My concern is BOLDED

Interesting Comments by Endyn on Toda B-D Cams: (plagiarised from Team-Integra: articles)
Valve problems can also be attributed to valve springs failing to control valve motion. I won't build any engine with Toda cams these days because there are no springs we've ever found that will last any length of time with them. When the springs go soft, valvetrain separation occurs and the valves typically end up being "dropped" on the seats, rather than eased to their seats by the closing ramps on the cams, thus pounding out the valves and seats.

The potential damage from weakened valve springs is that great in my opinion...at least with Todas. I also don't think their valve springs are up to the task either. If you (have) to run cams like those, you can't run springs that "fit" in an installed height that's relatively "stock". You MUST run a spring that has at least 1.400" installed height with about 68-70 psi on the seat.

We also have a tool that we've built that allows us to machine the tops of the valve guides down in height to get some much-needed clearance between the bottom of the spring retainer and the top of the valve seal. This tool fits in a collet on the Serdi machine and it not only machines the top of the guide, but it also machines the sides and step so the seal will actually sit lower.On heads running in engines with cams with .485" or higher lift, we always machine the top of the guides to maintain .060" clearance between the retainer and the seal. If you don't, oil is forced (by the retainer) through the guide, contaminating the mixture, and burning oil.

Is this a regular practice to machine valve guides for clearance? & How many of you have had oil burning problems that you would attribute to the cam and this concern of Larry's?

I would not consider the Toda B's to be THAT extreme with the following specs (although I do not know the ramp angle):
INTAKE lift - 12 mm, duration 255 @1mm
EXHAUST lift - 12mm, duration 245 @1mm

I was considering Skunk2 Stage 2 cams with higher lift:
INTAKE lift- 12.3 mm, duration 266 @ 1mm
EXHAUST lift - 11.8 mm, duration 262 @ 1mm


Modified by Takumi Fujiwara at 1:36 PM 3/1/2006

 

The oil problem is because if you don't have enough retainer to seal clearance the retainer smashes the seal into oblivion.At high rpm the valve will travel more than the lift of the cam just from inertia.Sixty thousands is a pretty universal number for seal to retainer clearance.Not enough clearance can damage the cam and rockers too.
Glenn

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by NJIN BUILDR &raquo;</TD></TR><TR><TD CLASS="quote">The oil problem is because if you don't have enough retainer to seal clearance the retainer smashes the seal into oblivion.At high rpm the valve will travel more than the lift of the cam just from inertia.Sixty thousands is a pretty universal number for seal to retainer clearance.Not enough clearance can damage the cam and rockers too.
Glenn</TD></TR></TABLE>

So what is the remedy? I'm a head noob, just trying to learn to make educated decisions in the future.

 

Its written in larrys article; you get the top of the guide and sorrounding area machined so the seal can sit lower; giving the retainer more space

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mmuller &raquo;</TD></TR><TR><TD CLASS="quote">Its written in larrys article; you get the top of the guide and sorrounding area machined so the seal can sit lower; giving the retainer more space</TD></TR></TABLE>

I'm wondering if this is a common practice, or is Larry just above and beyond?