With big aftermarket cams and pistons, the exact cam center can easily be different than with factory sprockets, especially if the head has been milled. Because Dustin already had adjustable cam gears installed, and because SRD was swamped and two deadlines had already passed for this story, we moved over to UMS Tuning. Tony Szirka, owner of UMS, put a cam degree wheel to the H22 and found that the cams were indeed off from zero on the cam wheels.
Relative to Crower specs, the cam wheel indicated that the exhaust cam was 5 degrees advanced and the intake advanced by 4 degrees. That's quite a bit, but our head did get decked for a truly flat surface, and this is a high performance combo, so it's actually not bad. Like the piston to valve clearance check, this is another must-do performance step to get maximum power. Tony says it's a three-hour job, but you could easily spend that much time on the dyno at way higher rates trying infinite combos and still not get it right. Plus, you run the risk of going too far and whacking a valve into a piston. Thanks to UMS for stopping what they were doing and getting this done.
Back on the dyno AGAIN, torque was massively improved. We had the added advantage of a Hondata s200 to tune everything like we were factory Honda engineers. Tuning on the small cam was going very well; however, switching to the big cam, we were again disappointed. Power climbed steadily to 5500, but then just went flat. After everything on the ignition side was checked and OK'd, Xact decided it had to be the exhaust.
Dustin's car had an OEM compatible DC 4-2-1 header with factory sized collector. It had no cat and a 2.5-inch exhaust, but according to Xact, it was clear the air just wasn't able to get out. SRD to the rescue again. Josh just happened to have an RMF-style 4-into-1 header with a 3-inch collector sitting at home. We quickly grabbed it and bolted it to the H22.
With the much larger header in place, power literally leaped to 198 from 166. It was starting to look like the Mahle guys weren't full of you know what. They just didn't tell us what header was on their car and, after that, it's now brick-in-the-head obvious that a large exhaust is a requirement for the 200-wheel hp club.
So we were 25-wheel hp up from when Dustin's car was healthy, back in January. Thirty-five horsepower was gained from the less-restrictive exhaust, and we knew there was more to be had. The air/fuel ratios were running dangerously lean past 7000 RPM (near 14:1) and the Hondata showed injector duty cycle at 100 percent. If we could get some more fuel to the engine, we would likely get more power.
Cranking on the adjustable fuel pressure regulator until it showed 70 psi at idle got us very little and at that pressure the injectors would soon fail. We had hit yet another wall! A day later and with 470cc/min injectors from Xact, the H22 was getting all the fuel it could swallow. This pushed power to 206. We'd hit the 30 wheel hp gain we'd set out to achieve. But with peak power at only 7200 rpm, we had to wonder if there wasn't more to be had.
Dustin's H22 had a stock intake manifold and we thought that might be the problem. Xact's Dynapack has a built-in pressure sensor, and connecting it to the manifold showed that vacuum was actually increasing with rpm. A sure sign of a restrictive intake. With a borrowed Skunk2 manifold and oversized throttle body, we were set to find more power.
And sure enough we got slapped again. Because this H22 was in Civic and not a Prelude, the manifold wouldn't fit without cutting the firewall-something Dustin did not want to do. Since his stock manifold already had the butterfly system removed, we figured we probably had enough runner volume, but the smallish throttle body may have been holding us back. So we port-matched the stock manifold to the Skunk2 TB and hit the dyno.
The dammed thing actually made less power! Not much less, but less. Manifold vacuum was higher too, which made no sense. Looking at the AEM cold-air intake tubing, we decided it could be the culprit. Disconnecting the tubing and letting the throttle body breath netted a 210-wheel hp run-like we expected.
But excessive vacuum at full throttle was still an issue. At this point, all we could figure was that the factory manifold just wasn't cutting it, and we were two issues overdue, so there was NO time to try anything else. 220-wheel hp could certainly have been possible, and with race gas, perhaps as high as 235 or 240. But, we bettered our achieved goal and the job was over.
On this painfully long journey, we learned some things that will certainly help you readers out-whether you're building an H, B, D or whatever Honda engine. Firstly, big cams need big compression. People are often disappointed with the results of aftermarket cams. Mostly, it's because the stock compression isn't what the cams were designed for. Secondly, high compression pistons must be checked for clearance with big cams. Same thing goes for the valvetrain. The rocker arms on the H22 had to be modified and used along with taller retainers to fit this cam. Letting all these things hit each other at high RPM will destroy more than just those parts.
Additionally, keep in mind that an engine is just an air pump. The cams control the amount of air that gets in and out. With big cams comes the need for better intake and exhaust. A 3-inch exhaust is a requirement for an engine of this size.
Finally, if you're doing all this, it's going to take more fuel. The stock 310cc/min injectors will quickly meet their match. As well, trying to manage all this with a fuel controller is futile. Running high-compression pistons, junk 91-octane fuel and stock timing is like dating twins-it's gonna be fun, but you're gonna get caught and it ain't gonna be pretty. Use a Hondata or something like it.
In the end, it wasn't as simple as Mahle had told us, but this combo is highly effective. The Mahle's have a street price of about $500 and the Crower cams are on sale for $500. The springs and retainers are also about 500 bucks, but with the right exhaust and tuning, this is nearly a 40-wheel hp gain with monstrous torque. There truly is no replacement for displacement.