Found some Ferrea springs (P/N: S10110) for the Scion that have good dimensional and technical specs, so Dennis is going to order a set and see how they work.
They're nearly the same as the Crow 2045, but with a slightly higher spring rate (180 vs 148) but not so high that we'll be beating up the cams and the rest of the valve train unnecessarily. I ran these by Kelford last night, and they're happy with them.
I had acquired some sample springs last year, did some measuring & testing on them, and compiled a valve spring comparison table. I just finished putting the Ferrea spring data in it and thought I'd post it up here to share.
I originally did this table as part of an exercise in finding good spring/retainer combinations that would work well for a Shim Under Bucket (SUB) conversion. The most suitable SUB retainers I found, that worked with the 1UZ's 6.0mm valve stems were the Nissan RB26 retainers, and the most reasonably priced in Titanium were from Manley and Supertech. Although both require springs with a larger ID than than stock, the retainers are fairly easy to machine down for smaller ID springs, so this should not be a showstopper for anyone.
The big table is sorted according to manufacturer, and basically the color coding of the cells is:
Green means it's pretty safe and should work fine
Yellow means it won't work under all conditions, or something needs to be modified
Orange means there's a problem - study the application carefully before proceeding
Note, the color coding recommendations apply only to fitment, not to spring pressures. Spring pressures are some of the black art of camshaft and valve train design, so if you decide to choose springs independently of your cam manufacturer, be sure to run their specs by them first.
If anyone has spring data they'd like to add to this table, by all means, send it and I'll put it in. Same with any corrections that are needed.
BTW, the Lextreme springs are a great solution
if you're running the whole Lextreme valve train, including the reground cams, taller valves and/or higher install heights. But, if you're running stock valves and stock install heights, you'll probably run into coil bind with them. You can't just throw in a set of these springs with a set of Stage 1 or 2 cams and your stock valves and retainers, and think you'll be OK. Be sure to run the numbers for yourselves.
If that table is a bit heavy to digest, here are the "best" picks, IMO: