I recently swapped built a mild 455 to swap for my 71cutlass’s 350. After the swap I cannotget the beast to idle very well. It is 30 over and other than installing anupdated cam and HEI ignition.

HydraulicFlat Tappet Cam. Good cam for street performance. Works with stock converter,headers and needs lower gearing with 350 c.I. motors. Good idle.
· AdvertisedDuration (Int/Exh): 275/275
· Duration@ .050 (Int/Exh): 225/225
· GrossValve Lift (Int/Exh): .508/.508
· LSA/ICL:108
· ValveLash (Int/Exh): Hyd/Hyd
· RPMRange: 1600-5500
· Includes:Cam & Lifters (#71951PR-16)

With the vacuum line plugged and at 650 RPM I time atbetween 9 and 10 degrees. When I connectthe line back to the vacuum control switch the engine pops up to about 1100 RPMin park. I put it in drive and the RPM drops to 600. After the engine heat s up and pull to a stopthe idle drops to 500 and then will stall out. I was always under the impression that thereshould be no vacuum advance at idle. AmI mistaken? I am pulling the vacuum fromthe Q-jet port to the right of the fuel line. Any help would be appreciated.

 

So with hei your timing is 9-10 initial timing ?

I think you should be at 12-15degrees if, I am not mistakin with the vac advance unplugged and capped.

I am no expert, so I will let others chime in and correct me if I am wrong

 

Shoot for 14 16 initial , and run your vac. Adv. From an ported source. Start there. Then start looking into adjusting fast idle and your idle mixture screws and what not. If you are poping up to 1100 rpm at idle your advnce is hooked up to an unported source.

 

Your timing is way off.

I always thought the Olds motors ran best at 20* advanced at 1100RPM's

 

I would leave the vacuum adv line disconnected and plugged until you get your timing sorted out. Your initial timing is definitely not advanced enough.