308 carb sync attempt #1 and questions

Actually, the next size is 57. That's what I'm using.

 

Birdman,

i have the book "Ferrari Guide To Performance" by Allan S. Bishop and it goes into detail about carbs. You want to borrow it?

 

I was having some slight popping at 70mph steady cruise, especially when it was cold outside. Very slight, very intermittent. I knew just a very small amount of extra fuel was needed. It worked. The beneficial side effect was that I could now lean out the mixture screws to the bare minimum consistent with smooth running. Prolonged idling, as in stop-n-go city driving was seriously carboning up the engine. HUGE cloud of black smoke when I finally stood on the loud pedal. With the slightly bigger jets and leaner mix screws, I'm burning very clean.

 

Great thread...............I spent 4 hours balancing the carbs last weekend. But still had the creeping idle problem even when balanced.

But its got a odd missfire and think the problem I am looking at now is a ignition and not a carberation issue. I follwed a different method than either of you guys.

I adjusted the throttle cable to a high idle about 1,500. I balanced the two left side carbs with the linkage. then balanced the right side carbs to the left.

then I adjusted it down to just under 1,000 rpm and set the idle stops so that the carbs balanced front to rear.

I didn't need to balance the left to right throats as they measured effectively the same with the tool I used. and I was about 4.25 turns out with idle mixture. THats where it was when I overhauled them.

 

No aftermarket stuff on this particular car. There is a pretty obvious ignition problem in my case. popping through the carbs is a very occaisional thing and irregular. However after havig run it for a while and immediatly upon shutdown you sometimes get a loud bang out of the exhaust. I assume that is from unburned gas ( there are Two test pipes on the car in leu of cats.) Plus you can hear an irregular beat to the exhaust , not a dead miss, its just a rough sound. I won't be able to tell you that the idle jets are untill I am with the car which may be a few days.

 

BTW, an easy way to temporarily achieve a fast idle is to jam a folded matchbook cover into the thermostatically (boy, that's a long word) controlled cold fast idle mechanism. Put it right where the linkage goody rides on the thermostat cam. This pulls on the linkage evenly, just like if you push on the throttle pedal.

 

true...........would have saved burning my wrist on the hot valve cover too.

 

Float adjustment. My mechanic advised me that at lower RPM's in turns they will sometimes starve and that a solution which helped was to adjust the floats.

Alternatively, he suggested, just stay in the gas, higher RPM's and full throttle will also help to alleviate it. Although, I have not tried solution #2 yet.

 

thanks birdman for the info, I ordered 60's today as well as carb kits, just in case.
Maybe I missed it but what are you running for exhaust?
When I switched to the flowmaster I got a lot of backfiring and pipping, especially on overrun. This almost disappeared with 140 mains and 200 ac's.

put the pedal down.
chris

 

[QUOTE=Birdman,

Will the old ANSA muffler i gave to you work? Also, stop by and pick up that book. It should give you some GREAT info as there is A LOT about carbs in it!!!!!!!!!

 

Hello Friends. I have read this whole thread (well, I skimmed some of it) and
although I have learned a lot - especially about the best balancing technique at
idle - I have another issue with my Euro-spec, single distributor, '79 308GTB
and I ask your help. Here are the observations. I would appreciate your
guesses as to the problem(s).

+ First of all, the car is bone stock. No modifications to the carbs or ignition at all.
+ No vacuum or fuel leaks found.
+ Car sat with old gas in it for a year, I added 3/4 tank of fresh 93 octane fuel. No
additives in the fuel except for the 15% alcohol used here in Houston.
+ Just finished a 'minor service', including belts.

+ The car starts and idles beautifully at about 1100 rpm and does not 'hunt'.
+ With no choke, the idle mixture 'smells' just a tiny bit rich.
+ When cold, it performs okay. I stay under about 3000 rpm until I see some oil heat.
+ When properly warmed up, the idle is still perfect, performance is as described below.

+ When accelerating mildly aggressively, away from standstill, there are no issues.
+ Upon gently opening the throttle from cruise, say at 2500-3000 rpm, there is a lag or
stumble.
+ Upon accelerating gently above 4500 rpm there is an intermittent and minor miss;
just enough to hear and feel
+ When given WOT, or close to it, the car runs fantastic without a single issue.

+ Upon overrun, especially after a little harder exercise, the engine sometimes 'spits',
'coughs' or produces what sounds like a carburettor backfire. Happens only once
on each overrun from higher rpm and happens intermittently.

Given all this info, please share any thoughts you have as to remedies to these issues.
Thank you.

 

Newman posted in Boxer thread yesterday that fuel mixtures today require a change to the emulsion tube??

I have no idea what that means maybe send him a PM to clarify.......it was to address a mid range stumble much as you are describing...

 

When was the last time you lubricated your distributor advance mechanism???

 

Ahemmm, uhhhh... never.

 

Well, you'll note in your Service Interval Charts that you should give it some love, every now and then!!

....exactly how I have no idea, I'll ask Ferda!

 

Thanks. I had to be honest. The car has been unloved lately as my silly, stinking job has eaten too much time. I just finished a 'minor service' on the car, except for the fluids and filters, which I will do this weekend. The rest of the required maintenance will follow. I have lubed the advance mechanism on my other (L4 and V12) British cars. Its just a drop of thin machine oil on the pivot points.

 

Wouldn't hurt..and give you a chance to survey and clean the cap and rotor...

 

Indeed.

 

Your idle speed should be 900-950 rpms. Did you verify the carbs are n sync'd not only at idle position but also when you hold the throttle open at about 2000rpms? There could still be a little adjustment needed in the linkages. The ignition timing should be set to 6 degrees at idle and 13 degrees at full advance, it's always good to check it with a timing light while reving the engine out.