shakey idle

[cameron2502]

Bought a 408 stroker crate engine and cannot get it to idle correct, ive changed carburetors, jetted up jetted down, put in a new distributor, ignition module, set timing all over the place and it still idles real shakey, it runs fine going down the road and runs good when you get on it but when you come to a stop it shakes terrible. any ideas what to try next.

[67vertman]

Does it die, or feel like it is going to die?  How does it feel if you increase the idle? (when does it smooth out?)

Sounds like a fuel issue to me, but you have changed most of those items. 

[moparmaniac59]

Have you checked for any vacuum leaks? How radical/type a cam does it have? (Hydraulic roller? solid lift? Flat tappet?)



                                                                          Matt B.

[Chryco Psycho]

Vacuum leak into the brake booster ? Cam lobe going flat ?

[cameron2502]

It never dies, i dont have a tach i would say around 1500 to 1600 rpm when it starts to smooths out, i have plugged off the vacuum port to the power brake booster and makes no difference, i pulled the intake off and check the lobes on the camshaft and they are good, camshaft specs are 545 Intake / .545 Exhaust & 241 Intake / 247 Exhaust duration @ .050 - 110 degree lobe separation, i know this cam isnt going to idle smooth but it shakes terrible at idle.

[cameron2502]

Forgot to add yes its a flat tappet cam and yes i have checked for vacuum leaks, i have not put a vacuum gauge on it yet thats my next move.

[73EStroker]

Could simply be a wild cam in there. Mine smooths out about 17-1800 but idles fine .. and real lumpy. Mind you I run a manual gearbox. Try checking the cam specs if you can.

[cameron2502]

checked vacuum had 8 in at idle in gear, checked compression cold engine, started out at 175 lbs the farther i went along all cylinders started dropping to around 105 to 110 rechecked the one that had 175 and it showed 105, could it be when the lifters are pumping up the valves not closing all the way.