valve springs swap

[willard]

Can I simply replace stock single valve springs (I guess "933") in my 906 heads (383 engine) with lunati 73815 springs or I have to buy specific retainers and locks?
OD and ID are  very close lunati vs stock: 1.500 vs 1.532 and 1.086 vs 1.089.

Of course load is different.

For the time being I run lunati 60302 with old stock springs and want to have the valvetrain done right and also degree the cam.

[femtnmax]

The OD is ok, and the ID is very close too.  I assume the Lunati springs have a damper, and the stock retainers and cylinder heads should have a step to contact the damper...sounds like it should work.
I would check for correct installed height of the springs at each valve, would not be surprised if spring shims are needed.  Keep the locks with the retainers, don't mix them up.
Your cam pick is not too radical, so spring loads should be more, but not extreme, so using the old retainers should work.  Remember to use Zinc rich cam breakin oil or diesel oil, and 2000 rpm minimum for first 20 minutes.
When you take the intake manifold/carb off, don't tip it alot, or upside down, etc.  Too much movement can stir up any dirt in the carb, then the engine won't run right when you go back together....happens once in a while, more so if your not careful.

Are you going to take the heads apart??  Would be a good time to shim valve springs, clean carbon off heads, valves, piston tops, and install new valve stem seals.

[willard]

The fact is I did the cam swap in may 2009 and drove the car till november. Than I did the whole resto but the shop reassembled the heads just cleaning them and checking valves plus some milling. Then I had some issues with the engine and the car is back at the shop where they had to shim rocker shafts a bit. I had new pistons installed and static CR of 9.6:1 but the car is still sluggish. The shop doesnt degree cams so when I get the car back I have to do it myself plus I want to be sure the springs are matched to the cam. That's the story

[femtnmax]

but the car is still sluggish.

Before you dive into it, do a compression check or better yet a cylinder leak down check.  A number of reasons for sluggish pep.  Timing chain/gears are not typically mismarked and advancing/retarding the cam 2-3* to dial it in won't make that big a difference if your car's real sluggish.
The 60302 cam is not too radical by any means, so thats not the problem, and weak valve springs show up at high rpm.   Make sure the distributor is installed correctly.  Is the ignition timing correct...did you check the harmonic damper "zero" vs TDC on #1 piston?  What about fuel mixture too rich?  What axle gear ratio, trany, and intake manifold combo?  Single plane intake with tall highway axle gears don't usually work well together, dual plane intake is better.  Just some ideas.

[willard]

I was struggling with the car's performance long time. There are 2-3 my posts in this section abut that. Anyway it's 3.23 open end, 727 auto, stock 11" converter, 1:9,5 383 with 140 psi of compression, 17" vacuum, 60302 cam not degreed (dot-to-dot), 906 unported heads, stock valvetrain and bottom end with KB400 pistons, holley street avenger vacuum sec 770 carb, MP dizzy with orange box, 12 deg initial timing, 38 total. stock fuel system and 25.5" tires.

CAr was recetly restored, incl engine so I'm sure what is in and the CR. The problem is before the overhaul it was a dog with old low comp pistons and 110-120 psi of pressure. The static CR was under 8,5:1. I hoped it's gonna rock with proper CR with new pistons but it is still not what I wanted. It is slightly stronger but doesnt light the tires easily. I'm worried about that little compression raise - only 20 psi when the static CR went up by 1 point - the cam was unchanged.

My shop is the best in poland but not that best... they do not degree cams while everyone here recommends it - so I have to do it myself when the cr is back. I thought springs my also be involved as I did nt change them while swapping the cam... that's the story.

[femtnmax]

Willard - have you driven it enough to seat the new piston rings?  With engine idling, remove the pcv valve from the valve cover and make sure there is strong suction thru the valve.  Then put it back onto the valve cover.  Next remove the breather hose from the other valve cover..the hose goes from the round metal filter can on the valve cover to the air cleaner.  With engine idling, there should be suction on the hose end of the metal can.  You should be able to lay a small piece of paper or toilet paper on the hose end of the can and the paper should be held there by vacuum.  If the paper falls off, or you feel any amount of pressure, these are caused by leakage past the piston rings.  The car may have poor performance if rings aren't seated to cylinder walls. 
I used to have a 340 duster with 3.23 axle gears and auto trany.  The 340 had a short stroke similar to your 383...I have to say that duster was not real fast out of the hole, it liked the highway speeds better.  You could drive that car at 160 km/hr all day long..  A friend had the same car/engine/trany with 3.55 gears and it made the car a whole lot more fun to drive around town.  Maybe you should consider changing axle gears. Just some ideas.