News

Stripping a single, dual points '76 308 GTB dissy

Discussion in 'Technical Q&A' started by paul 308, May 13, 2004.

  1. paul 308

    paul 308 Karting

    Jan 13, 2004
    110
    Guildford, Surrey UK
    Full Name:
    Paul Deslandes
    Having read lots of recent threads on setting up the points, (Mike Procopio and others) setting dwell with an electric drill to drive the dissy on the bench (great idea!) etc, I took the dissy off the car to have a look.

    How do you remove the star shaped cover plate to get the points out? After removing the three c/s screws, the bearing is tight onto the shaft so won't just pull off. I tried very gently tapping the shaft with a rubber mallet but it showed no signs of being keen to come free and I don't think a puller would be a good idea on a soft ali plate.

    Yelcab I know I should replace the points with electronics and probably will eventually, but I still need to get in there!!

    BTW, when electronic systems are fitted do they add a carb potentiometer so that load can be mapped? I don't understand how Ferrari got away without something to replace vacuum advance. IMO Economy and performance should go way up. I guess this is what the dual points setup was suppposed to do, at least in part, in the 308 GT4.
     
  2. Ferrari_tech

    Ferrari_tech Formula 3

    Jul 28, 2003
    1,527
    UK
    Full Name:
    Malcolm W
    It should come off with the method you have tried, try tapping the shaft with a small copper hammer - if it's still refusing to come off the bearing then a small two legged puller will do the trick.


    MW
     
  3. Doug

    Doug Formula 3

    Nov 13, 2003
    1,467
    Louisville KY
    Full Name:
    Doug
    Which way does the shaft go through. On the back of my dist. I have a c-clip around the shaft and 6 screws. I have tried tapping with a rubber mallet and it doesn't move. I need to get in to look at the advance mechanism and I can't find a dis-assembly procedure.
     
  4. Mike Florio

    Mike Florio Formula Junior

    Jun 19, 2003
    572
    NW Rural Nevada
    Full Name:
    Mike Florio
    Paul:

    That piece on top of the distributor held in place with three screws most people call a spider can be removed with a two-legged puller. Be sure to mark the orientation of the spider to allow access to the points for adjustment. The spider must be in place to properly gap the points.

    The distributor uses a mechanical advance located in the bottom of the distributor, under the points plate.

    Doug:

    To get to the advance mechanism on the bottom remove the six screws, The top bearing (the one in the spider), support the main casting and gently tap the shaft from the top with a fiber hammer. Don't mess up the top of the shaft - your rotor has to fit on there.

    Paul & Doug:

    I have learned from hard experience that you need to look at the advance mechanism periodically to check for proper lubrication. The second set of points is just a fixed 5 degree retard when the throttle is at idle. The mechanical advance provides 34 degrees of advance essential for proper engine performance.

    Unfortunately, to fully check the advance mechanism you need a (these days) rare distributor machine. A quick check can be accomplished by setting the timing at 7 degrees BTDC at idle, then checking again at 6000 RPM for 34 degrees BTDC (marked on the flywheel). This doesn't check that the advance curves are matched in the two distributors - just that they start and end at the same place.

    There are several threads in the archives on disassembling and lubricating the advance mechanism. Be very careful in disassembly to mark each piece (I use an egg carton and put each individual piece in a separate hole). Clean and lubricate (I use a synthetic hi-temp grease for the springs, sliders and pins, Bosch distributor grease on the arm sliders and shaft). Reassemble exactly the way it came apart.
     
  5. yelcab

    yelcab F1 World Champ
    Consultant

    Nov 29, 2001
    10,177
    San Carlos, CA
    Full Name:
    Mitchell Le
    Take a look at this for a picture:

    http://www.ferrarichat.com/discus/messages/10/1860.html

    If Peter Rychel is reading this, he will post a better picture. Peter always has the appropriate picture.

    Here is a rough procedure, some very small steps may be missing.

    0. Take out your distributor and place it right side up with the shaft fitting in an open slot of a table, or bench vise. Now, everything comes out toward the top.
    1. Remove the three countersink screws, and remove the spider plate with a small 2-prong puller if you have too. Does not take much force to pull the spider plate toward the rotor end of the shaft.
    2. you can now remove all the points. take a picture, make notes of where they may have to go back.
    3. use the smaller puller (you will need it now) to remove the bearing, put it aside
    4. see the E-clip around the shaft in the picture ? Remove that with a screwdriver. Now the shaft will slide out from the dizzy housing.
    5. You'll see all the mechanical advance mechanism, weights and springs that react diferently under centrifugal force to advance the rotation of the rotor. Be careful removing each piece, make very exact note of where they go, the different lengths of the springs, the number of small shims, weights, and where they go. You will need to clean them and put them back in the exact location. Disassemble only one distributor at a time, so that you always have a completely assembled reference to go back to if you forget.
    6. Go back to the shaft, remove another small clip (i think), and pull off another bearing. Do replace that blasted leaking O-ring where it seals against the cam shaft. Buy several frrom a dealer, they don't come in a universal O-ring set.

    Clean everything, put them back. Now really is the time to update to crane cams like what Peter was doing in the post link above.

    Like I said, Peter will post a better picture if he reads this post. He always has the perfect exact picture, some place. Peter, you're up next! I set you up just perfect for your entry.
     
  6. paul 308

    paul 308 Karting

    Jan 13, 2004
    110
    Guildford, Surrey UK
    Full Name:
    Paul Deslandes
    Thanks guys for the info. Its always best to check before tapping or pulling as you never know if there's a grub screw or 'c' clip or something you can't see holding the darn thing together.

    I have just one distributor on my UK 308GTB but with two sets of points, one for each bank, set at 45deg to each other. There is no retard points/throttle microswitch as with the dual distributor setup on the GT4, so all I get is static timing plus mechanical advance with increasing revs. I guess its important to set the two sets of points up at exactly 45deg offset to ensure accurate static timing on each bank. The flywheel has marks for each bank so its easy (!) to check both with a timing strobe. Better to get it right on the bench first though.

    If I can locate the Crane parts in the UK I might give it a go. I know from past experience what a difference it can make. I even built my own 'transistorised' ignition system about 30 years ago (God I feel old) and put it on a Triumph Herald (saloon car version of the Spitfire). Well, I thought it went better....
     

Share This Page