What started out as a simple dyno test to evaluate the performance differences between the small and large port Edelbrock three deuce intake manifolds ended up turning into a full blown test where seven different 3X2 intakes were compared on an engine in a back to back dyno test. The other intake manifolds being added to this test included three different intakes wearing the Edmunds brand, a Weiand intake and an Offenhauser intake. 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|
1 & 8
|Edmunds Ford 424||261.9||330.4||227.3||303.0||1646.9||
|Offenhauser No part #||250.8||311.5||215.6||287.1||1561.2||
|Mummert 1X4 intake w/600 Holley||291.9||346.0||244.8||323.7||1765.4||
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.
|Chart B – all values horsepower|
|rpm||Original PHRM Test||This Offy test||Edel573||Edel553||EdmdsDM-425||WeiandFM436||EdmdsDM-424D||EdmdsF-424|
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.
|Chart C – Lowend performance evaluation – values are ft/lbs torque|
|rpm||Edmunds DM-424D||Edmunds DM-425||Edelbrock 553||Weiand FM436||Edelbrock 573||Edmunds Ford 424||Offy|
|Overall scoring order||4||2||3||5||1||6||7|
|Revised scoring order||1||2||3||4||5||6||7|