Results 1 to 6 of 6

Thread: vacuum at idle?

  1. #1
    Garrett booster
    Join Date
    Dec 2005
    Location
    Hagerstown,MD
    Posts
    227

    vacuum at idle?

    What is the average vacuum at idle on a stock '88 turbo motor? I had about 13, advanced the cam 2 teeth and lost about 2". Think I'll try retarding it 3 teeth and see what that does. Any thoughts or suggestions?
    88 LeBaron convertible 2.5 T2 {garrett} w/555 T-U 3bar plus 40 cal mildly ported swirl w/back-cut valves 86 supra front mounted I/C 223whp@19psi 14.352 @ 99.25mph RETIRED '87 SC (GLHS CLONE) TII with stage II MP currently a/t '89 Voyager factory 2.5 turbo 5spd garrett, 3" from dp back '86 Chysler T&C TII conversion

  2. #2
    turbo addict
    Join Date
    Dec 2005
    Location
    Spokane, Wa
    Posts
    9,046

    Re: vacuum at idle?

    a healthy 2.2 should have 16-18" a 2.5 should be 18-20 at minimums.

  3. #3
    turbo addict
    Join Date
    Dec 2005
    Location
    Pickering, ontario
    Posts
    2,670

    Re: vacuum at idle?

    Ok, for starters, moving "teeth" at a time won't get you any more power anywhere. This has got to be done a few degrees at a time, usually in 2 degree increments. I would consider 16 inches or more to be about normal.

  4. #4
    Garrett booster
    Join Date
    Dec 2005
    Location
    Hagerstown,MD
    Posts
    227

    Re: vacuum at idle?

    Quote Originally Posted by shadow88 View Post
    Ok, for starters, moving "teeth" at a time won't get you any more power anywhere. This has got to be done a few degrees at a time, usually in 2 degree increments. I would consider 16 inches or more to be about normal.
    Thanks for the input. But suppose someone had installed the cam incorrectly. Like placing sprocket reference marks level instead of parallel to the head plane. I'm not actually looking for additional power right now anyway, but rather max vacuum at idle.
    88 LeBaron convertible 2.5 T2 {garrett} w/555 T-U 3bar plus 40 cal mildly ported swirl w/back-cut valves 86 supra front mounted I/C 223whp@19psi 14.352 @ 99.25mph RETIRED '87 SC (GLHS CLONE) TII with stage II MP currently a/t '89 Voyager factory 2.5 turbo 5spd garrett, 3" from dp back '86 Chysler T&C TII conversion

  5. #5
    Supporting Member Turbo Mopar Contributor zin's Avatar
    Join Date
    May 2006
    Location
    ca
    Posts
    4,479

    Re: vacuum at idle?

    You'll want to get an adjustable cam gear, set it to zero, then dial in the cam "straight-up" to see what "normal" would be,then bump it 2* at a time, both up and down. I'd bet you'll see the biggest changes within 6*+/-. I don't recall how many degrees one tooth represents, but it is a large swing, the kind that tends to swing you right past the "sweet spot".

    Naturally, you'd want to confirm proper "stock" pulley install, which can be a little tricky due to the engine's inclination towards the firewall and one's natural tendency to use something other than the head as a reference for what's "square". A mirror can help to see if the marks on the pulley align/square with the head. Hold it so it faces the pulley and look at it from the driver's side. There's also a timing light method, but would require the ignition timing to be set to zero, which might be a bigger pain.

    Might want to do a leak-down or compression test to see if it's practical to expect higher vacuum ...

    Mike
    "The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government - lest it come to dominate our lives and interests." - Patrick Henry

    Bad laws are the worst sort of tyranny.
    - Edmund Burke

  6. #6
    Garrett booster
    Join Date
    Dec 2005
    Location
    Hagerstown,MD
    Posts
    227

    Re: vacuum at idle?

    Quote Originally Posted by zin View Post

    Might want to do a leak-down or compression test to see if it's practical to expect higher vacuum ...

    Mike
    Yeah, it's beginning to look like with stock components 14" is as good as it gets.
    88 LeBaron convertible 2.5 T2 {garrett} w/555 T-U 3bar plus 40 cal mildly ported swirl w/back-cut valves 86 supra front mounted I/C 223whp@19psi 14.352 @ 99.25mph RETIRED '87 SC (GLHS CLONE) TII with stage II MP currently a/t '89 Voyager factory 2.5 turbo 5spd garrett, 3" from dp back '86 Chysler T&C TII conversion

Similar Threads

  1. GT vacuum
    By CSX153 in forum SRT-4 Neon & PT Cruiser
    Replies: 11
    Last Post: 04-29-2010, 12:41 AM
  2. Vacuum????
    By jason.weissinger in forum "I need help!"
    Replies: 4
    Last Post: 10-18-2009, 09:43 AM
  3. What is your idle vacuum-stock engine.
    By turbovanmanČ in forum Maintenance & General Tech
    Replies: 78
    Last Post: 04-25-2008, 09:34 PM
  4. Rough Idle almost no vacuum
    By whistlin' in forum "I need help!"
    Replies: 13
    Last Post: 02-26-2008, 09:32 AM
  5. Idle Vacuum Question
    By Dusty_Duster in forum Engine - Block, Piston, Heads, Intakes
    Replies: 6
    Last Post: 08-20-2007, 11:23 AM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •