offset valve seats

[Truckedup]

So.back to the OP's post,..the port is offset to the seat, so no change in guide and valve position?

[sbcharlie]

The seat is offset. Getting great horsepower and torque numbers.

[Fatman]

SbCharlie, can you please explain what this does with regards to port geometry/shape?

Or can you explain your process of what you are doing? I dont think i understand what you are doing.

[sbcharlie]

I going to make a you tube on this procedure first you remove valve seats. second you install on a fixture on a mill.third you level the head same as you would on a cylinder head machine. fourth you indicate in removed valve seat bore. now you offset the mill to bore out valve seat pocket.you can offset at 0,90,180, 270 degrees . I use 1 mm offset . this procedure enhances both air flow and port velocity.. you then machine new valve seat profiles into offset valve seats .

[jed]

Re: overview of offset valve seats
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Post by KnightEngines » Wed Dec 27, 2017 10:05 pm

I can, have & do do it in my Repco RVR.
It's rigid enough to cut with no pilot no probs.

I just set up off the guide, lock the head, then set up 2x dial indicators - 1 for each plane of movement. Then shut off the air to the machine - so head is only held in position by weight but is no floating. Then bump it to where I want it with a block of wood & hammer & flick the air back on so it's clamped & do the cut/s with some old tooling that's not ball head drive.

Tony could you give us real world numbers of HP, torque and CFM.

[Fatman]

I going to make a you tube on this procedure first you remove valve seats. second you install on a fixture on a mill.third you level the head same as you would on a cylinder head machine. fourth you indicate in removed valve seat bore. now you offset the mill to bore out valve seat pocket.you can offset at 0,90,180, 270 degrees . I use 1 mm offset . this procedure enhances both air flow and port velocity.. you then machine new valve seat profiles into offset valve seats .

When you "then machine new valve seat profiles into offset valve seats ." are you cutting just the seat angle (45 or whatever) itself and the chamber side top cut?

Are the angles below the 45 deg seat, for example a 60 and 75 cut, centered in the seat insert before the seat is installed in the head? Hope that makes sense.

[sbcharlie]

yes the contact seat angle is concentric to valve guide.the angles below will machine in off set to guide

[dhidaka]

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 ?

I have off-set valve guides approximately .020" outboard on 2-valve hemi motorcycles for increased valve-to-valve clearance. Any more than that and springs might interfere with the buckets. I begin with oversize valve guides. I made a fixture to hold the guides in my lathe, shimmed an offset into the setup and cut the guides down to stock OD. Works fine.