be able to maintain port size if the reed hangs out 5/8”.
My next move is going to be making one fit. One of the challenges I’m running into is all of reeds I’m finding are all wider than they are tall, forcing me to clock it 90 degrees.
 

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wme013

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Way back at the beginning of all things, one of the engines I worked on had a tapered 4 sided pyramid reed with a reed petal on each side. With the sides all equal it might help fitment. No idea about air flow. Can't remember which engine and found zip on google
 

Wesman07

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Probably these?


I am actively “cost engineering” (as we say in construction) the project. One day I’d like this to be considered a “red neck supercharger”. If I can make an oem production reed work, it will from $150-200 per reed to $50. It’s an avenue worth traveling.
 

sixtseventwo4d

Well-known member
How about a pyramid configuration but with the reeds on the inside of the cage, that way instead of it needing to fit into the head port, it could fit and face inside the intake; where there is more room for modification. I know you trying to fit it as close to the valve as possible, but for design modifications it would be more forgiving.
 

Wesman07

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I’d had thought about doing something similar but it gets complicated with the injector. The reeds would need to move about four to five inches back, more than doubling the volume between the valve and reed. It would be nice to have the injector down stream of the reed though.

The reed hanging out of the port will create another hurdle but I think it’s easy to get over. I’m thinking the reed will need a spacer between it and the head. Then, I would need a stepped flange washer made and use longer bolts to hold both manifolds on. Hopefully I can find a way to simplify that design.

My calculators shows the 1.5x1.3” port size flowing 205cfm, which passes the “smell test”. In order to keep the upper end of the power band, I’ll need to take the creative path rather than the easy one.

One thing I do have going for me is that I should be able to make up for a loss in flow by holding the intake valve open longer than usual. This would allow more time for cylinder fill without worrying about the losing bottom end power. The ideal cam profile would look like a large turbo cam with some overlap.
 
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