Ferrari Mailing List: Carb cleaner and tuning

[Rick Lindsay (richardolindsay]

Hi Doug, Rob, Francis, et al.,

Doug asked,

> Say, what did you use to soak the carb in?  I used to be able get Mechanix

> Brand stuff in a gallon can with a little screen gizmo.

Rob lives in California where environmental regulations are stiffer than most other states, so I can't answer for him, but I use Chem Dip.

http://www.berrymanproducts.com/products/eco-friendly-products/berryman-chem-dip-carburetor-and-parts-cleaner/

Its not the same formulation as the older stuff sold under the same name but it is really good. And as Doug wrote,

> Open the can and drop birds out of the air - yeah man, that stuff WAS

> goooood.

It was evil incarnate! It had a yellow-green color that coated (and stained) one's rubber gloves and the smell made the Texas City refineries smell like a rose garden. But it was a fabulous carb cleaner. The new stuff is also good but takes longer.

I disassembled my Webers (one at a time because some parts shouldn't be interchanged) and soaked all the bits, including the carb bodies, in new Chem Dip for 45 minutes to an hour. Following that, everything was washed in hot soapy (Dawn Dishwashing detergent) water paying particular attention to small parts. Air dry on a clean shop towel.

That last bit said; There is a large aftermarket supply of Weber parts, should something get misplaced. I use these guys but a Google search will reveal other options.

http://www.piercemanifolds.com/

Reassembly is just as Rob described. It will only go back together one way. All the tubes and jets are unique to their locations. Rebuild kits, available from the Weber parts vendors, are not cheap but they are correct. 

On the 308 engine, I recommend replacing the heat isolators under the carbs. As original, the insulators have integral gaskets so installation is easy.

One last bit of advice: Be VERY careful to not drop anything into the open manifold runners! There are spacers, little metal tubes about 6mm long, that set between the carb top and the air cleaner. They control the amount of compression of the air cleaner gasket by the lower half of the air cleaner housing. They often lift up as the air cleaner base is removed, placing them perfectly aligned to drop into the carburetor chokes! Horror! Still, all may not be lost if this happens.

It didn't happen to me - because I was paranoid and hyper-careful - but others have suffered this woe. They avoided a top end tear-down by NOT touching the throttles, and thereby keeping the butterflies closed, then retrieving the errant spacer with a slim magnetic pick-up tool. The spacers are steel so the process can work. If I ever faced that peril I would hold the butterfly closed via the linkage while 'fishing'.

So Francis,  Rob is right. The rebuild is simple if tedious, because of the extra care these tiny machines deserve. The real work happens after everything is rebuilt and bolted back on the engine.

Tuning Webers is not carburetor adjustment. This is done with parts; jets and tubes. And unless someone has buggered with the bits, a rebuild will put everything back as new. The work is balancing the eight chokes! I learned a few lessons while doing this. The only real cost was my time, and a few toasted fingers.

The process is simple, in design, and if followed, will produce great results. Short cuts cause one to start over. Here's the abbreviated plan.

1. Using an airflow meter with the engine at idle and warmed up, balance the airflow between the chokes of each carb. This step corrects any tiny variations in manufacturing, across the body.

2. Adjust the linkage between the left and right carbs of each bank, until all four chokes are balanced.

3. Adjust the linkage between front and rear banks until balanced 

4. Measure everything again and repeat the whole sequence, as required.

5. Set idle speed and do step 4 again.

The key step in this process is to do all of this on a warmed up engine! That is how you want the engine balanced because that is how you drive the car! There is enough thermal expansion of the linkeage to upset a cold balance, just from engine heat! Learned that one the hard way. And of course, this is the bit where fingers get toasted.

Robbie, et al., have probably shared this same information but sometimes it's good to reiterate. So Francis, once your rebuild and/or balancing is complete, write to us and describe the performance; at idle, at cruise, accelerating and in over-running. Subtle variations of those conditions tell us which little tweaks are needed to the carb setup. Once everything is right, as my 308GTB is now, the car is dream to drive, under all conditions. I just can't keep the smile off of my face and at times, I even want to giggle. :-o

-rick