Does a turbo motor need heavier valve springs?

[Crawdad]

2276
Panchitos 40x35
CB 2288 cam (=K8) .549 lift with my rockers
Turbo will be a RAD X25-550.
Looking to make 300 HP at 15 psi, revving to 6.5k , maybe 7k once in a while.

Mark Lawless at CB told me I should use VW650 springs. They're super heavy. I'm wondering what the folk wisdom is on this. 40x35 valves are relatively light. I have titanium retainers. Are VW650's overkill? I suppose pressure in the intake tract is trying to keep the valve open, so you might need a heavier spring. But you also have higher pressures in the chamber, trying to force the valve closed.

What is the consensus on valve springs in a turbo motor?
Thanks y'all.

[blue thunder]

I would definitely use a set of good quality dual valve springs, although 650's seem to be a bit overkill IMHO. I am not familiar with the cam you use, but if it is a 'steep-ramp design', heavier springs are recommended.

[my_medusa]

Use Numbers 1019
Chim them to your needs and rodney's recomandations.

https://logmech.se/eng/products/engine/ ... cessories/

[Bruce.m]

I have no experience but did some research on beehive spring fitment. The thread is in the type4 section. The downside is the lack of collective experience in VW uses.

[slayer61]

I think you know the answer already...

Mark Lawless at CB told me I should use VW650 springs.

Seems like a pretty good recommendation to me.

[nbuscemi]

Just adding my $.02...

I'm running Single High-Rev valve springs on my 1600cc on 10-12 psi boots to 6K rpm without any valve float, and that's with CB Turbo cam with chromoly pushrods. Stock valve springs will float before 5 psi (found this out the hard way). I'd imagine anything heavier that single high-revs would work just fine.

-Nick-

[Bruce.m]

There is some complexity. For example how much mass does the valve have. A stock sized valve is lighter than a larger performance valve which changes the spring requirement.

Also higher lift actually reduces risk of float as the pressure over the nose is higher & the spring has a higher resonance.

[Buggsy]

Yes on dual springs. I break my camshaft and lifters in on an engine stand with stock semi-hemi cut chambers and stock valve springs. These heads are cut for 94mm barrels. The low compression is compatible with any engine size, and the light springs are easy on the cam and lifters for break in. I run it at about 1800 rpm for an hour. Then I swap out to the heads that will be permanently installed. Break in on super heavy valve springs is risky to the camshaft.