Well, here we go again with another intake changing marathon. I had a lot of help on Saturday, from Shoe, F570rd, Doug S, Kurt G, and Jerry C. Shoe and I handled all the duties on Sunday. I couldn't have gotten it done without those guys, especially on Saturday when I was trying to split my time between the dyno and work on my Mach 1. A big thanks to all these guys for making this report possible.
It was a real thrash this weekend, testing a total of 9 intakes, all single fours. During the course of events we went through two big pizzas, two big bags of chips, countless cans of pop and about 40 beers (F570rd seems to like the stuff...). In any case, it was all worth it for the results we got. Here's a picture through the dyno window of Shoe, F570rd, and Kurt G on Saturday afternoon, working on an intake swap:
Saturday morning we started off with the Sidewinder intake. I'd been looking forward to this one, because of the manifold's reputation, and the potential for proving it out, or disproving it. We ran the first tests and got a little over 390 HP which I thought was a little disappointing. However, after we had removed the Sidewinder and started on the next intake, it finally dawned on me that I had been testing the Sidewinder with the open carb spacer, rather than the 4 Hole spacer (I couldn't believe I did that...). Based on previous results with similar dual plane intakes, I felt that we had been leaving HP on the table by using the open spacer. So, we decided to disregard the initial Sidewinder tests, and put the manifold back on for testing later.
The second intake to go on the engine was the S code factory cast iron intake. Shoe was particularly interested in this one, because it is such a common intake and often is removed in favor of an aftermarket unit. How bad was it? We stuck it on the motor to find out.
The results were 355 HP, which was underwhelming of course as compared to the other intakes, but pretty much in line with what we were expecting. Sitting on the floor was the other cast iron intake, a C4 part number which was found as the standard 4 barrel intake on pre-66 FEs. Kurt G said, "Well, as long as we're dating ugly girls, we might as well do this one too." So, off came the S intake and on went the C4.
The C4 intake looked about the same as the S code intake, except the carb was probably about 1/2" lower with this intake as it was with the S code. But, we were about to be treated to the first real surprise of this dyno session. The C4 intake really ran well, making a full 20 HP more than the S intake. The S must stand for Sucks, because the C4 just blew it away. Here's a graph of the corrected Torque and HP for these two intakes:
The C4 intake looks pretty unimpressive, but it really does the job as compared to the S intake. I went a little further with this analysis, and compared the C4 intake to the Edelbrock SP2P, and the Edelbrock Performer. Here is the chart:
The SP2P had previously been the low torque champion on this motor, but no longer. Not only does the C4 intake have it covered in low end torque, but it handily tops the SP2P at the higher engine speeds. Based on this information, the SP2P intake has no redeeming value LOL! (Well, light weight, I guess...) Furthermore, the C4 intake is nearly as good as the Performer intake at the higher engine speeds, and of course its a hell of a lot cheaper. We were all in awe of the performance of this "unassuming" little intake.
Everybody was tired of lifting cast iron by this point, so we switched to an aluminum intake for the next test. We decided to try out the Offenhauser 360 intake. This is kind of an oddball, basically a single plane intake, but with a split plenum, so that cylinders 1-4 draw through a common plenum, and cylinders 5-8 draw through another. Despite being single plane, the manifold is a low riser design. I've heard varying reports on this intake, so I was anxious to see how it would do.
The results were about 390 HP, and a somewhat depressed torque curve as compared to the high performance dual plane intakes I had already tested. I was hoping for something a little more spectacular, but this manifold apparently doesn't have it to give.
Weiand makes a manifold that is very similar to the Offy 360, called the Action+Plus intake. These are still available new. Looking at the two intakes side by side, they appear to be nearly identical. My original plan had been to just test the Offy, but then someone on the forum commented that there are some internal differences between the manifolds. So, when one came up on ebay I picked it up. Sure enough, where the Offy 360 has two completely different plenum areas, with only the milled slot in the plenum divider connecting them, the Weiand intake has a couple of huge holes in this same divider, effectively creating one huge plenum feeding all cylinders. I was really curious to see how this affected it on the dyno, but I figured it would do about the same as the Offy.
The surprising short answer: The Weiand intake is NOT a good design. It was down a full 35 HP from the Offy 360 intake. Further, the engine missed on the dyno pulls at high RPM with this intake; I can only assume that pulsing in the huge plenum affected the fuel distribution, or some other affect of the intake caused this problem, because the Offy never missed, and the next manifold we tried also did not miss. Here is a plot of the torque and HP from the Offy and the Weiand intakes:
Neither of these intakes is great, but the Weiand really did not work well on this engine. I'll test it on some other engines in the future, but I'm not gonna bet much on this one.
At this point it was early Saturday evening, and I had run out of cold beer, so Kurt G and F570rd took off for greener pastures. Shoe and I swapped off the Weiand intake, and installed the Sidewinder again. We were ready for Sunday.
I was anxious to get going around noon on Sunday, and Shoe was running a little late, so I started the testing at 12:00 sharp even though he hadn't arrived yet. After warming up the engine and checking the timing, I ran the first pull, starting with the open spacer again, just to confirm the numbers we got yesterday. They were the same within about 2 HP. Shoe arrived, and we swapped in the 4 hole spacer. As I suspected, power improved with the 4 hole, to 401 HP.
We felt better about the Sidewinder at that point; it was making power in the same range as the Performer RPM and the BT intake, more or less living up to its reputation. We decided to try some other spacer experiments on this intake. Frank Bowers had told me of some good results using the 4 hole and open spacers together, so we tried this on the Sidewinder, first with the 4 hole under the carb and the open spacer against the intake, and then vice versa. Finally, we tried two 4 hole spacer together, to make a 1" 4 holE spacer. None of these combinations provided the power that the single 1/2" 4 hole spacer did. Here's the results from the sidewinder tests:
It was still early in the day, and we had one more cast iron intake to test: the factory CJ intake. This intake had done very well on my brother's 428, so I was anxious to see how it would do on this engine. Shoe and I horsed it into position, and let 'er rip. By the way, Dave and I were averaging about one hour and 15 minutes on average today, from start to finish swapping intakes. I've never really wanted to be that good at this...
The CJ intake did even better on the 428CJ engine than it had done on my brother's 428. It was nearly the equal of the Sidewinder in HP, making almost 400, and its 478 ft-lbs of torque peaked 10 ft-lbs higher than the Sidewinder. No wonder Ford put that intake on this engine; it was extremely impressive. Also kind of unusual with this intake is that it didn't seem to be affected too much by the choice of spacer. I suppose this could be because of the 4 hole design of the manifold itself, as opposed to the two oval holes found in most of the dual plane intakes. In any case, here is the open and 4 hole spacer data for the CJ intake:
With the last cast iron intake out of the way, only two four barrel intakes, that are currently in my posession, were left: the Dove single four intake, and the Holley Street Dominator. We decided to do the Dove first.
I was not sure how the Dove intake would perform, because it is really not a good match to this engine. The Dove intake is designed for high RPM operation, and the the heads and cam on my dyno engine are geared more for midrange torque than top end HP. So, I was very curious how the Dove would do on this motor, guessing that it would be down substantially from the other intakes in torque, and maybe in HP also. Here's a photo of the Dove intake installed on the test engine:
We started the engine, and I was actually pleasantly surprised at how the engine still would idle at a reasonably low speed even with the Dove intake installed. The test results confirmed that it was down on torque as compared to the other intakes, but it did pretty well in the HP area, peaking at 410 HP, right around the same area as the Streetmaster. Here is a graph showing the results from the Dove intake, along with the results from the ported version of the Streetmaster intake:
Obviously, the Streetmaster is the better intake for this engine, but the Dove intake did better than I thought it would do, and no doubt as the dyno mules start to move up in HP, the Dove intake will show stronger performance.
Finally, we swapped off the Dove intake and installed the Holley Street Dominator. This is an unported intake, and appears very similar to the Streetmaster. I expected to get performance very similar to the unported Streetmaster's performance. We were not disappointed. Here is the data, showing the Holley Street Dominator as compared to the unported Edelbrock Streetmaster:
Performance between these two intakes is nearly identical, and I would expect that when I apply the same porting techniques to the Holley as I did to the Edelbrock, it will also show roughly the same performance. We will see...
I have three other single four intakes that I want to test: the Edelbrock Victor, the Offy Port-O-Sonic, and the Offy dual port. I hope to have acquired all three of those intakes within the next few weeks. In addition, I need to port match the Holley Street Dominator and the Edelbrock F427, so that when I get this engine back on the dyno, I can finish off the single four testing, and start the multiple carb tests. For now, this dyno mule is coming off the pump, and my supercharged FE will be going on in the next couple of weeks.
To finish off the day, Shoe and I decided to re-install the "baseline" intake, the Blue Thunder 428CJ manifold, and run some confirmation tests. This had been the first intake I had tested on this engine, back at the beginning of April, and it had made 400 HP. We wanted to re-run this intake as a verification of the stability of the tests.
I was expecting to see some variation from the early test, but I figured it would be on the order of 1% or so. Unfortunately, I was surprised and dismayed to find that the BT intake was now making peak HP in the 410-413 HP range. WTF??? What had changed? I went back over my weather data and checked everything, and it looked very good. The weather in early April was substantially different than it is now, but the correction factor should compensate for that, at least to first order. All my temperature, humidity, and barometric pressure data was accurate to my instruments in the dyno room, so that wasn't the issue. Hmmmmm.....
On Saturday morning I had been tempted to calibrate the dyno's torque link. I hadn't run it since late April, and I would have calibrated it, but everyone showed up around 9:00 raring to go, and I would have had to take the left side header off to hang the calibration bar on the engine and do the calibration. So, I decided not to do it at that time. Shoe and I decided to do it now. We pulled the left side header off the engine, hung the calibration bar on the dyno absorber, and started adding the weights. Sure enough, by the time we got to 500 ft-lbs, a 2% error had emerged; the dyno's torque link was reading 2% too high. Taking this into account, the BT intake's HP numbers would have dropped back to 402-405, which is pretty close to the original 400 HP numbers. I could live with that variation. But then, just as I thought I had this figured out, the dyno's torque link came back into calibration at the very high torque levels. So, at around 800 ft-lbs, the torque link appears to be calibrated correctly, but from 100-500 ft-lbs, it appears to be 2% high. Shoe and I speculated about the causes for this, but the truth is I don't have a good answer for the cause of this problem. I need to look into this more in order to be sure that what we are seeing is real. So, I will try to update on the forum what I find out over the next few days.
In any case, data from the testing done during this report may be higher than actual by 2% or so, if it turns out that the torque link really is out of calibration. And if that's the case, I'll probably take a day sometime in the future to test the top five or six intakes on the same day, just to make sure that I have good comparison data.
Nothing is easy...
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