Tag Archives: Y-Block

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 Ford – Dual Quad Testing on Aluminum Heads – Part II

With the iron 113 heads on the dyno mule, the Edelbrock #257 2X4 intake that had been ported by Joe Craine did exceed those numbers generated by the stock Mummert intake and single four barrel carb combination.  Now it was time to install the aluminum heads on the 312+ dyno mule and see how those same dual quad manifolds would fare.

As a result of changing the ported iron ‘113’ heads to a pair of CNC ported Mummert aluminum heads, it was necessary to establish a new target baseline.  The same stock Mummert intake and 750 cfm vacuum secondary Holley that had been used for the iron head baseline was again used for the aluminum head baseline.  While the iron heads made a peak number of 311 HP in the single four barrel format, the aluminum head baseline jumps to 375 HP with nothing but a cylinder head change.  This does give the dual quad intake testing a much higher target value to aim for.

The dual quad intake testing with the aluminum heads now gets more definitive simply due to the flow restrictions that were taking place in the iron heads being minimized.  This will allow any flow restrictions in the manifolds and carb pairs to come to the forefront.  With that in mind, the same intakes that were run on the iron heads are also run on the aluminum heads.  But added to the fray are also the Fenton, Edmunds, Hogan, and the ported Edelbrock FM255 intakes among others.

Here is a quick summary of how the different intakes performed on the aluminum heads without getting into the various carbs or other variables that were tested on each intake.  This particular list is ordered from worst to best using the best carb combination for each intake that was tested.

1. Edmunds D427                                       330 HP@5400, 343 TQ@3300

2. Ford EDB-C 1956 – modified        331 HP@5400, 352 TQ@4400

3. Ford ECG-D 1957 – stock                336HP@6000, 352TQ@3500

4. Ford EDB-C 1956 – stock                 338 HP@5200, 369 TQ@4200

5. Edelbrock 257 – Hogged out          339 HP@6100, 337 TQ@4900

6. Fenton D427                                             342 HP@5400, 364 TQ@4200

7. Edelbrock 257 – stock                         351 HP@6000, 355 TQ@4500

8. Mercury ECZ-C stock                          357 HP@6100, 367 TQ@4300

9. Edelbrock FM255 stock                     359 HP@6000, 370 TQ@4400

10. Hogans Tunnel Ram                           361 HP@6100, 342 TQ@5200

11. Mercury ECZ-C ported                    366 HP@6200, 375 TQ@4400

12. Edelbrock 257 – Ported by JDC     369 HP@6200, 378 TQ@4400

13. Edel FM255 – Ported by JDC        378 HP@6200, 370 TQ@4600

So with that being said, here are the breakdowns for each manifold that was tested.  The manifolds are now listed in the order in which they were run and tested on the 322” mule engine.

Click on picture for larger images.

Ported Edelbrock #257 Intake:

Upon establishing the single four barrel baseline value, the Edelbrock #257 intake that had been ported by Joe Craine was the first of the dual quad intakes to be reinstalled on the aluminum headed +060 over 312.  While that particular intake was the best of the lot on the iron heads and actually exceeded the baseline target for those heads, it came up just shy of the revised baseline or target for the aluminum heads.  This intake was tested with several pairs of carbs and here are the results for the best tuneup for each pair of carbs.  I’ll add that jetting changes on two carbs and especially the Teapots can be very time consuming.

L1434 Teapots (1957 2X4 carbs)    332 HP@5500, 365 TQ@3700

600cfm Edelbrocks                                 362 HP@6100, 367 TQ@4300

500cfm Edelbrocks                                 363 HP@6100, 366 TQ@4500

L1094-1 Linc Teapots (60P/82S jets)369 HP@6200, 378 TQ@4400

Carter AFB carbs

Carter AFB carbs 

Click on pictures for larger images.

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Merc ECZ-9424-C Intake (ported):

Next on the list was the hard to find 1956 Mercury dual quad intake.  In looking at this manifolds outward appearance, this one was originally based on the Edelbrock FM255 intake. There was already some prior port work performed on this intake and based on its overall performance, it was a good performer back in the day.  Here are the results with a variety of carbs tested upon it.

1956 Mercury Carter carbs (vac sec)        347 HP@6000, 353 TQ@4500

L1161-2 Teapots with KM mods                 354 HP@6000, 362 TQ@4400

L1094-1 Linc Teapots (60P/82S jets)       366 HP@6200, 375 TQ@4400

 

Click on pictures for larger images.

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1956 Ford EDB-9425-C Intake (stock):

This was the ’56 Ford offering which had the center to center carb spacing much closer together than the ’56 Mercury intake that was just tested.  The rear carburetor sits further forward on this manifold and appears to be more flow restricted as a result.  Here are the results for this intake.

L1268 Teapots (1956 2X4 carbs)         327 HP@5500, 360 TQ@3700

L1434 Teapots (1957 2X4 carbs)         333 HP@5500, 363 TQ@3500

L1094-1 Linc Teapots (60P/82S jets)  338 HP@5200, 369 TQ@4200

 

********************************

Merc ECZ-9424-C Intake (stock):

Another 1956 Mercury 2X4 intake but this time it’s a stock and unmodified version.  Here are the results.

L1434 Teapots (1957 2X4 carbs)            344 HP@5500, 364 TQ@3500

L1094-1 Linc Teapots (60P/82S jets)  357 HP@6100, 367 TQ@4300

 

Click on pictures for larger images.

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Edelbrock FM255 2X4 Intake (stock):

This is the Edelbrock intake originally designed for the ‘55/56 heads and was the predecessor to the highly touted Edelbrock #257.  This intake is also the basic design for the 1956 Mercury dual quad intakes which also posted similar performance numbers.  Here are the results.

L1434 Teapots (1957 2X4 carbs)         342 HP@6100, 358 TQ@4500

GM Carter 1.050” mech sec 4V carbs 356 HP@5800, 368 TQ@4500

L1161-2 Teapots with KM mods          358 HP@6100, 362 TQ@4500

L1094-1 Linc Teapots (60P/82S jets) 359 HP@6000, 370 TQ@4400

 

Click on pictures for larger images.

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Fenton ‘D427’ dual quad intake:

Here are the results for the Fenton intake which was an unmolested version (no porting).  This intake has ‘D427’ cast on its bottom which leads me to believe that many of the Fenton manifolds were using some of the older Edmunds molds in which to cast them up.

1956 Mercury Carter carbs (vac sec)  324 HP@6000, 357 TQ@3300

L1161-2 Teapots with KM mods           338 HP@5400, 354 TQ@4500

GM Carter 1.050” mech sec 4V carbs 341 HP@5400, 362 TQ@4400

L1094-1 Linc Teapots (60P/97S jets)  342 HP@5400, 364 TQ@4200

 

Click on pictures for larger images.

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Edmunds ‘D427’ Intake (stock):

Same drill, just another intake.  This time it’s with an Edmunds intake with the ‘D427’ part number cast on its bottom.

L1434 Teapots (1957 2X4 carbs)          321 HP@5400, 357 TQ@3500

L1094-1 Linc Teapots (60P/82S jets)  322 HP@5400, 351 TQ@3900

L1161-2 Teapots with KM mods           330 HP@5400, 343 TQ@3300

********************************

1956 Ford EDB-9425-C w/mods:

And now back to the 1956 Ford dual quad intake but one that has been heavily ported in the plenum openings somewhere along the way.  The carb openings themselves had been enlarged to accommodate carb adapters to fit later model carbs to it.  The individual four carb bore holes had been converted to the kidney shaped holes as found on the 1957 ECG 2X4 intake manifolds. This particular manifold had also been heavily milled on the intake gasket surfaces which had the port openings smaller than they needed to be.

L1434 Teapots (1957 2X4 carbs)          321 HP@5400, 354 TQ@3500

L1161-2 Teapots with KM mods           329 HP@5400, 352 TQ@3300

L1094-4 Linc Teapots (57P/82S jets)  331 HP@5400, 352 TQ@4400

********************************

Hogans 2X4 Tunnel Ram:

This was a unique piece that falls in the sheet metal intake category and had been drag raced previously on the Church Brothers 1955 Thunderbird with much success.  On their iron headed engine, it had made a best of 490 HP but when replaced by a nicely ported Blue Thunder intake with a single four barrel carb, 510 HP came to the forefront.  While the Hogans intake is in the shop to see what can be done to its innards (plenum mods) to get it back on par with the single four intake, it is being run again with its ‘as supplied’ plenum with a myriad of carb pairs as part of this dual quad test.  Here are the results.

L1094-1 Linc Teapots (60P/82S jets)  311 HP@6200, 307 TQ@5100

L1094-4 Linc Teapots (57P/82S jets)  324 HP@5900, 324 TQ@5200

Street Demon 625 cfm carbs                   350 HP@6100, 345 TQ@4900

L1161-2 Teapots with KM mods           354 HP@6000, 329 TQ@5300

Predator 930 cfm variable venturi      356 HP@6100, 352 TQ@5000

L7996 450 Holleys w/mech secs           360 HP@5800, 344 TQ@5400

L4224 660 Cntr Sqtr Holleys                 361 HP@6100, 342 TQ@5200

  

Click on pictures for larger images.

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Stock Edelbrock #257 Intake:

The Edelbrock 257 has long been considered to be the gold standard of YBlock dual quad intakes.  Here are the results for the stock Edelbrock #257.

L1434 Teapots (1957 2X4 carbs)          328 HP@5500, 353 TQ@4200

1956 Mercury Carter carbs (vac sec)  331 HP@6100, 352 TQ@3400

L1094-1 Linc Teapots (60P/82S jets)  333 HP@6100, 354 TQ@4200

L1161-2 Teapots with KM mods           344 HP@6100, 353 TQ@4400

GM Carter 1.050” mech sec 4V carbs 345 HP@6100, 358 TQ@4400

Street Demon 625 cfm carbs                   351 HP@6000, 355 TQ@4500

********************************

Edelbrock #257 “Hogged Out”:

On this particular intake, the plenum dividers under each carb had been completely removed which played havoc with the carburetor signal.  This intake had been run previously on the iron heads and was the worst performer of the manifolds tested on those heads.  It did not fare much better on the aluminum heads while low end throttle response proved to be even worse with the better flowing aluminum heads.  As a result, dyno pulls had to be started at 3500 rpms rather than the normal 2500 rpm start.  While one pair of carbs were run on this manifold in an inline setup, a pair of Offenhauser crossram adapters were also utilized and tested in an effort to help save the manifold.  Here are the results.

Inline: Street Demon 625 cfm carbs    272 HP@5100, 293 TQ@4600

Crossram: 660 Holley cntr squirters   339 HP@6100, 331 TQ@4500

Crossram: 625 Street Demon carbs     339 HP@6100, 337 TQ@4900

Those open plenums were not at all happy with the carbs sitting directly above them.  Installing the crossram adapters which both lengthened the runners as well as shielded the bottom of the carb directly from the ports was worth an easy 67 horsepower.  Even with a 67 HP gain, that manifold still comes in at the lower performance end of the list and still lower in output numbers than an unmodified #257 intake.  The lesson here is to be cautious in porting these manifolds as it is quite easy to go the wrong direction when attempting to increase the power levels.

  

 

Click on pictures for larger images.

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Ported Edelbrock FM255:

With the results being much better with Joe Craine porting the Edelbrock 257, it was decided to also see what Joe could do with the Edelbrock FM255 intake.  The stock FM255 actually performed better than the stock 257 so it stood to reason that a ported FM255 might also perform better than a ported 257.  Here are some of the results.

1956 Mercury Carter carbs (vac sec)  347 HP@6000, 359 TQ@3300

L9776 450 cfm mech sec Holley           349 HP@6100, 354 TQ@4500

L1434 Teapots (1957 2X4 carbs)          350 HP@6000, 362 TQ@3400

GM Carter 1.050” mech sec 4V carbs 353 HP@6100, 359 TQ@4400

L8007 390 cfm vac sec Holley               353 HP@6100, 360 TQ@3400

L1094-1 Linc Teapots (60P/82S jets)  361 HP@6100, 370 TQ@4400

L1094-4 Linc Teapots (57P/82S jets)  361 HP@6100, 371 TQ@4400

L1161-2 Teapots with KM mods           362 HP@6100, 362 TQ@4400

But this is where things get interesting.  It’s observed that the mechanical secondary carbs have some severe reversion coming back up through them when loading the engine at 2200-2500 rpms.  To alleviate this, a 2” HVH tapered carb spacer is installed under each carb. But going with what Joe Crane had seen in some air flow testing, the spacers were tested in both the conventional right side up configuration and upside down.  The upside down configuration looked like a better fit to the four holes existing in the carb adapters that were being used to accommodate using modern carburetors on the teapot flanged intake.  The spacers being upside down peaked at 372 HP with the 660 cfm carbs.  Regardless of looking better, the spacers being right side up while using the same carbs netted 378HP.  That’s a 6 HP change that didn’t cost anything but the time it took to reverse the spacers.  It becomes obvious at this point that there is no end to the number of variants that can be tested.

With the same L9776 450 cfm Holley carbs reinstalled but with the upside down HVH spacers now under them, there is an eighteen horsepower increase.  That’s pretty substantial for just a pair of carb spacers being installed.  The pair of 660 cfm center squirter Holleys are then bolted on with the spacers being tested in both positions and the performance again steps up another notch.  Here are the final numbers for both sets of these carbs.

L9776 450 cfm mech sec Holley   367 HP@6100, 350 TQ@3300

L4224 660 cntr sqrtr Holleys        378 HP@6200, 370 TQ@4600

The Offenhauser crossram adapters worked so well on the ‘hogged out’ Edelbrock 257 intake that it was decided to also try them out on a manifold that was already at the top of the field.  In this instance and on the ported FM255 intake, performance went backwards.  Here are the numbers.

Crossram: L4224 660 Holley       352 HP@6200, 357 TQ@4500

  

Click on pictures for larger images.

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Stock ECG-4224-D 1957 Ford:

And this manifold completes the dual quad testing.  It’s tested only with two different pair of model 4000 Holleys (Teapots).  Here are the numbers.

L1434 Teapots (1957 2X4 carbs)    326 HP@5500, 355 TQ@4100

L1161-2 Teapots with KM mods     336 HP@6000, 352 TQ@3500

*********************************

In Summary:

Although I was on the trail of a couple of Edelbrock M254 intakes to also include in the testing, getting either of the intakes here for the test just didn’t happen.  The M254 2X4 intake was designed for the smaller port Ford 239 and Mercury 256 heads so I suspect it would have really been flow restricted on the aluminum heads.  Without actually testing that particular manifold, I can only guess that its performance would have been on par with the Fenton and Edmunds intakes.

One thing that became clear throughout these tests was what worked for carburetor pairs on one intake manifold did not necessarily work for another intake.  While the Lincoln Teapots performed quite well on some of the basic low rise dual quad intakes, they failed miserably on the tunnel ram.  On that particular intake manifold, two different sets of Lincoln carbs were used and both sets simply would not throttle up properly.  It’s a good guess that there was just enough reversion from those short and straight runners to be upsetting the metering in those particular carbs.  The carbs essentially sit right on top of the runners on that particular setup.  But the pair of 1956 Teapots (List #1161-2) with the Karol Miller modifications shined in that particular application.  Still trying to figure that one out but the internal secondary vacuum signal has been altered significantly on the KM modified Teapots which may be compensating for any reversion taking place.  The 660 cfm center squirter Holleys also worked very well on that intake as compared to some of the other carbs tested but that was the application for which they were specifically engineered.  But on the throttle up, all eight barrels were wide open on the 660’s versus only four barrels initially open on the vacuum secondary KM modified Teapots.  Lots to think about.

So there you have it.  Most of the dual quad intakes that were available for the Y have been tested and compared against each other.  Only in the best of circumstances did a dual quad setup exceed those performance baseline values established by a stock unported Mummert single four barrel intake.  Porting definitely works but if running aluminum heads, you do have your work cut out in getting the air flow numbers high enough in the dual quad intakes to match the cylinder head flow.

The next installment of the dual quad testing will cover the results derived from testing the various dual quad air cleaners.  Stay tuned and until next issue, happy Y motoring.  Ted Eaton.

This article was originally published in The Y-Block Magazine, Issue #116, May-June 2013.