Valve Spring Selection for FI Built Head
 

Searching didn't provide much info on this.

I'm building an engine that with a forged bottom end, port and polished 99/00 Head, +1mm intake valves, +2mm exhaust valves, and stock Cams.

Shooting for 275 whp or so or whatever my little gt2560 can put out (overbuilt for track reliability). Redline isn't decided yet but I'd guess 7500 or so with some head room for over rev downshifts.

What springs are recommended for this build.

-supertech singles (56 lb @ 34.2mm)
-supertech doubles (63 lb @ 34.2mm)
-supertech doubles (74 lb @ 34.2mm)
-other??

I am using the 63# doubles with a similar setup except I run +1mm inconel exhaust. I also have shim under buckets and bumped my redline to 7500 until I have power to justify raising it to 8050.

With this current setup I made ~280hp/270tq to the wheels at 16psi. If I want to make 300 to the wheels I would need higher lift cams and adjustable gears as well as an intake (squaretop? tbody too?). That's probably the same path you would want to with this setup, with the goal being to level off or increase the power at that 6500+ drop in tq/hp.

What're you looking at for compression? Piston type? Rods? I have been surprised at the lack of talk on cams for turbo setups. There's a bit of info out there but it's overall pretty lacking for actual information.

Thanks for chiming in!

I ended up going with the 74 lb doubles just to be safe. From what I understand higher spring constant springs will have more frictional losses than lighter ones but help prevent valve float at higher RPM levels (especially with higher manifold pressures from the turbo).

I'm still deciding if shim under bucket is worth the cost. Less weight is never a bad thing but I haven't of any failures of the oem shim over bucket system and am not sure if its required for a 7500 red line.

CAMs might be an upgrade path down the road if I want more power but I think I'll have enough 5spd breaking torque without them.

I bought some eagle h-beam rods and am looking to get supertech pistons with probably a 9.0:1 compression ratio.

I reved my VVT head to 8,800 with the heavy double springs and stock shims, probably saw 8,800 200 times, never spit a shim.

Reved mine to 10,3K once (ST heavy doubles). No tendency of valve float... ;)
So they can be seen as unnecessary heavy for my cams/normal revs.

ST longer valves combined with MS SUB and stock cams can create a problem with very thin lash caps (about 1mm). One of mine lost its edges, the retainer split and the valve went where it shouldn't.

That was a poor call on the guy who setup the head.

The Mazda SUB place lash caps on the valve stem. Shave the stem too much and the shim contacts the keeper. Don't shave it enough the shims get to thin. I forget the limits but anything under what is sold off the shelf is considered unsafe. Machine shops sometimes shave the shims to unsafe specs. Happened to me too. I caught it before something bad happened.

If you buy the supertech SUB's you are much better off. The shim attaches to the post of the lifter not the stem of the valve. This allows more freedom to trim the valve tip.

Liar!

I checked, I actually did NOT install the stock shims under the valve springs, just the ones supplied with the springs.

I am going to be running the Eibach singles. $180 from Summit. They claim 66 lbs @ 39 mm / 200 lbs @ 27 mm. Lift 12 mm / Bind 24.2 mm. Looks like a middle option in price and pressure from OEM. Would like to hear some comments.

http://eibach.com/america/en/perform...-valve-springs
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There's also the PACALOY springs from kelford. KVS12 Mazda Valve Spring Set - BP1800, BPT and B6 - Kelford Cams

PACALOY is the spring material that revolutionized nascar motors in the 90's. Its it is to valve springs as a room temperature superconducting alloy would be to electrics.

I think I'm the only person on this forum using the PACALOY springs. They are spendy but they are worth the money.

If anyone decides to step up to these springs and wants a set of custom Titanium retainers hit me up and I will machine them for you.

I may take you up on that if I have anymore troubles with valves. Since you and I had the same problem I will be watching your new cam/spring setup closely.