Page 1 of 3 123 LastLast
Results 1 to 10 of 28

Thread: Jeep Vacuum Advance

  1. #1

    Default Jeep Vacuum Advance

    I've installed the Sniper on my 258 inline 6 on my '83 CJ7. I've done a few modifications to the engine, including a HEI ignition with vacuum advance. My problem is when I'm in fourth gear on the highway, I'm not getting the advancement the engine needs and it starts cutting out. I've advanced it as much as I dare, and it helped on the top end, so I know that's my problem (I first thought it was a fuel issue). Do I need to swap the vacuum advance HEI for a magnetic pickup? What would the part number be for say, a MSD? When I look up for a Jeep, they all give me the same vacuum advance. Thanks, Todd

    Click image for larger version. 

Name:	Jeep.EFI.jpg 
Views:	32 
Size:	100.3 KB 
ID:	2503

  2. #2

    Default

    Are you using the Sniper EFI for timing control? If yes, you should lock out all mechanical and vacuum advance mechanisms. If not, your timing behaves exactly as it did with a carb. So any issue you are facing probably is not directly related to the Sniper EFI. The may be related to installation errors, though. Have you checked for vacuum leaks?

  3. #3

    Default

    I have the vacuum port on the Sniper EFI connected to the vacuum on the distributor, so I guess I'm using it for timing control?
    The vacuum port gives one "draw" at WOT, but if you ease into the throttle, nothing happens. I've checked for leaks.

  4. #4
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    17,700

    Default

    Quote Originally Posted by RTIrvin63 View Post
    I have the vacuum port on the Sniper EFI connected to the vacuum on the distributor, so I guess I'm using it for timing control?
    No, ECU timing control doesn't use the distributor's centrifugal or vacuum advance mechanism. A locked out distributor distributor is used for ECU timing control. You'll need someone to help you with this.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  5. #5

    Default

    There are three vacuum ports. Are you using the one closest to the Sniper regulator (return line)?

    The vacuum port gives one draw.
    This isn't how the advance port works. It should be constant vacuum when applicable, not a single pulse.
    Last edited by Zmann; 09-03-2017 at 01:49 PM.

  6. #6

    Default

    So, from what I can tell, I would need to lock out the vacuum advance, get the MSD rotor cap, set the cap, etc. I think that's my problem, is that I didn't install the required cap. Here's a pic of where I have the vacuum line connected. I have an ACCEL HEI distributor now.
    Click image for larger version. 

Name:	Jeep.EFI.2_LI.jpg 
Views:	40 
Size:	67.7 KB 
ID:	2507
    After studying a little more, I see the adjustable MSD cap won't fit anything but MSD. What do you all suggest? Just get a MSD distributor (part number?), or go full bore with the 6A install? Thanks, Todd
    Last edited by RTIrvin63; 09-03-2017 at 05:47 PM.

  7. #7

    Default

    That's the correct vacuum port for vacuum advance. I'm not sure you distributor is capable of being converted to having the Sniper control timing? The MSD adjustable rotor only fits the MSD distributor, and you also need to lock out the mechanical advance if one is present. That being said, if it ran OK pre Sniper, it should run as good or better with the Sniper and no timing control.

  8. #8

    Default

    Zmann, until it gets in high gear and the engine loads up, it runs GREAT! Cranks great. Idles great. It just cuts out when it needs more advance. The more I study, the more I'm thinking I need a MSD distributor and let the ECU control timing. I'm just wondering if I need to up it to the 6A install? More is better, right?

  9. #9
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    17,700

    Default

    Forget the MSD distributor/magnetic pickup. What you need is a (Hall-Effect) Holley Dual Sync Distributor and an MSD 6A CD ignition box. You'll thank me.
    https://www.youtube.com/watch?v=1gI4FDfU2sI (Holley Sniper EFI - Dual Sync Distributor Installation Tech Video)
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  10. #10

    Default

    I read a little on the Holley dual sync distributor. Will that work with my Jeep? Do I need the cam sensor and all that stuff?
    UPDATE: Great videos, Danny. That looks like what I need to do! I had watched another video, and it just confused me. Thanks!
    Last edited by RTIrvin63; 09-03-2017 at 06:59 PM.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
About us
Holley has been the undisputed leader in fuel systems for over 100 years. Holley carburetors have powered every NASCAR® Sprint® Cup team and nearly every NHRA® Pro–Stock champion for four decades. Now, Holley EFI is dominating the performance world as well as our products for GM's LS engine. Holley's products also include performance fuel pumps, intake manifolds & engine dress–up products for street performance, race and marine applications. As a single solution, or partnered with products from other Holley companies - Hooker Headers, Flowtech Headers, NOS Nitrous, Weiand, Earl's Performance Plumbing, or Diablosport - Holley products can give you the edge you need over the competition.
Join us