Hi i have always had some issues with my idle after rebuild my 69 250 390 was rebuilt at a shop reputable one 2 locations here in so cal I had a cam put in a comp Dual energy 265/275 I have Patriot headers true Dual Dyno max super turbo 2.5 inch pipe the truck idles wierd I tried all the stuff corresponding with a few members like grounding the dist all the usual common sense stuff I took the carb off numerous times changed gaskets etc looked for vacum leaks etc still acts funny at idle it runs fine although there is a flat spot around 2k rpm that you can see on my AFR gauge and on my tach while driving , plenty of power though all through the range .

I took the valve covers off removed the rocker on one side made sure they were tourqe right and oiling bolt was in the right place I seen something inside the spring comp cam said it has single 940 springs and that thing inside is a dampner and it should had been removed at cam break in , well I have 400 miles or so now he said it happens all the time since it's a single spring people think you don't need to remove the dampner .

The rebuild shop did give me the card for the cam with the lift specs and all although if they did need to be removed I think it's kinda bad that they didn't hand them to me in a ziplock and say come back in 500 miles there's a charge but we will.put the dampners in , How critical is it in seating the valves with the dampner in there ????? I'm thinking I have a few valves that haven't seated.
The truck will idle one day in park at 19 inch vacum the next day it's at 15 ? Then it will be idling then get a burst of 1 to 2 inch of vacum all of a sudden drop and fluctuate never a steady idle spot on . The exaust sound funny at times as well

 

I've broken cams in with the damper springs. Not a bad idea to do it without them, but it can be done. What intake carb and spacer under the carb are you running ? Typically the idle will be rougher cold then smooth out when hot with any cam.

 

I have never taken them out and have never read any instructions or literature that said so. I doubt you can even get them out of the spring. They just don't really have any appreciable spring psi anyways, hence the term " damper " not spring.

 

It's a Holly 500 cfm 2bbl and 1inch spacer under I tried a different spacer 1/2 jomar laminate type no change the top end power is great with the 1" the 1/2 is min I can run with the big 50 cc pump under it I did have a issue at one time with this carb though I was using thread tape on the inlet to carb and when I put it in gear it was just die out so I had to take it apart blow out the Jets with air and then it ran again but now it's acting up i changed the disphram , idle needles and cork seals it's been like this for awile I'm about to take it off and put a 350 cfm Holly i had rebuilt in a box and see if it's carb or not . It started making a whistle sound when I gave it the gas lol ...this thing caused me some issues it was the choke plate it was new built last year but man .....

 

Ok so I rest a little easier on the dampners bieng the culprit compncsm said they should had been removed but I agree it's a dampner not a spring I doubt it was meant to be apart from the spring anyway .

 

The damper springs can be removed. I would try spraying carb cleaner around the carb and intake to see if there's a vacuum leak. If there is the carb cleaner will get sucked into the leak and you'll hear the idle change when it does. The whistling sounds like the throttle shaft has worn into the base plate causing a vacuum leak. Throttle springs that are too stiff will cause this.