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Great FE Intake Comparo - Report #1

April 9 2006 at 8:45 PM

Jay Brown  (Login jaybnve)

This weekend I began the Great FE Intake Comparo. Round 1 of the comparison testing is going to feature a total of more than 60 dyno test combinations with 20 different intakes, using my 428CJ as the dyno mule.

Just for starting information, here are some details on the engine:

- 428 + .030", ~10K miles on short block
- Stock Crank
- Lemans Rods
- Forged 10:1 pistons
- Factory windage tray
- Cobra Jet heads, stock valve size, 245 cfm @ .600" intake, 184 cfm @ .600" exhaust
- FPA tri-Y headers
- Edelbrock Performer RPM hydraulic cam, 236/236 @ .050", .572"/.572" lift
- Rollmaster timing chain
- Precision Oil Pumps rockers shafts, stands, and spacers
- Competition Cams (Dove) Rockers
- Iskenderian pushrods
- Holley 750 double pumper, 68/84 jets, 3.5 power valve, choke removed
- MSD distributor, 38 degrees total all in by 3000 RPM
- MSD Digital 6 ignition box, MSD wires, Blaster 2 coil

Intakes to be tested, most of which I have already acquired, are listed below:

- Blue Thunder 428CJ
- Factory cast iron 428CJ
- Factory PI
- Edelbrock Performer RPM
- Edelbrock Performer
- Edelbrock F-427
- Edelbrock Streetmaster
- Holley Street Dominator
- Edelbrock Victor
- Dove
- Offenhauser Port-O-Sonic
- Offenhauser 360
- Factory low riser 1X4
- Factory Sidewinder
- Edelbrock SP2P
- Factory low riser 2X4
- Factory medium riser 2X4
- Factory tunnel wedge 2X4
- Mickey Thompson cross ram
- Factory 3X2

I expect this testing to continue through the end of May, at which time I hope to have all the data for this engine. I plan to make a summary post at the end of the testing, and hopefully give weekly updates as I get data on the different intakes.

Test Conditions:

I wanted to test the manifolds with 4 hole and open spacers on this engine. Being effectively part of the plenum of the intake, I felt that the spacer tests should be included with the manifold tests, and considered part of the manifold. So, for each manifold I will test with a 1/2" 4 hole spacer, a 1/2" open spacer, and a 1" open spacer. I will use the best result of these three tests for each manifold. Also, I wanted to test the manifolds in both as cast and port matched configurations, so that I could determine how much change in power there was in both conditions.

Since some of the intakes in the test do not have heat risers, I determined that I would block all the heat risers in all the intakes in order to level the playing field in this regard. Also, I've had some experience with this engine and know that it likes 38 degrees total timing, so I will standardize on that for this testing. Finally, I decided to run all the tests on 110 octane race gas, both to have a standard fuel, and also to eliminate any possibility of detonation interfering with the test results.

Test Description:

In light of the results with the six manifolds I tested a couple of weeks ago on my brother's engine, I decided to start this weekend with the three top intakes from that test: the Blue Thunder 428CJ, the Edelbrock Performer RPM, and the Edelbrock Streetmaster. The BT intake was already on the engine from last weekend, but I pulled it off anyway to install the heat riser blocking plates and new intake manifold gaskets. After installation, I ran the dyno tests with the three spacers, and got the following results:

I thought this was kind of an interesting result, because the open spacers did not help with HP on this intake. I had the 427 MR version of this intake on my 492" FE, and I saw maybe a 5 HP increase with an open spacer. Not here. However, I did see a major drop in torque with the open spacers. So, for this engine, the BT is best with the 4 hole spacer, rather than an open spacer.

The BT intake has ports that are already the correct size for a 428CJ, so there was no porting work required, which meant I was done with this intake. Next up was the unported Streetmaster. This intake had shown an 18 HP advantage over the BT intake on my brother's milder 428. Not so this time; the unported Streetmaster showed very similar results to the BT intake (see my post from yesterday with this data). Since the Streetmaster has an open plenum, I didn't try the 4 hole spacer with this manifold, just testing the 1/2" and 1" open spacers. There was no significant difference in performance with these two sizes.

On Saturday night, I took my other Streetmaster intake, and did the porting to it recommended by Edelbrock. Rather than port it to the 428CJ port size, however, I ported it to the 427MR port size, so that it could also be tested on MR or Edelbrock heads. Also, in the plenum I did the Edelbrock-recommended rework. Here are photos of the unported plenum and the ported plenum, as well as a comparison of the port sizes:

This morning (Sunday) I got the modified Streetmaster installed on the engine, and ran the tests. Again, the choice of spacers did not seem to make any difference, but I used the 1" open spacer for the test results because that's what was recommended by Edelbrock. The end result was better performance from the rework, with a peak HP of 412. Here is the data:

This afternoon I pulled off the Streetmaster, and put on the Performer RPM. This manifold is in un-port matched condition at this point. Spacer testing with this intake yielded similar results as with the BT intake; the 4 hole spacer gave best torque, and the open spacers did not give any appreciable increase in HP. Here is the data for the different spacers; please note that on the first pull, with the 4 hole spacer, the engine sputtered a little at the lower engine speeds, so the data below 3000 RPM for this pull is probably not valid:

Using the best pulls from each engine, here is how they stack up:

So, the Streetmaster in ported form has retained its advantage over the unported Performer RPM and the Blue Thunder, but the gap is narrower with this engine as compared to with my brother's 428. Also, please notice that at the highest engine speeds, the BT intake is hanging on to power better than the other two intakes.

Here are peak and average HP and torque numbers (3000 - 5500 RPM) for these intakes:

Intake / Peak HP / Peak Torque / Average HP / Average Torque

Blue Thunder / 400.6 / 479.8 / 353.9 / 441.1
Streetmaster / 412.8 / 477.7 / 357.8 / 445.1
Performer RPM / 402.2 / 485.1 / 354.6 / 442.2

Next on the list is to pull the Performer RPM and port match it to 427 MR heads, and then re-test. I plan to complete this work sometime this week. I expect that there will not be a big difference from the port work, because the Performer RPM ports are not really small like the Streetmaster ports were. Nevertheless, only by testing will we know for sure, so I'll post those results when I have them.

A few other comments about this testing:

My post yesterday resulted in some controversy regarding the vacuum readings when testing the Streetmaster. Today, I tested the vacuum readings back to back on two of the Streetmaster pulls. First, here is a picture of the carb on the Streetmaster intake, showing both potential vacuum port locations:

The port I was using yesterday is the one on the left side of the picture, about in the middle of one of the intake runners, which is capped off in this photo. For all other tests today I used the vacuum fitting under the front of the Holley carb, where the vacuum line is shown connected in this picture. The back to back test results for vacuum are shown below:

Sure enough, the vacuum at the intake manifold runner is greater than the vacuum at the carb base plate. So, I must conclude that the location of the vacuum port on the intake does give an artificially high vacuum signal, perhaps related to the velocity of the intake air as it rushes past the port. Also, given the vacuum readings from under the carb, it is safe to say that the carburetor is not a restriction for this intake, so I did not swap on a larger carb to try on this intake.

Further on this topic, since on the previous test with my brother's engine I did not standardize the vacuum port location from manifold to manifold, I think that any conclusions drawn from the vacuum data of those tests should be discarded. From now on I will use the carb base vacuum fitting to collect the vacuum data during the dyno pulls.

One other topic came up on the forum yesterday, regarding how much power is consumed by the fan on the front of the engine. Mike (chipmechanic) had asked me to run a test, and to be honest I'm not sure what this test proves, but here is the Streetmaster intake, with and without a fan bolted on the front of the engine:

Looks like about 8 HP to turn this 7 bladed stainless steel Summit fan. I think the results would be different in front of a radiator, or while the car is running down the road, but FWIW, this data is valid when hanging the fan on the dyno engine.

That's all for now. I'll try to post any interesting interim data between now and next weekend, and another detailed update post next Sunday night - Jay

Jay Brown
1968 Shelby GT 500 Convertible, all aluminum 489" 1030 HP Supercharged FE
1969 XL Convertible, 460
1969 R code Mach 1, 706 HP 511" all aluminum FE, 10.457 @ 127.47, 2005 Drag Week Winner, Naturally Aspirated Big Block

This message has been edited by jaybnve on Apr 9, 2006 9:07 PM

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