FordMuscle Staff

A few years back the FordMuscle Forums were buzzing about a new small-block Ford cylinder head out of New Zealand. The company was Pro-Topline and guys in the states were clamoring to get their hands on them. Unfortunately it never materialized because the company went into receivership (what they call bankruptcy down-under) in 2003. The assets were subsequently purchased through a joint venture between Southern Performance Ltd. and Comp Cams. In case you don't know the history, Racing Head Service was a formidable cylinder head manufacturer and race engine building company in the 60's. To expand the business

Pro-Topline is now RHS. Not to be confused with Pro-Comp, a knockoff company casting poor-quality heads in China.

offerings the RHS partners started Competition Cams in the mid '70's. As the new business grew larger, the RHS operation and name was idled. The intent was always to bring the name and reputation back when the timing was right. The Pro-Topline situation became that opportunity.

The New Zealand foundry where the heads are cast is actually a purpose built operation for cylinder heads. Every head is CNC produced on a five-axis Mazak system. In fact, the guy who runs the place knows a thing or two about high-quality foundry operations. He had previously set up a wheel foundry which is the largest offshore supplier of wheels to Ford USA. Combine that level of experience with Comp Cams history of dominance in camshaft and valvetrain technology and you have the makings for what should be a very high-quality and high-performance cylinder head.

Critical Analysis
The point of this article, of course, is to find out just how they stack up.
We got our hands on a pair of their small-block Ford "Pro-Action" 180cc and 215cc heads. (There is also a 200cc available.) All three heads are offered in iron or aluminum with 58cc or 64cc chambers. You also have the option of fully-assembled or bare. A couple of noteworthy comments right off the bat. The RHS website and catalog list the 200 and 215 head as equipped with 2.08" intake valves, while the 180 head is supposed to have 2.02" valves. We're not sure why but our 180 heads also came with 2.08" valves. Secondly, note that these valves sizes will pose a piston to valve clearance problem for the stock-block crowd. You cannot put any of these heads on a 5.0L bottom end without notching the pistons, even with the stock cam. We've discussed this shortcoming in the catalog with Kevin Feeney, RHS's product manager. He agrees on this point and revealed there are plans (albeit long term) to introduce a smaller volume head with more 1.90" valves. Guys, send them a note if you want that and perhaps it'll happen sooner.

The 200 an 215cc heads come with 2.08" intake and 1.60" exhaust valves. The 180cc head is listed with a 2.02" valve but ours for some reason arrived with 2.08" seats and valves.

The port height and width on the 215cc head are 2.15" x 1.25" (use a FelPro 1262 gasket.) The 180cc head measures 2.00" x 1.15" (use a FelPro 1250).

We pulled molds of the 215cc intake runner (shown here) and the 180cc runner (right) to enable a better view of runner and port differences. Note how the 215cc runner has a taller roof and wider cross-sectional area (use the impression of the rocker stud boss as a point of reference.)

This is the RHS 180cc runner. The smaller dimensions keep velocity up, which is critical for a stock displacement street motor. As you'll see on the next page the 180cc head flows well up to .535" lift.

The widest portion of the runner area on the 180cc head measures at 1.800".

The widest portion of the runner area on the 215cc head measures at 2.020". The 215cc head takes off in flow after .500" valve lift.

Flow Testing with the Pros
We took the heads over to Watson Racing and Engineering LLC. in Concord, CA. Watson Racing is the brainchild of NHRA Pro-Stock racer Ben Watson. Calling it a machine shop doesn't do it justice. This place is 26,000 sq.ft. of pure high-end race engine development. More on this on the next page. Ben, who is busy 24/7 working on the Dewco Pro-Stock GTO, put us in touch with Mike Blackstone, the engine building and cylinder head porting guru. We immediately felt foolish with a set of as-cast heads going on a bench that sees heads with hundreds of hours of Mike's port work. Fortunately for us Mike is a knowledge junkie and was just as interested as we were in how the RHS heads would fare. More

(RHS Heads, Flow Testing)

In This Article:
Flow bench testing and analysis of RHS Pro-Action cylinder heads for small block Fords. These heads were formerly known as Pro-Topline.

RHS offers the Pro-Action heads (formerly called Cylcone) in three intake runner volumes, 180cc (back), 200cc (not shown), and 215cc (foreground). All three heads share the same exhaust runner. All the heads are offered in cast iron or aluminum, and available assembled or bare. They go for about $1500 a pair assembled.

The heads are delivered as-cast, no CNC porting. This makes the flow numbers even more impressive. The valve seats (phosphor-bronze on the exhaust and maganese-bronze on the intake) are hand blended to the bowls.

All of the heads share the same exhaust runner 75cc and 1.60" exhaust valve. The dual header bolt pattern in on all three heads as well for maximum porting flexability.

The assembled heads include some quality valvetrain parts, including 1.460" dual-springs, Comp Cams guideplates, and 7/16" studs. Valves are standard-fare in .100" over-length.
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