The wait is over as the new Mummert aluminum heads have now been run on an engine with the following results.  56 horsepower increase over the stock heads!!!!!!  In their first day, a total of 24 pulls were made with the aluminum heads to test a variety of timing, carburetion, carb spacer, jetting, and exhaust changes.  The aluminum heads themselves were tested as delivered and used in the ‘out of the box’ configuration with no porting being performed.

 

The engine used for the test is a +060 over 312 with the cast flattop pistons 0.025” in the hole and stock G heads that had only a good valve job with hardened seats installed and a 0.025” mill to clean up the deck side of the heads.  No port work.  The compression ratio calculates to be 9.2:1.  The engine is running the factory 1.54:1 rockers, Mummert single four intake manifold with a two inch four hole spacer, and a 750 cfm vacuum secondary carb.  The camshaft is a Crower Monarch grind ground on 110° lobe centers, 280° advertised, 238° @ 0.050”, and 0.430” lift at the valve after the lash is set.  Prior to the head test, a 465 Holley, a modified 600 Holley, and a 750 Holley were all tested and the 750 simply shined above the rest.  The 465 just gives up earlier and the 600 fell in behind the 750.  These same carbs were used with the aluminum heads with the performance order being the same but much more pronounced.

 

To keep the tests reliable and truly comparitive, both the iron and aluminum heads were ran back to back and on the same day.  The engine was ran first in the morning with the iron heads to get some baseline numbers.  The dyno numbers for the G heads are 286.1 HP @ 5300 rpms and 336.4 lbft torque @ 3400 rpms.  Although there was a 290HP number on one of the pulls, it was disregarded due to the water temperature being on the cool side.  These are still respectable numbers for stock unported G heads.

 

It took just a bit over two hours to swap out the iron heads to the aluminum versions.  The engine was then started, heated up, stopped, and allowed to heat soak.  At this point the valve lash was rechecked.  As an FYI, the heads grow about 0.004” from ambient to hot so setting the valve lash at 0.015” initially nets 0.019” hot.  After a series of dyno pulls to determine what the engine preferred for new ignition timing and fuel mixture attributes, the numbers for the aluminum heads are as follows:  340.6 HP @ 6100 rpms and 357.5 lbft torque @ 4400 rpms.

 

The new heads do like leaner fuel mixtures and considerably less total timing.  They are definitely more efficient.  Whereas the iron heads liked 38-40° total timing, the aluminum heads are happiest with 32-33° total on this particular combination.  Intial testing shows an Autolite 3924 spark plug being a good middle of the road spark plug to start out with.  Spark plug gap for the tests was at 0.035”.

 

With the 2” four hole carb spacer, the aluminum heads outperform the iron heads at all rpm ranges.  With the 2” tapered carb spacer and below 2800 rpms, the iron heads are only marginally better in torque than the aluminum versions, but after 2800 rpms, the aluminum heads simply run away from the iron versions with the best peak horsepower numbers.

 

With ‘out of the box’ aluminum heads and no port work, 1957 supercharged performance is now available without having to use the supercharger.  There is still some more dyno testing yet to be performed after which point the heads will be pulled off of the engine and disassembled.

Lorena, Texas (South of Waco)

Sweet!

Did you calculate average numbers?

Is it normal for aluminum heads to grow like that and affect the valve lash so significantly?

Do you think the aluminum heads might produce more torque than a ported iron head below 2800rpm?

And a not so important question but a curious one, does the leaner mixture actually result in better mileage?



I'm thinking this is going to be a particularly exciting year at Columbus!


Lawrenceville, GA

Hold on to your steering wheels, these things are going to give an awesome ride!

Ted, that is great baseline info for these heads! Can we automatically assume that these heads are going to be used on your EMC motor?

John - Hats off to a job well done! Let's hope Edelbrock will remain in there and do a good job for the Y block.

Daniel Jessup

Lancaster, California

aka "The Hot Rod Reverend"
check out the 1955 Ford Fairlane build at www.hotrodreverend.com

Here are some average numbers.  Keep in mind that the iron head numbers are biased larger because they are averaged to 5500 rpms while the aluminum heads are averaged to 6200 rpms.  Had the iron heads been taken to 6200 rpms, the iron head average numbers would have been considerably lower.

Iron heads w/4 hole carb spacer:     238.3 HP, 315.8 lbft TQ  (averages)

Alum heads w/4 hole carb spacer:   270.8 HP, 331.9 lbft TQ  (averages)

Alum heads w/tapered carb spacer: 271.7 HP, 329.5 lbft TQ  (averages)

The growth of the heads is perfectly normal with aluminum.  I see as much as 0.006” growth on SBF heads.  The combination of aluminum heads and an aluminum block on my FE sees a total of 0.025" growth.

At 2500 rpms, the iron heads had 298 lbft TQ while the aluminum heads with the same 4 hole spacer had 315.3 lbft TQ.  With a tapered carb spacer being substituted for the four hole spacer in conjunction with the aluminum heads, the iron heads were only slightly better for torque below 2800 rpms.

As far as fuel efficiency, John can answer this one better than myself but because the Brake Specific fuel numbers are lower and the engine does require less jetting to get more out of it, I’ll take a stab in the dark and say YES, the heads will get better fuel economy with the appropriate tuneup.

Lorena, Texas (South of Waco)

This particular pair of heads will go on a customers engine once final checkout is performed.  A different and fully prepped set of heads will go on the EMC engine.

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Lorena, Texas (South of Waco)

Great results. I would have estimated 320-330 horse. Not knowing the specifics of Teds engine I could not put it into EAP.

If an engine were built specifically for these heads with 0 deck, about 10.5 cr and possibly a bit shorter, higher lift cam and mildly ported heads 350+ horse power may be possible with a very streetable "Sunday go to Meeting", not racing, engine. This would back up my paper engine very closely. John you did good. Thanks for the info Ted. The ported heads should shine on your Engine Masters engine. 

What are the chamber sizes of the two heads tested?

I am also interested in what % of power increase could be attributed to higher CR?

6 VOLTS/POS. GRD. NW INDIANA

Wow! Great job "John" and "Ted"

Ted, Wouldn't the push rods grow maybe .001" after warm up? we always used the calculation of .003" of growth per foot of material (steel and Iron) for every 100 degrees above ambient temperature for the equipment I set up around the globe. Also I know that the aluminum grows at a much faster rate, the number 1 cause of snowmobile/dirtbike/four wheeler piston failures is the fact that people don't let them warm up before reving them up and the piston grows faster than the cylinder and they get a cold seizure.

I don't have handy the exact growth of the aluminum versus the steel for the same temperatures, but as the steel catches up, might it change that figure?

55 Vicky & customline

58 Rack Dump, 55 F350 yard truck, 57 F100

59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?

Chamber sizes are 65.7cc for the iron heads and 60.0cc for the aluminum.

For a ½ point compression ratio increase on iron heads, figure a 2% increase in peak horsepower numbers.  In this case where the heads were switched from iron to aluminum and the aluminum ended up being 0.6:1 higher for the compression ratio (cr), it’s a wash or net zero increase.  Simply put, aluminum just isn’t as efficient as cast iron in converting the combustion heat into power.  To offset the inefficiencies of aluminum in the combustion process, a given increase in cr is required to keep the power levels the same with everything else being equal.  Had the aluminum heads been designed with the same size combustion chambers as stock, then a portion of the power that was a result of improvement in head flow and combustion chamber design would simply have been lost due to  having to make up for the lost power due to the thermodynamic properties of the aluminum.  That’s the simple explanation.

Lorena, Texas (South of Waco)