All right

Please help me close on this dilemma.

Building a 0.5mm overbore 1.8 VVT, for turbo (3071 at 20psi on 91).

Will likely upgrade to SST +1 Supertech valves, because they fit Supertech pistons without additional machining.
Most run successfully stock valve springs, and I have a choice of 99/00 and 01-05 valve springs for that.

Other choices are Volvo Vs-855 and Eibach, and Supertech.
I rather not spend on Supertech, unless some special benefit is derived.

Stock are 46lb seat pressure.
Eibach 66lb, Volvo 66 I believe, Supertech single 56lb and double 75lb.

Another option is to shim OEM valves by adding 1 more stock shim, and it bumps from 46 to 62lb the pressure.

I feel like going from 46 to 66 or more is a big jump and with consequent increase in stress and wear on valve train.
So perhaps using custom 1/2 thickness OEM like shim would bump the OEM valve springs from 46 to 54lb (62-46=16, 16/2=8, 46+8=54), about right no the money additional seat pressure for stock redline.

Am I rightfully concerned, or should I just get really affordable Volvo valves and call it a day: I think $80 for set.

Thanks

 

Stock seat pressure on OEM springs and +1mm ST vales cost me a dropped valve at 7300, without boost.
Shim the seat pressure to what you like, the shims are not precision parts (material or dimensions), if you place them under the stock ones.

 

Niklas

Thank you for feedback.
Proposed shims would be OEM quality: i.e. Material dimension flatness machined/measured.
Not washer quality.

Stock valves are ok at stock redline
And even under boost
But we'd like to bump up pressure for added "safety".

 

I'm using the SuperTech duals (63lb) on my EFR VVT build. It was suggested by Brian at Fab9.

 

Thank you Brandit.
OK, so if they are suggested for EFR it's OK for another turbo application.
So higher spring rate is OK, that is what I am concerned with, and seems its not an issue.

 

I run the supertech heavy double springs, have rev'd them to the moon (8,800) and no failure. They're great.

 

I'm using Supertech Light Double Spring valvesrpings at 63# seat pressure. This is supposed to sustain revs to 8400rpm, max over rev of 8800.

I haven't pushed it past 7500, but haven't had any issues. How much boost do you plan on running and are you using oversize valves? These are things you'd have to consider a bit more than merely free reving the engine. You don't want the springs to be struggling against the manifold pressure you're trying to use, and since pressure is a function of area....

 

Thanks for great info
Seems higher spring rates are well within valvetrain capability.

 

I have revved to 10.3k once with the ST hard duals and the engine still lives (same cams as now). My ears however...
So they might be a bit unnecessary, i.e. valve-train losses.