Oversized valves, valve springs and retainers.

[speedmaster]

Anyone ever dyno all stock engines with oversized valves compared to oem? 16v or 20v.
Just want to know the power difference.

Oem retainers can be used with cams such as 304 10.5mm lift? Or are they safe enough to be revving under 9000 rpm?

Anyone used Performance Springs brand of valve spring? Some say crap. Some say good.

Just need to know before making good choices.

Thanks for your time.

[Jimmee1990]

You won't see much of a gain just using oversize valves as they really need the porting, cams and compression to go with them. There's definitely gains to be had, but they aren't cheap and there are many other areas you should be looking at first. If you're using cams that large I would suggest going to an aftermarket retainer like Supertech etc, it's cheap insurance. Australian Performance branded springs are okay for street engines, and more serious than that and TRD/Toda/Supertech/custom are a far more reliable option with regards to seat pressures and coil bind issues with big lift.

Realistically what is the RPM, flywheel horsepower and total cost you're looking for?

[speedmaster]

You won't see much of a gain just using oversize valves as they really need the porting, cams and compression to go with them. There's definitely gains to be had, but they aren't cheap and there are many other areas you should be looking at first. If you're using cams that large I would suggest going to an aftermarket retainer like Supertech etc, it's cheap insurance. Australian Performance branded springs are okay for street engines, and more serious than that and TRD/Toda/Supertech/custom are a far more reliable option with regards to seat pressures and coil bind issues with big lift.

Realistically what is the RPM, flywheel horsepower and total cost you're looking for?

Rpm... maybe 9500rpm
cnc ported head rated 210cfm @ 28".
Kelford 302 10.5mm

Horsepower was 171 at wheel. That was using Toda 264 272 9.0mm. Australia springs.

[oldeskewltoy]

cnc ported head rated 210cfm @ 28".

Any particular reason for CNC?

My port work (laregeport) typically flows to about 210 on the intake side (190.5 @ 25" = 212.8 @ 28"),





the exhaust side typically flows out to 156 @ 28"

[speedmaster]

loving it bro

[oldeskewltoy]

Oem retainers can be used with cams such as 304 10.5mm lift? Or are they safe enough to be revving under 9000 rpm?

I've used OEM retainers with a few 10mm, or higher lift cams... I've not heard of them failing... albeit I just finished the 2nd one just last week, and it is in transit to my client. Previous head was OST-017 it was an O/S valve head running some 10+mm cams. Springs used in these engines Toda in OST-017, and in the most recent one, OST-024, I used Ted's/Kamikaze springs.

[speedmaster]

Oem retainers can be used with cams such as 304 10.5mm lift? Or are they safe enough to be revving under 9000 rpm?

I've used OEM retainers with a few 10mm, or higher lift cams... I've not heard of them failing... albeit I just finished the 2nd one just last week, and it is in transit to my client. Previous head was OST-017 it was an O/S valve head running some 10+mm cams. Springs used in these engines Toda in OST-017, and in the most recent one, OST-024, I used Ted's/Kamikaze springs.

so you reckon my oems are good enough? nice to know someone who actually experienced this

[speedmaster]

https://www.dropbox.com/sc/tks6ppdhvktpnob/bvHO7parRf
here is my flow result

[oldeskewltoy]

depends... have each retainer checked first (for cracks), but the OEM retainers work with the Toda and TRD single springs, and the Toda say they are good to 10.5mm




Btw.... your flowbench chart says 20V... Again, I'm talking about 16V. springs and retainers are different... so you will have to check if the 20V retainers will work.

Got any photos showing the port work on the exhaust side??