Way back in the muscle car days, the easiest way to get more power out your engine was to put in a big, lumpy cam and some high-compression pistons. Without the bigger cams, higher compression pistons will get you extra power, but the two of them together usually make for a potent combination.
Last month, we wrote about Mahle's newest pistons for the H22. These true drop-in pistons for a stock block are an incredible breakthrough. The H22's block is all aluminum, with no steel sleeves like other Honda engines have. Instead, Honda casts a carbon-fiber matrix around the cylinder area. The carbon is strong enough to eliminate the need for steel sleeves. Porsche 944 engines are similar. The problem is that forged-aluminum pistons don't like pushing up and down in that all-aluminum bore.
Mahle was the first aftermarket company to take their experience in OEM and racing (including Formula 1) piston manufacturing and develop a forged H22 piston with a coating that is compatible with the H22's cylinder walls. Until the Mahle pistons came along, you had to sleeve your H22 to install forged pistons. Available in low-, stock- and high-compression versions, you can now do a lot more with your stock-block H22 than previously possible.
Talking with Mahle about their new pistons, they told us of a development project that involved a "high-mileage" Prelude with about 70,000 miles. The short version is that they installed their 11.5:1 pistons and a pair of aftermarket Japanese camshafts into this H22 and, with that, horsepower jumped by 30!
Well that sounded like a challenge to us. So with Mahle on board, we set out to duplicate the project with an H22 of our own. The good guys at Superior Racing Development in Tempe, Arizona, helped us locate Dustin Denson, whose '95 Civic coupe had a transplanted H22. Dustin dropped off the car and we started what became a nearly four-month project.
Mahle sent up a set of their drop-in 11.5:1 compression pistons and we started the search for cams. Mahle couldn't remember exactly what Japanese company had supplied the cams, but Brian Crower told us about his Crower cams having been revised with some of the fastest ramp rates available and manufactured with a new hardening process so we were game. Crower sent us a set of Stage 3 cams, springs and revised retainers specially made for these very high-lift cams.
But first things first, we needed to baseline the H22 Civic. Over to Xact Dyno in Tempe, where a group of third-gear pulls on the Dynapack netted us about 156-wheel hp. It seemed low to us and when we called the car's owner about it, he said that had to be wrong. The car had been tuned in January 2005 to 176-wheel hp. Looking at the power curve, (yellow line in dyno chart) we could see that the top end went really flat. Xact had seen this before and figured it was the pistons letting go. Sure enough, a compression check showed low numbers on every cylinder.
Regardless, this engine was about to get new pistons and we set to work at SRD, getting the head off and the old, dying pistons out. Jake at SRD got the head off and instantly saw the problem. Every piston had scored its cylinder wall, creating a lot of leakage. Also, judging by the yellowing on the cam oil-spray bars, it seemed as though the oil had not been changed in quite some time. That's the problem with swap motors; you never really know exactly what you're getting.
With the pistons removed, SRD decided the cylinder wall scoring was too deep to remove with just a bore smoothing and that we'd have to use the .25mm overbore Mahle pistons. Mahle quickly got us a set of their overbore pistons and the block went off to S&S Machine in Mesa, Arizona, for the overbore and cylinder prep process. Just as we explained in the March 2006 issue, this is a critical step and you need to make sure the shop you chose knows how to do it.
After all that, SRD put the engine back together and dropped it into the car. The next step was to set the clearance of the rocker arms. In addition to the rocker clearance, you'll also need to install revised retainers that allow for a higher installed height. The B16A and H22 have notoriously short installed heights (1.320 inches or less). The +.060-inch retainer raises the height, allowing more lift and preventing the retainers from hitting the valveseals. Crower dual valvesprings (good for 8000+ rpm) were installed, as were the raised-height retainers.
Before we could race off to Xact Dyno for tuning, SRD decided that using such a big cam and high-compression pistons required checking the piston-to-valve clearance. Sure enough, the exhaust valves hit the pistons. This Crower cam was a big boy. The good news was we wouldn't wreck anything; the bad news was it all needed to come apart so the pistons could be relief cut. Mahle is keen to mention that the pistons we received were released in small batches and that all future batches will have the necessary clearance relief cut into them. The moral of the story here is to pay to have unknown combos like this checked or you'll really pay later.
Finally, nearly three months into the project, the Mahle/Crower H22 was ready for the dyno to see if we could get the same results as the Mahle R&D crew. Off to Xact Dyno we went and pushed out some pretty crappy numbers. Believe us, there not even worth mentioning. Drawing on Xact's experience and placing a call to Crower gave us an idea.