E-Bodies.org Cuda Challenger Forum

Technical Shop => Engine, Transmission & Rear End => Topic started by: jamesroney on June 27, 2017, 11:09:09 AM

Title: 1970 383-4V normal engine vacuum
Post by: jamesroney on June 27, 2017, 11:09:09 AM
Hello,
I am working on my 1970 cuda with the N-code 383 engine.  It was recently rebuilt back to OEM specifications.  The engine runs fine, but it only generates 17 inches of vacuum at idle.

Can someone with a stock 383 tell me what they see for manifold vacuum at idle?

Thanks!
Title: Re: 1970 383-4V normal engine vacuum
Post by: HP_Cuda on June 27, 2017, 11:55:46 AM

Only 17" of vacuum? That's pretty darn good considering it's good to get 15".

What are you needing for vacuum for?
Title: Re: 1970 383-4V normal engine vacuum
Post by: 303 Mopar on June 27, 2017, 12:08:55 PM
Anything north of 12" will be fine for power brakes.
Title: Re: 1970 383-4V normal engine vacuum
Post by: Cuda Cody on June 27, 2017, 12:16:01 PM
17" is pretty good.  Most people would be thrilled to have 17".  With that much vacuum the carb should be able to idle really nice and plenty of vacuum for power brakes.   :bigthumb:
Title: Re: 1970 383-4V normal engine vacuum
Post by: jamesroney on June 27, 2017, 01:10:49 PM
Quote from: HP_Cuda on June 27, 2017, 11:55:46 AM

Only 17" of vacuum? That's pretty darn good considering it's good to get 15".

What are you needing for vacuum for?

I'm not really needing vacuum, but I am in the process of tuning the engine...but I didn't want to start working on it if I have a vacuum leak under the intake.  My vacuum gage has a big green spot that says "normal" in between 19 and 22 inches.  My cam is the Summit 6400 214/224 "mopar magnum" stock replacement cam.  It idles smooth, and doesn't lope much...so I thought it would generate higher vacuum.  I was hoping that someone with a good running original car could measure theirs.

thanks!
Title: Re: 1970 383-4V normal engine vacuum
Post by: Chryco Psycho on June 27, 2017, 05:06:06 PM
 :iagree:
!8 " ios the upper end for a stock magnum , start tuning it  :wrenching:
Title: Re: 1970 383-4V normal engine vacuum
Post by: RUNCHARGER on June 27, 2017, 05:30:32 PM
Yup, 17 and steady is great.