Valve springs for Forced induction

[1uz vl turbo]

I am currently tuning a twin t04E T66 1uz. Due to the size of the turbo's the power is increase to peak rpm. The problem is power is suddenly dropping off at 7000rpm, but the ignition and A/F ratios seem fine. At this rpm a valve rattle can be heard, and I suspect it is suffering from valve float due to the boost (11psi). Has anyone heard of this problem before? Are there higher pressure springs available?
Photo can be seen at http://members.optusnet.com.au/~adamgriffith

 

[Lextreme II]

www.lextreme.com/spring.html

 

[Zuffen]

VL,

If you decideto change springs remember you can change them without pulling the heads.

Old trick of the trade.

Remove the cams and feed string into the cylinder when below TDC. Wind engine over until it locks (sting locked) remove retainers and springs, replace springs & retainers. Move to next cylinder.

 

[1uz vl turbo]

Thanks Rod,
I hadn't heard that one.
I have since spoke to crow cams, and they sell heavier valve springs.
Stock 1uz - 45lb seat pressure, 55lb @ 300 thou.
Crow - 80lb seat pressure, 125 @ 300 thou.
$400 Australian for a set.
Crow have also just started billet cams for the 1uz. They are testing them on some drag cars. I am considering getting a set because my turbo efficiency peaks around 7000 plus rpm, and my cam peaks much earlier. I still need to find a price.

 

[Zuffen]

Vl,

Remember Kelfords make cams as well.

Looks like we're going from a famine to plenty on th cam front!

Adjustable cam gears are in the wings as well.

 

[Red Supra]

Do you mean Crower when you say Crow?

 

[1uz vl turbo]

No, I mean Crow Cams.
CrowCams Pty/Ltd
16 Colbert Road Campbellfield
Victoria Australia 3061
Phone: (61)(03)93570469
Fax: (61)(03)93570001

Here is the web site, I don't know if they have it listed on there yet.
http://www.crowcams.com.au/index.shtml

This place also sells cams etc.
http://www.camshaftshop.com/camshafts/search_results.php?PHPSESSID=995219f57aef88e5d3a3c44585687a93&search_string=lexus&search_filter=keyword_and

 

[SCV8]

you can buy an air fitting to screw into your sparkplug bore to hold the valves in for repairs also...

 

[1uz vl turbo]

The problem with using the air technique is that you can't clamp the spring together with a spring compressor because the head uses buckets instead of rockers. This means there is no room around the spring. If you just push on the top of the retainer, the air isn't enough to hold the valve closed.