Dyno day for Jim's 416 inch FE was today; here are the results from the best pull:
550.7 lb-ft @ 5000 RPM
601.0 HP @ 6400 RPM
A graph of the best pull is shown below:
Jim and I started with the engine about 8:30 this morning, and after a minor struggle getting his headers to fit the engine mounts on the dyno we had everything hooked up and ready to go by noon. Before attaching the left side header, I took the opportunity to check the calibration of the torque sensor on the dyno. I hadn't done this for several years, because every time I'd done it the calibration was right on. This time was no exception; there is almost zero error in the dyno's torque reading. I will put up a second post about the calibration process, so that people can see what is involved. Also, for anyone interested, the STP correction factor for today's weather in the dyno cell was 4.0%.
After finishing up the left side header installation we ran into one more issue, and that was that the drain plugs for the water jacket on each side of the block had not been installed. Naturally, we didn't discover this until I was filling the engine with water
After addressing that issue we checked for fuel leaks and set the initial timing, and then started the engine. The engine ran great right from the start. Jim had instructions from Blair to run the engine at 3000-4000 RPM for the first 25 minutes to break everything in, and then start making some lower RPM pulls to make sure the engine ran consistently before doing any higher RPM pulls. We did all that with no issues. The original timing setup per Blair's recommendation was 33 degrees total in the locked distributor. We had a 1" open spacer, 1" 4 hole spacer, and 1" Super Sucker spacer to try out, in various combinations. Original jetting for the 850 double pumper was 84/84 with blocked power valves, also per Blair's recommendations.
After the initial 25 minute run-in we let the engine cool for about 15 minutes, then did a cruise test, and finally started with some lower speed pulls, 3000 to 5000 RPM. Right away the pulls were perfectly repeatable, but we were getting A/F numbers in the high 13s, so we started jetting up. What we discovered along the way during the pulls was that this engine wanted to run on the lean side; we kept seeing 13+ for the A/F numbers, with jetting all the way up to 88/90. Finally we overkilled it and went to 93/96 jets. At that level the A/F numbers came into line nicely at around 12.7:1, but the power was down 10-12 HP across the entire RPM range. We went back to 90/90 jets and ran the final pulls with that combination.
We made a total of 18 dyno pulls on the engine. The last half dozen or so were for testing spacers. The best combination turned out to be the 4 hole spacer right under the carb, and then the open spacer under that. We tried the Super Sucker on top of the open spacer and it wasn't quite as good, but the difference was only about 1 average HP. We also tried the Super Sucker by itself, and it was down about 2 HP on average from the combination of the 4 hole and open spacers. Another example of how you just can't tell how these things are going to work on a given engine until you can actually test them.
At the end of the day we tried to bump the timing up to 35 degrees, and this also picked up a little power, but not very much, only a couple HP on average through the pull.
The engine sounded really good through the whole process. We made several pulls up to 6800 RPM with no hint of problems, and were going to make one pull to 7100 or so but we didn't end up doing that, just forgot about it until the engine was partially disconnected from the dyno. Overall this was a very successful day, and Jim has a really strong bracket engine that ought to run well for years. The engine looks good on the dyno (especially those kickass valve covers
), and I'm looking forward to seeing pictures of it in the car.
