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post #1 of 41 (permalink) Old 05-04-2014, 02:43 PM Thread Starter
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DCOE sync issues

I am working on this 1968 GT1300JR for a friend of mine and am finding many issues. It ran poorly when I brought it home last fall and spent the winter resolving everything else (wiring, interior, steering, etc). Now that it's nice weather again and most of the rest is done, I'm sorting the driveability. First thing I noticed, when checking the timing, the distributor had not been clamped down. There are lots of little issues like this that have frustrated me throughout. Many various people have been involved in this job over a few years... Now, on to the carbs.

I have read most of the posts on synchronizing DCOEs I could search on these forums (fora) and thought I'd use these instructions as a starting point;

Quote:
Originally Posted by alfaparticle View Post
From the Alfa Engine manual. It is the method that I use and I have never needed air flow meters, manometers, etc.
disconnect the linkage that connects the carbs to the gas pedal.
back out the idle speed screw.
back out the synchronization screw.
push up the synchronization arm that contacts the synch screw so that both carbs are fully closed.
Maintain the push on the arm and adjust the synch screw until it just touches the synch arm. I use a .003" feeler gauge.
slowly turn in the four idle mixture screws until they just seat then back them out 1 turn each if you have classic carbs or 4 turns if you have emissions carbs.
turn in the idle speed screw until it just touches the actuating arm, then give it one more turn
Reconnect the linkage and verify that there is some free play in it.
The engine should now start.
Adjust the idle speed screw until you are idling at about 1000 rpm
Turn in each mixture screw 1/4 turn, wait about 20 seconds and see if the revs change. Always adjust them all together as they should all be set the same. You want to find the point of maximum idle speed by turning them all in and out together. When you have it, adjust the idle speed screw for about 800 rpm.
DO NOT adjust the synch screw once you have set it properly.
I followed the sequence posted by alfaparticle and things would not behave as expected. Tried it again, same issue. Then again without satisfaction.

I ended up making an adapter for an old carb synchronizer I had for various twin carb Minis and an MGB I used to own. The sync showed that the front was not pulling as much air as the rear. A simple twist of the screw brought these into line. I also noticed the first/front barrel mixture screw does not have as pronounced affect as the other three.

It still has a huge bog or misfire between 2000 and 3500 rpm and I can't understand why. It's most noticeable at full throttle but can also be felt when slowly applying power.

Timing is correct. Advance is correct. Points are gapped. Plugs are new and gapped NGK BP7ES. Linkage is a bit tight - keeping pressure on the throttle (closed) when connected (the link from the bell crank to the carb spindles is fully shortened but is still a 1/4" too long but it will connect with a slight bit of pressure). The carb rubbers seem OK with pressure applied downwards or upwards not affecting the idle.

If anyone has had similar issues and can recommend a direction I should take next I would appreciate this greatly.

GT Junior 1300 Series 2, 1984 Spyder Veloce \(just visiting my place)
1973 1800ES, 1980 Mini, 1987 M6

Last edited by bhart; 05-04-2014 at 02:46 PM.
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post #2 of 41 (permalink) Old 05-04-2014, 02:54 PM
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What type of car do you normally work on ?

'64 Guilia Spider
'67 GTV
'68 Giulia Super

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post #3 of 41 (permalink) Old 05-04-2014, 03:44 PM
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It's worth keeping in mind that you're working on 46 year old carbs. The best suggestion I can give you is to remove the carbs and do a thorough strip and rebuild. When you have the carbs apart, check the internals and make sure they correspond to published oem settings. Alfa was careful with their carb settings and, on a stock engine, what they did was right.

Before you remove the carbs, however, you should check to see if the rubber mounts are leaking. The method you described isn't good enough. With the engine running spray some carb cleaner on the rubber mounts. If the idle speeds up you have a problem. Actually, if there are cracks on the outside of the carb mounts I'd replace them. New after market carb mounts aren't as good as the Pirelli originals, unfortunately, so be sure and check that the mounting faces on replacement mounts are flat or they'll leak are when installed.

If you don't have one, by all means get one or more Weber DCOE overhaul manuals. Heynes publishes a good one but there are other publishers with good manuals also.

Trust me, fresh Webers and new rubber carb mounts will transform an otherwise balky Alfa engine.

Jim . . . '72 Super 1300, '70, 1750GTV, 2nd series,
'62, Lancia Flaminia Zagato3c, 2nd series
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post #4 of 41 (permalink) Old 05-04-2014, 04:38 PM Thread Starter
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Quote:
Originally Posted by 101/105guy View Post
What type of car do you normally work on ?
Normally I work on control system software for educational installations. Trouble shooting is a way of life and I have learned to think logically and broadly when looking for solutions.

Cars - I am an import guy. Started with Minis... early crappy ones that needed to be fixed daily. MGBs were also on the radar which meant learning about king pins and lever shocks, etc. E30 BMWs which is where my first forays into tuning with software were experimented with but not fully enjoyed. After that the projects became bigger and more like restorations - a final Mini 1380 cc/ 120 HP (still have) Volvo 1800ES early Bosh fuel injection and York compressor AC (still have) then a complete (complete! every nut & bolt) restoration of a Land Rover Series III (still yes) and then the latest project was a 1964 Saab 96 - 3 cylinder, triple carb, 2 stroke that finding parts for is a challenge but is amazing and sounds like an Evinrude. Yes, they are normally stored at home (tight squeeze) and I try to drive them as often as I can.

Here's some pix of these latest;
Land Rover 1974 Series 3 88 Photos by MSVClassics | Photobucket

Daily driver? Jeep Grand Cherokee-older one with the 4.7HO and no computer nanny to slow you down in the deep snow.

GT Junior 1300 Series 2, 1984 Spyder Veloce \(just visiting my place)
1973 1800ES, 1980 Mini, 1987 M6

Last edited by bhart; 05-04-2014 at 05:05 PM.
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post #5 of 41 (permalink) Old 05-04-2014, 04:40 PM
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One turn out on the idle screws? Then start closing them? Wow. Anyway, this is what has always worked for me. Ensure all linkages are connected. Remove the air cleaner to allow access to the carb throats with a flashlight. Remove the four brass progression circuit plug covers to expose the three holes under each plug. Close all four idle speed screws, then back them out 2.5 turns. Obtain two small led flashlights, and shine them into the rear (firewall end) carb throats. Look down into the two exposed progression circuit openings and observe. Turn the idle speed screw until you can see light coming through all three holes in both carb throat progression circuits. Look carefully; adjust the idle speed screw until the rearmost hole of the three (the one closest to the engine) just begins to close off the light, then stop. Now move your flashlights to the front two carb throats. Use the synch screw to obtain the same sight picture (three illuminated holes in each progression circuit). Recheck the rear throats. Replace the four progression circuit plug covers and start the car, it will idle smoothly. Adjust from there if you want to. Use only the four idle speed screws now. If the car idles smoothly but is balking under load between 1500-3000 rpm or so, it's not the Webers. It's the ignition system. Likely a bad plug (yes, I know they are new- trust me), or plug wire, or rotor or cap. If you want to discuss further, PM me and we can talk.

Jim

Last edited by La Voce; 05-04-2014 at 04:47 PM.
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post #6 of 41 (permalink) Old 05-04-2014, 04:48 PM Thread Starter
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Quote:
Originally Posted by 180OUT View Post
It's worth keeping in mind that you're working on 46 year old carbs. The best suggestion I can give you is to remove the carbs and do a thorough strip and rebuild. When you have the carbs apart, check the internals and make sure they correspond to published oem settings. Alfa was careful with their carb settings and, on a stock engine, what they did was right.

Before you remove the carbs, however, you should check to see if the rubber mounts are leaking. The method you described isn't good enough. With the engine running spray some carb cleaner on the rubber mounts. If the idle speeds up you have a problem. Actually, if there are cracks on the outside of the carb mounts I'd replace them. New after market carb mounts aren't as good as the Pirelli originals, unfortunately, so be sure and check that the mounting faces on replacement mounts are flat or they'll leak are when installed.

If you don't have one, by all means get one or more Weber DCOE overhaul manuals. Heynes publishes a good one but there are other publishers with good manuals also.

Trust me, fresh Webers and new rubber carb mounts will transform an otherwise balky Alfa engine.
The carbs were re-built 5 years ago, while the resto was done, by our city's only Alfa specialist (started with the local Fiat/Alfa shop in the '70s) and he had a number of personal GT coupes over the years. They will only have a few hundred miles on them since being installed. I will try a spray on the mounts tomorrow.

I do have the Haynes Weber book and have been studying it. They don't deal with synchronizing though and I've been looking for some info on that, to be sure things are correct.

GT Junior 1300 Series 2, 1984 Spyder Veloce \(just visiting my place)
1973 1800ES, 1980 Mini, 1987 M6
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post #7 of 41 (permalink) Old 05-04-2014, 05:00 PM Thread Starter
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Quote:
Originally Posted by La Voce View Post
One turn out on the idle screws? Then start closing them? Wow. Anyway, this is what has always worked for me. Ensure all linkages are connected. Remove the air cleaner to allow access to the carb throats with a flashlight. Remove the four brass progression circuit plug covers to expose the three holes under each plug. Close all four idle speed screws, then back them out 2.5 turns. Obtain two small led flashlights, and shine them into the rear (firewall end) carb throats. Look down into the two exposed progression circuit openings and observe. Turn the idle speed screw until you can see light coming through all three holes in both carb throat progression circuits. Look carefully; adjust the idle speed screw until the rearmost hole of the three (the one closest to the engine) just begins to close off the light, then stop. Now move your flashlights to the front two carb throats. Use the synch screw to obtain the same sight picture (three illuminated holes in each progression circuit). Recheck the rear throats. Replace the four progression circuit plug covers and start the car, it will idle smoothly. Adjust from there if you want to. Use only the four idle speed screws now. If the car idles smoothly but is balking under load between 1500-3000 rpm or so, it's not the Webers. It's the ignition system. Likely a bad plug (yes, I know they are new- trust me), or plug wire, or rotor or cap. If you want to discuss further, PM me and we can talk.
Jim,
I had this procedure next on my list to try. Putting the flashlight into the carb makes more sense too since I've looked down the inspection holes and could not see enough to be accurate.

Plugs are new (yesterday) but it behaves the same as it did with the old Bosch-starts better though. I may look to the wires next - currently some bright red things with 'GT' on their sides. Maybe something less flashy and more reliable. Cap, rotor and condensor will have to be ordered.

GT Junior 1300 Series 2, 1984 Spyder Veloce \(just visiting my place)
1973 1800ES, 1980 Mini, 1987 M6
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post #8 of 41 (permalink) Old 05-04-2014, 05:10 PM
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Here is some very good information and it is free: http://www.lainefamily.com/images/WeberTuningManual.pdf

Ed Prytherch
79 Spider
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post #9 of 41 (permalink) Old 05-04-2014, 05:23 PM Thread Starter
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Thanks! and in English too.

There's a lot of detail here to go over. Nice drawings of the fuel circuits too - great artwork and easy to visualize. I'll have to find a few nights to go over this and make careful note of what's happening and under which circumstances.

Working with computers has forced me to learn patience and I may need it to uncover what's happening here.

GT Junior 1300 Series 2, 1984 Spyder Veloce \(just visiting my place)
1973 1800ES, 1980 Mini, 1987 M6
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post #10 of 41 (permalink) Old 05-04-2014, 08:11 PM
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Quote:
It still has a huge bog or misfire between 2000 and 3500 rpm and I can't understand why. It's most noticeable at full throttle but can also be felt when slowly applying power.
This sounds like the carbs are having a problem moving from the idle circuit to the main circuit. I wouldn't rule out a problem with the accelerator pump or jets. My guess is that this points to an internal problem.

Also, your difficulty in adjusting the idle-air screw on #1 throat, also signals an internal blockage. Webers in good working order will respond pretty much the same way to idle-air adjustments. If there's a difference, there's a problem.

Hint: I like to do my initial Weber adjusting with the throttle linkage unhooked. Depending on the bellcrank attachment, your's may be push-on spring-loaded or it may have the original curved spring clip fitted to the bottom of the bellcrank (or it may have nothing which is something you should fix). Check before you remove the linkage.

My long distance divination still points to gummed up carbs. I hope you don't have to take the carbs off but, if you do, they're very straightforward to work on.

Jim . . . '72 Super 1300, '70, 1750GTV, 2nd series,
'62, Lancia Flaminia Zagato3c, 2nd series

Last edited by 180OUT; 05-04-2014 at 08:16 PM.
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post #11 of 41 (permalink) Old 05-05-2014, 04:46 AM Thread Starter
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Quote:
Originally Posted by 180OUT View Post
Hint: I like to do my initial Weber adjusting with the throttle linkage unhooked. Depending on the bellcrank attachment, your's may be push-on spring-loaded or it may have the original curved spring clip fitted to the bottom of the bellcrank (or it may have nothing which is something you should fix). Check before you remove the linkage.
Yes, there is a return spring effect on the bell crank but I have not looked closely to see what it actually is. I did remove the linkage at the carbs for the adjustment.

I will go through the process of checking the throttle plates (again), this time with a couple of small LED flashlights in the carbs so I can actually see into the progression holes.

Gummed up carbs are possibly another reason for the random wonkiness. It is tempting to put some fuel system cleaner in the tank and see if there's any change. Tune UP In-A-Can... Failing that, if I pull the carbs, is a new aftermarket rubber isolator better or worse than an original old but sound part? I have had bad luck with the quality of some aftermarket parts - especially with the Land Rover suppliers in the UK.

GT Junior 1300 Series 2, 1984 Spyder Veloce \(just visiting my place)
1973 1800ES, 1980 Mini, 1987 M6
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post #12 of 41 (permalink) Old 05-05-2014, 05:49 AM
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About the same with repro Alfa parts. Some are good, others will give you fits !
Ihas been noted that some of the new rubber isolators are a different thickness other new ones.....but the old ones need to be checked.

'64 Guilia Spider
'67 GTV
'68 Giulia Super

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post #13 of 41 (permalink) Old 05-05-2014, 07:37 AM
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Quote:
Failing that, if I pull the carbs, is a new aftermarket rubber isolator better or worse than an original old but sound part? I have had bad luck with the quality of some aftermarket parts - especially with the Land Rover suppliers in the UK.
[/QUOTE]

Went through the same thing not too long ago with my Super. The best event is that you spray carb-cleaner or something similar on the rubber mounts and the revs immediately go up. Then you know for certain you have a bad mount. This doesn't always work, however. If the rubber mount is cracked, it's probably a good idea to think about changing it, oem or not.

As was reported sometime back on the bb, the problem with some of the aftermarket car rubbers is that the mounting surfaces aren't flat. So, you should check them with a straight edge. Gordon Raymond who is braver about this than me, removed the studs and dressed the mounting surface with sand paper mounted on a glass plate. Before I did that I'd check the UK suppliers and see if I could find nos Pirelli mounts. My Super ended up with 2 aftermarket mounts (which were flat) and two original mounts which were uncracked.

Jim . . . '72 Super 1300, '70, 1750GTV, 2nd series,
'62, Lancia Flaminia Zagato3c, 2nd series
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post #14 of 41 (permalink) Old 07-31-2019, 06:43 AM
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We are having the same problems, with a vacuum leak (shows up when starting fluid is sprayed at the soft mounts). I simply installed new soft mounts and assumed everything was good. Not so, we have the same result before and after new soft mounts. I was trying to not use Permatex as a sealer, but this looks like a potential fix? Where else could we have a vacuum leak?
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post #15 of 41 (permalink) Old 07-31-2019, 07:22 AM
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The last guy who did mounts on my car used Permatex and I spent a couple of hours cursing the SOB.

You used new paper gaskets, correct? Those and a thin smear of grease should've been all you need. You still get a leak when you spray the mounts?

Tom

1963 Giulia Spider (1750 engine)
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