Then, lucky for us, a savior came to the rescue! Enter Racing Head Service, RHS for short. RHS was at the forefront of cylinder head technology a few years back and then just kind of faded into the abyss. I really don’t know why but it happens. This is where Comp Cams and the Comp Performance Group came in and revitalized RHS making it part of the impressive group of companies owned by Comp. As of this writing RHS is just about running at 100%. Some of the castings such as mine still have the old Pro Topline insignia on them, but that’s not a bad thing. Eventually, all of the heads from RHS will say RHS. Most do now.
The important thing is that these heads flow quite well out of the box and respond very well to minor port matching and blending, and at a very reasonable cost. The heads I ended up with were the aluminum 200 cc “Pro Comp” units with a 58 cc combustion chamber. You have the option of a 64 or 58 cc chamber and I chose the 58’s because I am shooting for a 12.5:1 compression ratio. RHS set me up with the Hydraulic roller version for testing purposes (part # 35005-02). They come with dual springs rated for average hydraulic roller cams, stainless steel 2.02” and 1.60” valves, premium bronze guides, screw-in rocker studs and 5/16” guide plates, and 10* Super Lock retainers and locks. I ordered this part number because I figured it would be the most popular head for street/strip racers and give the readers a real world flow bench test of what you get “out of the box”.
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| A sanding roll took care of any burrs. | |
As the accompanying photos show, these heads are really nice as delivered. The only “issue” I have with not just RHS but virtually every cylinder head manufacturer is the
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I have flowed other brands before that make you wonder if it’s the right head! These were at least in the ball park. At .700” lift the RHS published numbers show 286 cfm @ 28” of water. My bench showed 264.2 cfm @ 28”. A difference of only 22 cfm. Not bad at all for an as-cast 200 cc runner and a 2.02” valve.
At .400” lift the published numbers were 259 cfm and my bench showed 212.10 cfm. Oops. Now we have a difference of 46.9 cfm! What I am attempting to illustrate is that this is why you shouldn’t expect the published numbers or look at just the peak flow. This is not a bad head. Actually it’s pretty good compared to some others. It’s just not quite what the advertising department wants us to believe. Nonetheless, I can make it work.
