shakin in monte
 

i have a 406 small block with edelbrock victor jr heads and intake its in a 86 monte carlo with a 5 speed t5 traNS runs greaT real fast but car will not run at cruising speeds the car shakes and bucks till you give it more gas then it smoothes right out ive tried messing with carb jetting and power valves with no success also replaced spark plugs with plugs edelbrock recommends with no help there either . any advise ?

slightly more timing at cruise rpm and or minor jet change.a booster venturi also might help.Ive run the same thing in my car,just takes time and twiddling,you are close

Could it be too much vacuum advance? Try diconecting the vacuum canister hose from the carb and plug the carb port, and test drive it. Easy to test.
If it helps, you can get a advance limiter from Summit made by Crane pretty cheap, and tune your vacuum adv. to your combo.
FWIW
ssmonty

i took out 72 jets and put in 76s in primary and advanced the timing it made very little differance seemed to lose top end then i broke a starter so i backed off timing vacuum advance i havnt tried but will soon

the 4 jet sizes up might be too much.

i know i plan on putting 74s in but didnt have any available

well looks like it is a vacuum advance problem with vacuum unhooked iy barely stutters at all