Some useful information regarding valve springs

[Ezekial]

Found out what the inner valve springs are from

GTiR SR20DET

Identical valve springs as in the VH45DE engine however VH doesnt run inner springs ... so if you use GTiR inner springs it gives a nice gain ... almost definate increased top end ... especially in turbocharged applications

So go and hit up all your mates that own GTiR's (the ones who have upgraded to hks cams and valve springs) for their old valve springs

[maxnix]

Alas, never imported into the US.

[elwesso]

Alas, never imported into the US.

but easy enough to get. Theres a few SR20DETs for sale in the BST forum, and SR20 parts are everywhere.

[Ezekial]

damn ... we didnt get them here either but they are common as hell now via jap importers

i ended up getting mine for nothing off a mate who blew up his GTiR engine and bought a spare and had it built ... 2 x 16 = 32

for the record ... i was told normal sr20 is different ... must be the solid lifters GTiR version

[elwesso]

what kind of gains would we get by doing this to a stock VH45 N/A?

[Ezekial]

unfortunately i cant answer that mate

perhaps one of the big wigs like Q45tech or maxnix etc can express their opinions?

[Q45tech]

Stiffer valve springs wear the cams and followers and seats faster. The HLA design must be changed to adjust for higher spring pressure.

Q45 rpm limits are dictated by the stroke [piston speed] and the strength of materials of rod bolts and rods. Titanium rods, etc

[Ezekial]

Stiffer valve springs wear the cams and followers and seats faster. The HLA design must be changed to adjust for higher spring pressure.

Q45 rpm limits are dictated by the stroke [piston speed] and the strength of materials of rod bolts and rods. Titanium rods, etc

no offence but that is just so generic. i was kinda hoping for some personal experience rather than a text book recital.

Of course they wear the cams more however a 20% increase in seat pressure to eliminate valve bounce and float in my case is hardly going to increase wear significantly

I've heard this all before. I didnt listen. I went the "terrible way" of regrind camshafts, thicker shims and uprated valve springs (on my other vehicle's engine) ... peak power rpm shifted from 6500 rpm to 9000 rpm!! max rpm shifted from 8000 to 10,000 rpm!! This was after the experts told me there was no gains to be had from valve springs. After nearly 2 years there is no sign of wear on the lobes or on the pre hardened shims. The cams were not hardened either. Just work hardened via 500 km's of easy driving. So you would think if any cams were going to wear it would have been these. no?

Now for the conrods ... correct me if i'm wrong but they are not forged so assumption of failure method would be bending. Given the size of them ... i cant see that happening.

Rod bolts ... i have wondered about these and you make a very good point there. I was thinking of matching up some arp bolts to suit but i cant see 7000 rpm being a problem given the excellent rod/stroke ratio and bore/stroke ratio

HLA design ... mind going into some more detail? i'm interested as to what will/could happen?

[defrag010]

Valve springs are a dependant mod, and you only need to upgrade them when you exceed the limits that the stock open and seat pressure will provide.

The main factors are camshaft lift and lobe ramp profile, and engine rpm. Without those variables, it makes no sense to go messing with spring pressure..

[Ezekial]

ever had an engine where the boost pressure was forcing the valves open?

[defrag010]

No, you would have to be on the barren edge to let manifold pressure create compression bleed fromclosed valves because the equivalent pressure of 30 psi in your intake port would equate to just a miniscule amount of actual force to move the valve open. 30 psi static barometric pressure would be about the equivalent to me mildly pressing it open with my finger.

Boost wasn't the cause, rather it sounds like you were just at the limit of your springs.