Category Archives: Engines

Oil Viscosity and Its Effect On Engine Power

It’s pretty well known that engine oil with a higher rated viscosity tends to rob power from the flywheel end of the engine. It’s this mentality that has the new car manufacturers using lighter weight engine oils in which to increase the fuel efficiency of their engines as well as pick up some additional power. The oil itself is not so much the power robber as is the oil pump and clearances which simply makes the pump work harder to move a higher viscosity oil throughout an engine. Higher or heavier viscosity oil drives up the oil pressure which in turn makes the oil pump work against a higher resistance. In this vein of thought, the oil pump is ultimately just another horsepower robbing accessory similar to the alternator or water pump. In the case of the oil pump, using lower viscosity oil allows it to turn easier which simply frees up some horsepower. In some racing venues, the volume of oil delivered by the oil pump is intentionally reduced with an oil pump rotor size reduction to minimize the horsepower losses associated with an oil pump that’s simply larger than it needs to be. OEM oil pumps are generally engineered on the ‘large’ side of specifications to insure adequate oil flow under a variety of conditions and to also compensate for a given amount of long term wear within an engine.

While dyno testing a high horsepower Ford Y-Block engine (570+HP), a significant drop in the peak horsepower numbers was noted when the oil was changed out for one with a higher rated viscosity. That particular engine had been initially started up and broken in with conventional 10W-40 oil. At the conclusion of that break-in and after making the prerequisite baseline dyno pulls, the oil was switched out to a 20W-50 racing oil at which point there was an immediate loss of ten horsepower. For both of these oils, the water and oil temperatures had been maintained within the same ranges which eliminated those two items as potential variables. While it was anticipated that there would be a horsepower loss with the higher viscosity oil, that loss being as much as ten horsepower was unexpected. It was this particular instance that would prompt a more complete dyno test using the 312 dyno mule where several different viscosities of oil would be run in a back to back fashion to clarify the effect on both the oil pressure and the power production.

While the rated viscosity on the container is a quantifiable value that can be worked with, the unknowns in this series of test are the shear properties of the various oils. Based on the final results of the tests, there are some differences not accounted for in examining just the viscosity ratings. It can be assumed that some of these differences are related to the shear properties imparted within the various oils by the different additive packages used to derive the various viscosity ranges. Another variable is the cycle time or how long the oil has been used within an engine. The first oil used in this test was well used versus the remainder of the oils being fresh out of the can bottle.

The +060 over 312 dyno mule is prepped with a set of mildly ported ‘posted’ big letter G heads, a stock Mummert aluminum intake, and a 750cfm vacuum secondary Holley carburetor. It is base-lined with the existing oil that’s already residing in the crankcase which is Valvoline conventional grade 10W-40. This particular oil is well used at this point and the engine is already past due for an oil change as the engine is fast approaching 300 dyno pulls with this oil. In fact, the oil pressure had been dropping off in the upper rpm range which was first thought to be bearing wear taking place. Six new dyno pulls are made on the engine with this oil in which to record data at varying engine coolant and oil temperatures. Once this oil was changed out with a 0W-20 full synthetic oil, all oil pressure issues went away which then indicated that the original oil in the engine was just simply ‘worn out’. For this particular 10W-40 oil, a separate chart and graph is included showing how this oil performed over time as it was showing some serious degradation after dyno pull number 250. For comparision purposes though and because all horsepower numbers needs to be using the same cylinder heads, the baseline numbers for the first oil tested puts the average oil pressure at 44 psi and the peak horsepower at 310. This oil was actually averaging well over 50 psi earlier in its life.

To help maintain a level of consistency in the testing, the same brand of oil is used so that viscosity measurements are not as varied as would be if using different brands of oil. It has been found in the past that the viscosity measurements between oil brands within the same rated viscosity oils are not the same. While the baseline test would be the Valvoline conventional 10W-40 oil that was already in the engine, the other oils to test would include Valvoline 0W-20 full synthetic, Valvoline 5W-30 semi-synthetic, Valvoline 10W-40 Max Life (syn blend), and Valvoline 20W-50 VR1 racing oil. The oil filter is also changed with each oil change and the filter of choice for this test is the Motorcraft FL-1A.

No additional additives are being used in this test although the zinc/phosphate amounts in the 0W-20 and 5W-30 oils are less than ideal for flat tappet camshafts. The zinc amounts in the remaining oils that are being used are more than adequate for flat tappet camshafts without the use of supplemental additives. I’ll add that at the conclusion of this test, there was absolutely no measureable wear to the valve train components although there were a number of dyno pulls made using oils with reduced amounts of ZDDP compounds. Here’s a chart showing the test results.


Oil Avg oil pressure Avg oil temp Peak Tq Avg Tq Peak HP Avg HP
Valvoline10W-40 conventional 44.19 psiSee Note 1 161.19°F 344.4 327.53 310.1 249.12
Valvoline0W-20 full synthetic 45.75 psi 170.16°F 346.4 327.92 307.9 249.26
Valvoline5W-30 conventional 48.84 psi 168°F 346.9 328.27 306.4 249.4
Valvoline20W-50 Racing 52.36 psi 169.32°F 342 323.11 301.9 245.52
Valvoline10W-40Syn Blend 51.77 psi 167.87°F 345.2 327.74 307.5 249.09

Note 1. This particular oil was nearing 300 dyno pulls on it and looks to be ‘worn out’ by the time this oil test took place. The following chart shows the oil pressure performance of the 10W-40 conventional oil at the different rpms during the course of it being in the engine under a multitude of different testing conditions. Of particular interest is how the oil is not maintaining the oil pressure in the upper rpm ranges after ~250 dyno runs have been made using it.

Ref # 372 409 447 492 541 599 624 649 662
Rpm Run#6 Run #43 Run #81 Run#126 Run#175 Run#233 Run#258 Run#283 Run#296
2500 53.7psi 51.6 46.3 50.9 50.5 47.5 46.0 42.5 42.5
3000 52.9 50.4 48.0 51.7 52.9 53.1 46.7 43.9 44.4
3500 54.2 51.2 49.0 51.3 53.2 54.0 48.6 44.6 46.4
4000 54.6 52.3 49.9 50.3 53.0 53.6 49.3 44.9 45.9
4500 54.6 51.9 50.9 50.8 53.0 51.5 50.2 46.3 45.3
5000 55.4 54.7 53.2 53.0 54.6 53.5 52.4 43.6 41.1
5500 57.7 56.9 54.0 55.1 55.9 55.3 53.5 43.5 42.7
Avg oil temp °F 149.3 146.0 159.1 144.7 138.1 139.2 149.8 165.1 161.2
Avg psi 54.7 52.7 50.2 51.9 53.3 52.6 49.5 44.2 44.0


But to put more emphasis on what was going on with this oil, the following graph shows the oil pressure on runs #81 and #296 on the same oil. These two runs were selected simply due to the oil temperatures being the most similar. The degradation in oil pressure in the upper rpms becomes quite noticeable on the well used oil versus the same oil that did not have as many dyno pulls on it.

Used versus well used oil

Click on picture for larger image.

In summary, that same significant drop in horsepower that was originally seen on the high HP Y when switching from 10W-40 to 20W-50 was also seen on the dyno mule. While it was a 10 HP drop on the high HP Y, it was still an 8 HP drop on the dyno mule. For the remainder of the oils tested, the range or difference from best to worst was only 3½ HP which makes all those oils reasonably close to each other from a performance standpoint. In this particular test, the best bang for the buck comes from using the 10W-40 oil which already has the prerequisite amounts of ZDDP for the flat tappet camshafts without the use of additional additives. The Y engines with their flat tappet camshafts does still require an oil with a sufficient amount of ZDDP or an additive to supplement the known lack of it in the oil. Most API ‘SN’ rated oils with 40W or higher in their labeling will have sufficient amounts of zinc & phosphorus compounds for flat tappet camshafts while oils with 30W or less in their labeling do not.

The surprise finding in this test was actually being able to see how the oil does indeed wear out or break down thus mandating an oil and filter change. This could very well be the results of contaminates that do not get filtered out. These contaminates then contribute to a reduced viscosity leading to cavitation issues not normally observed. A likely contributing factor is that this oil is being submitted to a multitude of full throttle power pulls which can put a more than normal amount of fuel past the rings and into the oil thus affecting the overall viscosity. If engine wear is to be minimized, then the oil and filter should be changed before the drop in oil pressure that was observed in these tests actually takes place. If I was to take a stab in the dark at how dyno pulls relate to real world vehicle mileage, then I’d say 250 dyno runs would equal ~3000 miles. Assuming the oil is not contaminated, then 250 dyno pulls on the same oil is the upper limit for this particular engine. More frequent oil changes sure will not hurt though.

As always, just consider this food for thought. Until next time, Happy Y Motoring.                              Ted Eaton.



Click on pictures for larger images.

This article was originally published in The Y-Block Magazine, Issue #119, Nov-Dec 2013

Intake Manifold Plenum Slots

In dyno testing the different intake manifolds on various engines, it’s found that the intake runner and plenum designs are main players in determining what the power curve for a particular engine combination will look like. One intake manifold feature that comes to the forefront on the aftermarket four barrel dual plane intakes is a slot in the divider located directly under the secondary side of the carburetor. These slots came into prominence in the late Sixties with the popularity and use of the Holley three barrel carburetors and that slot was simply required to allow the secondary throttle blade on those carbs to open without interference at the intake manifold. Although the three barrel carbs have been pretty much extinct for several decades, the practice of the intake manifolds being slotted by the manufacturers has remained. When the Blue Thunder intake for the Y engines was introduced, it too had that slot located at the rear of the divider under the secondary portion of the carb. I’ll hence forth refer to that slot as the ‘three barrel’ slot simply due to it working for that purpose.

For the Ford Y-Block engines, the two aftermarket intakes currently available are the Blue Thunder (BT) and the Mummert. In breaking with conventional practice, the Mummert aluminum intake manifold was introduced without that ‘three barrel’ slot in place. The BT intake being introduced a few years earlier has the slot. So that begs the question, exactly what effect does that slot have on the engines power curve if any?

Click on pictures for larger images.

To test the effect of the ‘three barrel’ slot on overall engine performance, four 1” tall four hole carb spacers are obtained and appropriately modified so they can be dyno tested. While one 4 hole spacer is left stock, another is modified with a slot across the secondary throttle bores. The other two spacers are machined so that they are dual ovals closely matching the dual oval configuration used in the plenums of both the Blue Thunder and Mummert intakes. Again, one of the dual oval spacers has the slot added so it’s across the secondary throttle bores while the other does not. To add another nuance to the tests, the slotted spacers are tested both right side up and upside down just to see if this provides an additional difference to the power curve. This makes for six different test variants which includes the four different spacers and then the two slotted spacers being run with slots down as well as slots up.


Click on pictures for larger images.

The dyno mule is the well tested +060 over 312 with a set of mildly ported G heads. The intake manifold being used for this test is the Mummert aluminum intake which is being used in lieu of the Blue Thunder intake simply due to the lack of a slot in the plenum divider. The carb is the 750 vacuum secondary Holley which has proven to be a solid performer on this engine in past tests. The camshaft is a Seventies era Crower Monarch grind with 238° duration at 0.050” on both the intakes and exhausts and ground on 110° lobe centers. The cam is installed with 2° of advance (108° intake lobe centerline). The net valve lift is 0.459” lift using the Harland Sharp 1.6:1 roller tipped rockers with the valve lash set at 0.019”.

The following chart shows the various dyno results. The *Score is calculated by adding the average torque and horsepower values together, multiplying by 1000 and dividing by the cubic inch (322).

Spacer > 4 holeNo slot 4 holeSlot up 4 holeSlot down Dual OvalNo slot Dual OvalSlot up Dual OvalSlot down
TQ –Peak 340 341 342 338 338 338
HP – Peak 298 303 302 302 302 302
TQ – Avg2500-5500 rpms 324 324 322 323 320 320
HP – Avg2500-5500 rpms 245 246 245 245 244 243
*Score2500-5500 rpms 1769 1772 1763 1766 1752 1751
TQ – Avg2500-3500 rpms 329 324 319 326 316 315
HP – Avg2500-3500 rpms 189 186 183 187 181 181
*Score2500-3500 rpms 1608 1582 1559 1593 1544 1538

In this case, the charts don’t tell the whole story so this is where a series of graphs come into play. The following two graphs show the HP and TQ results for the four hole spacers. There is a pronounced dip in the torque curve when the slots are incorporated into the spacers versus the dyno runs that are made without the 3 barrel slot in place.

Click on pictures for larger images.

The next pair of graphs shows the results of testing with the dual oval spacers with and without the three barrel slots. Again, that mid-range dip in the torque curve becomes more pronounced with the slots in place versus without.

Click on pictures for larger images.

This next pair of graphs simply compares the four hole carb spacer without a slot to the dual oval carb spacer also without a slot. Low end torque is enhanced with the four hole spacer while the top end horsepower is better with the dual oval spacer. No surprise there. This reaffirms the practice of putting the oval slots in the ECZ-B iron intakes for an increase in top end power.

Click on pictures for larger images.

What is obvious on the graphs comparing ‘slot’ versus ‘no slot’ performance is how the addition of a slot does make for a more pronounced dip in the mid range torque values. Based on past experience, that dip or mid-range drop in the torque numbers does look like it can be reduced by simply making the carb spacer taller. For this particular test, the carb spacer height was simply kept at one inch but past testing has shown that the two inch high carburetor spacers are a better choice for optimum horsepower and torque numbers on most Y engine combinations when using either the Blue Thunder or Mummert intake manifolds. There are instances where even more than two inches of spacer works so keep an open mind.

The addition of plenum slots do tend to help the overall performance scores and top end horsepower numbers when used on a 4 hole spacer design. When using ovals under the carbs rather than four individual holes, the same slots prove to be a detriment to the overall score values while top end horsepower values do continue to be higher. The low end performance is reduced with both spacer designs with the slots when compared to the same ‘no slot’ spacers. In summary, not having a slot in the plenum divider does enhance the low end torque values so it simply ends up being a case of exactly what kind of driving is being performed as to whether the intake plenum having a three barrel slot or not is going to be the best for a particular engine combination.

585 HP with 3″ of dual slotted carb spacers on Blue Thunder intake manifold.  Click on picture for larger image.

Until next time, happy Y motoring. Ted Eaton.

This article was previously published in The Y-Block Magazine, Jan-Feb 2014, Issue #120, Vol. 20, No. 6

Y-Block, 585HP without a supercharger or other form of power adder

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 2nd 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.



Click on pictures for larger images

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.



Click on pictures for larger images

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.

  Dyno - 1050 Dominator

750 Holley carb                750 QFT carb                  1050   Holley

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