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Correct Ignition for early Euro GT4 Running one set of points

Discussion in '308/328' started by robertgarven, Jul 24, 2023.

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  1. robertgarven

    robertgarven F1 Veteran
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    #1 robertgarven, Jul 24, 2023
    Last edited: Jul 24, 2023
    Friends,

    On my 1974 308GT4 euro version I am attempting to set the timing, and I'm getting all sorts of conflicting information from the WSM (workshop manual) and my Euro OM (owners manual). I hope some of the experts here can offer some opinions or direction.

    I've been having off idle stumbling which I thought were my carburetors. I couldn't find anything wrong there so I started checking my distributors. I was working on them for a while and I reached out to an expert Dave North in New Jersey who's ad I found in Forza, and I ended up sending my distributors off to him for a rebuild. He did an amazing job, and I highly recommend his services!! Now I'm trying to figure out how to set the static timing correctly.

    I'm only running one set of R1 points and I've been setting static timing at +6. But after looking closer at the book and talking to Dave, the R1 points should be set at AF16? What further complicates this process is my flywheel has a static advanced set at AF18, which clearly states in the owners manual to set the advance timing at, but but in the WSM there's a warning on page B35 saying you still need to set it at AF16°.

    If anyone could be of any help to help me try to figure this out I would be eternally grateful. BTW Dave set the distributors at the proper Euro 13° for this car. Here are some of the relevant pages.

    Thanks in advance for anyone helping out! I'm sorry I've been absent here for a while but I've been off with the band, which has left me less time than I would like to work on the Ferrari's!

    Rob
     

    Attached Files:

  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #2 Steve Magnusson, Jul 24, 2023
    It's about getting the correct 34 deg BTDC timing at 5000 crankshaft RPM. If your distributors have been set to the advance curve on page L15 (and you are only running R1 points), you would set the 1000 (crankshaft) RPM to 16 deg BTDC:

    16 deg BTDC (at 1000 crankshaft RPM) + (2 * 9 deg more dist advance at 2500 distributor RPM) = 34 deg BTDC at 5000 crankshaft RPM

    Whether you can get a stable 1000 RPM idle at 16 deg BTDC on R1 is another issue ;) -- will be interested to know if you can. IMO, if you want to run an R1 only system, you might be better off to have the distributors set to the advance curves shown on page O8 so that you can use a 6~7 deg BTDC R1-only idle timing at 1000 RPM and still get a 34~35 deg BTDC at 5000 crankshaft RPM.

    PS The note on page B35 is clear enough -- they just mismarked the flywheel at 18 deg BTDC and indicate how to "correct" that to be 16 deg BTDC.
     
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  3. robertgarven

    robertgarven F1 Veteran
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    #3 robertgarven, Jul 24, 2023
    Steve,

    Thanks! I knew someone like you would chime in. I have another problem these are the earlier distributors with the dog drives so it's not like the spline distributor where you just pull it off, turn it over one slpine and put it back in, you can only set them 90° apart. I never had one of those dog drive units before so I didn't mess with it. I'm just not sure how to set it up so it is safe to start the engine.

    I was so excited when I got the distributors back and the rotors lined up with where my marks were when I took them off. I put everything back together, the car had set for about a month so I took a few tries but it fired up and it was idling OK then it gave off a very loud backfire, I think from the exhaust. I immediately turned it off, then I thought maybe just too much gas in the carburetor so I started it up again and it backfired again so I shut it down till I could get some more advice. (The distributors on the rebuilt engine were pretty off from the baseline (some of the advances were 3-4 ° off from each other and one unit was topping out at 20°!) It actually ran fine all the way up to redline but was stumbling off idle.

    I put the car in neutral and turned the engine around to where the 18° mark is, the WSM it said put it 3 to 4 mm less advanced so I'm thinking I would be right about where the second number of 18 is?

    I'm running only one R1 set on my US 75 version and it runs amazing it's distributors are even missing half the weights and pins. I thought almost everyone that was still running distributors were running only one set of points. My 75 is an earlier engine with the earlier cams, why are the advance curves and static advance so different? I'm not sure what to do now.

    Rob

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  4. robertgarven

    robertgarven F1 Veteran
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    #4 robertgarven, Jul 24, 2023
    Steve and All,

    What do the guys running the single distributor in the Euro cars do they only have 2 sets of points. Is there anyway to change the thread title?

    Rob
     
  5. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #5 Steve Magnusson, Jul 24, 2023
    Agree - the "8" in the "18" is about where 16 deg BTDC would be.

    Except (probably) everyone who is doing that has the distributor advance set like shown on page O8 -- so you get the relationship that using 7 deg BTDC at 1000 RPM idle gives 34 deg BTDC at 5000 crankshaft RPM. I can't recall anyone specifically stating they have the dist advance curve on page L15 and are running R1-only at 16 deg BTDC at idle. Maybe someone is doing that, but most R1-only set-ups are on US version cars (i.e., dist advance curve set to page O8).

    The stock set-ups aren't that different -- the US cars have less advance at lowish RPM (idle to about 2000 crankshaft RPM), but are very similar above 2K to redline. It just happens that the US cars tolerate an R1-only set-up fairly well. If you want to run an R1-only set-up, you'll probably need to have the distributors advance set to the graph on page O8. If you want to use the advance curve on page L15 = you probably need R1 and R2 working as designed (so the idle timing can be a more reasonable 6 deg BTDC).

    The SPC shows that they only have two sets of points in the single distributor set-up, and my guess would be they are both R1 points and the advance curve is similar to page O8, but have never come across any clear F information about it.

    Just "report" your post #1 and ask a Moderator to change the thread title to what you want.
     
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  6. robertgarven

    robertgarven F1 Veteran
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    #6 robertgarven, Jul 25, 2023
    Steve and all,

    So the WSM says 3-4mm toward PM1-4. Im guessing that is about where the "1" is after the 18° mark is. I'm hoping this will work if not I'll have the distributors reset at the 16° advance.

    Rob
     
  7. Rifledriver

    Rifledriver Three Time F1 World Champ

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    #7 Rifledriver, Jul 25, 2023
    Last edited: Jul 25, 2023
    Pretty much in line with Steve, Ferrari tuning procedure they always taught was set it at the max spec and be sure the idle advance is kind of close. Dont stress about 2 degrees at idle unless you catch it detonation coming away from a stop.

    I have that book too and I do find some interesting conflicts in data. They say to time it at 5000 RPM but that is only a little more than half way through the curve. We typically set the 12s at 6500 or so for that reason.

    Been a very long time since I have tuned V8's with distributors.
     
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  8. robertgarven

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    #8 robertgarven, Jul 26, 2023
    Steve et all,

    Please bear with me I have been doing this over such a long period of time I have forgotten more than I remember!

    I'm really struggling here just to get the engine running again. When I took these units off the engine was running fine, just stumbling off idle, now I can't get it to run at all. I spent all day yesterday rotating the engine and marking several more of the timing marks, this is a very early engine *00084* and its flywheel has 18° marks so I moved over roughly 3.5 mm and marked a 16° mark, the rear 1-4 distributor lined up with the index mark on the distributor pointing at cylinder #1 in the diagram below. (see pic with me holding stick)

    I rolled over the engine to the 16° mark on the 5-8 bank and the rotor was not pointing to the index mark but to cylinder 8. Obviously not understanding what the WSM said I moved the rotor so it pointed to cylinder 5 where the mark was. I was all excited thinking this was the cause of my problem, put everything back together but the engine would not fire at all????

    It seemed like it was running on all cylinders the day before so I think I need a point that one rotor back at cylinder 8? BTW at 16° on the 5-8 bank the rotor was spot on to the index mark.
    I guess I need to move it back to where it was but that doesn't explain why I was getting such a radical backfiring which I've never heard in 30 years of 308 ownership. I've done this on my other 75 US GT4 several times in the past I've never had a problem ever. I just wanna get it running so I can throw the strobe light on there and see what's going on. I am attaching also the spec sheet about my distributors where they were and how perfectly they follow the 13° advance now. Obviously this was set up on the 16° advance before, so I'm not sure why it's not running better seeing how off the distributors were before and spot on now... I added a PDF because the JPEG was a little fuzzy

    Steve if you or anyone can help me get back on track I'd appreciate it. I probably should've posted this in a technical section.
    Note: I suppose it's because this is such an early engine but when I rolled past PM 1-4 there was no index mark on the cam cap under the oil filler cap?

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    5-8 at 16° pointing to #8 cylinder was running
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    moved it to #5 to match mark. I realize last night if the distributor is rotated around the mark would move with it it may be only that index mark is made for bench testing...?
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  9. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #9 Steve Magnusson, Jul 26, 2023
    Indicates that you are on the wrong crankshaft rotation. Put the flywheel at the PM1-4 mark WHEN the cam cap marks under the oil filler cap are roughly lined up = this is when the 1-4 dist rotor should be pointing at the notch in the 1-4 dist housing rim. Also make sure that the #1 cyl spark plug wire is connected to the terminal that the 1-4 dist rotor is point at when it's pointing at the notch on the 1-4 dist housing rim.

    Then rotate the crankshaft 90 deg CW (viewed looking at the crankshaft snout end) to the PM5-8 mark on the flywheel = this is when the 5-8 dist rotor should be pointing at the notch in the 5-8 dist housing and at the cap terminal holding the #5 spark plug wire.

    PS I'm still not hopeful that you will be able to run an R1-only set-up at 16 deg BTDC idle timing with the dist advance set to page L15 as they are now. The reason you were quasi-able to run an R1-only set-up before at 7 deg BTDC idle timing is that the old (initial) setting of your 1-4 dist advance was about 1/2 way between the advance curve on page L15 and the advance curve shown on page O8, and the old (initial) setting of your 5-8 dist advance was like on page O8. IMO, you should have your distributors reset to the advance graph on page O8 if you want to run an R1-only set-up at 7 deg BTDC idle timing.
     
  10. dino1971

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    #10 dino1971, Jul 29, 2023
    A quick note to point out that the OM and WFM are a bit difficult to read since they continuously switch between distributor advance (anticipo distributore) and engine advance (anticipo motore). The former starts at 0° and goes up to 13°. So, 13° distributor at 3400 rpm gives you 26° of engine advance with 35° being the target when floored. To get that with 13° of movement on the distributor, you need to begin at 10° BTDC just off of idle (if you are still running with R1/R2 points. This is unclear in the italian version, and the english and french translations are not any better.

    I have swapped my two distributor ignition with two lumenition optical pick-ups in the same distributor. A great (and nearly invisible) mod that takes all jitter, dwell, and (for the two distributor sets-up) differences in the advance curve timing, out of the picture!
     
  11. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #11 Steve Magnusson, Jul 29, 2023
    Last edited: Jul 29, 2023
    Will agree that it's confusing, and not well explained in the documentation, but the 34°~35° advance specification is at 5000 crankshaft RPM (not "when floored" -- i.e., not at redline). At 5000 crankshaft RPM, the euro distributor advance (page L15) is 9° at 2500 distributor RPM so:

    16° BTDC idle timing (R1) + 2 x 9° more advance = 34° BTDC (at 5000 crankshaft RPM)

    At 6800 crankshaft RPM, the dist advance increases further to 13° at 3400 distributor RPM. So the maximum (euro) advance is:

    16° BTDC idle timing (R1) + 2 x 13° more advance = 42° BTDC (at 6800 crankshaft RPM)
     
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  12. robertgarven

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    #12 robertgarven, Jul 31, 2023
    Dear Friends,

    It is a long story but the flywheel on this early engine has timing marks at 35°, 18° and 6°. At 5000 RPMs the engine is supposed to be at 34° advance. Initial advance for the set of R2 points I don't have installed was 6°, and for the set of R1 points installed it is supposed to be 16 right off idle.

    I added colored marks at 34° , 16° , and 8°. I set the initial advance to 8° as suggested by my old friend and expert Ferrari Tech, as he says the 308 engine likes to idle there. I went for a drive to warm up the engine and double checked that it was set at 8° but the car did not seem to like that setting. It felt like it needed more advance, at 5000 RPMs it was really straining and backfiring a bit.

    I returned home, set the advance to 16° on both distributors and went for a drive and it ran fantastic, exhilarated smoothly all the way to redline and it was just screaming. The only downside is that the idle is a bit high at between 1100 and 1200 rpms. I may try to adjust the idle speed on the carbs. Washed the car and it was happy. I am not experiencing the stumble off idle now, (which promoted this whole affair) as that was happening between 800 - 1100rpms, and with the engine running now at 1100-1200 rpms at idle that issue is solved for now. I was worried that I would not have much of a range of motion moving the distributor with the strobe light since it has the dog drive, but with the engine running just a slight movement of the distributor went from my markings for 6° to 16° with very little movement.

    This fine automobile hardly sees any stop and go driving, just having a bit of fun on the mountain roads right near my house, so I'm not sure what the downside of the higher idle would be other than wasting fuel. I will mess with the idle speed on the carbs, and see if they need any further attention. I really want to keep the mechanical bits together on this car since it's so nice. It was the one that had the frame off restoration by Al, who is actually auctioning off the original Paris show car he did at the same time.

    https://bid.goodingco.com/lots/view/1-7S8T37

    Steve, Wade, Brian and Dario, thanks for all the tips it's good to hear from you all. I've been so busy with the band I dont have much time to mess around with the Ferrari's as much as I would like, but I really miss it. I need to do it more, because my mind wasn't even wrapped around some pretty simple basics here that I forgot, like the dual rotation of the crankshaft. My dear friend Wade who goes by Ferrari tech here was also invaluable help to me, and I want you to know how much I value all of your friendship and camaraderie. Dave North at https://www.marellidistributorservice.com/ did a pretty amazing job getting the mechanical advance set near perfect in a short time. Everyone knows my love for Ferrari's, but if it wasn't for all of your help, my fantastic journey would be much diminished!

    Rob

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  13. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #13 Steve Magnusson, Jul 31, 2023
    This is why you'd be better off having the distributors reset to the advance curve on page O8 (as it will allow you to use less idle advance, but still give the 34-35 deg advance at 5000 RPM), or add the R2 points and set the (R2) idle timing to 6 deg BTDC. At 16 deg BTDC idle timing, I'll be surprised if you'll be able to reduce the carb airflow enough to get it down to 1000 RPM, and, even if possible, the idle speed will be more variable as teeny-tiny unrepeatability of the throttle plate idle positions will cause large RPM changes. JMOs.
     
  14. robertgarven

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    #14 robertgarven, Aug 1, 2023
    Steve,

    You are right, as always, but I think I'm gonna leave it like this just for a little while because I've been fighting a stumble just past idle for the last two years, took the carburetors apart couldn't find anything wrong there (Of course the were just rebuilt less than 3K miles ago), that's why I went down this route. I know it has to be the carbs and just need some advice on what parts to swap out to work with modern gas (all are stock Euro parts except the pump jet which I went 1 up and it did nothing). After warmed up it is idling at 1100 RPMs which is really only 100 more of then it is supposed to. I have a neighbor that lives two streets over that has a GT4 (he works a HAAS) and I stopped by and let him take a look and listen. At idle he said he couldn't tell it was too fast unless he looked at my tach. I know it's wrong, but if I get the idle down to correct 800 to 1000 RPMs and it still stumbles it's very unpleasant to drive, but I agree I need to sort this out. If someone has figured out the GT4 carb reboot I'll gladly try their formula!

    Our new albums coming out soon and new shows etc. So I'm gonna be busy for a bit. A few of our shows got canceled and so that where I found the time to tackle this brief service.

    You guys rock, here's a picture of one of our last big shows we opened for an English band Judas Priest there's 81,000 people. Here is a pic looking from my drums, big show in northern Germany "Waken" there were so many giant screens, some people stayed in the campground and watched the shows, they had a whole Mad Max mud pit car area 12 stages a 100 bands.....

    Rob

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  15. jgmblair

    jgmblair Formula Junior
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    #15 jgmblair, Aug 1, 2023
    Rob, still can’t believe you drive a red car and not a “Black Machine” ;)

     
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  16. dino1971

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    #16 dino1971, Aug 2, 2023
    Wow, I saw Judas Priest way back when I was young! Amazing and congratulations, it must have been incredible!
     
  17. sltillim

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    #17 sltillim, Aug 3, 2023
    No that would have been Elvis and I think Steve Miller - not Bad Company.... <<< see what i did there!

    Glad to see your still enjoying both your dinos Rob!
     
  18. Sergio Tavares

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    #18 Sergio Tavares, Aug 4, 2023
    very helpful, thank you much
     

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