Got some preliminary dyno results on this engine today; it peaked at 864 HP and 698 lb-ft of torque after all the tuning was finished up. I'm hoping to pick up another 10-15 HP tomorrow with some timing and fuel changes, but for the most part this is the power that the engine is going to make.
Friday night I got home from the usual family activities a little late to be starting a dyno session, and the situation with my fuel injectors was still bugging me, so I decided to take the evening and check out all of my injectors. I received a package from Summit on Friday with two brand new injectors in it, and in order to test them and compare them with my existing injectors I decided to make a little test fixture. I took a short section of spare fuel rail, machined it to accomodate fittings and an injector, and then machined a separate piece as a bracket that would hold the injector in place. Here's a photo:
Then I took my spare fuel pressure regulator and some fittings and attached it to the fuel rail, so that I could hook the test injector up to the fuel pump on the dyno:
I took a spare injector harness and soldered a pushbuton into one of the wires, then put alligator clips on the ends so I could hook it to the battery, then attached the whole setup to the dyno fuel system. When the fuel pump was on I could energize the injector and look at the spray pattern, so that I knew what to expect from all the injectors. From there I turned on my precision scale and using an old plastic oil bottle, I weighed the bottle empty, then sprayed fuel into it for exactly 60 seconds, and then weighed it again. From there I was able to calculate pounds per hour of fuel for the injectors. After running this test on the two new injectors, I removed the eight old injectors from the motor and ran them too. I got the following data on the injectors; numbers 9 and 10 are the new injectors:
1: 69.9 lbs/hour
2: 68.2 lbs/hour
3: 71.1 lbs/hour
4: 70.9 lbs/hour
5: 69.2 lbs/hour
6: 70.1 lbs/hour
7: 67.7 lbs/hour
8: 67.5 lbs/hour
9: 67.7 lbs/hour
10: 71.8 lbs/hour
This test made me feel a lot better about the injectors. They were all in the same ballpark for flow, and despite the fact that they were not being pulsed during this test, I felt that since the new injectors behaved about the same as the old injectors the old injectors were probably working fine. Looking at the numbers, I threw out the high and low flow rate injectors, and then separated the others into two groups with equal average flow, one for each side of the engine, to try to even up the side to side A/F readings that I would get.
This morning I spent a couple hours making some last minute adjustments and checks to the engine, and also hooking up the air induction system so that the dyno could monitor the engine's air usage. Here's a photo of the engine at this point:
After this was all finished up I had to make a run to get some more race gas and a new belt for the vacuum pump; I was almost out of adjustment for the existing belt, because it was too long. When I got back my friend JC (he of the Y-block persuasion
) was waiting to give me a hand. We had a quick bite to eat, and then I got started putting the new belt on. However, after it was installed I realized that it was bending the brackets that hold the vacuum pump in place and causing a pulley alignment issue when I tightened it sufficiently. This led to an hour long CNC project, where I built an additional brace for the vacuum pump to address this issue. Finally, around 1:30 I was ready to run so I fired the engine and let it warm up to an oil temperature of 160F. This was kind of the moment of truth for the oil pump and oil pressure issue; I had previously decided that if the oil pressure during the run increased past 120 psi I was going to have to pull the pan with the engine on the dyno. My first checkout pull went from 3000 to 4500 RPM, and the oil pressure peaked at about 108 psi; what a relief!
From there, I started tuning the engine in 500 RPM increments, starting from 3000 to 5000 RPM, then moving to 3500 to 5500, 4000 to 6000, etc. At the higher speed levels I started seeing a slight drop off in oil pressure on the top end. Reviewing the crankcase vacuum data in the dyno logs I saw that I was pulling around 15 inches of vacuum at speed, and I suspected that this was causing the oil pressure behavior. But we didn't know for sure; JC suggested that we film the sight glass I had installed on the side of the oil pan during a pull and watch to see what happened. I thought that was a pretty good idea, so I set my tripod and camera up on the left side of the engine, looking at the pan, and made the following video:
http://www.youtube.com/watch?v=y28pPcml59U&context=C417ba0cADvjVQa1PpcFO96Jdxl9sme8uDkAMZmmIXxBOxFFaXY6c=You can see the oil level go up and down before, during, and after the pull, but at no time did the oil level in the pan drop too far down, so I concluded that the vacuum pump was causing the oil pressure behavior, and as long as the oil pressure stayed at a reasonable level I didn't have to worry about it.
We continued tuning the engine and finally ran from 5500-7500 RPM. The engine made 719 lb-ft of torque at 5600 RPM, and 858 horsepower at 6900 RPM. I was pretty happy with that; a quick calculation showed that to be 1.65 HP/cubic inch, which is certainly a respectable number. But the engine was peaking in power too low; the torque converter for the Galaxie has a 6000 RPM stall speed, and I felt that a higher power peak would be more beneficial for running a good number at the track.
Since this is an individual runner intake manifold, one of the things I'd been itching to try was to tune the RPM band by shortening the injector ram tubes. I decided to give this a try, so with JC's help we pulled all the ram tubes off the intake manifold and cut them down from 9" overall length to 7" overall length. This took an hour or so, but wasn't that difficult, and by 5:45 we were up and running again. This time I started at 4000-6000 RPM and worked my way up to 5500-7500. I had to make some changes to the VE map to add fuel at the upper RPM ranges because the change in ram tube length definitely had an effect. The torque peak of the engine was shifted about 600 RPM up by the shortened stacks. In this configuration, average horsepower from 6000-7500 RPM was up about 13 HP over the longer tubes, so shortening the tubes was definitely a worthwhile exercise.
Here's a graph of the engine's power band from 5500 to 7500 RPM:
Here a graph of the power band from 4000 to 7000 RPM; note that this is two separate dyno pulls merged together, so some of the data points overlap:
Here's a graph showing the best results from 5500-7500 RPM with the two different injector stacks length. Looking at this data it appears that I got lucky, and adjusted the injector stacks to exactly the right length, because at 6000 RPM the HP curves are at an identical point, but from that point forward the shorter stacks take over. So, with the 6000 RPM converter cutting the stacks didn't cost me any power; its only a gain.
It is interesting to compare this engine to the original trim of my 585" SOHC. Compression ratio is the same, heads are the same, cams are the same, and the ignition system and EFI system and injectors are the same. This is a really instructive comparison of engine sizes, and really points out the differences very clearly. For the 585" engine, peak HP per cubic inch worked out to 1.60, while with the shorter stacks on the smaller engine, peak HP per cube was 1.66. So, the smaller engine made more power per cube. Makes sense; that would be expected. Also, with the exactly same setup but 65 more cubic inches, the 585" engine peaked at 931 HP, while the 519" engine peaked at 864. Again, seems to make sense. Here's a graph showing the 585" engine and the 519" engine together on the same chart. The differences are really obvious:
Which engine will be faster down the track? Duh. You can't beat cubic inches.
Finally, here's a video of one of the last pulls. I had a lot of trouble with my camera, trying to get it to take a decent video while showing the computer screen in the dyno room, but finally I got some reasonable results.
http://www.youtube.com/watch?v=2ma6-rlv01sThis thing sounds so good at 7500 I'm really tempted to take it to 8000 RPM on Sunday. But its not going to make any more power if I do that, and if I cut the stacks again I'll start losing power at 6000 RPM, and I don't want to do that either. Plus, 8000 RPM and a 4.5" stroke crank is 6000 feet per minute piston speed; Yikes! I might run it to 8000 anyway, just to listen to the freaking thing; it sounds so cool! If I do I'll post another video. Nothing like an 8000 RPM SOHC, after all...
