Eaton Balancing

The Holley model 4000 four barrel carburetor that came as original equipment on single four barrel equipped 1956 and earlier Fords, Mercurys, and Lincolns is not up to its full potential when used with the ’57 and up Y-Block distributors.  Just so we are all on the same page, these carbs are more commonly known as Teapots or Haystacks.  The problem with the late model distributor incompatibility originates in the Teapot’s internal circuitry that provides the vacuum signal to the distributor.  These carbs were originally designed to be used with the ’56 and earlier Load-O-Matic distributors and have a unique vacuum signal to work the vacuum only ignition advance distributors.  The oem or factory designed signal for the distributor combines both a venturi and staged vacuum source at the carburetor which is controlled to a large degree by a spark advance valve located on the side of the carburetor.  It is the venturi assisted part of the vacuum signal that makes this particular signal inappropriate for use with the later model distributors that use both centrifugal and vacuum advance features.  The venturi assisted part of the signal within the carb is also tied to the secondary diaphragm circuitry which makes for a very complicated carb circuit in its stock form.  This also means if the distributor’s vacuum advance chamber or the line connecting the carb to the distributor vacuum advance chamber is leaking, the carburetor’s secondary circuit is likely not opening when it should if it does at all.

So what’s all the fuss about?  If a Teapot carb is being used with a mechanical advance only distributor or the vacuum can is not being used on a ’57 and up distributor, then the distributor port at the front of the carb is simply plugged and all is well.  Ignition timing in this instance simply relies solely on the mechanical advance within the distributor.  Assuming the mechanical advance curve is adequate then the Teapot carb runs just fine with the plugged distributor port at the carburetor.  But….If that vacuum port is hooked up to the ’57 and newer distributor’s vacuum chamber, then the potential is there for excessive ignition advance when the throttle is opened to any degree beyond just the cruising position.  That could prove detrimental to the engine in the form of detonation or pre-ignition depending upon temperature, fuel octane, compression ratio, and a variety of other factors.

With all that being said, the Holley Teapot carbs can be successfully modified so that the vacuum advance signal is converted to a fully staged or ported signal that is fully compatible with the ’57 and newer Y-Block distributors.  The essence of making this happen is installing a new vacuum port or hose connection below the existing distributor port on the carburetor and then blocking that original distributor port.  While I did make that sound quite simple, in reality it’s almost that easy.

With the carburetor upside down, locate the small brass slotted screw on the underside of the carb.  This screw seals up the passageway that aligns with the passageway that intersects with the original distributor vacuum port opening.  When removed, you’ll see that the screw (Fig 1) will have a long stem on it which we will discuss again later.  Now with the front side of the carb facing you, locate the pressed in aluminum plug that aligns with the same passageway that the long stemmed screw plug was removed from.  Looking at the front of the carb, you’ll see three aluminum plugs all in a horizontal line roughly about 1” up from the base of the carb.  For the next part in this exercise, you will be working on the plug that’s to the far left of all of them (Fig 2).  Remove the plug.  Drilling a small hole and then tapping for a 10-32 thread (Fig 3) will allow a screw to be inserted and by using a screw driver under the head of the screw, the aluminum plug can simply be pried out of the hole (Fig 4).  Once the plug is removed, a nice ¼” diameter hole will be staring back at you.  If you peer into the hole, you’ll see a much smaller hole that goes into the throttle bore just above the throttle blades.  This is where the ported or staged vacuum signal originates (Fig 5).

   

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At this point, a piece of ¼” O.D. tube is required.  While ¼” O.D. steel brake line is suitable, I’ve also found that the aluminum fuel transfer tubes on the 600 cfm Holleys with the flat bowls works well for this also.  Regardless of what you use for the tubing, you’ll need a piece that is 1¼” or 1½” long or long enough to attach the rubber line that goes to the distributor to attach to once the tube is inserted in the ¼” hole.  With that said, drive that piece of ¼” tubing into the newly exposed hole in the front of the carb until it bottoms out (Fig 6).  Once bottomed out, the drilled channel above and below this inserted tube will be effectively blocked.

Now we are back to that long stem slotted screw that was removed earlier.  At this point, the stem is too long to allow the screw to be reinstalled back in its original hole with the freshly inserted tube now in place.  Cut off the stem portion of the screw and reinstall it back in its original hole (Fig 7).  While the new ¼” O.D. tube that was installed should have effectively blocked off this hole, reinstalling the bottom screw is simply a safety measure to insure there is no direct vacuum signal making its way back to the ported vacuum signal.  While not absolutely necessary, removing the spark advance valve (Fig 8) on the side of the carb and replacing it with a power valve block off plug will also insure that the vacuum secondaries are getting a full vacuum signal.  A leaking diaphragm in the spark advance valve at this point will keep the secondaries from operating correctly.  Be sure to also install a plug (3/8X24 thread) in the carb’s original distributor vacuum port as that port ties directly to the secondary activation circuit (Fig 8).  If it’s left open, the secondaries will not open as they should if at all.

   

Click on picture for larger image.

Once the carb is reinstalled on the engine, simply hook a hose at the new port on the carb and connect the other end of the hose to the vacuum advance chamber at the distributor.  With a timing light hooked up and with the engine running and idling, there should be no timing change with the hose either hooked or unhooked.  With the hose hooked up and with a slight increase in rpms, you should see a significant increase in ignition timing as compared to timing readings at the same rpms and the hose unhooked.  At this point you are done and ready to take a test drive.

Until next time, Happy Y Motoring.  Ted Eaton.

Originally published in Y-Block Magazine, Issue #114, Jan-Feb 2013, Vol. 20, No. 1

Just click on the topic you’d like to view.

Rocker Arm Geometry

Altering Rocker Arm Ratio By Varying The Pushrod Length

Camshaft Balancing

Camshaft and Lifter Failure Causes

Carburetor Spacer Testing

Cylinder Head Milling For A 1cc Reduction

Head Gasket Volume Calculations

Milling heads for a horsepower gain

Spark Plug Indexing

Spark Plug Side Gapping

Modifying the Holley Model 4000 (Teapot) for late model distributors

Modifying the Holley 94 two barrel carb for late model distributors

Ford Y-Block Aluminum Head Testing Part I

Ford Y-Block Aluminum Head Testing Part II

Ford Y-Block – 585HP without a supercharger or other power adder

Ford Y-Block – 318 inch buildup using aluminum heads

Ford Y-Block – 330 inchers, aluminum head and iron head versions are both dyno tested.

Ford Y-Block – Four Barrel Carburetor Testing Using the Iron ECZ-B Intake

Ford Y-Block – Neoprene Rear Main Seal Installation (also works for others)

Ford Y-Block – Warped Rear Seal Retainer

Ford Y-Block 292/312 Rear Cam Plug Installation

Building The Foundation For An Eight Second Ford Y

Blueprinting For An Eight Second Ford Y-Block

A 500 HP+ Ford Y-Block at the 2010 Engine Masters Challenge

Preparing a 375 inch Y-Block for the 2009 Engine Masters Challenge

A Ford Y-Block at the 2009 Engine Masters Challenge – Summary

Engine Masters Challenge Ford Y-Block Entry for 2007

The Ford Y-Block Engine – History and cubic inch particulars

Engine Balancing Part I

Engine Balancing Part II

Engine Balancing Part III

Engine Balancing Part IV

Engine Balancing Part V

Engine Balancing Part VI

While a dynamometer is a great tool for sorting out engine combinations, there are those instances where some of the data provided conflicts with other data also being recorded.  A case in point here is where the EGT’s (exhaust gas temperature) do not match up with the results of the oxygen sensors.  Typically when dynoing an engine it’s either the EGT’s or the oxygen sensors being used to adjust the air/fuel ratio but not both.  But having the capability to do both on the DTS dyno, it’s a nice plus to have all the data possible when doing these tests.  Most of the time the different sets of data do help to collaborate each other.  It’s when those data sets do not agree with each other is when the real questions arise.

Upon converting the 2010 Engine Masters Challenge Ford Y-Block engine from a street engine to a race engine for my 23T altered roadster, the disparity in readings between the EGT’s and oxygen sensors came to the forefront.  At the time, it was a head scratcher.  Although the EMC engine made respectable horsepower numbers in its new configuration as a race engine, I felt that it fell short of expectations when taking into full consideration the increase in compression ratio and using the longer duration camshaft.  Late evening brain storming sessions with racers and other engine builders had them suggesting that the engine was too large for the cylinder head flow and the heads were simply not supporting the additional cubic inches.  I saw this to some degree on the 403” Y that was built with the iron heads but was having a hard time buying this for the 375” Y combination using the ported Mummert aluminum heads.

But after plenty of time and much thought, I came to lean towards the idea that the exhaust system was over-scavenging.  Said another way, there was an excess of intake charge going into the headers during the valve overlap cycle and there was a portion of the intake charge essentially being wasted.  This assumption was based on that disparity between the EGT and oxygen sensor readings.  The EGT’s were running on the cool side while the oxygen sensors were saying ‘spot on’ in regards to the fuel mixture.  The spark plug readings were agreeing with the oxygen sensors while leaning and richening the fuel mixture based on the A/F readings was also agreeing with the power output numbers.

When the opportunity arose to build a similar engine for a customer, this was a perfect opportunity to validate the ‘over-scavenging’ theory and see if that was indeed where some lost power was hiding.   With that in mind, a 375” Y engine with the same compression ratio and similarly ported aluminum heads is assembled.  Two major engineering changes do take place in this engine and both changes are designed to reduce the amount of intake charge that’s lost during the overlap cycle.  The connecting rod length is shortened 0.450” (from 6.750” to 6.300”) which reduces the amount of dwell time the piston sees at TDC.  The other change is the camshaft lobe centerline angle which is increased from 108° to 112°; this reduces the number of crankshaft degrees that both the intake and exhaust valves are open together.  These two changes reduce the amount of intake charge that can be lost out the exhaust when the headers are working at their optimum.  The camshaft, other than the number of degrees on the lobe centerline angle, has the same specs as the one used on the revamped or racing version of the 2010 EMC engine.

The remainder of this new 375” engine is as follows.  The well seasoned C2AE-C 292 block has a November 1966 casting date and is finished bored to 3.859”.  The crankshaft is billet steel by Moldex using stock 292 main sizes but 1.889” sized Honda rod journals instead of the factory 2.188” sized journals.  The stroke is 4.000” and the Honda rod journal sizing helps to minimize any connecting rod to camshaft clearance issues that can become prevalent when doing stroker builds on the Ford Y-Block engines. The cylinder heads are Mummert aluminum and are ported by Joe D. Craine.  Because the Mummert aluminum intakes were unavailable at the time of this particular engine build, a Blue Thunder intake was utilized and is also ported by Joe Craine.  The static compression ratio is 13.56:1 and gets there using Diamond 9cc domed pistons that are ceramic coated on the domes and have a friction coating on the skirts.  The top and 2^nd groove piston rings are 1.2mm while the oil ring is a standard tension 3.0mm unit.  Using the 1.2mm rings not only reduces the amount of ring surface area against the cylinder wall, they also have a reduced radial tension due to the radial thickness (inward width) being less than the older and more conventional ring sets.  The connecting rods are out of the box 6.300” long Eagle’s utilizing a 0.927” pin and a Honda 1.889” rod journal.  While a main bearing support girdle is used to strengthen the bottom end, an Innovators West damper helps to keep unwanted crankshaft harmonics to a minimum.

   

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Nothing fancy about the oiling system on this engine.  The oiling system within the block itself remains basically as delivered from Ford with the exception of a machined groove in the center cam journal behind the cam bearing.  This particular modification insures an adequate flow of oil to the rocker arm assemblies without worrying about the softer cam bearing material pressing itself into the center cam journal groove and restricting the flow at that point.  Two extra holes are drilled into the oil filter adapter plate to insure a sufficient flow of oil into the filter in the higher rpm ranges.  The original Ford engineers likely had no idea that these engines would eventually be running repeatedly in excess of 7000 rpms and actually staying together.  A rebuilt Ford aluminum gerotor oil pump keeps the oil moving while a front sump oil pan seals up the bottom of the engine.  The standard volume oil pumps as supplied by Ford still work well in this application.

   

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The valve train centers around an Iskenderian camshaft with a 296° advertised duration and 263° duration at 0.050” lifter rise on both the intake and exhaust lobes.  As previously mentioned, the lobe centers are ground on 112°.  The cam is installed at 110° intake lobe centerline or 2° advanced while U.S. manufactured Hylift Johnson lifters are the lifter of choice for this combination.  A Rollmaster timing set (made in Australia) keeps the cam spinning in a set of Durabond cam bearings while Harland Sharp 1.6:1 roller tipped aluminum rockers pushes the net valve lift to 0.603”.  Isky beehive valve springs and Isky retainers are used to keep the valves in their respective places.  Due to the increase in valve spring pressure, pressurized oiling is used at the rockers thus eliminating the overflow tubes.  The pushrods are by Smith Brothers and have an 8.000” effective length.

Engine break-in on the dyno was a non-event.  The prerequisite twenty minutes at 2000-2600 rpms is used for cam break-in and during this time period, the dyno is repeatedly loaded and unloaded so that the engine sees ~100 HP at each dyno loading.  This puts enough heat into the piston rings to do a very quick seating of the rings to the cylinder walls.  For this engine, the customer provides Joe Gibbs 30W break-in oil while a Wix 51515R oil filter takes care of the filtration.  No additional additives are used.  I’ll add at this point that too much zinc/phosphate in the oil can cause ‘zinc overloading’ which is known to speed up pitting of the cam lobes.  Once break-in is complete, the valve lash is checked and it’s verified that the valve train is holding up just fine.  After the lash is adjusted to 0.016” hot for both the intake and exhaust valves, the engine is allowed to completely cool down to put a completed heat cycle into the valve springs.  This single step greatly prolongs valve spring life.  I’ll add that the valve lash with aluminum heads sees a 0.004” growth from cold to hot.  If doing an initial cold lash setting on aluminum heads, then set the valves ~0.004” less than what you want when they are hot.  This will get you in the ball park for the hot lash setting.

The first item on the agenda once testing commenced was to determine what the engine likes for ignition timing.  The distributor chores are taken care of with a #8383 MSD distributor and a set of MSD carbon core wires.  The black bushing supplied as an extra with the distributor is being used in conjunction with the light blue and light silver springs to provide an ignition advance curve that’s both short and all in by 3000 rpms.  With the Autolite #3923 spark plugs gapped at 0.035”, the engine shows a definite preference for 37° total timing.  Simply resetting the timing 1° above and below this causes a 6 & 7 HP drop depending upon which way you go.  Going 2° away from 37° simply drops the power numbers even more.  So 37° BTDC it is.

Once testing is completed, the engine is a solid 581+ HP performer.  Three different carburetors were used during this testing session.  While a 750 HP series vacuum secondary Holley (List #80529-1) makes 581 HP, a Quick Fuel 750 also with vac secondaries does slightly better at 582 HP.  But when a 1050 cfm Dominator Holley (List #8896-2) is tried on the engine with an adapter, the power level jumps up to 585 HP and that’s with this particular carb still on the lean side.   The torque values with the Dominator carb are also stout.  Because this engine is leaving the shop with the Quick Fuel carb on it, no further testing is done with the Dominator carb which leaves some higher HP numbers on the table.  Likely wouldn’t be 600 HP but would be crowding the 590 HP value.

So there you have it; a recipe for some serious Y horsepower.  Following this article are the dyno sheets with the various carbs.  That’s all for now and until next time, happy Y motoring.  Ted Eaton.

  

750 Holley carb                750 QFT carb                  1050 Holley Dominator carb

This article was originally published in The Y-Block Magazine, Issue #113, Nov-Dec 2012, Vol 19, No.6