Valve Spring Question

[4speedTerror]

Ok here we go again.

496 BBC
Comp Retro-Roller 294 540/560 110
Angus 1.7 roller rockers
Ferrea 2.250/1.94 valves
Pro-Topline 320 racing thunder heads.
Comp 943 valve springs....

So the motor pulls very hard till about 3800 rpm, then after that it feels like my valves are floating. The only thing i can think of is that these valve springs are WAY to light.....specs below:

O.D./I.D. = 1.55o/.812
Seat Press. = 240/1.900
Open Press = 598/1.2500
Coil Bind = 1.160
Spring Rate =551

Now to me, looking over these numbers.....it seems light.
I have talked to a few of my motor buddies, and they all say to get new triple springs, because the ones that i currently have are double. I have also ran the lash several times.... 0 lash then a 1/4 turn more. But i still have small backfires theough the carb, which i would say is because the intake valve is staying open because of the light springs? Timing is 38 total and the carb is right on the money.

lay it on me fellas

[pat mccarthy]

you said retro roller soild or hyd roller if it a hyd roller that s to much try 150 at 1. 900 set up try 68632 howards the iskloy endurance for soild roller springs i have them in a lot of big blocks 760 lift they work geat

[pat mccarthy]

the numer on the howards springs is 98632 sorry eyes are goning bad . the springs you have in this is close to what i run in soild roller drag engines with 760+ lift cams 240 seat pressure is way to much spring 150 seat and spring rate 413 and this is a big spring for your cam but it will work good did you bend a intake valve?

[blwn31]

4 speed, do you have the cam card? If so are the springs correct and are they set up correctly? If so call the Mfr. of the cam and talk to their tech dept. Just my 2 cents.

[1JohnnyO]

Yep, I agree with the others...the ones you have are already too much, I think....go with what the mfg. says...I run a solid roller w/ mid .600 lifts, and mine are about 175 seat and 460 open.. I also run the Howard's cams springs like Pat.

[C9x]

Sounds like the valves are mis-adjusted.
It is a solid lifter roller cam is it not?

Small and intermittent backfires through the carb at idle indicate valves too tight even if everything else is in spec.

Do a compression test and see what you come up with.