I Just got plain steel valves for my 3.0 V7. The heads are going to be shaved so I will end up with 11:1 compression.
The valve stem looks so damn wide, can I trim it down a little below the guides to improve flow and lose some weight?
Thanks.
- scott.venables
- Gold
- Posts: 117
- Joined: Wed Nov 01, 2006 11:00 pm
- Location: Melbourne, Australia
Re: Exhaust valves
You could convert to 8mm or 5/16" stems and then getting guides to suit. 9mm Is a strange size that's for sure. There might be a little machine work involved if you can't find some with the groove in the right place though.
Re: Exhaust valves
Trimming down the guides depends on your cam profile, valve spring strength and max RPM you'll be going. Imagine the force on the valve if you'd be getting a little float on closing at 7800 rpm and the extra strong springs whacking it onto the seat. That's what would cause deformation and eventually, breaking of the stem.
From what I hear from Guy Croft, the flow of a well ported head will hardly be influenced with thicker/thinner valve stems, it's mainly weight loss that is the benefit of trimmed down valve stems. At 9mm there may be a bit more influence, but the money spent on machining down the stems would probably be more beneficially used on a radiused 3 angle seat job or something like that.
From what I hear from Guy Croft, the flow of a well ported head will hardly be influenced with thicker/thinner valve stems, it's mainly weight loss that is the benefit of trimmed down valve stems. At 9mm there may be a bit more influence, but the money spent on machining down the stems would probably be more beneficially used on a radiused 3 angle seat job or something like that.
Re: Exhaust valves
Adding to that is that the real restriction in the 12v is the size of the intake runners (according to Jim K.).
hope that helps,
hope that helps,
MR1 Zig (I made rate!)
Machinery Repairman USNR
Machinery Repairman USNR