Dean was over at my place last weekend for a little FE dyno session. His 427 was put together to go in his 67 Fairlane and look bone stock, right down to all the casting numbers, the stock ignition system (except for an electronic module in the distributor) and the 427 Fairlane exhaust manifolds. It uses a factory 427 sideoiler block, the factory 427 $ crank, and aftermarket rods and pistons with a static compression ratio of 10.6:1. The medium riser heads have had a 3 angle valve job but no porting work, with stock valve sizes. The cam is an ISKY solid, with .525" lift and duration of 250 @ .050". When Dean brought the engine over the factory 427 exhaust manifolds were bolted on. These manifolds had been internally ported via the Extrude-Hone method, to hopefully improve the exhaust flow. However, the 427 Fairlane manifolds were pretty good manifolds to start with, only losing out in my manifold testing to the cast iron headers that came on the Galaxies. Induction is handled by the medium riser 2X4 intake, and the carbs that we started out with were 600 cfm carbs. Dean had also brought along a pair of 780 Holleys to compare with the 600s. He was hoping to get at least 425 HP out of the engine in this form, and then add a pair of headers just to see what the difference would be.
Dean arrived on Friday night just as I was pulling my old reliable 428CJ off the dyno. After last summer's disappointing dyno results on my 585" SOHC, there was some question as to whether or not the dyno was reading accurately. Seemed like the times I ran at Drag Week showed that the dyno wasn't the problem, but just to be sure a couple weeks ago I threw my old reliable CJ engine on there. This engine makes 425 HP over and over on 110 octane race fuel. Unfortunately, I was out of race fuel, so I backed the timing down 4 degrees and ran the engine on unleaded. It made 416 HP, so that was close enough with the reduction in timing for me to conclude that the dyno was still giving reliable results. By Friday night my testing was done, so I got the engine off the dyno and Dean and I spent the evening getting his engine installed and ready to run.
Saturday morning Dean, his brother, his nephew, and another friend showed up for the dyno session. After some last minute checks we got the engine running. It was a little hard starting, and we had to mess with the timing a little bit to get it to run, which was kind of a surprise because Dean had already had it running for a while on a test stand. In any case, we got it warmed up and then performed a cruise test. This is a test where the throttle is advanced and the dyno brake is manually increased to hold the engine at a certain speed. Data is collected, then the throttle is advanced some more, the brake is increased more, and the engine is again at that certain speed, but under more load. We collected data on Dean's engine at around 2500 RPM at loads of 30 to 150 lb-ft of torque. The data looked OK except that the engine appeared to be running really rich. A/F numbers were in the 9-10 range, which is way, way low. We decided to make a preliminary pull from 2500 to 4500 RPM.
The results of this pull were pretty disappointing. The engine sounded like it was missing, and horsepower peaked at around 350. First thing we did was pull a spark plug, but it didn't look bad, just a little carboned up. A/F from this pull was looking very fat, so Dean and his brother tore into the carbs to change to some smaller jets. Next pull we went to 5000 RPM, but had the same issue with A/F and missing, and the engine was also even further down on power. Jet size was reduced even further for the next pull, but again we did not see any improvement in the results.
After chewing this over for a little while, Dean decided he wanted to change to the 780 carbs. He didn't have any experience with the 600 carbs that were on the engine, and he had run the 780s before, so they were more of a known quantity. After this change, we ran another pull with high hopes, but had the same problems as before. Here's a graph of the dyno data from this test:
You can tell by the jagged appearance of the HP and torque curves that the engine just wasn't running right. We tried a couple more things without success, then finally Dean decided to change the plugs. I hardly ever think about plugs anymore, because I'm always running such high power ignition systems on the dyno, and they will fire nearly any plug. But Dean was getting his spark from the stock coil and stock wires. As soon as we started the pull with the new plugs in the engine, I knew we'd solved the problem. The pull sounded nice and clean, and sure enough we were up over 400 HP! Plus the A/F numbers were now looking much better; we had been rich before because the engine wasn't firing all the air/fuel mixture.
We made a few more jet changes to get the engine dialed in for A/F. Best pull with the exhaust manifolds is shown below:
430 HP! Dean was pretty happy with that number.
Last test we ran was to pull the 427 Fairlane exhaust manifolds off the engine and install a set of FPA headers. We were all rather curious to see what kind of a difference we would see with the headers compared to the ported and Extrude-Honed exhaust manifolds. Guesses about the power increase ranged from 20 to 45 horsepower. I asked a few people after the fact about this, and the guesses were more like zero power increase. The engine, however, did not agree. Here is a comparison between the exhaust manifolds and the headers:
By the numbers that is a peak horsepower increase of 43 HP, and of course the increase is across the entire power band of the engine. In addition, the engine was running lean now with the headers, and more power could probably have been had by jetting up. You can see by the shape of the curves that the engine needs more tuning before it will smooth out with the headers. However, Dean was planning to run it with the manifolds in the car, so we didn't want to make any more changes; these results were plenty good!
I expect that Dean will post some photos of the engine in the car when he gets it installed. Should be a pretty faithful reproduction of a 427 Fairlane!