How to improve Carb balancing & Performance

Nice idea! When I eventually get my feet wet with a Ferrari it will undoubtedly be a carb model and while I like that Webers stay in tune a long time, I know getting them there isn't easy for beginners. Your idea looks like a godsend for we shade tree guys. When you get it working, please post pictures and lots of details on how you go about it!

At the moment I'm good with my duel Strombergs which are a PITA but not nearly as bad as their reputation becuase I'm pretty sure even the "experts" have no idea how to get the most out of them; I do. Reading struggles here with Webers, I have a hunch getting them balanced is even harder given there are way more adjustment parameters. If you KNOW the air balance is good, it should make everything else a lot easier to troubleshoot.

Ken

 

I believe there is a thread or at least a couple of posts that have gone over this form of balancing. It sure looks more precise than a bouncing red ball.

Let us iknow how it goes.

thanks,
chris

 

Yea, but I dunno if the pics are still there.

Basically it lets you use the vacuum tool for a four carb motorcycle to balance them......nice!

 

If you have a mass air flow measuring device (e.g., Sychrometer), could you also please just make a measurement (using that device) of what's going down each carb barrel after you equalize the pressures under the throttle plates and post the results? TIA -- just interested in how different they might be.

 

You know you're working on a Ferrari when you keep your wallet handy at all times.....

 

I did the motorcycle carb-stick process and it is miles ahead of checking each throat separately, both at idle and off idle. As the Brits would say, it works a treat.
Tom

 

Tom,were your cam covers originally red or did you have them painted?From memory your working on a GT4.Is that correct.I to am undergoing a complete engine rebuild including,HC pistons,valves,head porting and polishing,2nd gear synchro,new clutch..etc..and am at the final stages and with a bit of luck it should be ready by the end of next week.Its been 10 long months and i'm looking forward to driving it again.I have also been taking alot of pics of the various stages and will post them when i finish.Good luck with your car

 

gees isn't that done yet..

I remember you asking me a hypothetical question a while ago... the car I hadn't even started yet back then, has now been done... and won category and class in Classic adelaide....and done 2000km

Why the delay?

 

tomoshea,

Your intake manifolds look a little different then those on my 78 GTS. What year is yours?

I was able to use the orifices originally holding the metal tubes used to purge the charcoal canister. This gave a barb poisition very similar to your setup. For those thinking of doing something similar, yet still want to retain the vacuum purge system, right angle barbs will likely be necessary to avoid interfering with the throttle linkage. For pictures. please scroll down to the bottom of:

http://ferrarichat.com/forum/showthread.php?t=73549&highlight=manometer

 

I wish I could answer you Phil But I can't.I started working onit helping out and we have been doing it at night as my mech is to busy and short staffed to do it during the day.Anyway we finally put it all together tonight and will hopefully drop it in on Saturday.The good thing that has come out of it is that I have learnt a little along the way.I'll post some pics soon

 

Tom its looking good.I had everything beadblasted and it came up like new.I also used a high temp aluspray on a few bits here and there but went for the satin polish cam covers

 

I did this on my 77. It does indeed provide greater precision and you could hear an audible difference after setting. As a reference to Steve's question, I found say a 1/2 kg/min flow difference would translate into about 2 inches of manifold vacuum. Given the cam profiles I was using usually resulted in somewhere around 4 inches of vac, depending on idle speed, this was a significant difference. I used a brass plug which had a small barb at 90 degrees all of which was pressed into the manifold.

Good luck with the project.
Philip

 

Thanks for the info Philip (but isn't that Kg/hr?) -- they should be close since the mechanical shapes/tolerances don't vary that much. I never had any great difficulty using the Synchometer, but have heard some other mass air flow meters are difficult to use (and can appreciate the great "ease of use" of a multi-channel manometer).

I have to say that I'm still unsure what's really "best" -- having the same pressure drop across the throttle plates or having each cylinder contribute the same power at idle (i.e., having the same amount of air entering each cylinder)? Probably doesn't matter that much on a healthy system (since even when using a Synchrometer getting them each within 1/2 Kg/hr isn't bad), but glad to hear other opinions/thoughts.

 

I have been doing carb balancing by ear, for many years. I have found this, in my experience, to be more accurate than the mechanical indicators (needle and floating ball). I have never used an electronic or mercury manometer for this purpose, so I can't comment on them.

Bill

 

I agree that the intention is that all the carbs are exactly physically identical so it shouldn't matter which method is used, but all mechanical parts have tolerances/differences so I think there could be a real (but admittedly small) difference between the two methods.

 

I believe there is a lot of BS spread around the world relating to carburettors going off balance.

Think about it, it is impossible for a carburettor to adjust itself.

What happens normally is the carburettor gets crap in it and this affects the jets, say a little water jelly or grit, etc. and blocking an emulsion tube hole or something.

What unfortunately then happens is NOVICE mechanic then fiddles with carb adjustment and makes them unbalanced. In some cases by playing with one choke he might solve the problem BUT NOT THE CAUSE, but normally he/she completely fncks it right up and even then the carb's get blamed.

My father (and Mum) used to run a car repair garage and the number of times my father had to retune/balance carbs for idiots was amazing, and he used to off at them for touching them in the first place. If your car suddenly starts running bad, you MUST always check electronics FIRST and then ensure that the carbs are 100% clean and operating properly ... only then reluctantly move on to balancing (again why would it alter ... time to grill car owner and get the truth that he/she played with it!!!!!!). More likely an air leak has developed because a gasket has failed ... again NOT the carbs fault.

I used to race an Alfa Sud engine and every season I would remove the carbs and fully clean them (without altering the settings) and I never in many, many seasons of racing had to alter the carb balance ... and they run as 4 individual carbs (same concept as Ferrari engines, Ferrari v8's just have more off them).

So yes this modification will make the first (and ONLY) balance easy to do but from then on PLEASE leave the adjustment screws alone.
Pete
ps: Cars with multiple carburettors should have locked engine compartments that only an experienced and qualified mechanic can open. I reckon this modification would solve all this 'yeah your carbs are/sound unbalanced' BS that floats around the amature car enthuisast world. Man it must piss Weber, Delorto, etc. off ...

 

Steve, yes, my bad.
Philip

 

absolutely correct mostly.

When valve clearances get adjusted, carb balance will need a small trim. And if cam timing gets changed for any reason, more tuning.

 

Innovative Technology sells a tuning tool which measures the fuel air ratio to enable power tuning of gas engines. It's call the LM-1 with accessories costs about $600. Will do all cars, cabs, fuel injection, etc,. Pelicanparts.com sells it.