Sunday, August 17, 2014

Carb Tuning #2: Tools needed, pre-tuning prep, & general pre-requisites

With a basic understanding established of what the various adjustments do on the Weber carbs fitted to a Dino lets now get ourselves ready to tune. In order to do this we will cover three items in this post:

- Tools needed
- Pre-tuning preparations
- General pre-requisites before getting started

Tools needed

In addition to a pair of ears to listen to the engine, there are only a few tools required to tune the carburetors.

#1 - A flat headed screwdriver to adjust the various speed and mixture screws. As a tip I make a small mark on one of the flats of the screwdriver to help me keep track of the number of turns and half-turns that I am making when adjusting the carbs. Remember these adjustments are made while the engine is running so it can be a little distracting and the mark helps quite a lot.





#2 - A carburetor synchrometer. It may sound fancy and expensive but a synchrometer is nothing more than a tool that measures airflow in the carburetor and costs less than $50. It is an essential tool for setting the carbs and makes you look really knowledgeable to casual observers when you use it.





#3 - Not totally essential but I like to use a digital timing gun to have a quick reference of the engine RPM's. It saves constantly looking into the car to reference the tachometer, acts as reference to check the accuracy of the tach, and is an essential tool anyways in the toolbox of someone who works on old cars. You may not need it to set up the carbs but it is required to make sure the ignition is working properly.



#4 - Lastly are some 8mm and 10mm wrenches to adjust the throttle linkage and the air bypass screw lock nuts. Simple stuff that should already be in the tool box.


Pre-Tuning Prep

Before getting started it is necessary to get your Dino (or other classic) ready to tune. The following is a checklist of things to do.

- Warm the car up to full operating temperature
- Remove the rear engine cover
- Remove the airbox cover
 
 
 
- Remove the nut (27mm wrench) that holds the crankcase breather assembly to the airbox. It is much easier to leave this entire assembly intact and remove it from the airbox rather than disconnecting all of the hoses that lead to it where visibility is greatly reduced.
 
Note the tape placed over the carburetor inlets to eliminate the chance of dropping anything down the carb openings. 

 
 
 
 
- Remove the nuts that hold the airbox to the tops of the carburetors. There should be 12 of them and can be removed using an 8mm socket. Also loosen the large hose clamp that connects to the ribbed inlet hose to the airbox.  



- Pull the airbox out being very careful not to loose any of the tube 'top hat' spacers that go under each of the nuts you previously removed. Some of these spacers may stay behind on the studs on the top of the carbs while some may come on the rubber sealing gaskets that are on the airbox. This is ok as long as you have all 12 of them accounted for once the airbox is removed.
 
 
 
- Re-connect the entire crankcase breather assembly. I used one plastic zip tie to hold the assembly in its finished position.
 
- I will add that some people disconnect the throttle linkage where it meets the #3 (left most when viewing the engine from behind) carburetor while others leave it connected. I have done it both ways with equal results always assuming that the assembly is free of un-necessary play or binding.
 
- If you are using one, connect your electronic timing light to act as your tachometer and take the pulse from the #3 cylinder. This is the rightmost cylinder on the rearward bank (the one closest to the distributor).
 
The previous list may seem like a lot but it can all be done in about 15-20 minutes. You are now ready to get started with your tuning.
 
General pre-requisites
 
All of the steps outlined in this post make some assumptions before tuning begins in earnest. Please be certain of the following before proceeding as carburetion is often cited as the cause of other problems:
 
Note that this list also works as a good troubleshooting guide if you struggle to get the carbs to setup properly. Setting the carbs is easy but you need to remember that everything around them need to also work well in order for the carbs to properly do their job.
 
1. Make sure your ignition system is working properly. This includes:
 
- Spark plugs are clean, of the correct type, and gapped appropriately
 
- Spark plug wires are in good shape
 
- Ignition cap and rotor are in good shape and not cracked
 
- Ignition advance mechanism is not seized and is operating properly. This can be tested on a running engine using your timing light. Testing that the distributor is properly advancing is very easy but is beyond the scope of this tutorial (we will cover this in a dedicated post in the future). We will proceed assuming that your distributor is advancing properly but note that this is one of the leading causes of poor running engines that are improperly diagnosed as carburetion issues.
 
2. Make sure the fuel system is working well. This includes
 
- Fresh fuel in the tank
 
- Fuel filter that is clean
 
- Fuel lines that are in proper shape and not cracking or deteriorated
 
- Throttle linkage that is properly lubricated and free of any play or binding.
 
- Make sure your float level is properly set on the carburetors. Here is a link to an excellent tutorial outlining this procedure:
 
 
- Make sure the carburetor has matching idle jets, main jets, and air correctors. Jetting may be different to stock but as a baseline here are the factory installed components on the Weber DCNF 40 carbs fitted to the Dino
 
Note: Do not always trust the sizes stamped on jets! These cars are old and lots of people have likely messed with them over the years. Quite often jets have been drilled out so their size is larger than what they show. I always check jets (even new ones) using a simple jet gauge. This is a tool with calibrated pins that either fit or don't fit into the jet openings and can be bought for about $15 on eBay or from whoever you buy your carburetor parts from.
 
3. Make sure the engine makes proper compression.
 
With everything apart this is a good time to check the compression of the engine. Again this is a separate procedure not covered in this tutorial but it is easy to find a YouTube video showing exactly how to test for proper and even compression. An engine with low compression can be tuned but having one or more cylinders with very low compression relative to the others will make proper tuning almost impossible. It is also good to know the health of your engine so a compression test is always a good idea if you do not know what condition your motor internals are in.
 
 
It may seem like a lot but really it is not. Being careful and methodical in setting up the carbs may not be glamorous but it is where the magic really is. Proper preparation and understanding of simple individual tasks is what will make you look like a factory trained carb tuning rock star.
 
Our next two carb tuning posts will cover idle and air correction adjustments followed by idle mixture adjustment. This will all be carried out on a running engine and again follows a structured approach that leaves little room for error. Stay tuned.
 

Thursday, August 14, 2014

Carb tuning #1: Weber DCNF carbs and their adjustments explained

With the car built and now on the road one of the most important items is ensuring that the carburetors are properly adjusted. This subject is often treated as some sort of black art that only the most skilled and special are able to do; TOTAL NONSENSE.

The reality is that carb adjustment can be done by the home mechanic to a very high level with minimal tools. What is necessary is a clear understanding of the various adjustments and how they affect the running of the engine. It is this understanding that a shocking number of 'experts' lack and our series of carb tuning posts are aimed at dispelling many of the myths out there giving Dino owners the confidence to tackle this project themselves.

To start we will look at the Weber 40 DCNF carb fitted to the Dino and identify and explain the parts that are touched when tuning the engine.

*Note that we will only address the high speed running circuit late in our posts. For now all the focus is on the items that affect the running of the engine below about 3000 rpm.

Below is an image of the carb fitted to a Dino. It is a dual throat construction where each throat feeds a single cylinder. As such the Dino has 6 cylinders so 3 carbs are fitted.


Now for an explanation of the marked parts:

Idle jet
- There are 2 idle jets per carb (one per throat & the 2nd one is not visible in the picture). Each jet acts totally independent of the other.

- Located under the screw in the photo is one of the idle jets. It is nothing more than a brass tube with a calibrated hole in it. These jets are available with larger or smaller holes depending on the amount of fuel you wish to introduce to the engine.

- Contrary to its name the idle jet supplies fuel to the engine up to about 3000 rpm so it is a vital part of the tuning equation. This will keep coming up so be clear on this point



Idle mixture adjustment screw

- Again there are two of these which act independently on each throat of the carburetor

- These screws can be adjusted down all the way to fully closed where no fuel gets to the engine during idle

- The adjustment of these screws are to be used ONLY to adjust the mixture at idle! Mechanics often turn these to correct low speed running problems and this is totally wrong. The idle screws are for idle ONLY.



Air bypass screws

- One per throat

- Allows for a compensation between throats of a single carburetor to equalize the flow between the two barrels.

- When properly adjusted, one of the air bypass screws is closed while the other is open a measured amount. We will discuss this setting later but if both are open the carb is not set correctly. In some instances both may be closed but for both to be open is not correct.



Idle speed screw

-  Because the each carb has only one throttle shaft that operates both throttle butterflies there is only one speed screw per carb.

- Think of the throttle butterflies as doors that allow the air/fuel mixture to enter the engine and the idle speed screw is a stop that controls how much the door closes. Because the engine needs a certain amount of air/fuel mixture in order to idle, the speed screw allows for a fine adjustment of how close to closed the butterflies are and is essential in setting the idle speed of the engine.

- The idle speed screw is one of the most tinkered with screws on the carb and is often opened far too much. Generally speaking if the screw is in more than 1.5 turns from the moment it contacts the throttle then it is turned too far.



Below are some more photos of some of the parts we mentioned allowing for a different perspective.






Summary

- Idle jets control the engine up to about 3000 RPM
- Idle mixture adjustment screws are to control idle only
- When properly set only one (or neither) of the air bypass screws are open; not both.
- Idle speed screw is used to set idle speed only and should be kept between about 1-1.5 turns from the first point of contact.

With the basic adjustment points explained the next in our series will look at the tools needed for the job of carb tuning as well as outlining the basic approach when setting the carbs. Future posts will take us step by step (with lots of photos) through the whole tuning procedure hopefully giving blog followers the confidence to do this job themselves.

Monday, July 21, 2014

Restoration Lesson #1: Do not believe in magical pixie dust



With our restoration mainly behind us we decided it would be a good idea to share some of the lessons we learned when restoring our Dino. While these lessons can be transferred to a number of different projects, they are the product of our observations and experiences in dealing with a multitude of vendors and workers in the restoration and automotive service field. Our experiences have been diverse but certain constants seem to continue to pop up over and over again and it is these patterns that will serve as the basis for a series of posts aimed at helping fellow classic car owners. With that said I shall introduce our first lesson:

Do not believe in magical pixie dust

I can already sense the looks of confusion but allow me to explain. The classic car service and restoration industry is inundated with mainly self-proclaimed experts who tout their services as being special and not available anywhere else. Spend any time at a car show and you will hear stories of a mythical mechanic who is 'the only person I trust my car to'. This is normally followed by some tale of an iconic mechanic he trained under, or some special connection he has to the factory, or how he only tunes engines at dawn, etc., etc., etc.

We have come to call this indulgent self-promotion 'magical pixie dust' where owners very much believe that supernatural occurrences take place while their car is being serviced or restored at the hands of their perceived vehicular savior. Of course I am glorifying things a little here but we have met a countless number of vintage car owners that speak of their chosen service facility with a reverence normally reserved for a magician or sorcerer.

The reality is that a vintage car was built by human beings and will be repaired by human beings with the goal of this lesson being that it is most important to judge ACTUAL RESULTS rather than be blinded by the reputation that a particular person or shop has. Reputation has some value but it is the result YOU get and the quality of service YOU receive that truly judges how competent a particular technician is.

We fell foul to this on a number of occasions during our project falsely believing tales that ended up being as founded as a handful of magical beans. In the end we learned to not get wrapped up in elaborate stories but to coldly and methodically judge results in a vacuum devoid of over hyped emotion. As soon as we started doing this the quality of our results really increased as we began working with REAL professionals who would tackle problems methodically and would reference proper technical texts to ensure the correct results.

In the end a car is nothing more than a machine with a large number of numerical specifications to its many parts. Assembling to these specifications using good mechanical practices is where the real experts shine and there is no magic about it.

Wednesday, July 2, 2014

Our Goals Exceeded: FCA National Meet Judging Sheet Received

Ferrari Club of America judging rules dictate that your judging sheet showing your deductions is sent to you a few weeks after the show. Up to this point all we knew is that we had scored 95 points or better to achieve a Platinum Award but did not know how close to 100 we did.

As previously stated 100 points hardly ever happens as judges get infinitely more picky as a car approaches a perfect score. On our end we were never arrogant enough to think we would score 100 either. After all we are just some newbie restorers doing our first Ferrari so we felt that we were bound to make a mistake somewhere along the lines that would be cause for deduction. In addition judging errors do happen so you must also take into account the human fallibility of the volunteers who evaluate the cars. With all this in mind we had set a goal of 98 points or better and worked hard towards that outcome.

Today the judging sheets came in and with it came a pleasant surprise. In the end we scored 99.5 points out of 100. With a half point being the smallest deduction possible we came as close to perfect as the rules allow which is better than we hoped for.


The obvious next question is: Why not 100? and What was the half point deduction for?

The answer to the second question is easier than the first so we will start with the low hanging fruit.

The leading edge of the doors on the Dino have a soft rubber trim on them that tucks under the rear edge of the front fender. When the trim is 100% brand new it takes a while for it to take its final set so from time to time it catches on the fender and sticks up a little. In our case we had our trim fitting well however when it was being loaded onto the truck for delivery it somehow got caught and spent 2 days bent backwards in the hot truck. When we unloaded for our final prep we saw the molding was deformed and did our best to get it set back into its correct position for the show. The extreme heat and humidity did not help our cause but we were able to get it to the point where 8 times out of 10 it would work well with time being the only proper remedy. Come show time the molding stuck ever so slightly when closing the door and we were deducted the half point because of it. With nothing more than a few days to heal itself the molding is now working perfectly again so all we can do is shrug our shoulders and call it one of those things that happen.

That said, we are realistic and believe that had it not been for the sticky molding at that moment  'something' would likely have been found (no car is perfect) as 100 scores are as rare as a 'hole in one' in golf.

99.5 Points at the Ferrari Club National Meet for a Dad and two brothers working in their spare time as total amateurs. We'll take it :)

Sunday, June 29, 2014

An empty parking lot: The first shakedown runs

With barely a single low speed kilometer on the clock since restoration, the time had now come to start running the car more seriously. While it would be great to just hop in and go for a cruise the reality is that for the car to run properly, hundreds of assemblies need to operate without problem.

Having had the whole car completely apart down to the disassembly of the clock, we felt that a progressive and metered approach to getting our Dino fully road worthy was called for. As such we have begun a process of progressively longer and more involved drives between which a comprehensive check of the tightness of all the fasteners is done. Racers call this giving the car a proper 'nut and bolt' and today was the first of these tests.

Lucky for us there is an enormous convention center only a few hundred meters from our office and today (being a Sunday) the entire complex was all but deserted. As such we had access to a number of roads and large parking lots on which to put our Dino through its paces. Operating in this controlled environment was great because it allowed us to really pay attention to the car without concern for other vehicles. Also should a mechanical problem arise we are not too far from home.

It all felt a little like those days way back when Dad would take us to a parking lot on a weekend to teach Paul or I to drive. For a good while we just circled the complex and with time built up more speed and confidence with the car. While keeping the engine within its break in max RPM we still managed some blasts up to about 70mph as well as some proper brake and cornering tests.

The test went well with no visible mechanical issues. The real proof will come when we get the car cooled and on the hoist for a comprehensive nut and bolt. If we don't find anything serious then the next run will be longer and on the public roads.