Hi everyone, been a while since my last post. Anyway, I have a TC Corty with a 351W w/ Edelbrock Performer RPM package e.g. heads, cam and manifold. I have mixed it up a bit by using a Demon 750 DP instead of the Edelbrock carb and Mallory ignition of the same specs as what Edelbrock recomends. The package is supposed to make max power at 6000rpm, ever since the build I have noticed a slight "crackle" at about 5500rpm, so i havn't been able to rev it any harder. I thought it was fuel delivery related so i fitted the biggest mech pump i could find. It is still pulling hard up to that point but makes the noise at 5500rpm. Finally went to a dyno day the other day, it got to 5500rpm and made the noise, the operator backed off (thanks to the guy, has good mechanical sympathy). He recons it is valve bouncing , but only on the left bank. This surprised me because the heads came from Edelbrock with the valves and springs installed. Anyone exerienced anyhting like this?

I had this problem with my Clevo at around the same RPM, i ended up putting shims under the springs and it solved my problems.
To hold the valves up you'll need a fitting to go into the spark plug hole that you can connect an air compressor to, once you fill the cylinders with constant compressed air the valves will stay up so you can remove the springs.
If you don't have a valve spring compressor then they are easy to make.
Get an old rocker arm and notch the end out so it sits on the retainer but gives you clearance around the collet to remove it, then weld a bar on the end of it for leverage.
I'll take a pic of one if i can find it.

Yes, I had 6025's on my XR with a small Crane Hydraulic roller. Edelbrock insisted that the springs were suitable but of course they weren't....bye bye two hydraulic rollers. Got the correct Crane springs and shimmed them to the required installed height and bingo revved all the way to 6200.
The fact that yours maybe floating on one side only suggests different installed heights...mic them up and you may find they either don't have the same number of shims from one head to the other or(less likely)the valve seats have been machined deeper in one head than the other.

Pete.

A batch of Edelbrocks did have issues with spring retainers being too soft and chewing out.. Yes I'd check spring height and spring tension...Keeping an eye on coil bind...