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offset valve seats

General engine tech -- Drag Racing to Circle Track

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sbcharlie
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offset valve seats

Post by sbcharlie »

here is a picture of a Harley Davidson twin cam with offset valve seat. they work quite well
DB719ED9-182A-43B7-B4BC-6B6B5CAA76D4.jpeg
4BC5FAFE-7CAD-4FFE-8E1E-3DFFCF80A5E6.jpeg
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sbcharlie
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Re: offset valve seats

Post by sbcharlie »

Pictures of the cylinder head
FA11425E-D625-42B8-997F-764F936BA6FA.jpeg
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sbcharlie
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Re: offset valve seats

Post by sbcharlie »

Machining offset seat
67A30AFB-B276-4B6A-B06C-9465D75C369B.jpeg
2ACBEEDA-9E73-42D8-82DA-C6C29CB223B1.jpeg
67A30AFB-B276-4B6A-B06C-9465D75C369B.jpeg
EBA75ED7-6608-4C05-9FB2-D5959892A198.jpeg
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Sparksalot
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Re: offset valve seats

Post by Sparksalot »

Interesting application of an age old speed "secret" of moving valve center(s) and or angles to gain performance. It still works if the application is happy with the change.

First did it in 1961 on a Studebaker V8. It worked. Many happy years followed.
jarmoyp
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Re: offset valve seats

Post by jarmoyp »

I have done this many times, moved valve centerlines.
Why to the hd twin cam? Is it because of valve overlap?
gordon
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Re: offset valve seats

Post by gordon »

On the Stude V8 which direction did you move the valve? EX or INT?
HDBD
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Re: offset valve seats

Post by HDBD »

This is different. He just moved the throat. The seat and guide are located stock
sbcharlie
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Re: offset valve seats

Post by sbcharlie »

No remove the stock seat. And then bore new seat pocket offset.
HDBD
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Re: offset valve seats

Post by HDBD »

OK I get it, guide and valve are still unchanged however.
jarmoyp
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Re: offset valve seats

Post by jarmoyp »

Ok. This is a very common way to make a seat by hand porting after seat job. It takes a couple of minute to do that move.
Truckedup
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Re: offset valve seats

Post by Truckedup »

Ok, for the stupid like me....How do you move a valve seat without moving the guide? You are talking lateral moves and not in or out ?
Motorcycle land speed racing... wearing animal hides and clinging to vibrating oily machines propelled by fire
jed
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Re: offset valve seats

Post by jed »

I can see the valve seat is moved but don't understand what it accomplishes?? The valve has not moved
In relation to the port.
jarmoyp
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Re: offset valve seats

Post by jarmoyp »

The throat or venturi is not round after offset portning. Short side radius is better after that move. I do this every time, for every head when porting.
jed
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Re: offset valve seats

Post by jed »

Thanks I get the concept. It seems that it would add a lot of dollars to the porting job for 8 off set intake seats and
8 exhaust seats. What is the return on investment in terms of CFM and torque.
HDBD
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Re: offset valve seats

Post by HDBD »

Good question, I would be more interested in hp and tq with a back to back test. Added flow does not always equal more of either
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