Advancing/Retarding Mechanical Advance
OpelGT.com is the premier Opel GT Forum on the internet. Registered Users do not see the above ads.
Results 1 to 8 of 8
Like Tree6Likes
  • 3 Post By RallyBob
  • 2 Post By RallyBob
  • 1 Post By RallyBob

Thread: Advancing/Retarding Mechanical Advance

  1. #1
    Just Some Dude in Jersey My location The Scifi Guy's Avatar
    Join Date
    Nov 2007
    Location
    Cöllingswööd, NJ
    Posts
    9,823
    Real Name
    Gördö
    Downloads
    6
    Uploads
    0

    Advancing/Retarding Mechanical Advance

    I have a RallyBob-modified dizzy in my car. The plates are locked together and he installed tiny adjusting screws in the mechanical advance stops. Harold mentioned some advice to Gordy about bending/adjusting the mechanical advance stops to advance the mechanical advance overall. In other words, have the mechanical advance kick in sooner/later, yet have the same range of advance.

    Okay, so's I gots them fancy little adjustin' screws in there and I haven't touched'em since he set it up for my 2.0 engine. Now I have a 2.4.

    Should I mess with those screws?

    How would I know that I need to advance when my mechanical advance advances?

    Or retard when my advance advances?

    Do I need to buy a partical accelerator to find out?

    Should I just start screwing around and see what happens?





  2. Remove Advertisements
    OpelGT.com
    Advertisements
     

  3. #2
    Project 1450 supporter... Site Supporter My location RallyBob's Avatar
    Join Date
    Mar 2002
    Location
    Spofford, NH
    Posts
    12,475
    Real Name
    Bob Legere
    Downloads
    0
    Uploads
    0
    Quote Originally Posted by The Scifi Guy View Post

    Should I just start screwing around and see what happens?




    I don't recommend it....
    My Flickr photos.
    C.R.L. 9/22/69 - 12/8/99, J.M.L. 3/3/43 - 6/15/04, D.M.L. 9/19/50 - 6/23/10
    E.G. Sauer 2/26/66 - 2/18/10. Rest in peace big guy...

    '70 GT 'Bonnie', '71 Ascona 4-dr turbo - winter beater, '71 Ascona 4-dr 'Turd' - rallycar, '72 Manta Rallye - hillclimb car, '72 Ascona wagon - 'Red', '72 Manta - caged street car, '73 Manta Luxus, '73 Ascona 2-dr, '74 Ascona 2-dr - Project X, '74 Manta Luxus - factory sunroof, '74 Manta ITB racecar, '75 Manta, '75 Sportwagon, '75 Manta - racecar

  4. #3
    Tennessean Site Supporter My location hrcollinsjr's Avatar
    Join Date
    Jan 2003
    Location
    Chapel Hill, TN
    Posts
    7,795
    Real Name
    Harold Collins
    Downloads
    2
    Uploads
    0
    "Harold" welds up the stops limiting the amount of advance. Not nearly as nice of a modification as what RB does, but it gets the job done. He also doesn't lock down the vacuum advance plates because it is a street engine with limited modifications. He usually sets initial advance in the 5° to 10° range with total advance mechanical advance coming it at a maximum of 36°. He has swapped one of the springs out in an attempt to smooth out the advance curve a bit. No real way to tell if that part was beneficial or not without some 'real' testing.

    I don't agree with automatically locking out the vacuum advance but will admit certain circumstances warrant this modification.

    Harold

    Harold

    P.S. Speaking in the 'third person' feels good, I might have to start doing it more often.

  5. Remove Advertisements
    OpelGT.com
    Advertisements
     

  6. #4
    Just Some Dude in Jersey My location The Scifi Guy's Avatar
    Join Date
    Nov 2007
    Location
    Cöllingswööd, NJ
    Posts
    9,823
    Real Name
    Gördö
    Downloads
    6
    Uploads
    0
    Quote Originally Posted by hrcollinsjr View Post
    "Harold"

    Harold

    Harold

    P.S. Speaking in the 'third person' feels good, I might have to start doing it more often.

    That Hayride guy is pretty smart.





    Hey, if you talk about yourself in the third person, isn't that really the second person? Wouldn't Hairold talking about Harrold talking about Herald actually be the 3rd person?




  7. #5
    Project 1450 supporter... Site Supporter My location RallyBob's Avatar
    Join Date
    Mar 2002
    Location
    Spofford, NH
    Posts
    12,475
    Real Name
    Bob Legere
    Downloads
    0
    Uploads
    0
    Quote Originally Posted by hrcollinsjr View Post
    I don't agree with automatically locking out the vacuum advance but will admit certain circumstances warrant this modification.
    In Gordon's instance, I prepped the distributor for his old 2.0 liter engine. It had a fairly healthy camshaft (coupled with what turned out to be a really worn out shortblock with bad compression), so the vacuum advance did nothing except stay fully advanced all the time, due to low operating vacuum.

    I restricted the total advance with the adjustable set-screws, so that Gordon could use more initial advance for improved response ( I seem to recall 10 degrees initial and 36 total). I locked the vacuum advance so there were no fluctuations in timing. I substituted the large stiff advance spring (with the loose loop) with another 'soft' spring to provide constant tension, so that the idle rpms came back to normal and didn't creep.

    Now, with his 2.4 engine, he can arguably use less total timing than his 2.0. Probably 32 degrees max.

    If he retarded his baseline timing by 4 degrees, he would have 6 degrees initial, and 32 degrees total. Given the larger displacement engine and stock camshaft, that's probably just about right.
    The Scifi Guy and gt alex like this.
    My Flickr photos.
    C.R.L. 9/22/69 - 12/8/99, J.M.L. 3/3/43 - 6/15/04, D.M.L. 9/19/50 - 6/23/10
    E.G. Sauer 2/26/66 - 2/18/10. Rest in peace big guy...

    '70 GT 'Bonnie', '71 Ascona 4-dr turbo - winter beater, '71 Ascona 4-dr 'Turd' - rallycar, '72 Manta Rallye - hillclimb car, '72 Ascona wagon - 'Red', '72 Manta - caged street car, '73 Manta Luxus, '73 Ascona 2-dr, '74 Ascona 2-dr - Project X, '74 Manta Luxus - factory sunroof, '74 Manta ITB racecar, '75 Manta, '75 Sportwagon, '75 Manta - racecar

  8. #6
    Member
    Join Date
    Nov 2012
    Location
    Australia
    Posts
    132
    Real Name
    Alex
    Downloads
    0
    Uploads
    0

    total advance with the adjustable set-screws

    Hi Bob, sounds like a good set up especially with a side draft Weber (having no vacuum advance port) it would be interesting to bang it on a dyno after a run while the engine is hot and see how much advance works best. Then set it 2 deg less for safety. Do you know what RPM it hits max advance? Like I said sounds like a good setup and Gordon is lucky to have it.

  9. #7
    Project 1450 supporter... Site Supporter My location RallyBob's Avatar
    Join Date
    Mar 2002
    Location
    Spofford, NH
    Posts
    12,475
    Real Name
    Bob Legere
    Downloads
    0
    Uploads
    0
    Quote Originally Posted by gt alex View Post
    Hi Bob, sounds like a good set up especially with a side draft Weber (having no vacuum advance port) it would be interesting to bang it on a dyno after a run while the engine is hot and see how much advance works best. Then set it 2 deg less for safety. Do you know what RPM it hits max advance? Like I said sounds like a good setup and Gordon is lucky to have it.
    Hmmm, I can't recall exactly, but usually by 3600-3800 rpms it's all in.

    This can be altered by changing spring rates, or by changing the mass of the counterweights.

    Lighter spring/heavier weights = earlier advance, while stiffer springs/lighter weights = later advance.

    How much mechanical advance (quantity in degrees) is controlled by those adjustable screws I added, but it doesn't affect how fast it comes in.

    Last edited by RallyBob; 03-01-2017 at 10:42 AM.
    The Scifi Guy likes this.
    My Flickr photos.
    C.R.L. 9/22/69 - 12/8/99, J.M.L. 3/3/43 - 6/15/04, D.M.L. 9/19/50 - 6/23/10
    E.G. Sauer 2/26/66 - 2/18/10. Rest in peace big guy...

    '70 GT 'Bonnie', '71 Ascona 4-dr turbo - winter beater, '71 Ascona 4-dr 'Turd' - rallycar, '72 Manta Rallye - hillclimb car, '72 Ascona wagon - 'Red', '72 Manta - caged street car, '73 Manta Luxus, '73 Ascona 2-dr, '74 Ascona 2-dr - Project X, '74 Manta Luxus - factory sunroof, '74 Manta ITB racecar, '75 Manta, '75 Sportwagon, '75 Manta - racecar

  10. #8
    7,000 Post Club My location wrench459's Avatar
    Join Date
    Jul 2005
    Location
    Milner, GA.
    Posts
    11,300
    Real Name
    Dan
    Downloads
    12
    Uploads
    0
    Not to be Captain Obvious here...:-)
    Mechanical/vacuum advance is more or less a compromise for any given running condition.

    oophs missed a owr.
    Last edited by wrench459; 03-01-2017 at 08:20 PM.

    Si vis pacem, para bellum "If you want peace, prepare for war"

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

    Similar Threads

    1. Mechanical Advance
      By gr_diver in forum 1B - Ignition System
      Replies: 3
      Last Post: 04-12-2009, 12:05 PM
    2. Mechanical and Vacuum Advance Query
      By namba209 (R.I.P.) in forum 1B - Ignition System
      Replies: 21
      Last Post: 04-01-2006, 05:18 AM
    3. Need some mechanical help in nj
      By jerseydave in forum General Discussions
      Replies: 1
      Last Post: 04-23-2005, 06:39 PM
    4. Mechanical advance distributor for 2.2 w/ Dual 40 DCOE's
      By ConreroGT in forum Opel Engine Performance Modifications
      Replies: 1
      Last Post: 04-02-2003, 01:19 PM

    Bookmarks

    Posting Permissions

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