car collector chronicles 08-10

8/9/2019 Car Collector Chronicles 08-10

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Volume III, Issue 8

smaller, but nevertheless critical

parts.

Step #1, to mention the obvious, isto remove the air cleaner housing. Indoing the actual rebuild, the very first

tool I reached for was my digital

Continued on Pg. 2 -

After far too much procrasti-nation, I finally undertook therebuild of the carburetor onThe Gray Lady. In the hopesthat readers may find my ex-perience helpful, I thought this

month I would discuss this pro-ject?

This project has been on the"to do" list since the fall of 2009.I finally made the determinationI would cross it off my list! Thefirst task was to order the re-build kit. I bought mine onlinefrom Daytona Parts Co.. Ipurchased it only after confirm-ing via email that the kit materi-als were ethanol compatible.The cost of the kit for a 55

Caddy was around $50.

In preparation I bought abunch of used Kent-Mooretools/gauges, and a Morosocarburetor stand. I also col-lected as much Rochester Car-

buretor info/data as I could.

TOOLS REQUIRED: Cam-era, box wrenches, flarewrenches, screwdrivers, ham-mer, needle-nose pliers, a goodmetal ruler with a set capable T-bar graded in 32nd's of an inch,

parts cleaning fluid, parts clean-ing brushes, toothbrush, q-tips,a source of compressed air andof, course, shop towels. De-pending on your circumstances,you may also need a tubingcutter, tubing bender and a tube

flaring tool.

Let's get a little nomenclaturedown at the start, to assure weare all on the same page whendescribing both the carburetorand the rebuild process. My useof the term carburetor refers to

the entire assembled unit. Inthis instance we are specificallyreferring to a Rochester 4GC, 4bbl. carburetor. It is made up of3 main parts. I shall refer tothem as the airhorn, fuel bowland throttle body. Each constitu-ent part has a number of

Rebuild of a Carb

GDYNets on the Web

WHERE YOU WILL FIND

GDYNets (me) on the WWW:

Daves Den -

http://GDYNets.WEBNG.com

Saved 62 -

http://www.freewebs.com/jeandaveyaros

The Gray Lady - 55 Cad de Ville

Car Collector Chronicles -

DAVES DEN: A websitedevoted to a myriad of inter-ests. Foremost is extensiveinformation on the Steel Cityof Gary, IN. There are alsoofferings on steel making, U.S.Steel-Gary Works, U.S. MarineCorps, M14 assault rifle, ofcourse Oldsmobile, and thetragic story of the murder of

Gary, IN Police Lt. Geo. Yaros.

SAVED 62: A website devotedto our 1962 Oldsmobile Dy-namic 88 convertible. The sitealso has a lot of information onOldsmobiles and its founder,

Ransom Eli Olds.

THE GRAY LADY: This web-site features our 1955 CadillacCoup de Ville and Caddy infor-

mation.

A GDYNETSPUBLICATION

2010, G. DAVIDYAROS. ALLRIGHTS RESERVED.

August 2010Car Collector Chronicles

Car Collector

Chronicles

Exploring:

Car collecting today

Classic rides

Reports from the field

Oldsmobile

Cadillac

Allant

Corvair

IN THIS ISSUE:

Rebuild of a Carb 1

GDYNetsOn the Web

1

Rebuild Photos 7

Coming NextIssue

7

EMAIL:[email protected]
http://www.daytonaparts.com/http://www.daytonaparts.com/http://gdynets.webng.com/http://www.freewebs.com/jeandaveyaroshttp://graylady.webng.com/http://www.scribd.com/people/view/7936333-davemailto:[email protected]:[email protected]:[email protected]://www.scribd.com/people/view/7936333-davehttp://graylady.webng.com/http://www.freewebs.com/jeandaveyaroshttp://gdynets.webng.com/http://www.daytonaparts.com/


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camera. I took pictures of the carb in place, from all sides and angles.This was so I would have a visual reference of how a properly in-

stalled carb should look when I got around to putting her back on theengine. I took shots of the linkage connections, automatic choke set-ting, etc. I also made a handwritten note of the choke setting. Here iswhat the carb looked like at the start of the project

I next disconnected all thelinkage, so the carburetorwould be free to come off themanifold once it was unbolted.Then I removed all the linesgoing to the carb: choke tube,fuel line and vacuum line (?).The question mark is therebecause there is a small di-ameter, flared metal line witha fitting attached to the baseof the carburetor/throttle body.This line runs down between

the underside of the intake manifold and the top of the engine valleycover, toward the back of the engine. I have yet to ascertain what thisline is for, or does? [NOTE: ==>] I have since ascertained that it is, infact, the distributor vacuum advance line.

Once I removed the four nuts from the intake manifold mountingstuds, the carburetor came off easily. (I was surprised at how much itweighed!) At this point I covered the intake manifold ports to preventdirt or parts from falling into the manifold, and ultimately the engine.

The airhorn is what one sees when looking down at the top of thecarburetor. In vintage cars, the air cleaner sits directly on top of it.The airhorn top is home to the accelerator pump and choke butterflyplate. On the right (passenger) side of the airhorn is the automaticchoke. The underside of the airhorn is where one finds the floats,power piston, float needles and seats.

With the carburetor on the workbench, I drew a diagram of the top ofthe airhorn, giving each airhorn screw a number. Each screw was re-moved and then labeled with the appropriate number. This permitsputting the same screw back into the same hole on reassembly. Onething I did notice when removing the airhorn screws was that none ofthem seemed to be terribly tight; nor were the carburetor mountingnuts for that matter. In fact, they all seemed to be rather loose for my

ROCHESTER CARBURETOR REUILDContinued

Car Collector Chronicles Page 2

The airhorn is

what one sees

when looking

down at the

top of the

carburetor.


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ROCHESTER CARBURETOR REBUILDContinued

taste. I wondered if they had ever been touched since being origi-nally installed over a half-century ago, = w a y=> back in 1954? Forinexplicable reasons, one of the 13 airhorn screws did not have alockwasher? Nor was there an in-line fuel filter in the system?

One of the airhorn screws also holds the carburetor ID tag. Whilenot critical to the operation of the carburetor, it is very important forboth identification and historical purposes. It provides the carburetormodel # and the manufacture date code. The numbers on my tagare 700790 and M4. For the date code, the letter "M" is the month.The number "4" is the year in the decade. M4 equates to Decemberof 1954. This is because M is the twelfth letter of the alphabet, in se-quence ("I" not being used to avoid possible confusion with the num-

ber 1.) Do not lose, or destroy this tag and be sure to reinstall it!

BE ADVISED: The folks at Daytona Parts must assume if you arebuying one of their rebuild kits that you know what you are doing.This is neither a good, nor a necessarily valid, assumption. (Eventhough I have turned a lot of wrenches on a lot of cars, and even re-placed carburetors in the past, this was my first ever carb rebuild.) Isay this as, the accompanying kit instructions are more than sparse.To determine what went where, I found myself visually comparing thereplacement parts with original parts I could spot and remove. Notthe best way of doing things, in my humble opinion! It is also a bitfrustrating, as not all of the supplied parts are actually used in the re-build.

Ok, back to the airhorn, specifically the underside. Here one findsthe float assemblies. The float assemblies are held in place with(drift) pins. These pins come right out by hand. Each float arm piv-ots on a needle which travels inside a needle seat. BE CAREFULHERE! It is critical that one observe which way the needle is posi-tioned inside the seat. It can be installed two different ways. NOTE:Make a written notation which is the seat end, and which is the pivotpoint end. To a first timer, which end is which is not readily apparentat first glance. With the needle removed, the needle seat comes outeasily with a wide, flat blade screwdriver. Be sure to put the suppliedgaskets on the new needle seats before installing them in the air-horn.

My floats had a slight coating of gunk on them. I presume thiscoating could affect float movement/travel? Consequently, it wasgently removed with a toothbrush. Once cleaned, the floats have tobe inspected for leaks. If a float has a pinhole leak, the float can fillwith fuel, and not function. A simple test is to place the float in a panof water. Does it float? If it does, all is ok! If not, you have to eitherrepair, or replace it.

The carburetor

ID tag, while not

critical to the

operation of the

carburetor, it is

important for

both

identification

and historical

purposes.

Car Collector Chronicles Page 3


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Car Collector Chronicles Page 4;;

ROCHESTER CARBURETOR REBUILD-Continued

A critical step in reinstalling the floats is to be sure to FIRST INSTALL THE AIRHORNGASKET. Once the float arms are in place the gasket will not go on! The airhorn gas-ket must be in place, as its absence throws all your measurements off. Measurements,what measurements? The float levels must bepreciselyset for the carburetor to func-

tion properly. The float levels determine when the needle comes off the seat, allowinggas to enter the carburetor fuel bowl. The float arm travel parameters determine the lowand high levels of gas in the fuel bowl. This is where use of a good ruler graduated in1/32nd's of an inch, with a settable T-bar, is critical. Technically, one could use theflimsy paper ruler that comes with the rebuild kit. Truthfully, I did not find it to be veryhandy, practicable or useful. All required measurements are taken from the undersideof the airhorn, with the ruler held tight against the gasket. Without it being in place, allmeasurements are off by the thickness of the gasket. The rebuild kit does provide ameasurement specification sheet. This sheet also tells you where to bend the float armto adjust for the needed measurements. A WORD OF CAUTION: The float assemblyis delicate. Handle it with care. Be prepared to have to make repeated measurements

and adjustments. When setting the float for the closed position, don't be surprised tofind that doing so may throw off the open position setting! One must also make sure thefloats are parallel, and are able to travel freely within the confines of the fuel bowl. Thebest way to assure this is, with the float arms in the closed position, does the airhorngasket clear the floats?

Now, it is time to start buttoning up the carb. First, install the throttle body back on thebottom of the fuel bowl, using the new gasket that comes in the rebuild kit. Next, insertthe new accelerator pump spring in the accelerator pump bore/well of the fuel bowl. Puta small amount of gas in the fuel bowl to ease the initial start. DO NOT TRY AND FILLTHE FUEL BOWL! I recommend filling it 1/3 full. Install the new accelerator pump inthe airhorn. Batten down the airhorn to the fuel bowl. When tightening the airhornscrews, use an alternating, criss-cross pattern.

The next step is to install the new idle adjusting needles/air mixture screws in thethrottle body. THE CURRENT SETTINGS OF THE OLD SCREWS MUST BE DETER-MINED BEFORE THEY ARE REMOVED. This is accomplished by counting and re-cording the number of turns to lightly seat each screw. Once that is accomplished, thescrews may be removed. The new air mixture screws are installed and lightly seated.Then, they are backed off the precise number of turns you previously recorded. This isyour starting point when adjusting the settings on your installed and running carburetor.

It is now time to clean the intake manifold gasket seat. Use a scraper to remove all

traces of the old gasket. TAKE CARE THAT NO GASKET DEBRIS ENTERS THE IN-TAKE MANIFOLD. Install the new carburetor gasket on the intake manifold. No gasketadhesive is required to be used here, or anywhere else in the carburetor.

HINT: Now is the best time to do any work you want to perform on the distributor. Youraccess to it will never be better. At the very least, check and set the point gap beforereinstalling the carburetor. Oil the distributor bearing while you are in the vicinity. In mycase, at this point I also installed an in-line NORS glass bowl type fuel filter. I cannotbelieve there wasn't one in place! Hopefully, the fuel filter will capture all the previouslyobserved gunk before it can enter the carburetor?


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Installation of the carburetor is the reverse of the removal. Put it in place and attach the studmounting nuts. Now, attach the linkage. Check that the linkage moves freely through its normalcycle. Then attach your fuel and vacuum lines, and the choke tube. At this point it is necessary toadjust your choke setting to assure it closes properly, and opens correctly during the engine warm-ing process. The choke butterfly should notbe tightly closed on a cold engine. In fact, the specssay there should be .040 clearance between the closed butterfly and the carburetor bore.

If the fuel bowl of the carburetor is bone dry at this point, it will take some pumping of the accel-erator pedal and considerable cranking of the engine to fill it. Remember, without gas in the fuelbowl, the engine will never fire.

Once she fires, adjust the idle adjusting needles/air mixture screws to fine tune the carb to run atits most efficient. Set the fast and slow idle speeds and enjoy your newly rebuilt carb!

Ok, now lets talk about mistakes made and things learned while rebuilding this carburetor -

MISTAKES MADE: So far [Day 1], the only mistake made was in the purchase of a carburetorstand. The one I bought accepts two different sized carburetor bases. Size selection is accom-plished merely by flipping it over. The problem, neither size matched the base of the Rochester4GC. While it was still able to be used, it did not work as well as a proper one would.

After proselytizing on the subject of determining idle adjusting needles/air mixture screws settings, Iproceeded to remove one without first counting the needed turns to seat it! So, I had to default to ageneric setting. Not good!

When I bent my fuel line tubing, I did not pay attention the location of the fittings. When I made mybend both fittings were at the same end of the tubing. Needless to say, that makes it impossible toslide the one fitting around the curve you have just created in the tubing!

LESSONS LEARNED: The taking of "before" pictures turned out to be more than helpful. I had toresort to one photo to properly reconnect the accelerator linkage.

If you are lucky, you will not need to replace any metal fuel lines. Unless one is experienced andadept at bending and flaring tubing, have someone perform this service for you. My initial attemptat trying to install the glass bowl in-line fuel filter was a disaster. It leaked like a sieve at every pos-sible connection! The first flaring tool I bought/used simply did not work. It would not grip the tub-ing tight enough to permit the flaring head to do its thing. The second one worked much better.The problem with the second tool is that the tube tended to crack/split at the flare during the proce-dure.

Bending of tubing is a bit of an esoteric art. It does require the use of a tube bending tool. My re-

quirement called for two 90 bends. That in itself is not that difficult. The problem arises from thefact that what is really required on one end is a compound bend. The 90 bend at the filter end isroutine, and no problem. However, to get the tube fitting to line up with the fuel filter fitting, the tub-ing needs to also be bent on its axis. That is no easy task! Since it is not, I am now looking at us-ing an angled fitting (elbow) on the fuel pump to attach the fuel filter in such a manner that it will lineup properly with the line running out of the fuel filter and into the carburetor. It is hard to explain,but when one is under the hood trying to make all the necessary connections, it becomes painfullyobvious what is required. [SEE: A very crude rendition of my fuel line on the next page.]

Car Collector Chronicles Page 5;


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_____|Carb |--------------------

|_____| /

/

/(o) Fuel Filter

|

Fuel Pump O ----- |

Much to my surprise and dismay, even though I took pains to be sure I did have gas inthe carburetor fuel bowl when I remounted it, the engine to date [Day 2] has yet to fire?I am getting explosions, but not sustained firing?

[Day 3] I have removed the fuel filter entirely, and have reverted (temporarily) to usingthe original line, sans filter, that ran from the fuel pump to the carburetor.

When I was finished I found, to my chagrin, that I had a check ball left over. That I didmade no sense. So, I sent off an email to the Daytona Parts Co. folks asking what itwas, and where it went. To their credit, I did receive a very prompt reply. The leftovercheck ball goes in the bottom of the accelerator pump bore/well. A spring sits on top ofit, and the accelerator pump sits on top of the spring. Depending on the position of theaccelerator pump during operation, the left over check ball controls the flow of fuel toeither the carb fuel bowl or the primary venturi cluster. Without it being installed, all fuelentering the carb went to the fuel bowl. Without it being installed, pumping the gaspedal only yielded exercise of the ankle/foot muscles! Duh! No wonder the car wouldnot start? I never did figure out what happened to the original, missing check ball?

[Day 4] The carb is again removed from the engine and opened up to install the leftover check ball in the accelerator pump well/bore. After installing it, closing the carbback up and remounting it on the engine, with a little cranking she fired and ran!(Shouts of Its alive! were heard to emanate from the car barn.) I will admit, at first shesounded a bit like a concrete mixer. Once I got the engine warmed and the carb able toidle on her own, I was able to make the necessary idle adjusting needle/air mixturescrew adjustments to simulate normal operation. Then I checked operation on accel-eration. She accepts the gas feed and has very good response.

I also have my fuel line leak situation rectified. It took an hour of searching throughparts cabinets and catalogs with my local NAPA parts guy to find the right 90 elbows,male-to-male fittings, etc., but the fuel pump now sends the gas from the tank into the

filter before going onto the carburetor, and it does it without leaking! There now is onlya single tube running from the fuel filter-out port to the carburetor, and it has a singlebend of 80 or so. The fuel pump is now directly connected to the fuel filter-in port viafittings, eliminating the need of any tubing there. This part of the project was bettersuited for the skills of a plumber, than a mechanic. Nor am I at all ashamed to acknowl-edge that not only is plumbing not my forte, but that also, I hate plumbing!

BOTTOM LINE: Carburetors are not as complicated as they appear. It does not take aspecialist to do a rebuild. An individual who regularly works on/maintains cars (by that I


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mean more than merely changing oil and anti-freeze) is certainly up to the task. What itdoes take is a solid base of knowledge of engine mechanics, a bit of patience, lots ofattention to detail and clean working conditions. If you are contemplating taking on thistask, I hope you find my experience as a first time carb rebuilder to be of help. Don't be

afraid to give it a shot. My advice is, by all means go for it! Go to the GDYNets GrayLady web site for more info on the rebuild and Rochester carbs.

Here are some pics of the work in progress:

Ok, I have had my say for this month. Now it is your turn! I invite/encourage submis-sion of your comments, opinions and contributions, and ask that you help spread theword about our pub. Everything sent shall indeed be reviewed by me. Submissionsshould be sent to CCC at: [email protected]

_______________________________________

-- RESTORE 'EM, AND DRIVE 'EM!

COMING NEXT ISSUE: Car Barn Activity GM Marketing Put a Shine on that Baby Quiz
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