Trouble with the Mix? on a 308 carb synch.

There are much more talented people on this site than I but here is my $0.02

From my experience unless you have a carb failure, there isn't much need to adjust the webers if they have been set up properly to begin with. I would go through the ignition first to ensure your spark and timing are perfect, then look for vacuum leaks at the carb bases, the various hoses, etc. Once those possibilities have been eliminated I would then go back to the carb synch procedure.

Let's see if others agree or have different suggestions.

 

agreed. carbs do not change settings "all of a sudden". unless there was a large elevation change, or a change to the air going in, or the exhaust, the carbs should be ok. timing timing timing! is key on carb cars. points ignition sucks. Ferrari;s more so because of the mechanical advance as opposed to vaccum. your points degrade with time, and should be checked , cleaned and adjusted as often as 5000k miles ot so, depending on use. if the weights are sticking in one dizzy, the car will run like crap. ask me how i know. check your timing, the dwell and condition of the points. clean the terminals inside your caps and look for carbon tracking or cracks. next check the spark plugs, they ( usually) will give vast amounts of info, but if you have been working with the carbs they may be of little use to "read" this time. once the timing is ok and the advance is working ( imagine that), then do the carb sync dance again. my new to me GTB is getting a pertronix set up to rid me of the points, but it will not solve the problem of the advance weights nor the issue of 27 year old dizzy internal parts. i will go to the next step ( distributerless) if i keep this car more than 6 months or so.
i learned a valuable lesson, in that the idle mixture screws contorl AIR in more ways than they control fuel. be careful how you set them or you will be running off the progression circuit all the time ( dead rich plug indication, fuel smell ).

best.

 

Carreaper, points do not suck!! They simply require greater attention in initial set up, and periodical maintenance. I agree the twin dizzy set up is a bit more fiddly to synchronise, but a UK type single distributor with twin points is very reliable.

Also carreaper, there is no car on the planet that uses vacuum advance. Many older cars have a vacuum mechanism on the distributor and it is used to RETARD the timing on over run as an efficiency aid, all "vacuum" distributors use mechanical advance bob weights. The classic Mini Cooper are a prime example...all the std cars have vacuum dizzies, but all Coopers have the vacuum removed and a more aggresive mechanical advance...much like the 308 series in fact.

Anyway, apart from that your advice is bang on. Don't even think about touching carburettors until cam and ignition timing operation has been verified!!

 

walawdog, in addition to verifying that your ignition condition and timing is correct and if it is and you're still experiencing this problem, you may have vacuum leaks in and around the carbs that is causing this problem.

I experienced this on my car when I had leaks from the throttle shaft bearings (which had run dry - no grease left in them). It caused the car to run terribly with alot of back-firing and sluggish performance. You may have the same problem, or maybe you have leaks around the carb base gaskets, or from other gaskets on the carb bodies.

You can detect these leaks by spraying starting fluid at these areas, or a safer method of using a stethescope and listening for hissing noises from these areas.

 

my new to me GTB is getting a pertronix set up to rid me of the points, but it will not solve the problem of the advance weights nor the issue of 27 year old dizzy internal parts. i will go to the next step ( distributerless) if i keep this car more than 6 months or so.
best.[/QUOTE]
I had mine converted to pertronix's a few years ago. The guy that did mine put both pick up units in one dizzy so that you don't need to set each dizzy. Who is doing yours and are you doing both dizzys ? By the way I went with Bosch blue coils and eliminated the bypass resistor. Works great.

 

This will take some work, so do one thing at a time systematically.

1. Make sure your engine has decent compression (does not have to be perfect)
2. Timing has to be correct, they are set independently for each bank
3. Distributors have to work properly, points and condensors have to be in good condition (not perfect, just good), advance mechanism must work and synch up front to back. Many people have converted to 1 point, or no points with electronic ignition after they fully rebuild the distributors.
4. Don't mess with unknowns, if your carbs are that old, rebuild them with new kits. It is not hard and not that expensive if you do it yourself.
5. Do a vacuum check and fix the leaks
6. Then synch your carbs. Once they are in, they will stay that way for years.

 

How do I check my points and condensers? I've seen a lot of threads on carbs, but none on setting points and condensers?

My car is running fine, but I doubt the points were checked before I got it a year ago and I have no idea what condition they are in.

The mechanical advance in the dist. was working when I set the timing 6-months ago and I can only assume that is OK.

 

i said what i said with a sense of humor! its my opinion that many of these cars from the points era, earned a reputation for bieng unreliable because 1) the techs owners and techs did not keep the cars running in top shape and check the ignition and timing on a regular basis 2) Ferrari's , Lcars ect are usually not driven as often as they should be, making the problems worse from lack of use.

i have never seen a Mini Cooper. but i know more about OLD GM carbs and ignitions systems than most folks. using engine vaccum to curve the ignition timing is a far better way than relying on the weights and springs alone. out of over 140+ cars i have had, RARELY did i have a problem with the one wire GM vaccum advance dizzy. i converted every single Corvette , Trans Am and Camaro i had to the 1 wire electronic ignition. keeping points on say a 1969 Camaro is ridiculous , unless its a show car. HAVING points on a high reving ferrari engine up to 1979 ( USA) or so is equally ridiculous.

the cars are old. the weak ignition system coupled with the crappy fuse block equals cars problems, and a very real fire hazard.

always check the timing and points first, before messing about with the carbs. the vaccum draw assures the timing is where it needs to be when the engine needs it. relying on just the mechanical weights is always a problem, and with the very high humidity ( 90%+) here, the dizzy's always need "some" attention. if i keep the car, i am going to try a few things. i have some ideas that may turn into marketable products. best! michael

 

I had mine converted to pertronix's a few years ago. The guy that did mine put both pick up units in one dizzy so that you don't need to set each dizzy. Who is doing yours and are you doing both dizzys ? By the way I went with Bosch blue coils and eliminated the bypass resistor. Works great.[/QUOTE]


i am waiting for Summit racing to send me the parts. they dont sell the blue coils and told me i should use the Pertonix matched coils for the system. they said they were internally ballasted also. i will see when the stuff gets here. i figured i would put the system in, but as FerrariFixer pointed out, you must still make sure the mechanical advance is working properly and not use the new ignition sysytem as a crutch, and ignore the proper set up of the mechanical advance system.
the Norwoods single dizzy conversion is very appealing and does away with the mechanical weights and expensive Ferrari caps as it uses some other dizzy cap. ( GM ? Ford? ) from what i have read on the subject, puting both pickups in the one distributer is the way to go. i have a few ideas i want to try.................

 

you will need feeler gauges and a dwell meter to make sure your points are working as they should. i would have to read up on how to check the mechanical advance. the distributers usually have to be removed and checked with a machine through thier whole operating range . if it aint broke and runs well, i would not mess with it. points degrade every 5000 to 7000 miles ( i think) i dont keep my cars long enough to worry about it. i am sure some of the other folks here can give you a more through explanation than myself.

 

Anthony,

A certain amount of "don't fix what ain't broke" applies. If you want to go through the expense of converting your car to breakerless ignition - that's fine, but just be advised that a great deal of us are using our cars regularly and at the track and they have nearly stock ignitions in them. The only mod I made 17 years ago was to add "hotter" coils. The ignition components were new when I set the car up at that time and they haven't been replaced yet. I can pull 7 grand whenever I want with no miss-fires as long as the plugs are kept clean.

As far as setting up points, the best way is to pull the distributors out and set them up using the comfort and convenience of your workbench.

Best wishes on your solution.

 

I still don't like points. When I 1st got the car it ran well for about a month and then one day 1 bank would fire intermittently. I thought the engine was going to bloe. I diagonised the problem to the set of points had a loose point head. Not a wire but the actual point head was loose. So I went to look for a conversion but didn't want to do the crane thing and add the control boxes. I found this guy in Calf. who did the conversion with pertronix units in 1 dizzy. So I sent him the dizzy and he rebuilt it and did the twin pertronix setup. I put it in and set the timing and 2 years later I haven't touched it. Buy the way I still have the same set of plugs that were changed at the same time. Oh I only put on 15000 miles so we'll see how it last in 5 or 10 more years. I've converted all of my old cars to breakerless ign. More reliable IMO.

 

That must have been fun to diagnose. Do you have the single Euro distributor in your car?

 

Nope , US twin dizzy's. I had to take out the dizzy that was not firing or was intermittent. I looked at the points for a good half hour just setting the gap and remeasuring. As I was sliding in the feeler gage I noticed one side of the points head moving. I pulled the points out and could rotate the head in the bracket . Could not keep a consistent gap. Ended up soldering the head to the bracket , filed the points and reinstalled the points. Ran fine until I did the conversion 2 weeks later.