Y-Block Ford – 3X2 Intake Testing

A Fenton manifold was not included in the testing simply due to one not being readily available at test time but there is some information out there pointing to the Fenton manifolds being cast in the same molds as the Edmunds intakes.  But as found in the testing, not all the Edmunds intakes are created equal so the same could be likely said for the Fenton intakes.

Because there was an Offenhauser 3X2 intake throwed into the mix, this was deemed a good opportunity to determine if the Offy intake used in the May 1971 Popular Hot Rodding Magazine (PHRM) Y buildup contributed at least in part as to why that particular Y engine buildup failed to make notable horsepower numbers.  Here are a few of the details of the PHRM Y buildup for those of you that are unfamiliar with the article or perhaps just need the memory jogged.  The engine was a +060 over 312 with popup pistons, ported G heads, and an Engle #324 camshaft with 292° duration and 0.480” lift.  The compression ratio is not noted but is expected to be in excess of 10½:1 based on some of the information given. The Offy 3X2 intake being used for the magazine test was outfitted with Stromberg 97’s with #48 jets all the way around.  Here are the horsepower numbers from that original PHRM build.

2000 rpm         96 hp

2500 rpm         117 hp

3000 rpm         151 hp

3500 rpm         173 hp

4000 rpm         204 hp

4500 rpm         242 hp

5000 rpm         251 hp

5500 rpm         258 hp

6000 rpm         245 hp

Click on pictures for larger images

But now back to the present.  For this new round of intake manifold testing, a +060 over 312 with flattop pistons 0.025” in the hole with stock and unported ‘G’ heads is being used. This is the same engine that was used for the carburetor test in issue #97 of YBM.  The camshaft is also the same being the 280° Crower Monarch with 238° duration at 0.050”, ground on 110° lobe centers, installed 2° advanced, and has a measured lift of 0.434” at the valve after the lash is adjusted at 0.019” hot.  A set of prototype Harland Sharp 1.6:1 aluminum roller tipped rocker arms are being used at this point.  The static compression ratio is 9.2:1 and 91 octane pump gasoline is being used for all testing.  The headers are the stepped headers that were used for the 2009 and 2010 EMC Y engine project along with the same Magnaflow muffers.  The carbs were dialed in and jetted using the Edelbrock 573 intake and then remained like that for all the intake manifold testing.  Jetting was #48’s in all three carbs.  All dyno runs were performed between 2500 & 5500 rpms.

Click on pictures for larger versions.

When it was all said and done, the Edelbrock 573 came out on top at 279 peak hp and the Offenhauser intake was at the bottom of the heap with 251HP.  28 horsepower separated the best from the worst on the 3X2 manifolds which can be considered a bunch.  To validate that the engine was still in good condition and not degrading as the testing was taking place, the first manifold that was run was reinstalled at the end of the 3X2 test session and it confirmed that the engine was still performing flawlessly.

There was still some time left at the end of the day which allowed the new and recently released Mummert aluminum 4V intake to be installed on the engine with a modified 600cfm vacuum secondary Holley.  That change alone upped the horsepower to 292.  Keep in mind that it was only taking ~35 minutes to change each intake which says a lot for the help that was on hand and was a big part in making this test happen in a timely manner.  Pre-planning also helped in that thermostat housings and excess water and vacuum holes on each intake were taken care of in advance.  Intake manifold bolts where they were different were also on hand.  It’s always great when a plan actually works out as intended.

As with any dyno data, much more can be gleaned from it than just the peak values.  By examining the average values, there are other attributes that stand out that can help to clarify additional differences in engine performance.  In order to accurately score or rank each intake manifolds performance, the average horsepower and average torque values for each dyno pull were added together, divided into the cubic inch of the engine, and multiplied by 1000.  Thanks goes to the Engine Masters Challenge group for working out a scoring methodolgy that gives a better determination of how engines with varying parts and/or combinations can be accurately compared to each other.  Chart A (below) lists the manifolds in order from best to worst based on their scores but also breaks down each manifolds performance by peak and average numbers.  The performance numbers for the recently released Mummert 4V intake are also listed at the bottom of that same chart.

At the conclusion of this test, there was sufficient data to determine if the Offenhauser intake in that original 1971 PHRM test was a major contributor in why that particular engine performed so poorly.  Although the average horsepower and torque values were slightly higher on this new test, the original test did have subtly better peak numbers which I’ll attribute to the differences between the compression ratios and the cylinder heads.  The heads used in the original test were ported versus the stock and unported G heads being used in this test.  The compression ratio as well as the larger camshaft being used in the PHRM test should have also contributed to much higher numbers versus the 9.2:1 CR in this test and the smaller Crower camshaft that was being used.  But overall, the results were quite similar.  In summary, the Offenhauser intake had much to do with the dismal performance of the Y in that original test.

Chart A – overall performance evaluation
3X2 Intake	Peak HP	Peak Tq	Avg HP	Avg Tq	Score	Order in which tested on engine	Overall Perf Ranking
Edelbrock ‘573’	279.3	336.0	235.8	312.8	1703.7	1 & 8	1
Edmunds DM-425	266.5	336.1	231.2	308.1	1674.7	7	2
Edelbrock ‘553’	270.1	334.1	231.0	307.5	1672.4	3	3
Edmunds DM-424D	260.1	338.6	229.7	307.3	1667.7	6	4
Weiand FM436	266.2	332.1	229.3	305.6	1661.2	4	5
Edmunds Ford 424	261.9	330.4	227.3	303.0	1646.9	5	6
Offenhauser No part #	250.8	311.5	215.6	287.1	1561.2	2	7
Mummert 1X4 intake w/600 Holley	291.9	346.0	244.8	323.7	1765.4	9	Not a 3X2 intake

Chart B breaks down the horsepower results of each manifold using the same rpm format as was published in that original magazine article.  Had any other brand of three deuce manifold been used in that 1971 test, the results would have been much better.

Looking at the dyno data from the perspective as to which 3X2 intake manifolds would be the best from a daily driver point of view and not as a drag strip performer, only the torque numbers in the 2500-3500 rpms range were examined.  This did change up the order somewhat but the Offenhauser intake in this case still remains at the bottom of the heap.  No matter how the Offy intake was examined, it remained the poorest performer of the group.  Chart C summarizes the data and rearranges the various 3X2 intake manifolds in a best to worst ranking when only the torque values in the 2500-3500 rpm range are being considered.

Special thanks goes out to those persons who loaned their 3X2 intakes for this testing.  If not for the generosity of these people, this test would not have happened in the detail in which it did.  With this particular test completed, future testing of some other variables are already being planned.  Cylinder head testing and exhaust system testing are in the works.

That’s all for now.  Ted Eaton

This article was originally published in the Y-Block Magazine, May-Jun 2010, Issue #98