please help!!!...valve float maybe??

[jsynhon]

ive got a 306,carbureted with a holley street avenger 675cfm. its got a .512 lift comp cam dual pattern. at 5200rpm the motor experiences severe "valve float" or what i thought it to be. ive changed the valve springs to accomodate a .550 lift. ive replaced the distributor as well to an msd unit. ive also changed the msd 6al out as well. ive even put 1.6 roller rockers. still no change. im out of ideas. could my cam be too radical for stock lifters and make them collapse under load or is my carb too big?? any ideas??

 

[347HO]

What does valve float feel like or sound like?
What do your plugs look like after you do a run to 5500 on clean plugs?
What is your camshaft timing?
What length pushrods after you check for pushrod length?
Pedistal, stud mount or shaft rocker setup?
What was your PTV clearance?
So your springs are good for .550"... but what tension are they on the base and on the nose?
So many things can be wrong here... you'll have to do some checks IMO.

 

[Brian@PAR]

As was stated it could be many things. It would be helpful if we knew what you are actually experiencing instead of saying it's valve float.

The cam sounds like it's a 281 HR. If that is the case it calls for 986 spring which is a dual set up with 322# of rate. I've attached the spec sheet so you can compare ALL the specs to what you have. If your springs don't match up then they need to be changed even if this is not the cause.