308 carb idle question, w/ A/C on-off...?

This is not going to help very much... Just to say, mine does not have this problem.

It is strange that yours should be so sensitive to load.

If you look at the colour of the sparkplugs, is there anything to indicate that it is running extra weak, or even extra rich?

The book gives the idle speed at 1000 plus-minus 100 rpm so you have some room for leeway.

Setting the idle speed with the throttle stop screws is correct as far as I remember but you have to watch not to affect the balance between the front and the rear banks.

Once I started fiddling with the carbs I found I wasn't happy until I'd done the full monty, balancing, mixture with colortune and CO meter and so on.

Which is probably why this subject is such an old chest-nut.

good luck

 

10-14 mpg does sound low. Around 20 is probably correct unless you drive very fast!!

birdman has done a good thread on tuning the carbs in a 308 :

http://ferrarichat.com/forum/showthread.php?t=20179&highlight=weber

and yes, black electrodes would be too rich, very light brown/grey is weak.

 

Oops, I was thinking in british mpg. 20 british is about 17 US mpg

No there is no AC idle circuit.

Somone else may like to chime in to say if Gregs speed difference with the AC is normal though..

 

Sorry, I just saw this.

Greg, I have a small difference in idle speed with the AC on or off, but not that much. My first vote would be to install that Electromotive you have had sitting in your garage for 2 years. That will help a lot. The electromotive makes the car much more immune to outside factors because the timing is rock solid. That said, even when I was running points, I didn't have that much issue with the AC slowing the idle speed.

I have never gotten much better than 16 MPG (highway) and around town I get 14-15.

Birdman

 

Greg,
I'm just guessing that the sanden compressor puts more load on the car at idle than the york compressor that the car came with. Could be wrong, but that seems like the most likely explanation.

As for setting the idle, it is really a part of the carb synch procedure. I would be inclined to start all over on the carb synch to be sure it is right. But if you don't want to do it yourself, be sure that the person who does actually has a clue. People that can synch carbs are few and far between. The first and only time I let someone else "tune" my 308 they made it worse, not better.

If the carbs are synched right, you should not have to touch the idle mixture screws to tweak the idle speed. Each throttle stop (idle) screw should be doing 1/2 the work of holding the butterflies open a fraction of a mm at idle. So each one should be "helping" to hold. There is too much play in the linkage for one to do the work for both banks. If you are not using a synchrometer to do this, you will likely never get it right. It's a no brainer with a synchrometer and they are cheap. Just go through the tutorial on my site. A monkey can do it if he can follow directions!!

www.birdmanferrari.com

Birdman

 

I have a 78 with a Sanden compressor. My idle drops also. I set my idle to around 1300 or so in the summer time when I use the a/c pretty much all of the time. If I set it to 1000 rpm it will lug down around 600 or so. It only takes a few minutes to adjust and you only have to do it in the spring and fall. I wouldn't worry about it.

 

Greg,
A little tid bit I remember, re your gas mileage....A couple of months ago there was a thread on gas mileage for early 308's. Do a search, if you can, to find it and you will see that most people reported getting 10-15mpg (shockingly low) but, this was , I believe in city. I was a little concerned, since I am looking for just one of those cars. But hey, its a Ferrari, right??

 

I set my idle at 1100 rpm and the AC only takes about 100 rpm. Normal setting without AC is set at 1000 rpm. Also I am still getting 17mpg on the open road (60-70mph) but in the city I get about 10. I just can't or don't want to take it out of 2nd/3rd gear. Just like the sounds. Enjoy the ride

 

1st the fast idle cam is out of the loop. I do not have it functioning. Next there is an adjustment on my linkage for the fast idle cam. This is what I use to adjust the idle. The carbs are adjusted without the linkage attached so all of the tune up settings are made. Then I hook up the linkage and set the idle speed. Note after the normal carb adjustments (1/2 turn on idle screws ) I usuall get an idle speed of around 800 rpms. So I just adjust the fast idle screw (this lifts the idle stops together) to 1100 rpms and off I go. I loose about a 1oo rpms because of the AC drag.

 

I one of the "last 3 guys", and hope Ive helped in small way, but as I've said, I am looking, dont own one yet. Hope to soon!!!!!!!!

 

TOO MUCH!!! Stai scherzando, eh???? Now you let out the beans and the mystery behind my screen name is out (LOL)!

My parents are also from Sicily....Siracusa. Do you speak any of it, sicilian/proper Italian?

Still cant believe i was able to covet the name of Pippo on a forum having to do with Ferraris .....anyway, hope your carbs work out ok.

Joe

 

I don't know anything about the 308, but if the Sanden is pulling that much power, is it possible make a bracket and install an idle stop solenoid? They are readily available from any parts store.

 

Now THAT'S a good idea!

 

Greg,

I am anxious like you to find out more about this idle solenoid, as when I do get my 77 308, I too will be facing AC issues perhaps, and want to be up on it (it gets hot here in FL!). Did 3 ac systems myself here, but not in a ferrari/carb car.

Joe