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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 » Thu Jan 16, 2020 1:43 pm

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 » Thu Jan 16, 2020 3:03 pm

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 » Fri Jan 17, 2020 4:35 pm

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 » Sat Jan 18, 2020 3:10 am

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 » Sat Jan 18, 2020 7:17 am

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 » Sat Jan 18, 2020 1:58 pm

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 » Sat Jan 18, 2020 3:08 pm

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 » Sat Jan 18, 2020 3:30 pm

No remove the stock seat. And then bore new seat pocket offset.

HDBD
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Re: offset valve seats

Post by HDBD » Sat Jan 18, 2020 7:23 pm

OK I get it, guide and valve are still unchanged however.

jarmoyp
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Re: offset valve seats

Post by jarmoyp » Sun Jan 19, 2020 10:32 pm

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.

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Re: offset valve seats

Post by Truckedup » Mon Jan 20, 2020 7:36 am

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 » Mon Jan 20, 2020 9:13 am

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.

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Re: offset valve seats

Post by jarmoyp » Mon Jan 20, 2020 9:24 am

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 » Mon Jan 20, 2020 9:50 am

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.

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Re: offset valve seats

Post by HDBD » Mon Jan 20, 2020 11:33 am

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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